TY - JOUR
AU - Sarmento,, S.
AB - Abstract The combination of fluoroscopically guided interventional procedures with computed tomography (CTF) has become widespread around the world. The benefits of CTF include the ability to obtain a real-time visualization of the entire body, increased target accuracy and improved visualization of biopsy needles. Modern CTF units work with variable frame rates for image selection, and therefore the dose distributions for patients and staff can considerably vary, creating growing concern in terms of the occupational exposure of interventionists and the drawback of a higher exposure of the patient. A literature review of the latest CTF publications is summarized in this article. A wide range of CTF studies reveal different treatment methods used in clinical practice, and therefore the differences in the exposures between them; as well as in the radiation protection tools and dose monitoring. Further optimization of radiation protection methods, harmonization of exposure patterns as well as training and education of CTF staff on the basis of the information in the survey, are strongly recommended. INTRODUCTION The application of ionizing radiation in medicine constitutes the most important contribution to the exposure of the population from man-made sources(1), which is now equal or even higher than radiation exposure to natural sources, for the first time in human recorded history, at least in the USA(2). The contribution from medical applications of ionizing radiation to population exposure FROM MAN-MADE SOURCES comprises ∼95% of the collective effective doses to the world population, mainly in countries with advanced healthcare systems. The regulatory radiation protection infrastructure that has been established in most countries is focused mainly on the justification of medical exposures and its optimization for the reduction of radiation doses to patients and staff. However, the current national systems of health protection and safety of occupationally exposed workers to high doses of radiation still need to be strengthened to ensure compliance with the new requirements given in the revised European Directive(3) and in related radiation safety guides(4). Special attention must be given to the adequate training of medical specialists in radiation protection, including end users and regulators responsible for appropriate dose registries and quality management at the national level(5, 6). Imaging procedures involving fluoroscopy, connected with higher radiation load of the staff, are nowadays replacing conventional radiographic examinations, due to the health and economic benefits of their application. The rapid growth of modern technologies allows for better treatment and diagnostic results, while it leads to an increase in the number of fluoroscopy-guided procedures, involving also the extended use of low dose computed tomography fluoroscopy (CTF) as a new method in current day-to-day medicine(7, 8). Fluoroscopy is a technique that uses X-rays to produce moving medical images, in contrast with the still frames obtained by conventional radiography techniques; Analogously, CTF is a technique that uses computed tomography (CT) scans to emulate fluoroscopy, that is, a time-dependent analysis of medical images by using a computational tomography device. As such, CTF can be defined as a technique that reconstructs and produces stable imaging and provides an effective real-time guidance during interventional procedures. It overcomes the classic limitations of ultrasound imaging and conventional fluoroscopy (CF) and matches the advantages of CT-quality images with the speed of fluoroscopic guidance(9). This method allows users to select one of two common operational modes: continuous (real time) or intermittent (quick check). One of the benefits is the possibility of immediate correction for depth and direction of needles during percutaneous procedures. The above-mentioned characteristics have made CTF a popular image guiding tool for various types of non-vascular and therapeutic interventions. In practical terms, ‘fluoroscopy’, in CTF is only used by analogy with its conventional radiology counterpart. The only common thing is that both techniques are based on X-ray imaging to give the impression of real-time imaging display. The radiation protection for CTF differs from the CF mainly in terms of the excessive radiation dose to the radiologist's hands (10). This article intends to review the data published in the literature, mostly concerning dose assessment of staff and patients during CTF procedures, and the methodology used for this purpose, which includes dose measurements and related computational simulations. For clarity, in this article, CTF is any CT procedure for which an individual remains in the scan room during the procedure. A thorough analysis of current publications found in dedicated Radiation Protection, Radiation Physics and Medical Application journals was performed. The existing international Guidelines, Recommendations and ISO Standards, currently published by recognized international institutions, such as the International Committee on Radiation Protection (ICRP), the European Commission (EC), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), among others, were also comprehensively analysed relative to the main radiation protection rules for CTF, together with existing recommendations. HISTORICAL BACKGROUND AND CLINICAL USES OF CTF Since its introduction into radiology ~30 y ago, CT has been used as a guidance tool for various percutaneous interventions(11). Since 1980, CT technology has made rapid progress with the development of slip ring technology, X-ray tubes with improved heat capacity, sub-second rotation times, fast array processors and the development of partial reconstruction algorithms(9). As a more accurate method of lesion localization, percutaneous needle biopsies it started to be frequently used in interventional radiology (IR), allowing for improved diagnostics of less accessible lesions, mainly in the lung, pleura and mediastinum. A decrease in the need to perform diagnostic thoracotomies under anesthesia has also been reported(12, 13). CTF opened up the potential to place the needle in small pulmonary lesions, or in deep mediastinal nodes, while easily visible neighboring vascular and cardiac structures could be safely avoided. Biopsy of the small pulmonary lesions radically improved the early diagnosis, with better prognosis of the successful therapy. The problem with the lack of real-time imaging of the interventional procedures, which limited the application of CTF in situations where respiratory motion caused displacement of the lesion, has been overcome through innovations of hardware and software of CT scanners(14, 15). They modified a third-generation CT scanner by adding a high-speed array processor to increase the image reconstruction speed of CT images. This technique allows the image to be updated at a rate of six frames per second and provides the operator a nearly real-time display of CT images. An early study(16) reported the results of 57 interventional procedures performed on patients with real-time guided CTF. Also, in 1994, the US Food and Drug Administration(17), granted the approval for the routine use of CTF in patients. Further developments in CT technology, mainly the increase of frame rate, wide and variable fields of view, better spatial resolution and the multiple slice acquisition and image display, increased the use of CTF guidance among others: precise needle placement, core biopsies, fluid collections aspirations, catheter insertion and drainage, local drug injections, radiofrequency ablations, placement of marking coils before stereotactic radiotherapy, lumbar nerve root blocks, vertebroplasty, arthrodesis of the spine and arthrography, etc(15, 18). More recent improvements in CT scanner technology, such as angular beam modulation (ABM), indicate the strategies for reducing the high radiation exposure to the staff(19). RELEVANT INTERNATIONAL RECOMMENDATIONS, GUIDELINES AND STANDARDS New technologies available for IR centered on the use of computing, the introduction of new detectors and imaging devices(20) have improved the diagnostic imaging and offered new, non-invasive choices for advances in clinical practice. However, these developments have not been supported by justification and optimization studies to ensure that these new procedures are performed at the lowest possible doses. Consequently, the radiation protection of both patients and staff in CTF is also a key issue. Note that CTF in the scope of this article is related to any CT procedure for which an individual remains in the scan room during the exposure. International recommendations, uniform safety standards to protect the health of workers and patients against the dangers arising from ionizing radiation are by and large well understood(21). The Guidelines for radiation protection are generally based on the recommendations of the ICRP. In the area of IR, the importance of justification and optimization of exposure was a central theme of the general ICRP 103 Recommendations(22), and more details regarding the medical exposure of patients are given in the ICRP 105 Recommendation(23). In interventional procedures, management of patient doses is the appropriate mechanism to avoid unnecessary radiation exposures. These regulations have now been introduced in the new International Basic Safety Standards (BSS), published by the International Atomic Energy Agency (IAEA), as well as in the revised European BSS prepared by the EC(3, 4). One of the main issues of these documents is that more effort is needed to optimize the protection of interventional staff and appropriate monitoring of the eye lenses, as well as the further development of diagnostic reference levels in IR, as a tool of optimization(24). These regulations will be soon incorporated into the regulatory documents of all countries, either members of the EU or countries involved in the activities of the IAEA. The Guidelines for occupational radiation protection in IR, published jointly by the Cardiovascular and Interventional Radiology Society of Europe and the Society of Interventional Radiology, stress the importance of occupational radiation protection not only during the fluoroscopically guided procedures but also during CT-guided procedures, including CTF(9). These Guidelines also point out that the name ‘CT fluoroscopy’ can be misleading, because real time in CTF imaging is significantly different from that of CF. Also, in both techniques, the equipment, technique of performance and the radiation protection tools are different. Revised ICRP recommendations(25) include consideration of effects of radiation on health arising from non-cancer effects. Some of these effects are not determined solely at the time of irradiation but can be modified after radiation exposure. Therefore, previously called deterministic effects are now referred to as tissue reactions. Recent epidemiological studies have suggested that the eye lens may be more radiosensitive than previously considered. There is evidence of opacities after chronic exposure over several years, which can progress into lens opacities or cataracts(26) so that the threshold in absorbed dose for the eye lens is now considered to be 500 mGy, a factor of 10 lower than before. There exist some practices where potential significant eye lenses exposures are identified, while the whole body doses are below the limits (interventionalists, operators in nuclear medicine, etc.)(23). Moreover, ICRP 118(25) emphasizes the need to be aware of the absorbed dose threshold for circulatory disease may be as low as 0.5 Gy to the heart or brain, which could be reached during some complex interventional procedures. Optimization of protection should be applied in all exposure situations and not only for whole body exposures, but also for exposures to specific tissues, notably to the heart, cerebrovascular system and eye lens. As a more accurate method of the lesion localization, percutaneous needle biopsies started to be frequently used in IR, allowing better diagnostics of less accessible lesions, mainly in the lung, pleura and mediastinum. Reducing the need to perform diagnostic thoracotomies under anesthesia has been reported(12, 13). Based on the new statements in the ICRP Recommendations(22, 23, 25), on the Draft of the revision of ISO Standard 15382(27, 28) and on the TECDOC of IAEA(29), the ICRP recommends for the occupational exposure in planned exposure situations: an equivalent dose limit for the eye lens of 20 mSv y−1, averaged over defined periods of 5 y. Together with the reducing of the eye lens dose limit, there is a need to foster the implementation of the reference quantity Hp (3) in practice, as well as, to establish the conditions for monitoring of the operational quantity Hp (3), to prepare the calibration procedure and conversion factors for the real fields of radiation(28). For implementation of the Medical Exposure Directive (97/43/EURATOM), into the legislative requirements related to radiation protection training of medical professionals, the EC published ‘Guidance on Education and Training in Radiation Protection for Medical Exposures’(6). Update of this document is specially intended to Radiation protection training program in IR(5). A radiation protection training program was developed in order to familiarize IR personnel to radiation protection and facilitate ongoing training on patients and staff radiation protection, in the ORAMED project(30). For patient doses management ICRP published Guidelines on managing Patient Doses in Multi Detector Computed Tomography (MDCT)(31). The document recommends that MDCT system operators need to understand the relationship between patient dose and image quality. Scanning protocols cannot simply be transferred between scanners from different manufacturers and should be determined for each MDCT. If the image quality is appropriately specified by the user, and if suited to the clinical task, there will be a reduction in patient dose for most patients. Understanding of some parameters is not intuitive and the selection of image quality parameter values in automatic exposure control systems is not straightforward. Examples of some clinical situations have been included to demonstrate dose management, e.g. CT examinations of the chest, the heart for coronary calcium quantification and non-invasive coronary angiography, colonography, the urinary tract, children, pregnant patients, trauma cases and CT-guided interventions. CT is increasingly being used to replace conventional X-ray examinations and it is important that patient dose is given careful consideration, particularly with repeated or multiple examinations. In the ICRP 87 Recommendation(32), one chapter is addressed to the issue of staff exposure, during CTF procedures. It is stated that staff exposure is higher as they have to be present inside the CT room, near the gantry, with a strong probability that their hands may be located in the primary beam. Also, the IAEA TECDOC 1641 recommends the reduction of radiation doses from CT fluoroscopy, to both patients and physicians(33). Although current Guidelines for individual monitoring of staff working in IR are not specific for CTF procedures. Also, ICRP 85(34) documents that skin doses reaching 3 Gy in one procedure, or 1 Gy in the procedure likely to be repeated, should be recorded in the patient file, preferably with a dose map included, and that the patient should be invited for follow-up of possible acute reactions, up to 10–14 d after the exposure (for the deterministic effects usually the threshold dose of 2 Gy is considered). Modern fluoroscopic devices often provide an estimate of entrance skin dose, but CT scanners indicate only the value of computed tomography dose index (CTDI), or dose length product (DLP), which are difficult for the interpretation of the effective dose. Useful data are published in the ORAMED project publications(35). Moreover, studies show that during CTF examinations(36) the source of the scattered radiation is always slightly to the side of the interventionist, rather than directly to the front. In that case, considerable exposure of the arm facing the CT gantry can be observed. Optimization of individual monitoring requires a good understanding of typical dose distributions in CTF-guided procedures. Also it is very important to measure the eye lens doses, due to the reduced dose limit proposed in the ICRP and IAEA recommendations. TYPICAL CTF PROCEDURES Clinical CTF procedures With the development of the non-surgical treatment options in radiation oncology, percutaneous biopsies have become increasingly important in patient workup. A percutaneous biopsy of a suspected mass is usually done under local anesthesia in the patient. It is a very fast method of obtaining information about the tumor tissue (anatomopathological staging). There is also a general trend toward the less invasive treatment options, and often therapeutic interventions, such as abscess drainage, pleural fluid drainage or hepatobiliary interventions, are used as an alternative to the classical surgery(9). Interventional procedures that can be performed under CT guidance can also be performed faster and more easily with the help of CTF guidance, usually without increasing patient dose. Patient dose may even decrease when CTF is used, because beam-on times may slightly decrease. Proper control over the staff exposure should create the basis for keeping the dose rates at a minimum. Some procedures that might not be attempted using conventional CT guidance, e.g. lung biopsies of small lesions in patients which cannot cooperate with the breath holding may be performed successfully under CTF guidance(37). Because of the risk of high staff exposure, some studies recommend to use CTF guidance only in cases where it presents a clear benefit over CT guidance(38). There are several publications reporting the use of CTF in clinical practice, giving the detailed survey of the most typical CTF procedures, as well as their frequencies in various countries(39–45). Special attention to the application of CTF guidance for various interventional procedures, including biopsies, fluid collection aspirations, catheter insertion and drainage, radiofrequency ablation, lumbar nerve root blocks, ethanol injection inside the tumors and vertebroplasty has been previously reviewed(46–49). A biopsy under CTF guidance typically starts with a helical CT-scan of the region of interest, which is used to locate the lesion and to plan the percutaneous approach. A complete diagnostic scan is usually not necessary, since most patients have their most recent lesion well documented. Once the approach has been planned, a location on the skin is marked. After that, a sterilized drape is placed on the patient, the region where a needle is to be inserted is sterilized and local anesthesia administered. Some procedures may require contrast medium administration. CTF is then used to guide the insertion of the needle, until it has reached the desired location. The technical scan parameters of CTF procedures are selected according to the scan region and patient size, and have to be as low as possible to achieve proper image quality. When the biopsy needle is located into the lesion, fluoroscopy to check its location is necessary. To avoid excessive exposure of hands of the interventionist standing next to the patient during the CTF procedure, two different scanning techniques have been developed, which are described in the next section. Scanning techniques: real-time method and quick-check method Several authors(50, 51) described two different approaches to the use of the CTF guidance during interventional procedures. The real-time method involves continuous imaging while manipulating the needle at the same time, and therefore requires the use of a needle holding device to keep the hands of the operator out of the scanning plane. The other one is the quick-check method(50), which utilizes only intermittent imaging to check the position of the needle, allowing the operator to retract his hands during the irradiation. Both described methods are also known as continuous and intermittent methods, respectively. With the continuous method, the position and trajectory of the needle can be followed in real time, but the use of the needle holding device is limiting the tactile feedback and the grip. Unfortunately, manual manipulation of the needle under continuous imaging is impossible because it would lead to doses exceeding the occupational dose limit to the hands of the operator. The quick-check method uses the same targeting methods as the traditional CT guidance, but has the advantage of direct communication with the patient and represents a significant reduction in the number of time intervals between needle manipulation and imaging. When respiratory motion causes lesion displacement, as it is the case with lung biopsies, the real-time CTF procedure is the optimal performance, allowing confirmation of that the guide sheaths remain in its original position and the biopsy forceps are passed correct distance into the lung periphery. This ensures the high diagnostic yield and reduces the possibility of pneumothorax occurrence. The application of the quick-check method requires the cooperation between the patient and physician. In this case, a breath hold monitoring system is recommended to help the patient to resume a constant position for breath holds, reducing the variance of the lesion position during the imaging steps of the intervention(37, 38, 46–52). RADIATION RISK DURING CTF GUIDING PROCEDURES Patient risk There are many reports in the literature of skin injuries from fluoroscopic interventions(2, 26, 53, 54). Since 2 Gy is generally considered the threshold for deterministic effects, ICRP 85 recommends that skin doses exceeding 3 Gy in one procedure, or 1 Gy in a procedure likely to be repeated, should be recorded in the patient file and the patient recalled for a follow-up 10–14 d after the procedure(34). On the basis of experience learned from the literature, most radiation injuries could be prevented by optimization and prevention of the exposure, in such a way that the combination of all parameters leads to acceptable image quality together with minimum patient exposure(55). During CTF-guided interventions, there is cumulative irradiation of the same skin area. While modern fluoroscopy equipment provides an estimate of ESD, the CT scanners indicate only CTDI and DLP, which are difficult quantities for most physicians to interpret. Moreover, DLP in CTF is usually small compared to typical values for diagnostic exams, because only a very small length of the patient is (cumulatively) irradiated. Occupational risk CTF imaging is significantly different from CF in both equipment and technique, and the radiation protection concerns are also different(10). For instance, during CTF-guided procedures the source of scattered radiation (the portion of the patient being irradiated) is always slightly to the side of the interventionist, rather than directly in front, so there is considerable exposure of the arm facing the CT Gantry(36). Hand exposure during CTF-guided procedures is particularly problematic, because needle advancement occurs in the tomographic plane. Even using the quick-check method, side-handle manipulation of the needle during irradiation may occur(47). Recent data suggest that the finger tips may be significantly more exposed to radiation than the base of the finger where ring dosimeters are usually worn(56). Recently there has been particular concern regarding occupational dose to the lens of the eye in interventional radiologists(26). New data from exposed human populations suggest that lens opacities or cataracts occur at doses far lower than it was previously believed(57). Statistical analysis of the available data suggests absence of a threshold, although if one does exist, it is possible that it is <0.1 Gy. Additionally, it appears that the latency for radiation cataract formation is inversely related to the radiation dose. According the ICRP statement, the threshold in the absorbed dose for the lens of the eye is now considered to be 0.5 Gy (instead of previously used value of 2 Gy). For planned occupational exposure, ICRP recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined period of 5 y, with no single year exceeding 50 mSv (the previous limit was 150 mSv y−1). ICRP changed also the Statement on Tissue Reactions Early and Late Effects of Radiation in Normal Tissues and Organs and introduced the term of ‘tissue reaction’, instead of detriment effect, for the exposure of eye lens(25). Since the equivalent dose of the eye lens is not directly measurable, according to the contemporary concept of ICRP(58), the personal dose equivalents Hp (10) or Hp(0.07) were used for conservative eye lens dose estimates. Relevant findings are now available that in some cases Hp (10) underestimates and Hp (0.07) overestimates the dose to the lens of eye(59). From Figure 1 it can be seen that the quantity Hp (0.07) strongly overestimates the eye lens dose at photon energies below 30 keV and the Hp(10) underestimates Hlens for low photon energies, as well as for low electron energies. Figure 1. Open in new tabDownload slide Energy dependence of Hp(d) to Hlens for photons (taken from ICRP 74). Figure 1. Open in new tabDownload slide Energy dependence of Hp(d) to Hlens for photons (taken from ICRP 74). TECHNICAL POSSIBILITIES OF DOSE REDUCTION Tools for reduction of staff exposure Interventional radiologists performing CTF-guided procedures should always wear protective devices such as lead apron, thyroid shield, lead gloves and lead glass eyewear(47). Lead aprons and thyroid shields provide efficient protection to the internal organs(36, 48, 60, 61). The lead equivalent of commercially available goggles is similar to that of lead aprons; therefore, the use of protective eyewear should also prove sufficient protection to the eye lenses. However, there is still the potential for considerable exposure of body parts not shielded by the lead apron, particularly the hands of the radiologist. Several methods have been proposed to reduce hand exposure(27). Needle holder The use of needle holders allows manipulation of the biopsy needle under continuous imaging by keeping the hands out of the image plane. Dedicated needle holders have been developed(40, 62–70), and the so-called I-I device, which is commercially available(62), presented in Figure 2, helps to advance the biopsy needle under CTF guidance while reducing the irradiation of the hands. Instead of dedicated needle holders, some authors prefer metallic sponge forceps or towel clamps due to their widespread availability, lightweight, strength, ease of sterilization and relatively low cost(8, 50, 60, 64). Figure 2. Open in new tabDownload slide The I-I device (I-I device, Hakko, Tokyo, 2000) for needle placement, made of acrylate resin, which does not cause artefacts on CT images. Figure 2. Open in new tabDownload slide The I-I device (I-I device, Hakko, Tokyo, 2000) for needle placement, made of acrylate resin, which does not cause artefacts on CT images. Opinions differ as to how easy it is to use needle holders in CTF-guided biopsies. Some authors report no difficulty(40, 70), while others argue that needle holders decreases tactile feedback and grip, making it difficult to maneuver the needle or exert sufficient inward force(8, 50, 60, 61, 64). Robotics A robotic arm mounted on the CT couch and controlled from the scanner console would eliminate the need for the interventionist to be exposed to radiation during the procedure. A study reports 23 robotically guided percutaneous interventions performed without complication using a research prototype system(65) but, until now, such robotic units are not yet commercially available. However, this solution may be a long-time way from practical widespread implementation, due to budget and practical limitations such as the loss of tactile feedback. Angular beam modulation A very interesting option is already commercially available from some manufacturers is an incomplete scanning arc when operating in fluoroscopy mode. As a 240° rotation is sufficient for image reconstruction purposes, the X-ray beam can be switched off within a 120° sector centered above the patient, while the tube rotates continuously(19). There is an obvious analogy between this idea and the traditional ‘under couch geometry’ used in CF, which reduces the amount of backscattered radiation directed toward the hands and upper body of the interventionist. The downside in CTF is that the maximum skin dose to the patient may be slightly increased (about a factor of 1.3) if the machine maintains the integrated milliamp seconds per rotation, as this will then be delivered to a smaller skin area in comparison to 360° scanning(9). However, measurements with thermoluminescence dosimeters placed in an anthropomorphic phantom indicated that the effective dose to the patient could actually be reduced with ABM, at the same time significantly decreasing the dose to the operator's hand(19). Further measurements are needed to quantify the degree of protection afforded by this system, and the potential increase in patient skin dose(66). SHIELDING AND RADIATION PROTECTION TOOLS Shielding During the CTF procedures, only dedicated equipment should be used and positioned properly in an adequately shielded room. First of all, special attention should be paid to the positioning of the table shield, important mainly for the assisting persons who, in many cases, at least in CF procedures are standing close to the primary beam or moving around the table, but whose legs are not protected unlike the main operator(67). The second most important shielding device is represented by the ceiling suspended shield. This should be placed as close to the patient as possible. The combination of transparent ceiling shield and lead drapes that touch the patient is very efficient(68), as the exposure can be reduced, e.g. reduction of the eye dose (2–7 times)(67). The use of a lead drape placed on top of the patient adjacent to the scanning plane has been suggested as a means to reduce the scattered radiation directed toward the operator(39, 68). In this study, measurements using a cylindrical acrylic phantom (CTDI phantom) show that this provides a significant reduction (of ~70–80%) in backscatter exposure(65). Further measurements using anthropomorphic phantoms confirmed the efficacy of this method, and showed that even better results could be obtained using 360° shielding: a lead drape wrapped around the phantom, or two lead drapes, one placed under the phantom and another on top(39). Placing a heavy lead drape on a debilitated patient may be a problem, but lightweight materials providing similar attenuation are commercially available(36, 46). With an anthropomorphic phantom(41) the effects of other shielding possibilities were investigated, namely a fenestrated lead curtain on the CT Gantry and a corner drape (a lead curtain hanging from table level at the junction of the Gantry and the table). The typical individual radiation protection tools (shielding gloves, lead collars, lead glasses, as well as various types of lead aprons) are described in detail in many publications(9, 39, 42). Optimized imaging parameters The main source of exposure for the interventionist is, besides the possibility of the direct beam on the hand, the radiation scattered from the patient and therefore reducing patient dose will also reduce staff exposure. Typically, CTF procedures are performed with much lower tube current than in conventional CT. Slice thickness is also important and it has been shown that a decrease from 10 to 5 or 2 mm can result in a significant reduction of personnel exposure (reduction of 50–80%). However, decreasing slice thickness, tube current or tube voltage will also decrease image quality. Imaging parameters should be carefully optimized for each scanner to ensure the lowest possible dose rate that still provides the necessary visualization of the target lesion(68). Optimum imaging parameters will also depend on patient body mass, and therefore may vary between countries, for the same scanner model. CT fluoroscopic images for lung interventional procedures were obtained with 3 different tube voltages and 3 different tube currents for each patient, in a group of 32 patients who gave written informed consent(43). Weighted CTDI per second was obtained for each set of scan parameters. For a set slice thickness of 6 mm and 0.75 s per rotation, acceptable image quality was achieved for 94% of the patients with 120 kV and 10 mA (1.18 mGy s−1) and for all patients with 135 kV and 10 mA (1.48 mGy s−1). Mean patient weight in this study was 55.7 kg, with a mean body mass index of 21.6(43). DOSE ESTIMATION FOR STAFF AND PATIENT Staff dosimetry Whole body doses Unlike conventional CT, CTF requires personnel to remain in the CT room next to the patient during the whole procedure. Since tube currents are higher than in CF, the distance of an operator from the imaged patient body region is usually smaller and as the X-ray tube rotates, the operator could receive considerable amounts of radiation dose from scattered non-uniform radiation(7). The standard practice of preventing exposure of the medical staff members from scattered radiation by wearing protective clothes (lead aprons, thyroid collars, gloves, glasses) can lead to some problems in the adequate estimation of personal effective doses, E, with one dosimeter(44). In most countries, the estimate of the personal dose equivalent, Hp(10), measured with a dosimeter is recorded into the personal dose record as recommended by the ICRP(34). The quantity Hp(10) is a good estimate for the effective dose when the worker is uniformly exposed over the whole body in anterior–posterior direction to photons with energies above 1 MeV. A single dosimeter worn under the lead apron gives the exposure of the sensitive organs in the trunk provided that the dosimeter is positioned on a part of the body facing toward the X-ray source. Even when a thyroid collar is worn, some organs remain only partially shielded, so in this situation the dosimeter will underestimate E. A single dosimeter worn outside the apron can lead to significant overestimation of E while dosimeter worn under the apron can lead to underestimation of the effective dose. The ICRP recommends the development of double-dosimetry protocols for staff in the IR departments(34). However, until today there is no consensus about a suitable algorithm for the assessment of E in the presence of the protective clothes as well as the number of dosimeters, their location and the adequate correction factors(57). This problem should be taken into account during reviewing individual exposure of the CTF staff: there is no uniform approach to monitoring the whole body doses of CTF workers. A single dosimeter is worn either under the apron, or over the apron: at a collar level(45, 69) or at a chest level,(7, 43, 44, 68, 69) or two dosimeters are worn(36, 58, 59). For some staff members, the presence of a thyroid collar could be optional. Dosimeters Routine staff whole body dose monitoring is carried out by measurements of Hp(10) with optically stimulated luminescence dosimeters(45), electronic personal dosimeters (EPD)(49, 69, 70), film badges(60, 61) and thermoluminescence dosimeters(36). Dose ranges In publications radiation dose estimates are expressed in various ways(40, 45, 50, 63, 69, 71), the terms ‘radiation dose’, ‘radiation exposure’ and ‘dose equivalent’ are sometimes used, the values partly given as radiation doses (Gy) and partly as dose equivalent (Sv), even rem(58, 72) and Mr(43) units occurred. Measured radiation doses and the doses calculated with radiation dose rates which are presented in the literature might vary widely, especially taking into account the position of the dosimeter and the protection used. The reported ranges of whole body doses measured by either TLD or electronic dosimeters were 0.7–48 µSv per procedure of transjugular intrahepatic portosystemic shunt (TIPS) when the dosimeter was placed on the collar outside the lead apron and the value was not corrected for attenuation of the apron(69). The authors estimated that the mean dose per procedure was below 10 µSv for radiologists and below 1 µSv for radiographers. One radiologist performing ~70% of the procedures evaluated during this study throughout 1 y would receive an Hp(10) of 0.4 mSv owing to radiation exposure from the CT-guided interventions. Correcting Hp(10) conservatively for attenuation of the lead apron with a factor of 5 they concluded that the cumulative annual dose due to CTF would be <0.1 mSv for this radiologist. The dose ranges measured by EPD worn outside the lead apron at breast level were 0.05–1.6 mSv(48, 69, 72). Hp(10) measured for each procedure were the highest for the interventional radiologist (median, 14 µSv; maximum 1636 µSv), followed by the assisting radiologist (median 5 µSv; maximum 1884 µSv) and the radiation technologist (median 1 µSv; maximum 133 µSv)(48). The occupational effective dose was assessed as 20% of the measured occupational dose equivalent taking into account the lead-equivalent thickness of the applied lead apron (0.5 mm at the front), as well as the use of a thyroid shield and the relatively high tube voltages that are used in CTF(48). So the actual median effective dose was 3 µSv for the interventional radiologist and <0.4 µSv for the assisting radiologist and radiation technologists(48). The maximum occupational effective dose per procedure reached nearly 0.4 mSv for radiofrequency ablations(48). For CT-guided TIPS procedures, the reported average doses to the angiographer and the sonographer measured by EPD outside the lead apron at upper chest level were 199 and 282 µSv, respectively, for Hospital A and also 55 and 53 µSv, respectively, for Hospital B(70). The median effective dose per procedure was estimated as one-eighth of penetrating dose outside the apron (taking into account 0.5 mm lead-equivalent lead aprons with separate thyroid collars as well as lead glasses): the values for the angiographer and sonographer were 26 and 30 µSv in Hospital A and 4.4 and 3.5 µSv in Hospital B(70). The reported ranges of monthly readings in case of two film badges were 0–0.1 mSv for the dosimeter worn under the lead apron, and 0.1–1 mSv for the one above the lead apron(58, 59). Another study showed that, it is possible to measure dose values per procedure with whole body dosimeters based on TLD-100 detector material(36). Above the lead apron, the dose values at the waist level were between 0.02 and 0.08 mSv, while at chest level the values varied between 0.03 and 0.20 mSv. Preliminary estimates of the effective dose E were performed based on the expression recommended in the Portuguese legislation E = Hp (10)u + 0.05 Hp (10). With the values provided by the chest dosimeters, the effective dose per procedure ranged from 0.03 to 0.07 mSv(36). Hand doses There is a persistent concern regarding the operator's hands and fingers irradiated when guiding needles or when other interventional tools are used within the direct beam of the CT gantry. Even if constant caution is taken to avoid the primary beam entering with operator's hands, the risk of accidents still exists, as illustrated in Figure 3. Figure 3. Open in new tabDownload slide Operator position during CTF procedures. Figure 3. Open in new tabDownload slide Operator position during CTF procedures. Another potential risk to the operator arises from scattered radiation since the interventional radiologist has to work close to the radiation beam. Doses to the operator's hands were studied by many authors, but often the results of measurements in literature are partly given as radiation doses (Gy) and partly as dose equivalent (Sv). As dose equivalent values weighted for X-rays do not differ from the radiation exposure values, the data can be compared. Radiation exposure in mrad or dose equivalent in mrem also occurred. The radiologist's finger/hand doses reported in available publications (see Table 1) as a result of either TLD or electronic measurements were in the 0.1–7.3 mGy per procedure (locally on a single finger it can reach 36 mSv) range(19, 36, 40, 41, 47, 61, 62, 68, 73). Table 1. Comparison of published values for operator's hand dose per procedure and estimated or measured hand dose rates. Author . Method . Position . Comment . Hand dose per procedure (mSv) . Hand dose rate (mSv s−1) . . . . . Min . Max . Mean . Paulson (2001)(41) TLD Finger 0.3 Paulson (2001)(41) Estimate 25 cm 0.64 Carlson (2001)(7) TLD Finger 0.1 1.0 Daly et al. (1999)(14,57) TLD Finger 0.1a 9.7a 1.76a 0.004 Daly et al. (1999)(14,57) Next month 0.1a 1.3a 0.13a Silverman et al. (1999)(46) Estimate 10 cm 3.05 0.039 Gianfelice et al. (2000)(71) Estimate 10 cm 0.464 0.905 0.018 Nawfel et al. (2000)(65) Estimate 10 cm 2.2 0.024 Nawfelet al. (2000)(65) Lead drape 0.007 Nawfelet al. (2000)(65) TLD Finger 17.7a Buls et al. (2003)(43) TLD Hand 7.34 0.759 0.005 Nickoloff et al. (2000)(72) Estimate 20 cm 0.97 2.42 0.010–0.025 Neeman et al. (2006)(37) EDD 10 cm 0.0388 0.565 Hohl et al. (2008)(18) TLD 0.11 Hohl et al. (2008)(18) TLD ABM 0.08 Pereira et al. (2011)(32) TLD Finger 0.06 36.29 Bissoli et al. (2003)(70) Estimate 10 cm Continuous 1.32 0.03 Bissoli et al.(2003)(70) Estimate 10 cm Quick check 0.65 Bissoli et al. (2003)(70) Estimate 10 cm Mixed 2.75 Irie et al. (2001)(36) TLD Finger 1.1 3.6 2.0 0.1 Irie et al. (2001)(61) TLD Finger Lead plate I-I holder 0.1 0.055 Stoeckelhuber et al. (2005)(35) EDD 10 cmb 0.69 0.0395 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Gloves 0.195 0.0093 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Lead drape 0.063 0.0032 Stoeckelhuberet al. (2005)(35) EDD 10 cmb Lead drape and gloves 0.02 0.0012 Kato et al. (1996)(68) Estimate 4 cm 1.6 0.027 Author . Method . Position . Comment . Hand dose per procedure (mSv) . Hand dose rate (mSv s−1) . . . . . Min . Max . Mean . Paulson (2001)(41) TLD Finger 0.3 Paulson (2001)(41) Estimate 25 cm 0.64 Carlson (2001)(7) TLD Finger 0.1 1.0 Daly et al. (1999)(14,57) TLD Finger 0.1a 9.7a 1.76a 0.004 Daly et al. (1999)(14,57) Next month 0.1a 1.3a 0.13a Silverman et al. (1999)(46) Estimate 10 cm 3.05 0.039 Gianfelice et al. (2000)(71) Estimate 10 cm 0.464 0.905 0.018 Nawfel et al. (2000)(65) Estimate 10 cm 2.2 0.024 Nawfelet al. (2000)(65) Lead drape 0.007 Nawfelet al. (2000)(65) TLD Finger 17.7a Buls et al. (2003)(43) TLD Hand 7.34 0.759 0.005 Nickoloff et al. (2000)(72) Estimate 20 cm 0.97 2.42 0.010–0.025 Neeman et al. (2006)(37) EDD 10 cm 0.0388 0.565 Hohl et al. (2008)(18) TLD 0.11 Hohl et al. (2008)(18) TLD ABM 0.08 Pereira et al. (2011)(32) TLD Finger 0.06 36.29 Bissoli et al. (2003)(70) Estimate 10 cm Continuous 1.32 0.03 Bissoli et al.(2003)(70) Estimate 10 cm Quick check 0.65 Bissoli et al. (2003)(70) Estimate 10 cm Mixed 2.75 Irie et al. (2001)(36) TLD Finger 1.1 3.6 2.0 0.1 Irie et al. (2001)(61) TLD Finger Lead plate I-I holder 0.1 0.055 Stoeckelhuber et al. (2005)(35) EDD 10 cmb 0.69 0.0395 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Gloves 0.195 0.0093 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Lead drape 0.063 0.0032 Stoeckelhuberet al. (2005)(35) EDD 10 cmb Lead drape and gloves 0.02 0.0012 Kato et al. (1996)(68) Estimate 4 cm 1.6 0.027 aMonthly. b15 cm holder that keeps a 10-cm distance between the handle and the beam. Table 1. Comparison of published values for operator's hand dose per procedure and estimated or measured hand dose rates. Author . Method . Position . Comment . Hand dose per procedure (mSv) . Hand dose rate (mSv s−1) . . . . . Min . Max . Mean . Paulson (2001)(41) TLD Finger 0.3 Paulson (2001)(41) Estimate 25 cm 0.64 Carlson (2001)(7) TLD Finger 0.1 1.0 Daly et al. (1999)(14,57) TLD Finger 0.1a 9.7a 1.76a 0.004 Daly et al. (1999)(14,57) Next month 0.1a 1.3a 0.13a Silverman et al. (1999)(46) Estimate 10 cm 3.05 0.039 Gianfelice et al. (2000)(71) Estimate 10 cm 0.464 0.905 0.018 Nawfel et al. (2000)(65) Estimate 10 cm 2.2 0.024 Nawfelet al. (2000)(65) Lead drape 0.007 Nawfelet al. (2000)(65) TLD Finger 17.7a Buls et al. (2003)(43) TLD Hand 7.34 0.759 0.005 Nickoloff et al. (2000)(72) Estimate 20 cm 0.97 2.42 0.010–0.025 Neeman et al. (2006)(37) EDD 10 cm 0.0388 0.565 Hohl et al. (2008)(18) TLD 0.11 Hohl et al. (2008)(18) TLD ABM 0.08 Pereira et al. (2011)(32) TLD Finger 0.06 36.29 Bissoli et al. (2003)(70) Estimate 10 cm Continuous 1.32 0.03 Bissoli et al.(2003)(70) Estimate 10 cm Quick check 0.65 Bissoli et al. (2003)(70) Estimate 10 cm Mixed 2.75 Irie et al. (2001)(36) TLD Finger 1.1 3.6 2.0 0.1 Irie et al. (2001)(61) TLD Finger Lead plate I-I holder 0.1 0.055 Stoeckelhuber et al. (2005)(35) EDD 10 cmb 0.69 0.0395 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Gloves 0.195 0.0093 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Lead drape 0.063 0.0032 Stoeckelhuberet al. (2005)(35) EDD 10 cmb Lead drape and gloves 0.02 0.0012 Kato et al. (1996)(68) Estimate 4 cm 1.6 0.027 Author . Method . Position . Comment . Hand dose per procedure (mSv) . Hand dose rate (mSv s−1) . . . . . Min . Max . Mean . Paulson (2001)(41) TLD Finger 0.3 Paulson (2001)(41) Estimate 25 cm 0.64 Carlson (2001)(7) TLD Finger 0.1 1.0 Daly et al. (1999)(14,57) TLD Finger 0.1a 9.7a 1.76a 0.004 Daly et al. (1999)(14,57) Next month 0.1a 1.3a 0.13a Silverman et al. (1999)(46) Estimate 10 cm 3.05 0.039 Gianfelice et al. (2000)(71) Estimate 10 cm 0.464 0.905 0.018 Nawfel et al. (2000)(65) Estimate 10 cm 2.2 0.024 Nawfelet al. (2000)(65) Lead drape 0.007 Nawfelet al. (2000)(65) TLD Finger 17.7a Buls et al. (2003)(43) TLD Hand 7.34 0.759 0.005 Nickoloff et al. (2000)(72) Estimate 20 cm 0.97 2.42 0.010–0.025 Neeman et al. (2006)(37) EDD 10 cm 0.0388 0.565 Hohl et al. (2008)(18) TLD 0.11 Hohl et al. (2008)(18) TLD ABM 0.08 Pereira et al. (2011)(32) TLD Finger 0.06 36.29 Bissoli et al. (2003)(70) Estimate 10 cm Continuous 1.32 0.03 Bissoli et al.(2003)(70) Estimate 10 cm Quick check 0.65 Bissoli et al. (2003)(70) Estimate 10 cm Mixed 2.75 Irie et al. (2001)(36) TLD Finger 1.1 3.6 2.0 0.1 Irie et al. (2001)(61) TLD Finger Lead plate I-I holder 0.1 0.055 Stoeckelhuber et al. (2005)(35) EDD 10 cmb 0.69 0.0395 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Gloves 0.195 0.0093 Stoeckelhuber et al. (2005)(35) EDD 10 cmb Lead drape 0.063 0.0032 Stoeckelhuberet al. (2005)(35) EDD 10 cmb Lead drape and gloves 0.02 0.0012 Kato et al. (1996)(68) Estimate 4 cm 1.6 0.027 aMonthly. b15 cm holder that keeps a 10-cm distance between the handle and the beam. The doses and the dose rates at the hand's position (see the last column in Table 2) varied significantly depending on the type of procedure (e.g. the RF ablation represents the highest dose to the staff per procedure since this procedure requires a longer fluoroscopy time), on parameters of a CTF protocol (with substantial decrease in scatter exposure with the lower exposure technique), on distance from the scanning plane, section thickness, dosimeter position as well as on the use of protective tools: acrylic needle holders and a lead drape. Table 2. Radiation dose to the radiologist's hand during continuous CTF with and without radiation protection devices. Radiation dose values are an average from the measurements taken at the three times for the 5, 10 and 20 s fluoroscopy times(35). Group . Needle holder length (cm) . Lead drapes . Radiation protection gloves . Radiation dose (µGy) . Dose rate (µGy s−1) . 5 s 10 s 20 s A 15 − − 240 360 690 39.5 B 15 − + 34 112 195 9.3 C 15 + − 16 32 63 3.2 D 15 + + 6 13 20 1.2 E 35 − − 80 120 230 13.2 F 35 − + 20 30 60 3.3 G 35 + − 2 3 7 0.4 H 35 + + 1 2 3 0.2 Group . Needle holder length (cm) . Lead drapes . Radiation protection gloves . Radiation dose (µGy) . Dose rate (µGy s−1) . 5 s 10 s 20 s A 15 − − 240 360 690 39.5 B 15 − + 34 112 195 9.3 C 15 + − 16 32 63 3.2 D 15 + + 6 13 20 1.2 E 35 − − 80 120 230 13.2 F 35 − + 20 30 60 3.3 G 35 + − 2 3 7 0.4 H 35 + + 1 2 3 0.2 Table 2. Radiation dose to the radiologist's hand during continuous CTF with and without radiation protection devices. Radiation dose values are an average from the measurements taken at the three times for the 5, 10 and 20 s fluoroscopy times(35). Group . Needle holder length (cm) . Lead drapes . Radiation protection gloves . Radiation dose (µGy) . Dose rate (µGy s−1) . 5 s 10 s 20 s A 15 − − 240 360 690 39.5 B 15 − + 34 112 195 9.3 C 15 + − 16 32 63 3.2 D 15 + + 6 13 20 1.2 E 35 − − 80 120 230 13.2 F 35 − + 20 30 60 3.3 G 35 + − 2 3 7 0.4 H 35 + + 1 2 3 0.2 Group . Needle holder length (cm) . Lead drapes . Radiation protection gloves . Radiation dose (µGy) . Dose rate (µGy s−1) . 5 s 10 s 20 s A 15 − − 240 360 690 39.5 B 15 − + 34 112 195 9.3 C 15 + − 16 32 63 3.2 D 15 + + 6 13 20 1.2 E 35 − − 80 120 230 13.2 F 35 − + 20 30 60 3.3 G 35 + − 2 3 7 0.4 H 35 + + 1 2 3 0.2 It was estimated that the lower exposure technique (80 vs 120 kVp) would correspond to a 60% reduction in personnel hand exposure(68). An attenuating lead drape placed 2.5 cm caudal to the scanning plane reduced the scattered exposure rate by 71% while a reduction in the section thickness from 10 to 5 or 2 mm can result in personnel exposure reductions of 50–80%. For the staff, the hand dose will be the critical factor with regard to regulatory dose limits. Considering an annual dose limit to the skin of 500 mSv to the extremities for a classified worker (ICRP 1991) along with the values presented in the article by Buls et al.(47) a physician could annually perform ~350 CTF procedures before reaching the dose limit (using scanner settings of 120 kVp and 90 mA). One of the earlier papers(71) reports about measurements of the absorbed dose rates and obtaining the conversion coefficient corresponding to the effective energy (35.33 keV) based on the half-value layer of the beam (3.45 mm of aluminum). They calculated the corresponding dose equivalent rates and estimated that the operator's hand dose under exposure in the direct beam can reach 120 mSv per procedure, thus restricting the annual number of procedure to four taking into account the 500 mSv year limit only. To reduce the exposure to the interventionalist's hand, it was suggested(19) using the ABM mode when the X-ray tube was turned off between the 10 and 2 o'clock positions, while the tube current—time product per reconstructed image is maintained. As the X-ray tube is turned off in the 120° sector above the patient, the direct irradiation of the operator's hand by the primary beam is very limited resulting in a relative dose reduction of 72% in case of primary beam irradiation and of 27% for scattered radiation. The radiation dose to the operator's hand was estimated in several studies(39, 41, 45, 50, 74, 75) by using data from phantom measurements. They investigated the effect of a lead drape on the phantom surface adjacent to the scanning plane, the use of thin radiation-protective gloves and the use of different needle holders. The results are summarized in Table 2. It was shown that the long needle holder decreased the dose rates by 30%. Lead drapes reduced the dose rates up to 97.3%. The lead shield is more effective with the long needle holder than with the short needle holder. Radiation protection gloves resulted in a 76.6% dose reduction. The combination of lead drapes, protective gloves and long needle holder decreased the dose rates by 99.6%. Double-layer radiation-protective gloves in addition to double-layer 360° phantom shielding and a fenestrated gantry drape garnered dose reductions to the operator's hand of ~97.1% at 5 cm (from 1.792 to 51.77 µGy) and 93.1% at 10 cm (from 564.6 to 38.81 µGy) from the scan plane after a 30-frame acquisition(38). Manual assist devices become cumbersome and hard to control with greater length, which suggests that 10–20 cm is an ideal length for such devices. A detailed study of doses to fingers was presented by Pereira et al.(36) for eight CTF-guided procedures, namely six lung and two bone biopsies. In each procedure, the interventional radiologist was allocated a glove with 11 extremity TLD detectors. The dosimeters were inserted on the glove's casings, two per finger and one on the wrist. Radiation reduction examination gloves (Boston Scientific) were used over this glove and a third sterilized one was worn on top. The results demonstrate a considerable dose variation from 0.06 up to 36.29 mSv depending on both procedure and detector position (either base or tip of a finger, see Table 3). Table 3. Hp (0.07) dose values measured in each procedure with the 11 extremity detectors inserted on the center hand glove: tip (A) and base (B) of each finger and one on the wrist (mSv) (32). . Procedure . Thumb . Index . Middle . Ring . Little . Wrist . . A . B . A . B . A . B . A . B . A . B . 1 LLung 1.09 0.58 6.99 0.85 1.97 17.58 5.16 16.76 4.71 7.56 0.27 2 LLung 14.96 2.19 3.63 2.74 7.61 2.00 36.29 0.98 2.86 0.94 0.27 3 RLung 1.89 0.91 19.31 4.11 4.57 16.35 5.59 14.45 4.68 7.37 0.38 4 LLung 3.43 0.42 2.95 0.33 2.25 0.44 5.72 0.19 0.40 0.20 0.10 5 Lung 0.14 0.05 0.08 0.06 0.06 0.10 0.09 0.09 0.07 0.36 0.07 6 MLung 2.92 0.53 9.41 0.58 4.97 0.54 5.07 0.36 4.68 0.35 0.25 7 Bone 0.06 0.17 0.07 0.06 0.06 0.06 0.06 0.06 0.08 0.08 0.08 8 Bone 2.76 3.37 2.46 11.12 2.79 25.76 2.42 8.28 2.27 7.03 0.57 . Procedure . Thumb . Index . Middle . Ring . Little . Wrist . . A . B . A . B . A . B . A . B . A . B . 1 LLung 1.09 0.58 6.99 0.85 1.97 17.58 5.16 16.76 4.71 7.56 0.27 2 LLung 14.96 2.19 3.63 2.74 7.61 2.00 36.29 0.98 2.86 0.94 0.27 3 RLung 1.89 0.91 19.31 4.11 4.57 16.35 5.59 14.45 4.68 7.37 0.38 4 LLung 3.43 0.42 2.95 0.33 2.25 0.44 5.72 0.19 0.40 0.20 0.10 5 Lung 0.14 0.05 0.08 0.06 0.06 0.10 0.09 0.09 0.07 0.36 0.07 6 MLung 2.92 0.53 9.41 0.58 4.97 0.54 5.07 0.36 4.68 0.35 0.25 7 Bone 0.06 0.17 0.07 0.06 0.06 0.06 0.06 0.06 0.08 0.08 0.08 8 Bone 2.76 3.37 2.46 11.12 2.79 25.76 2.42 8.28 2.27 7.03 0.57 Table 3. Hp (0.07) dose values measured in each procedure with the 11 extremity detectors inserted on the center hand glove: tip (A) and base (B) of each finger and one on the wrist (mSv) (32). . Procedure . Thumb . Index . Middle . Ring . Little . Wrist . . A . B . A . B . A . B . A . B . A . B . 1 LLung 1.09 0.58 6.99 0.85 1.97 17.58 5.16 16.76 4.71 7.56 0.27 2 LLung 14.96 2.19 3.63 2.74 7.61 2.00 36.29 0.98 2.86 0.94 0.27 3 RLung 1.89 0.91 19.31 4.11 4.57 16.35 5.59 14.45 4.68 7.37 0.38 4 LLung 3.43 0.42 2.95 0.33 2.25 0.44 5.72 0.19 0.40 0.20 0.10 5 Lung 0.14 0.05 0.08 0.06 0.06 0.10 0.09 0.09 0.07 0.36 0.07 6 MLung 2.92 0.53 9.41 0.58 4.97 0.54 5.07 0.36 4.68 0.35 0.25 7 Bone 0.06 0.17 0.07 0.06 0.06 0.06 0.06 0.06 0.08 0.08 0.08 8 Bone 2.76 3.37 2.46 11.12 2.79 25.76 2.42 8.28 2.27 7.03 0.57 . Procedure . Thumb . Index . Middle . Ring . Little . Wrist . . A . B . A . B . A . B . A . B . A . B . 1 LLung 1.09 0.58 6.99 0.85 1.97 17.58 5.16 16.76 4.71 7.56 0.27 2 LLung 14.96 2.19 3.63 2.74 7.61 2.00 36.29 0.98 2.86 0.94 0.27 3 RLung 1.89 0.91 19.31 4.11 4.57 16.35 5.59 14.45 4.68 7.37 0.38 4 LLung 3.43 0.42 2.95 0.33 2.25 0.44 5.72 0.19 0.40 0.20 0.10 5 Lung 0.14 0.05 0.08 0.06 0.06 0.10 0.09 0.09 0.07 0.36 0.07 6 MLung 2.92 0.53 9.41 0.58 4.97 0.54 5.07 0.36 4.68 0.35 0.25 7 Bone 0.06 0.17 0.07 0.06 0.06 0.06 0.06 0.06 0.08 0.08 0.08 8 Bone 2.76 3.37 2.46 11.12 2.79 25.76 2.42 8.28 2.27 7.03 0.57 Despite the results are preliminary, the authors state that the wrist dose value ranging from 0.07 to 0.57 mSv in all procedures could not be representative of the hand values. The wrist doses comprise only 0.7–2.7% of the highest value measured for fingers in each procedure. It is stressed that the index, middle and ring fingers received the highest dose values. Thus, a variety of techniques have been used to reduce doses to the hands. Holders for biopsy needles reduce doses by increasing the distance from the scan plane(41, 50, 62, 63, 71, 73), although this may decrease tactile feedback and lead to longer fluoroscopy times(8). Good results have been reported using a device for holding and advancing the biopsy needle, which is available commercially(62). The placing of a lead drape or plate under the operator's hand has been reported to reduce the scatter dose by 50–75%(40, 44, 63), while the use of fenestrated shielded drapes reduced dose by 20–35%(42). Reductions in dose of 15–45% have been reported through the use of protective gloves, depending on the type of glove used(64, 75). The use of double-layer radiation-protective gloves combined with a double-layer 360° phantom shield (without the fenestrated gantry drape) still significantly reduced the operator's hand dose by 92.3% at 5 cm and by 90% at 10 cm from the beam(38). Therefore, the use of this combined shielding technique is strongly suggested for operator safety. Doses to the eyes and thyroid Although the physician's hands will most likely receive the highest levels of exposure, the thyroid and eye lens are also at risk. Studies(45, 68) have estimated that a radiologist could have the mean radiation dose for eye lens of 0.007–0.048 mSv per procedure. Other studies(47) have converted the ESD measured in air to the dose to the eye lens and the dose to the skin of the hands, taking into account X-ray mass energy absorption coefficients (µen/ρ) from the United States National Institute of Standards and Technology(76). The 1990 ICRP recommended conversion factors were 1.02 for the eye lens dose and 1.08 for the skin dose (soft tissue)(77). For a group of 82 consecutive patients, the following mean values were determined per procedure: staff ESDeye = 0.210 mSv; staff, ESDthyroid = 0.240 mSv. Considering an annual dose limit of 20 mSv to the lens of the eye(77), the annual number of procedure above the limit would be higher. For such values, it is recommended that staff protection is complemented with a thyroid collar and protective leaded eyewear. Measurement of Hp (3) is recommended(24, 30). Based on the new statements in the ICRP Recommendations, together with the reducing of the eye lens dose limit, there is a need to foster the implementation of the reference quantity Hp(3) in practice, as well. Depending on the used methods for eye lens dosimetry, as well as on the application of protection tools and working skills, conversion factors between the proposed personal dose equivalent quantity Hp (3) and the Air Kerma were estimated, based on realistic simulations of the human eye(78). The most important factor contributing to the dose variation is the use of eye glasses. Measurements of the attenuation indicate that screens can give protection by a factor of 30(79). In fact, a recent study found that the use of lead glasses significantly reduces the eye lens dose, and, moreover, that the shape and design of the glasses will have an impact in the dose reduction(80, 81). The wearing of lead glasses will provide effective protection, but there are issues of comfort and practicality. The spectacles are heavy and may slip down from the bridge of the nose, which creates a particular problem when performing sterile procedures, so the decision about whether lead spectacles are appropriate should be made by the operator. The use of ceiling suspended shields is recommended, and if used properly these will protect the whole head and neck from scattering. Patient dosimetry In CTF it is important to distinguish effective dose that is usually similar to the doses from conventional CT and cumulative patient skin doses that can be potentially of greater concern. The overview of measured and calculated patient doses by different authors is given in Table 4. Table 4. The overview of measured and calculated patient doses by different authors. Authors . CTF procedures . CTF technique and . Method of . Reported patients doses . Paulson et al. (2001)(41) 220 IR procedures Spinal injections (57) Spinal biopsies (17) Abdominal and pelvic biopsies (57) Fluid aspirations (20) Catheter drainages (58) Quick check (87%) Real time (2%) Combination (11%) Mean CTF time: 17.9 s/procedure (1.2–101.5 s) Mean mA value: 13.2 mA (10–50 mA) Tube voltage 140 kVp Indirect measurements with TLD on phantom Maximum dose rate on the surface of the phantom was 0.18 and 0.177 cGy/s ESD = 32 mGy (for mean CTF time of 17.9 s) Buls et al. (2003)(43) 82 procedures Biopsy (46) Drainage (12) Aspiration (10) RF ablation (14) Intermittent fluoroscopy Quick check method Median CTF time: 123 s Quick check method Median CTF time: 123 s Mean mA value: 90 mA Tube voltage: 120 kVp Direct measurements on patients with TLDs Median ESD = 374 mSv (maximum ESD = 1020 mSv) Nickoloff et al. (2000)(72) 78 procedures (various biopsies) CTF time 100 s Tube voltage: 120kVp Tube current: 30 mA Indirect measurements by CTDI on acrylic phantom ESD rate for body: 24 cGy/min (77 cGy for 100 s) ESD rate for head: 46 cGy/min (40 cGy for 100 s) Binkert et al. (2003)(76) 28 procedures (glenohumeral injection of contrast material) Mean CTF time: 28 min Quick check method Tube voltage: 120 kV Tube current: 50 mA Indirect measurements by CTDI on acrylic phantom with pencil chamber Effective dose = 0.22 mSv Bissoli et al. (2003)(70) 60 procedures Biopsies (39) Drainage (5) Shoulder arthrocentesis (12) Hepatic neoplasm ablations (4) Continuous CTF method (6): Mean values: 120 kV, 51 mA, 3mm, 44 s Quick check (50): 120 kV, 88 mA, 2 mm, 13 s mixed (4): 120 kV, 86 mA, 2-3mm, 55 s Calculated dose to patient with mean parameters using body phantom Continuous method: mean dose to patient skin:176 mSv Quick check method: mean dose to patient skin:88.4 mSv Mixed fluoroscopy: mean dose to patient skin:374 mSv radiation dose by time unit (phtanom,120 kV, 50 mA): 5300 µSv/s Carlson et al. (2001)(7) 203 procedures Biopsies 146 Catheter drainage 27 Aspirations 30 CTF time 1.2–187.6 s Tube voltage: 120 kVp Tube current: 10–50 mA Indirect by CTDI and from measurements of tube potential, tube current, collimation and total fluoroscopy time ESD: median 43 mGy (range 2–829 mGy) Hohl et al.(2008)(18) Tube voltage, 120 kVp; tube current–time product per reconstructed image, 30 mAs; rotation time, 0.5 s Indirect measurements on Rando phantom with TLD 0.25 mSv/s Neemanet al. (2006)(37) Simulation of toraxic and abdominal procedures 120 kVp; 30 mA Indirect measurements on Rando phantom with an electronic dosemeter Toraxic Abdominal Eye 0.061 0.005 Thyroid 0.183 0.007 Chest 0.004 0.065 Navel 0.04 0.005 Ovaries 0.009 0.245 Testicles 0.004 0.032 Keat et al.(2001)(47) 120 kV; 50 mAs;10-mm slice thickness Patient MSD = 0.4–0.8 and E = 0.06 mSv Authors . CTF procedures . CTF technique and . Method of . Reported patients doses . Paulson et al. (2001)(41) 220 IR procedures Spinal injections (57) Spinal biopsies (17) Abdominal and pelvic biopsies (57) Fluid aspirations (20) Catheter drainages (58) Quick check (87%) Real time (2%) Combination (11%) Mean CTF time: 17.9 s/procedure (1.2–101.5 s) Mean mA value: 13.2 mA (10–50 mA) Tube voltage 140 kVp Indirect measurements with TLD on phantom Maximum dose rate on the surface of the phantom was 0.18 and 0.177 cGy/s ESD = 32 mGy (for mean CTF time of 17.9 s) Buls et al. (2003)(43) 82 procedures Biopsy (46) Drainage (12) Aspiration (10) RF ablation (14) Intermittent fluoroscopy Quick check method Median CTF time: 123 s Quick check method Median CTF time: 123 s Mean mA value: 90 mA Tube voltage: 120 kVp Direct measurements on patients with TLDs Median ESD = 374 mSv (maximum ESD = 1020 mSv) Nickoloff et al. (2000)(72) 78 procedures (various biopsies) CTF time 100 s Tube voltage: 120kVp Tube current: 30 mA Indirect measurements by CTDI on acrylic phantom ESD rate for body: 24 cGy/min (77 cGy for 100 s) ESD rate for head: 46 cGy/min (40 cGy for 100 s) Binkert et al. (2003)(76) 28 procedures (glenohumeral injection of contrast material) Mean CTF time: 28 min Quick check method Tube voltage: 120 kV Tube current: 50 mA Indirect measurements by CTDI on acrylic phantom with pencil chamber Effective dose = 0.22 mSv Bissoli et al. (2003)(70) 60 procedures Biopsies (39) Drainage (5) Shoulder arthrocentesis (12) Hepatic neoplasm ablations (4) Continuous CTF method (6): Mean values: 120 kV, 51 mA, 3mm, 44 s Quick check (50): 120 kV, 88 mA, 2 mm, 13 s mixed (4): 120 kV, 86 mA, 2-3mm, 55 s Calculated dose to patient with mean parameters using body phantom Continuous method: mean dose to patient skin:176 mSv Quick check method: mean dose to patient skin:88.4 mSv Mixed fluoroscopy: mean dose to patient skin:374 mSv radiation dose by time unit (phtanom,120 kV, 50 mA): 5300 µSv/s Carlson et al. (2001)(7) 203 procedures Biopsies 146 Catheter drainage 27 Aspirations 30 CTF time 1.2–187.6 s Tube voltage: 120 kVp Tube current: 10–50 mA Indirect by CTDI and from measurements of tube potential, tube current, collimation and total fluoroscopy time ESD: median 43 mGy (range 2–829 mGy) Hohl et al.(2008)(18) Tube voltage, 120 kVp; tube current–time product per reconstructed image, 30 mAs; rotation time, 0.5 s Indirect measurements on Rando phantom with TLD 0.25 mSv/s Neemanet al. (2006)(37) Simulation of toraxic and abdominal procedures 120 kVp; 30 mA Indirect measurements on Rando phantom with an electronic dosemeter Toraxic Abdominal Eye 0.061 0.005 Thyroid 0.183 0.007 Chest 0.004 0.065 Navel 0.04 0.005 Ovaries 0.009 0.245 Testicles 0.004 0.032 Keat et al.(2001)(47) 120 kV; 50 mAs;10-mm slice thickness Patient MSD = 0.4–0.8 and E = 0.06 mSv Table 4. The overview of measured and calculated patient doses by different authors. Authors . CTF procedures . CTF technique and . Method of . Reported patients doses . Paulson et al. (2001)(41) 220 IR procedures Spinal injections (57) Spinal biopsies (17) Abdominal and pelvic biopsies (57) Fluid aspirations (20) Catheter drainages (58) Quick check (87%) Real time (2%) Combination (11%) Mean CTF time: 17.9 s/procedure (1.2–101.5 s) Mean mA value: 13.2 mA (10–50 mA) Tube voltage 140 kVp Indirect measurements with TLD on phantom Maximum dose rate on the surface of the phantom was 0.18 and 0.177 cGy/s ESD = 32 mGy (for mean CTF time of 17.9 s) Buls et al. (2003)(43) 82 procedures Biopsy (46) Drainage (12) Aspiration (10) RF ablation (14) Intermittent fluoroscopy Quick check method Median CTF time: 123 s Quick check method Median CTF time: 123 s Mean mA value: 90 mA Tube voltage: 120 kVp Direct measurements on patients with TLDs Median ESD = 374 mSv (maximum ESD = 1020 mSv) Nickoloff et al. (2000)(72) 78 procedures (various biopsies) CTF time 100 s Tube voltage: 120kVp Tube current: 30 mA Indirect measurements by CTDI on acrylic phantom ESD rate for body: 24 cGy/min (77 cGy for 100 s) ESD rate for head: 46 cGy/min (40 cGy for 100 s) Binkert et al. (2003)(76) 28 procedures (glenohumeral injection of contrast material) Mean CTF time: 28 min Quick check method Tube voltage: 120 kV Tube current: 50 mA Indirect measurements by CTDI on acrylic phantom with pencil chamber Effective dose = 0.22 mSv Bissoli et al. (2003)(70) 60 procedures Biopsies (39) Drainage (5) Shoulder arthrocentesis (12) Hepatic neoplasm ablations (4) Continuous CTF method (6): Mean values: 120 kV, 51 mA, 3mm, 44 s Quick check (50): 120 kV, 88 mA, 2 mm, 13 s mixed (4): 120 kV, 86 mA, 2-3mm, 55 s Calculated dose to patient with mean parameters using body phantom Continuous method: mean dose to patient skin:176 mSv Quick check method: mean dose to patient skin:88.4 mSv Mixed fluoroscopy: mean dose to patient skin:374 mSv radiation dose by time unit (phtanom,120 kV, 50 mA): 5300 µSv/s Carlson et al. (2001)(7) 203 procedures Biopsies 146 Catheter drainage 27 Aspirations 30 CTF time 1.2–187.6 s Tube voltage: 120 kVp Tube current: 10–50 mA Indirect by CTDI and from measurements of tube potential, tube current, collimation and total fluoroscopy time ESD: median 43 mGy (range 2–829 mGy) Hohl et al.(2008)(18) Tube voltage, 120 kVp; tube current–time product per reconstructed image, 30 mAs; rotation time, 0.5 s Indirect measurements on Rando phantom with TLD 0.25 mSv/s Neemanet al. (2006)(37) Simulation of toraxic and abdominal procedures 120 kVp; 30 mA Indirect measurements on Rando phantom with an electronic dosemeter Toraxic Abdominal Eye 0.061 0.005 Thyroid 0.183 0.007 Chest 0.004 0.065 Navel 0.04 0.005 Ovaries 0.009 0.245 Testicles 0.004 0.032 Keat et al.(2001)(47) 120 kV; 50 mAs;10-mm slice thickness Patient MSD = 0.4–0.8 and E = 0.06 mSv Authors . CTF procedures . CTF technique and . Method of . Reported patients doses . Paulson et al. (2001)(41) 220 IR procedures Spinal injections (57) Spinal biopsies (17) Abdominal and pelvic biopsies (57) Fluid aspirations (20) Catheter drainages (58) Quick check (87%) Real time (2%) Combination (11%) Mean CTF time: 17.9 s/procedure (1.2–101.5 s) Mean mA value: 13.2 mA (10–50 mA) Tube voltage 140 kVp Indirect measurements with TLD on phantom Maximum dose rate on the surface of the phantom was 0.18 and 0.177 cGy/s ESD = 32 mGy (for mean CTF time of 17.9 s) Buls et al. (2003)(43) 82 procedures Biopsy (46) Drainage (12) Aspiration (10) RF ablation (14) Intermittent fluoroscopy Quick check method Median CTF time: 123 s Quick check method Median CTF time: 123 s Mean mA value: 90 mA Tube voltage: 120 kVp Direct measurements on patients with TLDs Median ESD = 374 mSv (maximum ESD = 1020 mSv) Nickoloff et al. (2000)(72) 78 procedures (various biopsies) CTF time 100 s Tube voltage: 120kVp Tube current: 30 mA Indirect measurements by CTDI on acrylic phantom ESD rate for body: 24 cGy/min (77 cGy for 100 s) ESD rate for head: 46 cGy/min (40 cGy for 100 s) Binkert et al. (2003)(76) 28 procedures (glenohumeral injection of contrast material) Mean CTF time: 28 min Quick check method Tube voltage: 120 kV Tube current: 50 mA Indirect measurements by CTDI on acrylic phantom with pencil chamber Effective dose = 0.22 mSv Bissoli et al. (2003)(70) 60 procedures Biopsies (39) Drainage (5) Shoulder arthrocentesis (12) Hepatic neoplasm ablations (4) Continuous CTF method (6): Mean values: 120 kV, 51 mA, 3mm, 44 s Quick check (50): 120 kV, 88 mA, 2 mm, 13 s mixed (4): 120 kV, 86 mA, 2-3mm, 55 s Calculated dose to patient with mean parameters using body phantom Continuous method: mean dose to patient skin:176 mSv Quick check method: mean dose to patient skin:88.4 mSv Mixed fluoroscopy: mean dose to patient skin:374 mSv radiation dose by time unit (phtanom,120 kV, 50 mA): 5300 µSv/s Carlson et al. (2001)(7) 203 procedures Biopsies 146 Catheter drainage 27 Aspirations 30 CTF time 1.2–187.6 s Tube voltage: 120 kVp Tube current: 10–50 mA Indirect by CTDI and from measurements of tube potential, tube current, collimation and total fluoroscopy time ESD: median 43 mGy (range 2–829 mGy) Hohl et al.(2008)(18) Tube voltage, 120 kVp; tube current–time product per reconstructed image, 30 mAs; rotation time, 0.5 s Indirect measurements on Rando phantom with TLD 0.25 mSv/s Neemanet al. (2006)(37) Simulation of toraxic and abdominal procedures 120 kVp; 30 mA Indirect measurements on Rando phantom with an electronic dosemeter Toraxic Abdominal Eye 0.061 0.005 Thyroid 0.183 0.007 Chest 0.004 0.065 Navel 0.04 0.005 Ovaries 0.009 0.245 Testicles 0.004 0.032 Keat et al.(2001)(47) 120 kV; 50 mAs;10-mm slice thickness Patient MSD = 0.4–0.8 and E = 0.06 mSv The available CTF equipment allows the selection of a wide range of the X-ray tube voltage, tube currents, slice thickness and tube rotation time. The variations of these settings influence the patient dose and also through associated scattered radiation the staff doses. The overview of measured and calculated patient doses by different authors is given in Table 4. Doses to patients were measured and evaluated by several authors either by direct measurements on patients or indirect measurements by using different phantoms. It is difficult to compare the reported data about patient doses from the literature due to different factors influencing on the dose. It is well known that tube current has nearly linear relationship with dose if the exposure conditions are the same. Decreased tube current and exposure time will lead to reduced patients dose and also staff doses because most of the staff doses are due to scatter radiation. By applying the different CTF methods (e.g. quick-check method, continuous method or mixed fluoroscopy) the mean dose to patient's skin can be reduced by factor of 4 (from 374 to 88.4 mSv) if quick-check method is used according to calculated data through a body phantom. Two studies(47,73,82) reported extensive in vivo measurements and compared the measured data with published data for various CTF procedures. The published values of CTF screening time can vary from ~1.2 to 840 s due to complexity of procedure, applying different techniques and settings and the level of operators’ experience which lead to wide variation of both staff and patient doses. In the literature there are only several studies that used in vivo dose measurements on patients. Most of the studies used different phantoms which allow standardizing the patient size and investigating influence of settings parameters but cannot take into account real size, movement and position of the patient. It is very difficult to state the exact patient dose during CTF due to many influencing factors therefore it is important to balance all these parameters keeping in mind ALARA principle. Patient dose reduction techniques, which lead also to decrease in the scatter levels and staff doses reduction, can include several recommendations that should be implemented in radiological departments to apply quick-check methods whenever possible instead of continuous mode to reduce radiation exposure; to apply lower scanner parameters (tube current, tube potential and slice thickness) with maintaining adequate quality of images for particular anatomical region of interest; to use a lead drape on the patient to reduce patient's dose and also reduce scatter radiation from the patient to the staff; to provide operator's training, as a well-trained operator, i.e. skilled in performing CTF procedures, as well as aware of all the factors influencing the dose and also conscious of all the radiation protection measures (lead drape, collar, glasses, needle holders, etc.) is able to reduce doses both to patient and staff. COMPUTER MODELING AND SIMULATIONS In the last years, the use of realistic computational phantoms together with Monte Carlo (MC) methods has been increased, specifically in dose assessment in CT(83). Computational simulations can be more accurate than measurements, and allow for more detailed studies, which are difficult to implement in experiments. Computational simulations and modeling of CTF can function as a complementary tool to dosimetric measurements in body extremities or eye lens, using TLDs or other types of detectors for their capability in predicting radiation dose with specific scan protocols and realistic anatomical phantoms(84). The main advantage of these techniques is that they permit the simulation of different types of exposure scenarios, without having to resort to ‘real-life’ measurements. Moreover, direct dose measurements are generally performed using simplified physical phantoms that often can only lead to a mere rough estimation of the organ dose delivered to the patient. The quantity Hp(3) cannot be immediately quantified and MC provides a means to determine dose conversion coefficients. Several studies in the field of the X-ray CT were performed using MC methods. In particular, CT equipment has been successfully modeled by means of several state-of-the-art MC codes(85). These have usually compared measurements performed in a normal CTDI phantom and MC simulations of the same setup. One of the biggest challenges in modeling CT equipment relates to the fact that most MC codes are ‘static’ making the simulation of the moving radiation sources, as it occurs in CT, a challenge for the simulations. Some works(86) simulate the continuous movement of the CT scanners, by modifying the source code in order to make it suitable for continuous source movement. However, modifying the source code for some MC tools (as for example MCNP) is not a trivial task, since they function as a ‘black box’ programs and thus serious modifications are, if not impossible, very difficult to achieve. Another study(87) uses a different approach, and the continuous X-ray source movement is well modeled by averaging out several discrete positions (at least 16). Using this method, it is possible to achieve an agreement between CTDI100 measured and simulated values, with deviations of ~5%. Finally, one study proposes the use of 4D MC (the 4th dimension being time), to assess the dose in real time for high-resolution scenarios(84). As per the author's knowledge, there is very scarce work done so far on modeling specific interventional CTF procedures. One study(88) was aimed at studying the dose distribution in a hand phantom during interventional procedures. One main result of this study was that the hand regions which are not directly exposed to the primary X-ray beam receive only a few percentage of the total dose with respect to the directly exposed ones. Nevertheless, a dose monitoring of the medical staff who receive only scatter radiation is necessary, since in a real-time CT fluoroscopy procedure the long exposure time can represent a serious hazard. The utility of MC models to sketch out protocols needs to be supported more rigorously. Particularly, the right protocols to be used in each CTF procedure (i.e. pulmonary CTF-guided biopsy or fluoroscopy coronary angiography), where different parameters, as the patient shape and size, tube current, beam collimation and X-ray energy spectrum are considered, can be easily included in MC models. Furthermore, another MC study focused on CT fluoroscopic procedures and absorbed dose to patients, found that for an adult, the peak skin dose can be 37% higher than that estimated with a standard measurement phantom. The results also show that the energy imparted to a phantom is mainly influenced by phantom size and is nearly independent of phantom position (within 3%) and shape (up to 5% variation)(89). Finally the MC-GPU tool, which is a GPU-accelerated X-ray transport simulation code that can generate clinically realistic radiographic projection images and CT scans of the human anatomy, using cross-section data from PENELOPE 2006, was recently developed by the US Food and Drug Agency for clinical use(90). CONCLUSIONS The presented review intended to summarize the published results of the dosimetric and radiation protection problems arising during the application of CTF-guided interventions. Nearly all studies included in the review agree with the statement that the use of the CTF system allows rapid image reconstruction and has the capability to provide image corrections of the direction and depth of the guiding needles for more and more types of non-vascular and therapeutic interventions. However, the popularity of broader exploitation of CTF interventions is limited by the concern regarding the potential exposure of both staff and patients from direct skin exposures, as well as, from scattered radiation. There is a general consensus in the literature about the need for further work in optimization of radiological protection during CTF-guided procedures and the harmonization of the exposure patterns, verified under the clinical conditions, or proved on phantoms. Recently published results of higher eye lens sensitivity to ionizing radiation suggest more attention to the eye lens protection and dosimetry. 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TI - A Review of Radiation Protection Requirements and Dose Estimation for Staff and Patients in CT Fluoroscopy
JF - Radiation Protection Dosimetry
DO - 10.1093/rpd/ncw231
DA - 2017-05-01
UR - https://www.deepdyve.com/lp/oxford-university-press/a-review-of-radiation-protection-requirements-and-dose-estimation-for-JKyx0bWmax
SP - 518
VL - 174
IS - 4
DP - DeepDyve
ER -