DOSIMETRY DURING PERCUTANEOUS CORONARY INTERVENTIONS OF CHRONIC TOTAL OCCLUSIONS

DOSIMETRY DURING PERCUTANEOUS CORONARY INTERVENTIONS OF CHRONIC TOTAL OCCLUSIONS ABSTRACT Percutaneous coronary interventions (PCI) of coronary chronic total occlusions (CTO) increase the risk of high radiation exposure for both the patient and the cardiologist. This study evaluated the maximum dose to the patients’ skin (MSD) and the exposure of the cardiologists during CTO-PCI. Moreover, the efficiency of radioprotective drapes to reduce cardiologist exposure was assessed. Patient dose was measured during 31 procedures; dose to the cardiologist’s extremities were measured during 65 procedures, among which 31 were performed with radioprotective drapes. The MSD was high (median: 1254 mGy; max: 6528 mGy), and higher than 2 Gy for 33% of the patients. The dose to the cardiologists’ extremities per procedure was also of concern (median: 25–465 μSv), particularly to the left eye (median: 68 μSv; max: 187 μSv). Radioprotective drapes reduced the exposure to physician’s upper limbs and eyes; especially to the left side (from −28 to −49%). INTRODUCTION During interventional procedures, high doses may be delivered to the patient’s skin, potentially exceeding the threshold for radioinduced skin injury(1). Percutaneous coronary interventions of coronary chronic total occlusions (CTO-PCI) increase the risk because of protracted use of fluoroscopy, numerous images acquisitions and use of localised beam incidences. Whereas this represents isolated yet acute exposure for the patients, the medical staff may perform two to three CTO-PCI in a day in addition to general PCI and diagnostic examinations, resulting in an important cumulative dose over their complete career. Cumulative doses to the extremities and the lens of the eye of the staff are of particular concern. Studies(2, 3) have shown that annual cumulative dose to interventional physicians can exceed the limits proposed by the International Commission on Radiological Protection (ICRP)(4, 5). To decrease physician’s exposure, personal protective equipment, such as lead aprons and lead glasses, as well as room protective equipment, such as ceiling suspended shields and table curtains, are available in most operative rooms. More recently, lead-free, disposable drapes—to be positioned on the patient to protect the physicians against backscattered radiation—have been made available in the operative rooms. Although such drapes have been commercially available since 1998 in the United States and 2002 in Europe, their reported use during PCI procedures is rather scarce in the scientific literature(6–8), and detailed dosimetry at the level of the eyes and the hands is rare. Such studies are, however, necessary to help to assess the balance between costs/burdens and benefits of any such protective equipment. The goal of the study was to perform a detailed investigation of the dose to the patient’s skin and the staff extremities during CTO-PCI. In addition, the efficiency of radioprotective drapes to reduce staff exposure during CTO-PCI was assessed. MATERIAL AND METHODS Study population and procedures Starting from February 2014, 65 patients undergoing CTO-PCI have been prospectively included depending upon availability of the dosemeters, and separated into two study groups. During the first part of the study, procedures were performed according to customary practice (control group); while in the second, a lead-free radioprotective drape (Radpad® red grade: 0.375 mmPb equivalence at 90 kV stated by the manufacturer) was placed on the patient according to manufacturer recommendations (Radpad group, Worldwide Innovations & Technologies, Inc., Lenexa, USA). Procedures were performed by two experienced CTO-PCI operators(9) from the UZ Brussel and the Ziekenhuis Oost-Limburg, respectively. The procedures were performed on a Siemens Artis DfC system and on a PHILIPS Allura Xper FD20 system, respectively. In both hospitals, room shielding equipment (ceiling suspended shield, table curtain) and individual shielding equipment (lead apron and thyroid collar) were used. Lead glasses were available too. For each procedure, demographic (including age, gender, height, weight, chest dimensions and body mass index (BMI)) and angiographic characteristics were collected. The patients were subdivided into four BMI categories (underweight BMI < 18.5; normal 18.5 < BMI < 25; overweight 25 < BMI < 30; obesity BMI > 30). Data were analysed according to the treated coronary vessels included the circumflex artery (CX), left anterior descending artery (LAD) and right coronary artery (RCA). Occasionally, the left main coronary artery (LMCA) or an obtuse marginal branch (OM) was treated. The procedure cumulative air kerma at interventional reference point (Ka,r), the air kerma area product (PKA), the fluorography time (FT) and the number of cinegraphy acquisitions were extracted from the dose report at the end of the examination. For individual cinegraphy acquisitions, the Ka,r, PKA, FT, frame rate (frame/s) and beam angulation were also extracted. The J-CTO (Multicenter CTO Registry of Japan) score(10) was used to grade the CTO complexity, based on the presence of five negative (angiographic) characteristics (i.e. blunt entry shape of the proximal CTO cap, visible presence of calcification on angiography, tortuosity at the proximal CTO cap and/or CTO body (≥45°), a prior failed attempt, and a long CTO lesion length (≥20 mm) (as determined by the eye-ball method and/or the balloon or stent size as a reference)). Each characteristic was assigned one point. The procedures were then subdivided into four groups according to their score: easy (0), intermediate (1), difficult (2) and very difficult (≥3). Dosimetry In total, 86 thermoluminescent detectors (TLD), LiF:Mg,Ti material (MTS, Institute of Nuclear Physics, Krakow, Poland), were used for patient maximum skin dose (MSD) measurement. The TLD were attached to a piece of fabric, forming a 72 × 32 cm2 grid, and wrapped around the patient chest, facing the x-ray source and centred on the patient’s spine. This enables one to draw a map of the cumulative skin dose. However, to account for the limited resolution of the point-detector grids (i.e. the risk of not having a detector positioned in the MSD region, hence, underestimating the patient’s dose), measurements were corrected. In practice, the MSD values were divided by the median underestimation resulting from point detector measurements during PCI, numerically computed by Dabin et al.(11) TLD for patient dosimetry were calibrated free in air in a RQR5 reference field(12) in a second-standard calibration laboratory; unexposed dosemeters were kept for background determination. Staff dosimetry was performed according to the Oramed protocol(13). TLDs wrapped in a pouch were positioned on the main operator at seven different locations, including the left and right middle finger; left and right wrist; left and right leg (a few centimetres below the lead apron); and between the eyes. In addition, a TLD inserted in a dedicated eye lens dosemeter (EyeD™, Radcard, Poland) was positioned on the left temple (ED). If lead glasses were worn, the eye lens dosemeter was positioned above them to assess the dose to the unprotected eye. One TLD set was used per procedure; unexposed TLD were kept for background determination. Unlike patient dosimetry, LiF:Mg, Cu, P material (MCP-N, Institute of Nuclear Physics, Poland) was selected for staff dosimetry because of its greater sensitivity to low doses. Staff detectors were calibrated according to ISO norms N60 reference beam(14) against personal dose equivalent Hp(0.07) for extremity dosemeters and Hp(3) for eye lens dosemeters(4). Measurement uncertainty The uncertainty associated with the staff dosimetry was estimated as the square root of the sum of the squared independent uncertainty sources. The considered sources were: individual sensitivity (1.6%), repeatability (1%), fading (3%), calibration (3.8%), energy (4%), angular response (4%) and background determination. For doses smaller than 10, 20 and 40 μSv, the uncertainty (k = 1) was mostly dominated by the uncertainty in the background determination, and was estimated to be ~40, 25 and 15%, respectively; the uncertainty was ~8% for doses ≥40 μSv. For the MSD measurements, the uncertainty associated with the limited resolution of the TLD grid was also taken into account in the uncertainty budget as proposed in Dabin et al.(11), in addition to the sources mentioned above for the staff dosimetry. Monte Carlo simulation method(15) was used to combine the TLD measurements and the—non-normally distributed—uncertainty associated with the grid resolution (12%). An overall (k = 1), non-normally distributed uncertainty of 25% was estimated. The uncertainty associated with the displayed PKA and Ka,r were 9 and 6% on the PHILIPS Allura Xper FD20 system, respectively, and 8 and 8% on the Siemens Artis DfC system. Those uncertainties were obtained by comparing the system-displayed Ka,r and PKA values with measurements performed with a calibrated dosemeter and a system for measuring the size of the irradiated field (for the PKA) for a kV-range from 80 to 110 kV. Statistical analysis Procedural, demographic, angiographic and dosimetric data were analysed using descriptive statistics. Continuous data were tested for normality using both the Shapiro–Wilk test as graphical methods. Differences between distributions were tested using Welch’s t-test. If departure from normality was observed, pairwise Welch’s t-test was used on the rank of the sorted data; otherwise, pairwise Welch’s t-test was directly used on the qualitative data. One- or two-tailed test were chosen as appropriate. Categorical data were tested using the Pearson’s chi-square test. Correlations between MSD and procedure parameters (Ka,r, PKA, fluoroscopy time), BMI and complexity score were estimated using the Pearson coefficient (R2) and/or Spearman rank test (rs), as appropriate. A p-value of ≤0.05 was considered significant. All statistical analyses were carried out using R (version 3.3.1; R Foundation for Statistical Computing, Vienna, Austria). Boxplots are used to give graphical description of some data distributions. Horizontal lines (from bottom to top) represent the first, second (or median) and third quartile; squares and circles (outside whisker range) represent averages and outliers, respectively. Whiskers extend from the first quartile minus interquartile range up to the third quartile plus interquartile range. All doses measured on the operator were normalised to the procedure-cumulated PKA, in order to account for the difference in radiation use during the procedures. Dose readings below the detection limit were set to the detection limit. RESULTS Study population and procedures Overall, 65 procedures were included during the study period, 34 without and 31 with the radioprotective drape. In both groups, the majority was male and either overweight or obese, without any significant differences. Likewise, the dosimetric indicators (Ka,r, PKA and fluoroscopy time) showed no significantly diverging trends between both groups (Table 1). From the analysis of a subset of 24 procedure dose reports, left anterior oblique (LAO), posterior anterior (PA) and right anterior oblique (RAO) projections were accounting for 42, 35 and 23% of the cumulative cinegraphy PKA, respectively. Purely lateral projections were rarely, if ever, used. The dose reports contained no detailed information on the projection contribution in fluoroscopy mode. Table 1. Demographic, dosimetric and clinical parameters of the study population, classified according to the use of the RADPAD drape.   Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0        Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0      Values are given as n = number of cases, median [min, max], interquartile range (Q1–Q3) or percentage (%). The mean J-CTO score ± standard deviation is also reported as it is traditional medical practice. BMI, body mass index; Ka,r, cumulative air kerma at interventional reference point; PKA, air kerma area product; PKA,Fluoro, fluoroscopy contribution to PKA; PKA,Graphy, cinegraphy contribution to PKA. Table 1. Demographic, dosimetric and clinical parameters of the study population, classified according to the use of the RADPAD drape.   Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0        Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0      Values are given as n = number of cases, median [min, max], interquartile range (Q1–Q3) or percentage (%). The mean J-CTO score ± standard deviation is also reported as it is traditional medical practice. BMI, body mass index; Ka,r, cumulative air kerma at interventional reference point; PKA, air kerma area product; PKA,Fluoro, fluoroscopy contribution to PKA; PKA,Graphy, cinegraphy contribution to PKA. The overall J-CTO complexity was comparable in the Radpad and control groups (1.9 ± 1.0 versus 1.8 ± 0.9, p = 0.56). Patient dosimetry Patient skin dose measurements were available for 89% (n = 31/34) patients of the Control group; the demographic, dosimetric and clinical parameters of this subset of procedures were comparable to the complete control group. Median MSD was 1254 mGy (range: 33–6528 mGy), the distribution of the MSD was strongly right-skewed. For 71% of the procedures (n = 22/31), the MSD was below 2000 mGy; all but two (94%) were below 4000 mGy. No significant difference was observed between the mean MSD of the different complexity groups; pooling the procedures into two complexity groups (≤1 versus ≥2) did not result in a significant difference in MSD either (p = 0.65). The correlation between the MSD and the PKA or Ka,r (rs = 0.84 and 0.86 with p < 0.0001, respectively) was rather linear (R = 0.75 and 0.74, respectively). The correlation was lower between the MSD and the fluoroscopy time (rs = 0.68, p < 0.0001) or the BMI (rs = 0.42, p = 0.02), and was poorly linear (R = 0.56 and 0.46, respectively). The spatial distribution of the MSD location was evaluated for 31 procedures using the TLD grids positioned on the patients’ back (Figure 1). MSD were more frequently observed on patient’s middle back region (62.5% (n = 19/31)) from 28 to 44 cm horizontally; than on patient’s right (25%; n = 8/31) or left side (12.5%; n = 4/31). MSD were also more frequent towards the top of the patients’ chest. Figure 1. View largeDownload slide Spatial distribution of the maximum skin dose (MSD) location. Three first rows of thermoluminescent detector (TLD) grids are represented as red dots; rows were positioned at 4 cm intervals. Measurements grids were centred horizontally on patient’s spine (TLD location = 36 cm). Left side of the figure is patient’s left side and bottom of the figure points towards patient’s feet. Figure 1. View largeDownload slide Spatial distribution of the maximum skin dose (MSD) location. Three first rows of thermoluminescent detector (TLD) grids are represented as red dots; rows were positioned at 4 cm intervals. Measurements grids were centred horizontally on patient’s spine (TLD location = 36 cm). Left side of the figure is patient’s left side and bottom of the figure points towards patient’s feet. Staff extremity and eye lens dose Staff dose measurements were obtained in 65 procedures, of which 34 (24 in Genk and 10 in Brussel) were performed without radioprotective drape and 31 with (19 in Genk and 12 in Brussel). In 12% (n = 8/65) of the procedures, some TLD measurements were excluded from the analysis as the TLDs could not be read (i.e. broken). Lead glasses were worn in 56% (n = 19/34) of the control procedures and in 74% (n = 23/31) of the Radpad procedures. Lead aprons, thyroid shield, suspended ceiling screen and table curtains were used during all procedures. Detailed statistics of the extremity and eye lens dose without the use of a radioprotective drape (control group) are given in Table 2. Table 2. Exposure per procedure at different location during CTO-PCI (n = 34). Doses are given in terms of Hp(0.07) for all locations but the left eye (Hp(3)).   Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265    Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265  Table 2. Exposure per procedure at different location during CTO-PCI (n = 34). Doses are given in terms of Hp(0.07) for all locations but the left eye (Hp(3)).   Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265    Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265  Efficiency of radioprotective drapes The use of the radioprotective drapes resulted in a reduction in the dose to the operator left extremities (hand and eyes): the median normalised dose to the left eye, finger and wrist decreased by 49, 28 and 47%, respectively; the average normalised dose to the eye and wrist decreased by 40 and 38%, respectively, while the mean dose to the finger increased by 13%. The decrease in normalised dose was confirmed statistically, by a significant dose decrease observed for all left locations but the leg. For the operator right side, the dose was also lower with decrease in median (mean) dose to the eye, finger and wrist of 25% (20%), 15% (5%) and 39% (21%), respectively. Nevertheless, the dose decrease was significant for the wrist only. In Figure 2, the normalised doses are presented for the physician’s left side, since this side is of primary concern for radiation protection and no significant differences were observed for the right side. Figure 2. View largeDownload slide PKA-normalised doses to the operators’ left eye and extremities with (Pad) and without use of Radpad (NoPad). Left eye (LE), between eye (ME), left finger (LF), right finger (RF), left wrist (LW), right wrist (RW), left leg (LL) and right leg (RL). Figure 2. View largeDownload slide PKA-normalised doses to the operators’ left eye and extremities with (Pad) and without use of Radpad (NoPad). Left eye (LE), between eye (ME), left finger (LF), right finger (RF), left wrist (LW), right wrist (RW), left leg (LL) and right leg (RL). DISCUSSION Patient dosimetry This study confirms the higher patient MSD during CTO-PCI compared with general PCI (Table 3). The median MSD values reported in the present study are considerably higher (1.5–3 times higher) than the values reported for overall PCI(16–18). This is not surprising considering the higher CTO complexity over general PCI, as highlighted by the higher PKA values and fluoroscopy times. Moreover, it is well known that beam incidence is usually limited to a narrower region of the patient’s body during PCI-CTO procedures, resulting in more localised exposure of the skin. Table 3. Comparison of MSD and PKA in this study with literature.   MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)    MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)  aRoom a. bRoom b. Table 3. Comparison of MSD and PKA in this study with literature.   MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)    MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)  aRoom a. bRoom b. Specific reports of MSD during CTO-PCI are scarce in the literature. Suzuki et al.(19) measured MSD twice as large as the values presented in our study. This most likely due to the larger use of radiation as indicated by higher median PKA values (~2.5 times higher) and fluoroscopy times (20% longer). The threshold for skin effect was rather frequently exceeded, with about one-third of the procedures (n = 9/31) above 2 Gy; two procedures were above 4 Gy (4.8 and 6.5 Gy). The spatial distribution of the MSD was predominantly localised on the patient’s middle back and right side (77.5%; n = 27/31). This observation is coherent with the frequent use of PA and LAO projections (35 and 42% of the cumulative cinegraphy PKA, respectively). The high MSD values stress the importance of dose optimisation. Dose reduction measures are well-known (among others: minimising the number of cine runs, avoiding steep lateral angulations, keeping the detector as close as possible to the patient, storing fluorographic images), and extensive reviews and guidelines are available in the literature(20, 21). In the interest of the patient, the physicians should strive to vary frequently the beam angulation and the incidence region on the patient, particularly during CTO-PCI. However, this may be difficult to achieve in practice, since only few angulations provide the best visibility of the treated vessel. Evidently, operators tend to use one or more specific angulations during the procedure. In addition, the lowest cinegraphy frame rate should be applied, without compromising image quality. This should be assessed for each specific X-ray unit. Although frequently referred to as patient dose, the PKA is not the dose to the patient skin, but the cumulative energy delivered to the patient’s whole body. The PKA can only be used as a rough predictor of the MSD given the poor linear relationship (Figure 3). The same remark applies to the Ka,r. Yet, PKA and Ka,r values of 200 Gy cm2 and 2.7 Gy could be used as local alert levels for dose to the skin of 2 Gy. However, higher MSD threshold could be used(5) to limit the number of patient follow-up and avoid unnecessary workload. For instance, a MSD threshold of 4 Gy would correspond to 400 Gy cm2PKA and 6 Gy Ka,r. Ideally, skin dose mapping software tools, allowing real time follow-up of the MSD during the procedure, would be best to steer patient follow-up. Nevertheless, those software tools are not widely available yet and need to be thoroughly validated. Figure 3. View largeDownload slide Maximum skin dose (MSD) delivered to the patient during CTO-PCI as a function of (a) the cumulative air kerma at interventional reference point (Ka,r) and (b) the air kerma area product (PKA), and linear estimate (black line). The dashed line is the 2000 mGy limit. Figure 3. View largeDownload slide Maximum skin dose (MSD) delivered to the patient during CTO-PCI as a function of (a) the cumulative air kerma at interventional reference point (Ka,r) and (b) the air kerma area product (PKA), and linear estimate (black line). The dashed line is the 2000 mGy limit. Staff extremity and eye lens dose During all procedures, the x-ray tube was positioned on the left side of the physician. Consequently, doses to the physician’s left side were higher than to the right side. The highest doses were observed at the left leg (up to 3684 μSv for a single procedure). The particularly high doses to the legs were explained by the position of one physician who occasionally crossed the table curtain with his legs. Aside from the legs, also the left hand (i.e. wrist and fingers)—which are the closest to the patient and the most difficult to protect—received particularly high radiation doses. If only the doses from CTO-PCI are extrapolated to annual cumulative dose, considering the median dose values per procedure and an annual workload of 100 procedures, no extremities would be at risk of exceeding or even of being close to the 500 mSv ICRP limits(4). The highest doses would be 47 mSv to the left leg and 14 mSv to the left hand (i.e. wrist). On the contrary, a left eye dose of 7 mSv, though well below the 20 mSv limit(5), would be of greater concern since a physician can perform yearly hundreds of other irradiating procedures next to CTO-PCI. This result emphasises the importance of the use of personal protection such as lead glasses. In Table 4, the doses and the PKA-normalised doses of the staff of the present study were compared with three kinds of cardiac procedures (general PCI, radiofrequency ablation (RFA) and pacemaker and defibrillator implantations (PM/ICD)) from the Oramed study(13). For all measurement locations but the fingers, the median doses were higher in the present study; in particular, the median doses to the left eye was twice as high as the dose from PM/ICD and general PCI procedure. For the fingers, the doses from PM/ICD were considerably higher. This again stresses the high complexity and exposure burden of CTO-PCI, specifically when compared with general PCI procedures. Nevertheless, the median normalised doses were usually lower, regardless of the measurement position, in the present study. In particular, the median normalised doses were considerably higher (1.5–24 times higher) during PM/ICD procedures. In other words and for an equal use of the X-ray imaging (PKA), the staff was less exposed during CTO-PCI compared to other procedures. Table 4. Comparison of operator exposure with Oramed data(13). Doses (μSv) are reported as median (max), and normalised doses (μSv/(Gy cm2)) are reported as median (max). Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Table 4. Comparison of operator exposure with Oramed data(13). Doses (μSv) are reported as median (max), and normalised doses (μSv/(Gy cm2)) are reported as median (max). Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Efficiency of radioprotective drapes There was a statistically significant decrease in median normalised dose to the physician’s left side (decreases in finger, wrist and eye dose of 28, 47 and 49%, respectively), but the leg, when the radioprotective drape was used. Surprisingly, a 13% increase (yet non-significant) in the mean—normalised—dose to the left finger was observed. However, this is explained by the sensitivity of the mean to extreme values. The findings of the present study are in general agreement with the trends previously reported in the literature for PCI procedures(6–8). Those studies focused mainly on the dose at the chest level and therefore cannot be directly compared. However, Murphy et al.(8) performed measurements at the level of the mid-arm. They obtained dose reduction of ~50%, which is in good agreement with the decrease in median dose of 28 and 47% at the level of the left finger and wrist, respectively observed in our study. Next to shielding equipment, various techniques exist to minimise staff dose, often bearing the additional benefit of decreasing patient’s dose. However, dose reduction measures, as mentioned above, might not always be followed owing to procedural difficulties. For those complex procedures, the use of radioprotective drapes might be considered, as it potentially decreases the dose to the cardiologist’s unprotected regions (i.e. the hands, forearms or eyes if no glasses are worn). To limit costs, the feasibility of re-using (sterilising) the drapes, for instance by inserting them in a protective pocket, should be investigated. Clinical studies inherently bear several limitations which can bias their results (see below). Monte Carlo simulation can alleviate some of those limitations and enable independent study of the influence of specific examination parameters. For this reason, the efficiency of radioprotective drapes for different beam angulations, drape compositions and positions on the patient is currently investigated using Monte Carlo simulation. Study limitations Although a grid of 86 of detectors was positioned on the patients for the skin dose measurements, it is possible that the MSD was missed or underestimated if strong, localised dose gradients were present. This issue had been studied elsewhere(11) and the reported MSD values were corrected accordingly. Although the study included more than 30 measurements for the patients, the number of cases was relatively limited. However, such dosimetric studies are very labour-intensive in practice. It is well-known that PKA poorly correlates with physician’s exposure; nevertheless, it is currently the best and most frequently applied dosimetric indicator available to account for different exposure conditions of the physicians. In addition, to alleviate this issue further, procedures were grouped and tested according to CTO complexity and BMI. The risk remains that the composition of both study groups might not match in terms of patient’s characteristics, procedure complexity or dosimetric indicators. Nevertheless, perfectly matched groups are difficultly achievable in clinical studies(8) and no significant differences were found between the group compositions. CONCLUSION In general, MSD values measured during CTO-PCI were high, confirming the higher complexity of those procedures compared to general PCI. PKA value of 400 Gy cm2 and Ka,r values of 6 Gy, corresponding to a MSD of 4 Gy could be used as local alert levels to steer dermatologic follow-up. The dose per procedure to the cardiologist’s extremities was generally high; in particular, dose to the left side was considerably higher. While taking into account the annual dose limits, the dose to the left eye was of greater concern. This stresses the need for protection equipment such as lead glasses. When a radioprotective drape (Radpad®) was used, a reduction in operator’s extremities (hands and eyes) exposure was observed. The reduction seems to be clinically important taking into account the total number of procedures annually performed (not only CTO-PCI). In combination with the standard shielding equipment, radioprotective drapes therefore appear as a useful tool to further decrease physician exposure. ACKNOWLEDGEMENTS The authors are grateful to all the medical and technical staff who participated in the measurements. CONFLICTS OF INTEREST Jo Dens receives grants from TopMedical (Distributor of Asahi Intecc co. materials), Boston Scientific, Vascular Solutions and Orbus Neich for teaching courses and proctoring. In addition, he is member of the advisory board of Boston Scientific. Joren Maeremans is researcher for the Limburg Clinical Research Program (LCRP) UHasselt-ZOL-Jessa, supported by the foundation Limburg Sterk Merk (LSM), Hasselt University, Ziekenhuis Oost-Limburg and Jessa Hospital. REFERENCES 1 Balter, S., Hopewell, J. W., Miller, D. L., Wagner, L. K. and Zelefsky, M. J. Fluoroscopically guided interventional procedures: a review of radiation effects on patients’ skin and hair. Radiology  254( 2), 326– 341 ( 2010). Google Scholar CrossRef Search ADS PubMed  2 Vanhavere, F. et al.  . Measurements of eye lens doses in interventional radiology and cardiology: final results of the ORAMED project. Radiat. Meas.  46( 11), 1243– 1247 ( 2011). Google Scholar CrossRef Search ADS   3 Carinou, E., Ginjaume, M., O’Connor, U., Kopec, R. and Sans Merce, M. Status of eye lens radiation dose monitoring in European hospitals. J. Radiol. Prot.  34( 4), 729– 739 ( 2014). Google Scholar CrossRef Search ADS PubMed  4 International Commission on Radiological Protection. The 2007 recommendations of the international commission on radiological protection. Ann. ICRP  37( 2–4), 1– 332 ( 2007). 5 International Commission on Radiological Protection. ICRP statement on tissue reactions/early and late effects of radiation in normal tissues and organs—threshold doses for tissue reactions in a radiation protection context. Ann. ICRP  41, 1– 322 ( 2012). 6 Shorrock, D., Christopoulos, G., Wosik, J., Kotsia, A., Rangan, B., Abdullah, S., Cipher, D., Banerjee, S. and Brilakis, E. S. Impact of a disposable sterile radiation shield on operator radiation exposure during percutaneous coronary intervention of chronic total occlusions. J. Invasive Cardiol.  27( 7), 313– 316 ( 2015). Google Scholar PubMed  7 Alazzoni, A. et al.  . Randomized controlled trial of radiation protection with a patient lead shield and a novel, nonlead surgical cap for operators performing coronary angiography or intervention. Circ. Cardiovasc. Interv.  8( 8), e002384 ( 2015). Google Scholar CrossRef Search ADS PubMed  8 Murphy, J. C., Darragh, K., Walsh, S. J. and Hanratty, C. G. Efficacy of the radpad protective drape during real world complex percutaneous coronary intervention procedures. Am. J. Cardiol.  108( 10), 1408– 1410 ( 2011). Google Scholar CrossRef Search ADS PubMed  9 Brilakis, E. S. et al.  . A percutaneous treatment algorithm for crossing coronary chronic total occlusions. JACC Cardiovasc. Interv.  5( 4), 367– 379 ( 2012). Google Scholar CrossRef Search ADS PubMed  10 Morino, Y. et al.  . Predicting successful guidewire crossing through chronic total occlusion of native coronary lesions within 30 minutes: the J-CTO (Multicenter CTO Registry in Japan) score as a difficulty grading and time assessment tool. JACC Cardiovasc. Interv.  4( 2), 213– 221 ( 2011). Google Scholar CrossRef Search ADS PubMed  11 Dabin, J. et al.  . Characterisation of grids of point detectors in maximum skin dose measurement in fluoroscopically-guided interventional procedures. Phys. Med.  31( 8), 1112– 1117 ( 2015). Google Scholar CrossRef Search ADS PubMed  12 International Electrotechnical Commission. Medical diagnostic X-ray equipment—radiation conditions for use in the determination of characteristics. IEC 61267 ( 2005). 13 Donadille, L. et al.  . Staff eye lens and extremity exposure in interventional cardiology: results of the ORAMED project. Radiat. Meas.  46( 11), 1203– 1209 ( 2011). Google Scholar CrossRef Search ADS   14 International Organization for Standardization. X and gamma reference radiation for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy—Part 4: Calibration of area and personal dosemeters in low energy X reference radiation fields. ISO 4037-4 ( 2004). 15 Joint Committee for Guides in Metrology. Evaluation of measurement data—guide to the expression of uncertainty in measurement (GUM) ( 2008). 16 Domienik, J., Papierz, S., Jankowski, J., Peruga, J. Z., Werduch, A. and Religa, W. Correlation of patient maximum skin doses in cardiac procedures with various dose indicators. Radiat. Prot. Dosim.  132( 1), 18– 24 ( 2008). Google Scholar CrossRef Search ADS   17 Bogaert, E. et al.  . A large-scale multicentre study of patient skin doses in interventional cardiology: dose-area product action levels and dose reference levels. Br. J. Radiol.  82( 976), 303– 312 ( 2009). Google Scholar CrossRef Search ADS PubMed  18 Journy, N., Sinno-Tellier, S., Maccia, C., Le Tertre, A., Pirard, P., Pages, P., Eilstein, D., Donadieu, J. and Bar, O. Main clinical, therapeutic and technical factors related to patient’s maximum skin dose in interventional cardiology procedures. Br. J. Radiol.  85( 1012), 433– 442 ( 2012). Google Scholar CrossRef Search ADS PubMed  19 Suzuki, S., Furui, S., Isshiki, T., Kozuma, K., Koyama, Y., Yamamoto, H., Ochiai, M., Asakura, Y. and Ikari, Y. Patients’ skin dose during percutaneous coronary intervention for chronic total occlusion. Catheter. Cardiovasc. Interv.  71( 2), 160– 164 ( 2008). Google Scholar CrossRef Search ADS PubMed  20 Miller, D. L., Balter, S., Schueler, B. A., Wagner, L. K., Strauss, K. J. and Vano, E. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology  257( 2), 321– 332 ( 2010). Google Scholar CrossRef Search ADS PubMed  21 Miller, D. L., Vañó, E., Bartal, G., Balter, S., Dixon, R., Padovani, R., Schueler, B., Cardella, J. F. and de Baère, T. Occupational radiation protection in interventional radiology: a joint guideline of the cardiovascular and interventional radiology society of Europe and the society of interventional radiology. Cardiovasc. Intervent. Radiol.  33( 2), 230– 239 ( 2010). Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

DOSIMETRY DURING PERCUTANEOUS CORONARY INTERVENTIONS OF CHRONIC TOTAL OCCLUSIONS

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0144-8420
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Abstract

ABSTRACT Percutaneous coronary interventions (PCI) of coronary chronic total occlusions (CTO) increase the risk of high radiation exposure for both the patient and the cardiologist. This study evaluated the maximum dose to the patients’ skin (MSD) and the exposure of the cardiologists during CTO-PCI. Moreover, the efficiency of radioprotective drapes to reduce cardiologist exposure was assessed. Patient dose was measured during 31 procedures; dose to the cardiologist’s extremities were measured during 65 procedures, among which 31 were performed with radioprotective drapes. The MSD was high (median: 1254 mGy; max: 6528 mGy), and higher than 2 Gy for 33% of the patients. The dose to the cardiologists’ extremities per procedure was also of concern (median: 25–465 μSv), particularly to the left eye (median: 68 μSv; max: 187 μSv). Radioprotective drapes reduced the exposure to physician’s upper limbs and eyes; especially to the left side (from −28 to −49%). INTRODUCTION During interventional procedures, high doses may be delivered to the patient’s skin, potentially exceeding the threshold for radioinduced skin injury(1). Percutaneous coronary interventions of coronary chronic total occlusions (CTO-PCI) increase the risk because of protracted use of fluoroscopy, numerous images acquisitions and use of localised beam incidences. Whereas this represents isolated yet acute exposure for the patients, the medical staff may perform two to three CTO-PCI in a day in addition to general PCI and diagnostic examinations, resulting in an important cumulative dose over their complete career. Cumulative doses to the extremities and the lens of the eye of the staff are of particular concern. Studies(2, 3) have shown that annual cumulative dose to interventional physicians can exceed the limits proposed by the International Commission on Radiological Protection (ICRP)(4, 5). To decrease physician’s exposure, personal protective equipment, such as lead aprons and lead glasses, as well as room protective equipment, such as ceiling suspended shields and table curtains, are available in most operative rooms. More recently, lead-free, disposable drapes—to be positioned on the patient to protect the physicians against backscattered radiation—have been made available in the operative rooms. Although such drapes have been commercially available since 1998 in the United States and 2002 in Europe, their reported use during PCI procedures is rather scarce in the scientific literature(6–8), and detailed dosimetry at the level of the eyes and the hands is rare. Such studies are, however, necessary to help to assess the balance between costs/burdens and benefits of any such protective equipment. The goal of the study was to perform a detailed investigation of the dose to the patient’s skin and the staff extremities during CTO-PCI. In addition, the efficiency of radioprotective drapes to reduce staff exposure during CTO-PCI was assessed. MATERIAL AND METHODS Study population and procedures Starting from February 2014, 65 patients undergoing CTO-PCI have been prospectively included depending upon availability of the dosemeters, and separated into two study groups. During the first part of the study, procedures were performed according to customary practice (control group); while in the second, a lead-free radioprotective drape (Radpad® red grade: 0.375 mmPb equivalence at 90 kV stated by the manufacturer) was placed on the patient according to manufacturer recommendations (Radpad group, Worldwide Innovations & Technologies, Inc., Lenexa, USA). Procedures were performed by two experienced CTO-PCI operators(9) from the UZ Brussel and the Ziekenhuis Oost-Limburg, respectively. The procedures were performed on a Siemens Artis DfC system and on a PHILIPS Allura Xper FD20 system, respectively. In both hospitals, room shielding equipment (ceiling suspended shield, table curtain) and individual shielding equipment (lead apron and thyroid collar) were used. Lead glasses were available too. For each procedure, demographic (including age, gender, height, weight, chest dimensions and body mass index (BMI)) and angiographic characteristics were collected. The patients were subdivided into four BMI categories (underweight BMI < 18.5; normal 18.5 < BMI < 25; overweight 25 < BMI < 30; obesity BMI > 30). Data were analysed according to the treated coronary vessels included the circumflex artery (CX), left anterior descending artery (LAD) and right coronary artery (RCA). Occasionally, the left main coronary artery (LMCA) or an obtuse marginal branch (OM) was treated. The procedure cumulative air kerma at interventional reference point (Ka,r), the air kerma area product (PKA), the fluorography time (FT) and the number of cinegraphy acquisitions were extracted from the dose report at the end of the examination. For individual cinegraphy acquisitions, the Ka,r, PKA, FT, frame rate (frame/s) and beam angulation were also extracted. The J-CTO (Multicenter CTO Registry of Japan) score(10) was used to grade the CTO complexity, based on the presence of five negative (angiographic) characteristics (i.e. blunt entry shape of the proximal CTO cap, visible presence of calcification on angiography, tortuosity at the proximal CTO cap and/or CTO body (≥45°), a prior failed attempt, and a long CTO lesion length (≥20 mm) (as determined by the eye-ball method and/or the balloon or stent size as a reference)). Each characteristic was assigned one point. The procedures were then subdivided into four groups according to their score: easy (0), intermediate (1), difficult (2) and very difficult (≥3). Dosimetry In total, 86 thermoluminescent detectors (TLD), LiF:Mg,Ti material (MTS, Institute of Nuclear Physics, Krakow, Poland), were used for patient maximum skin dose (MSD) measurement. The TLD were attached to a piece of fabric, forming a 72 × 32 cm2 grid, and wrapped around the patient chest, facing the x-ray source and centred on the patient’s spine. This enables one to draw a map of the cumulative skin dose. However, to account for the limited resolution of the point-detector grids (i.e. the risk of not having a detector positioned in the MSD region, hence, underestimating the patient’s dose), measurements were corrected. In practice, the MSD values were divided by the median underestimation resulting from point detector measurements during PCI, numerically computed by Dabin et al.(11) TLD for patient dosimetry were calibrated free in air in a RQR5 reference field(12) in a second-standard calibration laboratory; unexposed dosemeters were kept for background determination. Staff dosimetry was performed according to the Oramed protocol(13). TLDs wrapped in a pouch were positioned on the main operator at seven different locations, including the left and right middle finger; left and right wrist; left and right leg (a few centimetres below the lead apron); and between the eyes. In addition, a TLD inserted in a dedicated eye lens dosemeter (EyeD™, Radcard, Poland) was positioned on the left temple (ED). If lead glasses were worn, the eye lens dosemeter was positioned above them to assess the dose to the unprotected eye. One TLD set was used per procedure; unexposed TLD were kept for background determination. Unlike patient dosimetry, LiF:Mg, Cu, P material (MCP-N, Institute of Nuclear Physics, Poland) was selected for staff dosimetry because of its greater sensitivity to low doses. Staff detectors were calibrated according to ISO norms N60 reference beam(14) against personal dose equivalent Hp(0.07) for extremity dosemeters and Hp(3) for eye lens dosemeters(4). Measurement uncertainty The uncertainty associated with the staff dosimetry was estimated as the square root of the sum of the squared independent uncertainty sources. The considered sources were: individual sensitivity (1.6%), repeatability (1%), fading (3%), calibration (3.8%), energy (4%), angular response (4%) and background determination. For doses smaller than 10, 20 and 40 μSv, the uncertainty (k = 1) was mostly dominated by the uncertainty in the background determination, and was estimated to be ~40, 25 and 15%, respectively; the uncertainty was ~8% for doses ≥40 μSv. For the MSD measurements, the uncertainty associated with the limited resolution of the TLD grid was also taken into account in the uncertainty budget as proposed in Dabin et al.(11), in addition to the sources mentioned above for the staff dosimetry. Monte Carlo simulation method(15) was used to combine the TLD measurements and the—non-normally distributed—uncertainty associated with the grid resolution (12%). An overall (k = 1), non-normally distributed uncertainty of 25% was estimated. The uncertainty associated with the displayed PKA and Ka,r were 9 and 6% on the PHILIPS Allura Xper FD20 system, respectively, and 8 and 8% on the Siemens Artis DfC system. Those uncertainties were obtained by comparing the system-displayed Ka,r and PKA values with measurements performed with a calibrated dosemeter and a system for measuring the size of the irradiated field (for the PKA) for a kV-range from 80 to 110 kV. Statistical analysis Procedural, demographic, angiographic and dosimetric data were analysed using descriptive statistics. Continuous data were tested for normality using both the Shapiro–Wilk test as graphical methods. Differences between distributions were tested using Welch’s t-test. If departure from normality was observed, pairwise Welch’s t-test was used on the rank of the sorted data; otherwise, pairwise Welch’s t-test was directly used on the qualitative data. One- or two-tailed test were chosen as appropriate. Categorical data were tested using the Pearson’s chi-square test. Correlations between MSD and procedure parameters (Ka,r, PKA, fluoroscopy time), BMI and complexity score were estimated using the Pearson coefficient (R2) and/or Spearman rank test (rs), as appropriate. A p-value of ≤0.05 was considered significant. All statistical analyses were carried out using R (version 3.3.1; R Foundation for Statistical Computing, Vienna, Austria). Boxplots are used to give graphical description of some data distributions. Horizontal lines (from bottom to top) represent the first, second (or median) and third quartile; squares and circles (outside whisker range) represent averages and outliers, respectively. Whiskers extend from the first quartile minus interquartile range up to the third quartile plus interquartile range. All doses measured on the operator were normalised to the procedure-cumulated PKA, in order to account for the difference in radiation use during the procedures. Dose readings below the detection limit were set to the detection limit. RESULTS Study population and procedures Overall, 65 procedures were included during the study period, 34 without and 31 with the radioprotective drape. In both groups, the majority was male and either overweight or obese, without any significant differences. Likewise, the dosimetric indicators (Ka,r, PKA and fluoroscopy time) showed no significantly diverging trends between both groups (Table 1). From the analysis of a subset of 24 procedure dose reports, left anterior oblique (LAO), posterior anterior (PA) and right anterior oblique (RAO) projections were accounting for 42, 35 and 23% of the cumulative cinegraphy PKA, respectively. Purely lateral projections were rarely, if ever, used. The dose reports contained no detailed information on the projection contribution in fluoroscopy mode. Table 1. Demographic, dosimetric and clinical parameters of the study population, classified according to the use of the RADPAD drape.   Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0        Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0      Values are given as n = number of cases, median [min, max], interquartile range (Q1–Q3) or percentage (%). The mean J-CTO score ± standard deviation is also reported as it is traditional medical practice. BMI, body mass index; Ka,r, cumulative air kerma at interventional reference point; PKA, air kerma area product; PKA,Fluoro, fluoroscopy contribution to PKA; PKA,Graphy, cinegraphy contribution to PKA. Table 1. Demographic, dosimetric and clinical parameters of the study population, classified according to the use of the RADPAD drape.   Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0        Control group (n = 34)  Radpad group (n = 31)  p-value  Median [min; max] or %  Q1–Q3  Median [min; max] or %  Q1–Q3    Demographic data   Age (years)  63.0 [42; 89]  55.0–71.5  65.0 [50; 90]  59–74  0.22   Gender (% males)  80  —  91  —  0.35   BMI (kg/m2)  27.3 [18.9; 51.1]  24.7–30.8  28.3 [19.4; 41.9]  25.9–31.6  0.78  Dosimetric indicators   Ka,r (mGy)  1649 [365; 6345]  872–3031  1975 [185; 4859]  1171–2887  0.77   Total PKA (Gy cm2)  141.9 [23.8; 406.8]  66.4–268.9  147.1 [14.4; 382.6]  101.2–189.0  0.70   PKA,Fluoro  83.2 [16.3; 254.2]  43.7–158  86.6 [8.1; 313.6]  63.7–132.1  0.89   PKA,Graphy  57.6 [7.4; 176.6]  30.8–104.6  54.0 [4.9; 152.1]  36.7–77.6  0.37   Fluoroscopy time (min)  29 [8; 69]  20–61  38 [7; 97]  18–60  0.59   MSD (mGy, n = 31)  1254 [33; 6528]  681–2290  —  —  —  Clinical factors   Treated vessel (%proc)  0.44    CX  11.4  —  9.1  —  —    LAD  14.3  —  21.2  —  —    LMCA  2.9  —  0  —  —    OM1  0  —  6.1  —  —    RCA  71.4  —  63.6  —  —   J-CTO score (%proc)  0.31    0  5.7    12.5        1  34.3  —  15.6  —  —    2  34.3  —  37.5  —  —    ≥3  25.7  —  34.3  —  —   All groups (mean ± SD)  1.8 ± 0.9    1.9 ± 1.0      Values are given as n = number of cases, median [min, max], interquartile range (Q1–Q3) or percentage (%). The mean J-CTO score ± standard deviation is also reported as it is traditional medical practice. BMI, body mass index; Ka,r, cumulative air kerma at interventional reference point; PKA, air kerma area product; PKA,Fluoro, fluoroscopy contribution to PKA; PKA,Graphy, cinegraphy contribution to PKA. The overall J-CTO complexity was comparable in the Radpad and control groups (1.9 ± 1.0 versus 1.8 ± 0.9, p = 0.56). Patient dosimetry Patient skin dose measurements were available for 89% (n = 31/34) patients of the Control group; the demographic, dosimetric and clinical parameters of this subset of procedures were comparable to the complete control group. Median MSD was 1254 mGy (range: 33–6528 mGy), the distribution of the MSD was strongly right-skewed. For 71% of the procedures (n = 22/31), the MSD was below 2000 mGy; all but two (94%) were below 4000 mGy. No significant difference was observed between the mean MSD of the different complexity groups; pooling the procedures into two complexity groups (≤1 versus ≥2) did not result in a significant difference in MSD either (p = 0.65). The correlation between the MSD and the PKA or Ka,r (rs = 0.84 and 0.86 with p < 0.0001, respectively) was rather linear (R = 0.75 and 0.74, respectively). The correlation was lower between the MSD and the fluoroscopy time (rs = 0.68, p < 0.0001) or the BMI (rs = 0.42, p = 0.02), and was poorly linear (R = 0.56 and 0.46, respectively). The spatial distribution of the MSD location was evaluated for 31 procedures using the TLD grids positioned on the patients’ back (Figure 1). MSD were more frequently observed on patient’s middle back region (62.5% (n = 19/31)) from 28 to 44 cm horizontally; than on patient’s right (25%; n = 8/31) or left side (12.5%; n = 4/31). MSD were also more frequent towards the top of the patients’ chest. Figure 1. View largeDownload slide Spatial distribution of the maximum skin dose (MSD) location. Three first rows of thermoluminescent detector (TLD) grids are represented as red dots; rows were positioned at 4 cm intervals. Measurements grids were centred horizontally on patient’s spine (TLD location = 36 cm). Left side of the figure is patient’s left side and bottom of the figure points towards patient’s feet. Figure 1. View largeDownload slide Spatial distribution of the maximum skin dose (MSD) location. Three first rows of thermoluminescent detector (TLD) grids are represented as red dots; rows were positioned at 4 cm intervals. Measurements grids were centred horizontally on patient’s spine (TLD location = 36 cm). Left side of the figure is patient’s left side and bottom of the figure points towards patient’s feet. Staff extremity and eye lens dose Staff dose measurements were obtained in 65 procedures, of which 34 (24 in Genk and 10 in Brussel) were performed without radioprotective drape and 31 with (19 in Genk and 12 in Brussel). In 12% (n = 8/65) of the procedures, some TLD measurements were excluded from the analysis as the TLDs could not be read (i.e. broken). Lead glasses were worn in 56% (n = 19/34) of the control procedures and in 74% (n = 23/31) of the Radpad procedures. Lead aprons, thyroid shield, suspended ceiling screen and table curtains were used during all procedures. Detailed statistics of the extremity and eye lens dose without the use of a radioprotective drape (control group) are given in Table 2. Table 2. Exposure per procedure at different location during CTO-PCI (n = 34). Doses are given in terms of Hp(0.07) for all locations but the left eye (Hp(3)).   Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265    Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265  Table 2. Exposure per procedure at different location during CTO-PCI (n = 34). Doses are given in terms of Hp(0.07) for all locations but the left eye (Hp(3)).   Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265    Median [min; max] (μSv)  Q1–Q3 (μSv)  Left eye  68 [25; 187]  42–130  Between eyes  25 [3; 244]  14–75  Left finger  101 [10;988]  38–164  Right finger  43 [8; 174]  25–113  Left wrist  139 [14; 728]  71–320  Right wrist  92 [9; 404]  38–201  Left leg  465 [19; 3684]  185–1011  Right leg  118 [19, 834]  57–265  Efficiency of radioprotective drapes The use of the radioprotective drapes resulted in a reduction in the dose to the operator left extremities (hand and eyes): the median normalised dose to the left eye, finger and wrist decreased by 49, 28 and 47%, respectively; the average normalised dose to the eye and wrist decreased by 40 and 38%, respectively, while the mean dose to the finger increased by 13%. The decrease in normalised dose was confirmed statistically, by a significant dose decrease observed for all left locations but the leg. For the operator right side, the dose was also lower with decrease in median (mean) dose to the eye, finger and wrist of 25% (20%), 15% (5%) and 39% (21%), respectively. Nevertheless, the dose decrease was significant for the wrist only. In Figure 2, the normalised doses are presented for the physician’s left side, since this side is of primary concern for radiation protection and no significant differences were observed for the right side. Figure 2. View largeDownload slide PKA-normalised doses to the operators’ left eye and extremities with (Pad) and without use of Radpad (NoPad). Left eye (LE), between eye (ME), left finger (LF), right finger (RF), left wrist (LW), right wrist (RW), left leg (LL) and right leg (RL). Figure 2. View largeDownload slide PKA-normalised doses to the operators’ left eye and extremities with (Pad) and without use of Radpad (NoPad). Left eye (LE), between eye (ME), left finger (LF), right finger (RF), left wrist (LW), right wrist (RW), left leg (LL) and right leg (RL). DISCUSSION Patient dosimetry This study confirms the higher patient MSD during CTO-PCI compared with general PCI (Table 3). The median MSD values reported in the present study are considerably higher (1.5–3 times higher) than the values reported for overall PCI(16–18). This is not surprising considering the higher CTO complexity over general PCI, as highlighted by the higher PKA values and fluoroscopy times. Moreover, it is well known that beam incidence is usually limited to a narrower region of the patient’s body during PCI-CTO procedures, resulting in more localised exposure of the skin. Table 3. Comparison of MSD and PKA in this study with literature.   MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)    MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)  aRoom a. bRoom b. Table 3. Comparison of MSD and PKA in this study with literature.   MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)    MSD median (mean) (Gy)  PKA median (mean) (Gy cm2)  Fluoroscopy time: median (mean) (min)  Present study  1.25 (1.69)  142 (170)  29 (37)  Suzuki et al.(19)  2.7 (3.2)  (445)  (45)  Domienik et al.(16)  0.83a; 0.38b  120a; 63b  8.9a; 6.7b  Bogaert et al.(17)  0.46 (0.70)  65 (82)  —  Journy et al.(18)  0.7 (0.92)  (69)  9 (11)  aRoom a. bRoom b. Specific reports of MSD during CTO-PCI are scarce in the literature. Suzuki et al.(19) measured MSD twice as large as the values presented in our study. This most likely due to the larger use of radiation as indicated by higher median PKA values (~2.5 times higher) and fluoroscopy times (20% longer). The threshold for skin effect was rather frequently exceeded, with about one-third of the procedures (n = 9/31) above 2 Gy; two procedures were above 4 Gy (4.8 and 6.5 Gy). The spatial distribution of the MSD was predominantly localised on the patient’s middle back and right side (77.5%; n = 27/31). This observation is coherent with the frequent use of PA and LAO projections (35 and 42% of the cumulative cinegraphy PKA, respectively). The high MSD values stress the importance of dose optimisation. Dose reduction measures are well-known (among others: minimising the number of cine runs, avoiding steep lateral angulations, keeping the detector as close as possible to the patient, storing fluorographic images), and extensive reviews and guidelines are available in the literature(20, 21). In the interest of the patient, the physicians should strive to vary frequently the beam angulation and the incidence region on the patient, particularly during CTO-PCI. However, this may be difficult to achieve in practice, since only few angulations provide the best visibility of the treated vessel. Evidently, operators tend to use one or more specific angulations during the procedure. In addition, the lowest cinegraphy frame rate should be applied, without compromising image quality. This should be assessed for each specific X-ray unit. Although frequently referred to as patient dose, the PKA is not the dose to the patient skin, but the cumulative energy delivered to the patient’s whole body. The PKA can only be used as a rough predictor of the MSD given the poor linear relationship (Figure 3). The same remark applies to the Ka,r. Yet, PKA and Ka,r values of 200 Gy cm2 and 2.7 Gy could be used as local alert levels for dose to the skin of 2 Gy. However, higher MSD threshold could be used(5) to limit the number of patient follow-up and avoid unnecessary workload. For instance, a MSD threshold of 4 Gy would correspond to 400 Gy cm2PKA and 6 Gy Ka,r. Ideally, skin dose mapping software tools, allowing real time follow-up of the MSD during the procedure, would be best to steer patient follow-up. Nevertheless, those software tools are not widely available yet and need to be thoroughly validated. Figure 3. View largeDownload slide Maximum skin dose (MSD) delivered to the patient during CTO-PCI as a function of (a) the cumulative air kerma at interventional reference point (Ka,r) and (b) the air kerma area product (PKA), and linear estimate (black line). The dashed line is the 2000 mGy limit. Figure 3. View largeDownload slide Maximum skin dose (MSD) delivered to the patient during CTO-PCI as a function of (a) the cumulative air kerma at interventional reference point (Ka,r) and (b) the air kerma area product (PKA), and linear estimate (black line). The dashed line is the 2000 mGy limit. Staff extremity and eye lens dose During all procedures, the x-ray tube was positioned on the left side of the physician. Consequently, doses to the physician’s left side were higher than to the right side. The highest doses were observed at the left leg (up to 3684 μSv for a single procedure). The particularly high doses to the legs were explained by the position of one physician who occasionally crossed the table curtain with his legs. Aside from the legs, also the left hand (i.e. wrist and fingers)—which are the closest to the patient and the most difficult to protect—received particularly high radiation doses. If only the doses from CTO-PCI are extrapolated to annual cumulative dose, considering the median dose values per procedure and an annual workload of 100 procedures, no extremities would be at risk of exceeding or even of being close to the 500 mSv ICRP limits(4). The highest doses would be 47 mSv to the left leg and 14 mSv to the left hand (i.e. wrist). On the contrary, a left eye dose of 7 mSv, though well below the 20 mSv limit(5), would be of greater concern since a physician can perform yearly hundreds of other irradiating procedures next to CTO-PCI. This result emphasises the importance of the use of personal protection such as lead glasses. In Table 4, the doses and the PKA-normalised doses of the staff of the present study were compared with three kinds of cardiac procedures (general PCI, radiofrequency ablation (RFA) and pacemaker and defibrillator implantations (PM/ICD)) from the Oramed study(13). For all measurement locations but the fingers, the median doses were higher in the present study; in particular, the median doses to the left eye was twice as high as the dose from PM/ICD and general PCI procedure. For the fingers, the doses from PM/ICD were considerably higher. This again stresses the high complexity and exposure burden of CTO-PCI, specifically when compared with general PCI procedures. Nevertheless, the median normalised doses were usually lower, regardless of the measurement position, in the present study. In particular, the median normalised doses were considerably higher (1.5–24 times higher) during PM/ICD procedures. In other words and for an equal use of the X-ray imaging (PKA), the staff was less exposed during CTO-PCI compared to other procedures. Table 4. Comparison of operator exposure with Oramed data(13). Doses (μSv) are reported as median (max), and normalised doses (μSv/(Gy cm2)) are reported as median (max). Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Table 4. Comparison of operator exposure with Oramed data(13). Doses (μSv) are reported as median (max), and normalised doses (μSv/(Gy cm2)) are reported as median (max). Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Ref  Proc.  Unit  Left eye  Between eyes  Left finger  Right finger  Left wrist  Right wrist  Left leg  Right leg  Present study  CTO-PCI  μSv μSv/(Gy cm2)  68 (187) 0.5 (1.7)  25 (244) 0.3 (7.1)  101 (988) 0.6 (7.8)  43 (174) 0.4 (4.1)  139 (728) 1.1 (13.6)  92 (404) 0.7 (7.1)  465 (3684) 4.8 (9.9)  118 (834) 1.1 (4.8)  Donadille 2011  PCI  μSv μSv/(Gy cm2)  32 (820) 0.7 (7.7)  23 (644) 0.6 (5.4)  66 (5000) 1.8 (30.1)  32 (503) 0.9 (6.9)  83 (1775) 1.8 (35.4)  47 (579) 1.1 (14)  37 (1567) 1.2 (26.4)  29 (1232) 0.7 (8.4)  RFA  μSv μSv/(Gy cm2)  18 (880) 0.8 (16.3)  16 (633) 0.6 (66.6)  28 (896) 1.1 (26.9)  17 (446) 0.7 (18.6)  51 (1838) 2.1 (43.2)  28 (880) 1.1 (85.5)  32 (1819) 2.4 (22.4)  30 (780) 1.2 (14.8)  PM/ICD  μSv μSv/(Gy cm2)  28 (1083) 1.9 (88.3)  21 (810) 1.8 (106.5)  164 (6564) 13.1 (192.8)  104 (4328) 9.6 (252.9)  98 (4852) 8.2 (120.2)  81 (3825) 7.8 (207.8)  67 (4996) 6.8 (191.2)  64 (4046) 7.1 (255.3)  Efficiency of radioprotective drapes There was a statistically significant decrease in median normalised dose to the physician’s left side (decreases in finger, wrist and eye dose of 28, 47 and 49%, respectively), but the leg, when the radioprotective drape was used. Surprisingly, a 13% increase (yet non-significant) in the mean—normalised—dose to the left finger was observed. However, this is explained by the sensitivity of the mean to extreme values. The findings of the present study are in general agreement with the trends previously reported in the literature for PCI procedures(6–8). Those studies focused mainly on the dose at the chest level and therefore cannot be directly compared. However, Murphy et al.(8) performed measurements at the level of the mid-arm. They obtained dose reduction of ~50%, which is in good agreement with the decrease in median dose of 28 and 47% at the level of the left finger and wrist, respectively observed in our study. Next to shielding equipment, various techniques exist to minimise staff dose, often bearing the additional benefit of decreasing patient’s dose. However, dose reduction measures, as mentioned above, might not always be followed owing to procedural difficulties. For those complex procedures, the use of radioprotective drapes might be considered, as it potentially decreases the dose to the cardiologist’s unprotected regions (i.e. the hands, forearms or eyes if no glasses are worn). To limit costs, the feasibility of re-using (sterilising) the drapes, for instance by inserting them in a protective pocket, should be investigated. Clinical studies inherently bear several limitations which can bias their results (see below). Monte Carlo simulation can alleviate some of those limitations and enable independent study of the influence of specific examination parameters. For this reason, the efficiency of radioprotective drapes for different beam angulations, drape compositions and positions on the patient is currently investigated using Monte Carlo simulation. Study limitations Although a grid of 86 of detectors was positioned on the patients for the skin dose measurements, it is possible that the MSD was missed or underestimated if strong, localised dose gradients were present. This issue had been studied elsewhere(11) and the reported MSD values were corrected accordingly. Although the study included more than 30 measurements for the patients, the number of cases was relatively limited. However, such dosimetric studies are very labour-intensive in practice. It is well-known that PKA poorly correlates with physician’s exposure; nevertheless, it is currently the best and most frequently applied dosimetric indicator available to account for different exposure conditions of the physicians. In addition, to alleviate this issue further, procedures were grouped and tested according to CTO complexity and BMI. The risk remains that the composition of both study groups might not match in terms of patient’s characteristics, procedure complexity or dosimetric indicators. Nevertheless, perfectly matched groups are difficultly achievable in clinical studies(8) and no significant differences were found between the group compositions. CONCLUSION In general, MSD values measured during CTO-PCI were high, confirming the higher complexity of those procedures compared to general PCI. PKA value of 400 Gy cm2 and Ka,r values of 6 Gy, corresponding to a MSD of 4 Gy could be used as local alert levels to steer dermatologic follow-up. The dose per procedure to the cardiologist’s extremities was generally high; in particular, dose to the left side was considerably higher. While taking into account the annual dose limits, the dose to the left eye was of greater concern. This stresses the need for protection equipment such as lead glasses. When a radioprotective drape (Radpad®) was used, a reduction in operator’s extremities (hands and eyes) exposure was observed. The reduction seems to be clinically important taking into account the total number of procedures annually performed (not only CTO-PCI). In combination with the standard shielding equipment, radioprotective drapes therefore appear as a useful tool to further decrease physician exposure. ACKNOWLEDGEMENTS The authors are grateful to all the medical and technical staff who participated in the measurements. CONFLICTS OF INTEREST Jo Dens receives grants from TopMedical (Distributor of Asahi Intecc co. materials), Boston Scientific, Vascular Solutions and Orbus Neich for teaching courses and proctoring. In addition, he is member of the advisory board of Boston Scientific. Joren Maeremans is researcher for the Limburg Clinical Research Program (LCRP) UHasselt-ZOL-Jessa, supported by the foundation Limburg Sterk Merk (LSM), Hasselt University, Ziekenhuis Oost-Limburg and Jessa Hospital. REFERENCES 1 Balter, S., Hopewell, J. W., Miller, D. L., Wagner, L. K. and Zelefsky, M. J. Fluoroscopically guided interventional procedures: a review of radiation effects on patients’ skin and hair. Radiology  254( 2), 326– 341 ( 2010). Google Scholar CrossRef Search ADS PubMed  2 Vanhavere, F. et al.  . Measurements of eye lens doses in interventional radiology and cardiology: final results of the ORAMED project. Radiat. Meas.  46( 11), 1243– 1247 ( 2011). Google Scholar CrossRef Search ADS   3 Carinou, E., Ginjaume, M., O’Connor, U., Kopec, R. and Sans Merce, M. Status of eye lens radiation dose monitoring in European hospitals. J. Radiol. Prot.  34( 4), 729– 739 ( 2014). Google Scholar CrossRef Search ADS PubMed  4 International Commission on Radiological Protection. 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Google Scholar CrossRef Search ADS PubMed  8 Murphy, J. C., Darragh, K., Walsh, S. J. and Hanratty, C. G. Efficacy of the radpad protective drape during real world complex percutaneous coronary intervention procedures. Am. J. Cardiol.  108( 10), 1408– 1410 ( 2011). Google Scholar CrossRef Search ADS PubMed  9 Brilakis, E. S. et al.  . A percutaneous treatment algorithm for crossing coronary chronic total occlusions. JACC Cardiovasc. Interv.  5( 4), 367– 379 ( 2012). Google Scholar CrossRef Search ADS PubMed  10 Morino, Y. et al.  . Predicting successful guidewire crossing through chronic total occlusion of native coronary lesions within 30 minutes: the J-CTO (Multicenter CTO Registry in Japan) score as a difficulty grading and time assessment tool. JACC Cardiovasc. Interv.  4( 2), 213– 221 ( 2011). Google Scholar CrossRef Search ADS PubMed  11 Dabin, J. et al.  . 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Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

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Radiation Protection DosimetryOxford University Press

Published: Jan 17, 2018

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