Real time patient dosimetry in
the cath lab: Can you see what
Charles E. Chambers, MD
Hemantha K. Koduri, MD
Heart and Vascular Institute, Penn State College of Medicine,
Charles E. Chambers, MD, Penn State Hershey Medical Center, 500
University Drive MCH047, Hershey, PA 17033.
Real time radiation dose monitoring in the cath lab may
provide immediate feedback for potential dose reduction
Radiation dose monitoring to predict potential tissue injury
utilizes equipment measured air Kerma at the interventional
reference point (IRP) with then calculated specific tissue
peak skin dose.
The role of the cath lab Quality Committee is not only to
assess individual high dose radiation cases but also to create
processes and assess new technologies to assure radiation
dose is best utilized in all cases.
Radiation safety is an important component of interventional cardiol-
ogy. This skill set is incorporated into the invasive cardiologist’s
required armamentarium of device knowledge combined with an
awareness of patient variables when performing highly complex cases.
Assessing the effectiveness of best practices for radiation safety
requires both in lab patient dose tracking as well as post-procedure fol-
low-up of high dose patient exposure. Ichimoto et al., in this issue of
CCI, address the potential for procedural radiation dose reduction
through a technique providing visual real time patient dosimetry for
operator radiation dose awareness .
All fluoroscopic equipment sold in the US since 2006 has been
required to display procedural dose. Fluoroscopy time, not impacted by
frame rate or high dose requirements of steep angulation, is not an
accurate measure of dose . True dose measures include: Total air
Kerma at the interventional reference point (IRP) (K
, Gy), and air
Kerma area product (P
, also referred to as cumulative
air Kerma, is the X-ray energy delivered to air at the IRP, which is
measured at a point in space 15 cm on the X-ray tube side of isocenter.
is used to assess the linear threshold potential for skin injury,
referred to as deterministic effects. P
, also referred to as dose area
product (DAP), is the product of air Kerma and X-ray field size. As this
impacts more than skin dose, it is more reflective of the linear non-
threshold probability based potential for genetic injury or cancer risk,
referred to as stochastic effects. Peak skin dose (PSD, Gy) is the maxi-
mum dose received by a focal area of skin directly correlating with the
probability and severity of deterministic effects. PSD is not measured
directly in the lab but is/can be calculated based upon dose rate, total
beam “on” time, and X-ray geometry details. When a significantly high
is identified, it is essential to initiate early post-procedure estima-
tion/calculation/validation of PSD with a qualified physicist .
Despite the reporting of procedure dose on the in-lab monitor, fur-
ther dose reduction may be achieved with immediate operator dosime-
ter feedback, as suggested by Ichimoto et al. in this current CCI study.
This retrospective study with small patient sample showed statistically
significant reduction in radiation dose (K
) and num-
ber of cine runs in PCI patients with a skin dose tracking system (DTS)
compared with PCI patients without DTS. This occurred despite no dif-
ference in fluoroscopic and procedural time between both the groups.
While not reducing dose for diagnostic cath, the benefit of a red light
to remind an operator of the basic concepts of dose reduction, “Time,
Distance, Shielding” through instantaneous feedback, may further
decrease patient dose for PCI. Though not addressed in this study,
patient dose reduction similarly benefits operator and staff. These
efforts support the multiple society papers emphasizing the need for
best practices in radiation safety [3,4].
All aspects of radiation safety are the responsibility of the Catheteri-
zation Laboratory Quality Committee, mandatory for PCI facilities. High
radiation dose cases should be reviewed by this committee, charged to
define a high dose case, often defined as a K
greater than 5–7Gyfor
committee review and >10 Gy for physicist involvement . Though
JCAHO has established 15 Gy as a sentinel event, case evaluation by
peer review is required to assess the multiple patient and procedural
variables to determine standard of care . Interventionalists realize that
predicting adverse events is difficult and case termination infrequently
possible based upon a single number on a monitor. This review process
should occur routinely in high dose cases, not just the rare potential
JACHO defined sentinel events. Establishing radiation safety as a quality
parameter in the cath lab reinforces the traditional teaching of ALARA (As
Low AS Reasonably Achievable). This concept emphasizes the importance
of dose reduction utilizing current techniques as well as exploring poten-
tial additional beneficial modalities, as that proposed by Ichimoto et al.
The potential benefits from real time dose monitoring to provide
immediate feedback for dose reduction during PCI are inherently
Catheter Cardiovasc Interv. 2018;91:723–724. wileyonlinelibrary.com/journal/ccd
2018 Wiley Periodicals, Inc.
Received: 8 February 2018
Accepted: 9 February 2018