Data and methods to assess occupational exposure to personnel involved in cardiac catheterization procedures

ARTICLE IN PRESS Physica Medica ■■ (2016) ■■–■■

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Original Paper

Data and methods to assess occupational exposure to personnel involved in cardiac catheterization procedures Kostas Perisinakis a,b,*,1, Georgia Solomou a,1, John Stratakis a,1, John Damilakis a,b,1 a b

Department of Medical Physics, Medical School, University of Crete, P.O. Box 2208, Heraklion 71003, Crete, Greece Department of Medical Physics, University Hospital of Heraklion, P.O. Box 1352, Heraklion 71110, Crete, Greece

A R T I C L E

I N F O

Article history: Received 12 October 2015 Received in revised form 1 February 2016 Accepted 18 February 2016 Available online Keywords: Occupational exposure Cardiac catheterization Effective dose Eye-lens equivalent dose

A B S T R A C T

Purpose: To provide normalized scatter exposure data and methods for reliable estimation of cumulative effective dose and eye-lens equivalent dose to personnel involved in fluoroscopically guided cardiac catheterization (FGCC) procedures. Methods: An anthropomorphic phantom was placed supine on the table of a modern digital C-arm angiographic system and 17 different fluoroscopic projections commonly employed during FGCC procedures were represented. Scatter exposure rates at the waist and eye level were measured for varying exposure parameters and position in the operating room. The effect of beam field size, patient size, use of radioprotective garments and small variations in projection angulation and table height on scatter radiation was investigated. Results: Apart from the position and use of radio-protective garments, radiation burden to operators during fluoroscopic guidance was found to remarkably depend beam field size (>45% reduction if a 10 × 10 cm2 instead of 15 × 15 cm2 fluoroscopy beam is used) and patient size (>25% increased scatter for obese patients). In contrast, the variation of measured scatter exposure from a given projection was found to be <10% when the source to skin distance was altered by ±10 cm or beam angulation of a specific projection was altered by ±10°. Conclusion: Presented scatter exposure data charts and methods allow for prospective and retrospective estimation of effective dose and eye-lens equivalent dose to personnel involved in any FGCC procedure. Projection specific maps of scatter exposure produced may enhance familiarization of involved medical staff to good radiation protection practice and optimization of working habits in the cardiac catheterization lab. © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Introduction Fluoroscopically guided cardiac catheterization (FGCC) procedures have revolutionized the management of patients with cardiovascular diseases. Being of minimal invasiveness compared to surgery, (a) diagnostic coronary catheterizations (DC) and percutaneous coronary interventions (PCI) to diagnose and treat coronary artery stenosis or structural heart disease, (b) cardiac catheter ablations (CA) to destroy arrhythmiogenic foci and (c) cardiac resynchronization therapeutic (CRT) procedures to treat arrhythmias through pacemaker or intracardial defibrillator implantation,

* Corresponding author. Medical Physics Department, Faculty of Medicine, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece. Tel.: +30 2810 392564; fax: +30 2810 394933. E-mail address: [email protected] (K. Perisinakis). 1 These authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

have considerably decreased patient morbidity and mortality [1,2]. The remarkable recent advances in catheter and x-ray imaging technology have boosted the frequency of standard FGCC and provoked the introduction of novel procedures of increasing complexity. The high number of FGCC procedures performed annually over the last two decades has been accompanied with an ever increasing concern regarding the hazards associated to radiation exposure to the exposed medical and paramedical personnel involved [2–4]. Cardiac FGCC procedures require prolonged fluoroscopic guidance, which may occasionally exceed 1 h, while operators are situated in proximity to the exposed patient, thus subjected to scatter exposure. Therefore, FGCC operators who have been practicing for a long period of time may be subjected to radiation hazards that should not be disregarded [5,6]. The International Commission on Radiological Protection (ICRP) has identified FGCC procedures as an area of medicine where the control of occupational exposure is of particular importance [7].) The current framework of radiological protection of occupationally exposed medical workers was described in ICRP 2007 recommendations wherein yearly limits of 20 mSv for cumu-

http://dx.doi.org/10.1016/j.ejmp.2016.02.006 1120-1797/© 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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Table 1 The fluoroscopic projections investigated. Projectiona

Abbreviation

Posterior-anterior Posterior-anterior/caudal 30° Posterior-anterior/cranial 30° Right anterior oblique 30° Left anterior oblique 30° Left anterior oblique 45° Right anterior oblique 45° Left lateral Right lateral Left anterior oblique 40°/caudal 25° Left anterior oblique 40°/cranial 25° Right anterior oblique 40°/caudal 25° Right anterior oblique 40°/cranial 25° Left anterior oblique 20°/caudal 20° Left anterior oblique 20°/cranial 20° Right anterior oblique 20°/caudal 20° Right anterior oblique 20°/cranial 20°

PA PA/CAU30 PA/CRA30 RAO30 LAO30 LAO45 RAO45 LLAT RLAT LAO40/CAU25 LAO40/CRA25 RAO40/CAU25 RAO40/CRA25 LAO20/CAU20 LAO20/CRA20 RAO20/CAU20 RAO20/CRA20

a All projections were centered to the simulated heart of the phantom and naming of right/left and cranial/caudal projections is defined by the position of the detector with respect to the axis vertical to the table, whereas PA corresponds to the postero-anterior projection with image intensifier above patient thorax.

Figure 1. Scatter exposure data acquisition arrangement.

lative effective dose and 150 mSv for eye-lens equivalent dose were defined [8]. In the light of latest scientific evidence supporting a higher eye-lens radiosensitivity than previously considered, the recommended limit for cumulative eye-lens equivalent dose was recently revised to 20 mSv per year [9]. Apparently, reliable estimates of the yearly cumulative effective and eye lens doses are required to optimize working practices and define maximum workloads of occupationally exposed medical personnel involved in FGCC procedures. Occupational exposure from FGCC procedures is influenced by many factors such as (a) exposure parameters (operating kV and mA, inherent and added filtration of the X-ray beam, field size, time of fluoroscopy and number of frames in cine acquisitions, (b) exposure geometry (projection of X-ray beam, position of the occupationally exposed individual in the operating room), (c) use of radioprotective garments, glasses and barriers and (d) patient size [10–12]. The motivation of the current study was originated by the insufficiency of published scatter radiation exposure data required for the estimation of effective dose and eye-lens equivalent dose to occupationally exposed medical personnel involved in modern FGCC procedures. The aim of the present study was to provide a complete set of data and methods that could allow for a simple and reliable assessment of cumulative effective and eye lens equivalent dose to any medical staff member involved in a sequence of different FGCC procedures. Methods Patient exposure simulation A floor-mounted digital C-arm angiographic system Siemens Axiom Artis (Siemens, Enlargen, Germany) was used. Equipped with a 38 cm circular image intensifier, this unit employs automatic exposure control to concurrently adapt x-ray tube current and voltage. The unit had an inherent total beam filtration of 5 mm Al with additional filters of 0.0–0.9 mm Cu selected automatically according to procedural needs. A Rando anthropomorphic phantom (Alderson Research Labs, Inc., USA) was placed supine on the table of the fluoroscopic unit to represent the exposed patient, as shown in Fig. 1. Made of soft, lung and bone tissue-equivalent materials to closely

simulate the internal human anatomy, this phantom represents an average adult individual 1.74 in height and 74.6 kg in weight with a thorax perimeter of 91 cm. The focus to entrance skin surface distance for the postero-anterior projection was 67 cm, the focus to image intensifier distance was 110 cm and the beam size at the entrance skin surface was set to 15 cm × 15 cm. The C-arm was appropriately moved to represent successively 11 different fluoroscopic projections commonly involved in FGCC procedures. These projections are shown in Table 1. To represent the worst case scenario, all radioprotective devices such as table mountable shields and ceiling suspended protective barriers had been removed prior to exposure data acquisition. Occupational exposure data charts Exposure rates were measured at specific locations around the patient table over a 50 cm × 50 cm grid to cover all possible positions of the medical stuff involved in FGCC procedures. Spatial coordinates of each point of the grid were set with respect to the vertical axis passing through the isocenter of the system used. For each projection and position in the operating room, exposure data were obtained for all combinations of three different tube voltage values i.e. 60, 70 and 81 kV and three different total filtrations of the x-ray tube i.e. 5, 8 and 11 mm Al. These filtrations values were achieved with added filters of 0.0, 0.1 and 0.2 mm Cu, correspondingly. All exposures were performed in service mode where automatic exposure control was deactivated and exposure parameters were set manually. Scatter exposure rates in μSv/h were measured at operator’s waist and eye level i.e. 110 and 160 cm from the floor, correspondingly, using a Victoreen 451P-DE-SI-RYR (Fluke Biomedical, Cleveland, OH) and a Thermo 2120S (Thermo Fisher Scientific, Waltham, MA) ion chamber survey meters, appropriately mounted on a movable serum holder (Fig. 1). Survey meters were appropriately calibrated by the manufacturer to provide ambient dose equivalent H*(10) exposure rates in μSv/h [13]. A portable kerma area product (KAP) meter (KermaX-plus DDP, IBA Dosimetry GmbH, Schwartzenbruck, Germany) was mounted on the x-ray tube to record the KAP rate for any preset combination of tube voltage and beam filtration. Spatial 2-d maps of exposure rate were derived for all projections shown in Table 1, taking into account the symmetry between specific projections e.g. the map for RAO45 was considered to be the mirrored LAO45 map along patient axis. Measured scatter exposure rates from a specific fluoroscopic projection

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were divided with the corresponding KAP rate to produce normalized scatter exposure data. Investigation on factors affecting measured scatter exposure Scatter exposure data at various positions in the FGCC operating room from PA, RAO and LAT projections were also obtained for 10 × 10, and 12.5 × 12.5 and 17.5 × 17.5 cm2 fluoroscopy beam field size at entrance skin surface, to study the effect of fluoroscopic beam field size on the measured exposure rate. Regression analysis was employed to derive an equation providing a correction factor for any beam field size at entrance skin surface different than 15 × 15 cm2. To study the effect of patient body size on occupational exposure, scatter exposure data at various positions in the FGCC operating room from PA, RAO and LAT projections were indicatively obtained for phantoms of increased size. The Rando phantom thorax size was modified using bolus material. Bolus is made of a homogeneous, tissue equivalent gel with a density of 1.03 g/cm3 (CIVCO Medical Solutions, Kalona, IA). The bolus material is formed in malleable rectangular sheets of 2 cm thickness and can be cut to any shape with scissors. Regression analysis was employed to derive an equation providing the correction factor applicable for the specific patient size. To study the effect of x-ray source to patient skin distance on occupational exposure, scatter exposure data were also obtained changing table height by ±10 cm, i.e. changing focus to skin distance from 57 to 77 cm keeping the focus to image intensifier distance at 110 cm. It is noted that patient skin to x-ray source distance variation occurring in clinical practice between different laboratories and fluoroscopy systems is expected to be within the above range. To study the effect of varying beam angulation on measured scatter exposure rate, exposure data at selected positions in the FGCC operating room from PA and RAO projections were indicatively obtained for altered beam angulations by ± 10° in either craniocaudal or/and latero-lateral axis. The effect of using radioprotective garments The use of protective lead apron-thyroid collar and lead glasses may reduce the effective dose and eye-lens equivalent dose, correspondingly, received by occupationally exposed workers. Monte Carlo simulation was employed to determine the exposure reduction factor achieved by using radioprotective garments. Reduction factors were derived for different values of operating tube voltage and protective garment lead equivalence and compared to corresponding data extracted from a previously published report on radiological shielding calculations [14]. Effective dose and eye-lens equivalent dose estimation Effective dose (E) and eye lens equivalent dose (ELD) to an operator facing the patient and standing at a specific position (p) in the FGCC operating theatre when a specific fluoroscopic projection is used may be estimated using the following formulas

E proj = NE proj ( p, kV , filtration) × KAPproj × CF field size × CFpatient size × CFPb apron

(1)

ELDproj = NELDproj ( p, kV , filtration) × KAPproj × CF field size × CFpatient size × CFPb goggles

(2)

where NEproj and NELDproj are the dose equivalent exposure rates in μSv/h at the waist and eye lens level, correspondingly, normalized

3

to KAP of the specific fluoroscopic projection produced for the specific tube voltage and filtration, KAPproj is the cumulative KAP recorded for the specific projection, CFfield size is the correction factor for the specific beam field size at entrance skin surface, CFpatient size is the correction factor for the specific patient size and CFPb apron and CFPb goggles are the correction factors for the specific lead apron and lead glasses worn by the operator, correspondingly. For the range of x-ray beam quality of fluoroscopic beams employed in cardiac catheterization procedures, measured H*(10) at the waist level and eye level was conservatively assumed equal to the effective dose and the eye-lens dose equivalent, respectively. The total E and ELD from a specific FGCC procedure for which n different projections are involved, may be derived by summing up the contributions of each projection:

E = ∑ proj =1 E proj

(3)

ELD = ∑ proj =1 ELDproj

(4)

n

n

It is noted that above formulation refers to antero-posterior orientation of the worker with respect to patient body i.e. the scatter radiation is incident on the front of the body. Results Projection-specific scatter exposure per KAP unit at specific locations inside the operating room with respect to the X-ray beam entrance skin surface of the patient are presented for varying exposure parameters in Tables E1–E34 (Tables E1–E17 for the waist and E18–34 for eye-lens level) provided as Online Supplemental Material. Scatter exposure maps around the treated patient investigated projections are indicatively presented in Fig. 2 for fluoroscopic imaging at 75 kVp tube voltage, 8 mm Al total filtration and 15 × 15 cm2 beam field. The variation of measured scatter exposure rate at any location in the operating room from a given projection was found to be minor when the source to skin distance was altered by few cm. Differences in measured exposure rates <10% were observed for changes in the source to patient skin distance of ±10 cm. Low variation (i.e. <8%) in measured scatter exposure rate was also observed when beam angulation of a specific projection was altered by ±10°. In contrast, scatter exposure from a given projection was found to significantly depend on the skin entrance beam field size as indicatively shown in Fig. 3 for the PA projection. Similar behavior was found for all other projections for the fluoroscopy beam field size variation range commonly occurring in clinical practice i.e. from 10 × 10 to 20 × 20 cm2 since deviations from the regression line shown in Fig. 2 were up to 10%. The regression line shown in Fig. 2 may be used to derive the correction factor CFfield size applicable to Eqs. (1) and (2), when a different than 15 × 15 cm2 skin entrance beam field size is used. Scatter exposure rate from a given projection was found to significantly depend on patient size as indicatively shown in Fig. 4 for the PA projection. Similar behavior was found for all other projections with deviations being less than 6%. The regression line shown in Fig. 3 may be used to derive the correction factor CFpatient size applicable to Eqs. (1) and (2), when the patient has a chest circumference different than 91 cm. Occupational exposure reduction factors achieved by radioprotective clothing shown in Table 2 were found to deviate by <4% from values extracted using previously published data [14]. Data shown may be used to derive the correction factors CFPb apron and CFPb glasses applicable to Eqs. (1) and (2), when the operator wears a lead apron-thyroid collar or/and lead glasses with lateral protection appropriately worn close to cheeks.

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LLAT

LAO40CRA25

LAO45

LAO40CAU25

LAO20CRA20

LAO30

LAO20CAU20

APCRA30

PA

APCAU30

RAO20CRA20

RAO30

RAO20CAU20

RAO40CRA25

RAO45

RAO40CAU25

RLAT

Figure 2. Maps of scatter exposure rate at the waist level from fluoroscopic projections commonly used in FGCC procedures. Areas of high and low exposure are indicated in red and blue, correspondingly. Data shown correspond to an x-ray tube with a total filter of 8 mm Al operating at 75 kVp. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Discussion In the current study, 2d-spatial maps of scatter exposure rate were produced to cover any possible position of physicians and other personnel in the cardiac catheterization lab and any fluoroscopic projection commonly employed during FGCC procedures. Scatter exposure data charts and methods provided here may be used to estimate the cumulative effective dose and eye-lens equivalent dose to an operator involved in a FGCC procedure. Data required for this estimation comprise (a) the position of the worker in the operating room with respect to patient thorax, (b) the exposure parameters per projection i.e. tube voltage (kV), total filtration of x-ray beam (mm Al), fluoroscopy beam field size, and total KAP per projection, (c) patient thorax size and (d) the Pb-equivalent thickness (mm Pb) of protective garment employed. It is noted that, modern fluoroscopy equipment installed in most cardiac catheterization labs may continuously record exposure parameters and provide a report of the procedure at the end. All above exposure parameters re-

quired for the radiation burden estimation may be extracted from this report. The use of presented data and methods for the estimation of occupational exposure to an operator involved in a FGCC procedure is illustrated in the following example. An operating physician was standing at the right side of the patient trunk 50 cm along patient axis and 50 cm along lateral axis with respect to the center of fluoroscopy beam during a PCI procedure requiring prolonged fluoroscopic guidance along PA, LAO40/CRA25 and RAO30 projections of heart area. Recorded exposure parameters and data regarding beam field size, patient size and radioprotective garments are shown in Table 3. Scatter exposure rates at the position of the physician and correction factors for the specific beam field size, patient size and use of radioprotective garments determined using current data are also presented in Table 3, along with projection-specific cumulative effective and eye-lens equivalent dose estimates produced through Eqs. (1)–(4). It is noted that when tube voltage is different from 60, 70 or 81 kV or/and total beam filtration different from 5, 8 or 11 mm Al, interpolation may be employed to use data pro-

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Y=0.156 + 0.00382 X (R=0.999) 1.2

Dose estimates

Effective dose (μSv)

Extracted/calculated dataa

1

μSv/cGy m waist level

353 831 591

Field size (cm2)

12 × 12 13 × 13 12 × 12

Projection

0.8

2.2 (313)b 5.8 (386)b 2.0 (135)b Total = 10 (834)b

1.0

Input data

0.4 150

200

250

300

4

100

0.27 0.53 0.53

0.6 CFgoggles (%)

Correction factor for field size

1.4

0.39 (142)c 0.48 (90)c 0.10 (19)c Total = 1.0 (251)c

Eye-lens equivalent dose (μSv)

5

105

110

115

120

Figure 4. The effect of patient size, expressed as thorax circumference, on the measured scatter exposure rate.

Table 2 X-ray beam transmission factors (%) of commonly used lead radioprotective garments.a mm Pbb kVp

0.25

0.35

0.50

0.75

1.00

50 60 70 80 90 100

0.513 1.90 3.28 6.20 9.00 11.1

0.133 0.320 1.49 3.30 4.98 6.76

0.023 0.230 0.534 1.15 2.47 3.66

0.002 0.014 0.113 0.155 0.380 2.10

<0.001 0.002 0.028 0.290 0.430 1.10

a b

Data were derived for a total beam filtration of 5 mm Al. Equivalent thickness of Pb in mm.

1.225 1.225 1.225

CFpatient size CFfield size

3

148 178 75

1

μSv/cGy m eye level

2

2

1.125 1.125 1.125

c

100

Patient thorax circumference (cm)

Extracted/calculated data from 1Tables E1–E34 of Online Supplemental Material, 2Fig. 3, 3Fig. 4 and 4Table 2. Without lead apron-collar. Without lead goggles.

95

a

90

b

1.00

PA 65 8 1.108 LAO40/CRA25 70 8 0.516 RAO30 70 8 0.287 Operating physician’s position: X = 0 m, Y = 0.5 m Patient thorax circumference = 100 cm Lead apron 0.35 mm Pb Lead goggles 0.5 mm Pb

1.05

KAP (cGy·m2)

1.10

Filtration (mm Al)

1.15

kVp

Waist level

1.20

2

Correction factor for patient size

1.25

Table 3 Example of effective dose and eye lens equivalent dose estimation for an operating physician during a FGCC procedure.

Eye level

1.30

Waist

vided in Tables E1–E34. Also, tube voltage and beam filtration may continuously be adjusted during FGCC procedures performed with modern systems. However, for a specific projection of fluoroscopic guidance tube voltage and beam filtration remains practically unchanged. In any case, the mean tube voltage and beam filtration for each fluoroscopic projection should be used in the calculations. Also if the size of patient is different than Rando

Eye

4

Figure 3. The effect of fluoroscopy beam field size at entrance skin surface on the measured scatter exposure rate.

0.71 0.80 0.71

CFapron (%)

Field size (cm )

0.70 1.49 1.49

2

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phantom a correction factor should be applied as illustrated in the example. The number of similar procedures required for exceeding one of the 20 mSv annual limits for effective dose and eyelens equivalent dose is 2000, which may be considered as the maximum permissible workload regarding the specific procedure. It is noted that, the corresponding maximum workload if the operating physician did not use any radioprotective garments would be only 24. Despite the new reduced eye lens equivalent dose limit was considered in above estimations, maximum workload was found to be determined by the effective dose rather than eye-lens equivalent dose limit. It is noted, however, that the latter finding may be not valid when operators use lead glasses without lateral protection or/and lead glass that do not fit on the face. If a less optimistic goggles reduction factor of 10% was assumed, maximum workload would have been determined by eye lens equivalent dose limit. Despite the many studies and published results on occupational effective dose and eye lens dose estimates from Monte Carlo data or from the readings of personal dosimeters worn by operators [10–12,15–17], only few studies may be found in literature on normalized scatter exposure data for fluoroscopic guidance during FGCC procedures performed in modern C-arm units. Theocharopoulos et al. [18] provided normalized exposure data for only a specific FGCC electrophysiology procedure involving definite fractions of PA, LAO40/ CRA25 and RAO25 fluoroscopic guidance. Besides, Baptista et al. [19] provided projection-specific normalized exposure data but only for PA, LLAT and RAO30 fluoroscopic projections and for a specific combination of ceiling suspended radioprotective barrier and radioprotective garments. Also, latter data referred to only 4 standard positions in the cardiac catheterization lab, which were not accurately defined relative to patient table. Apparently, data provided in both above studies cannot be applied for any kind of FGCC procedure, since considerably different fluoroscopic projections may occur in clinical practice. In both the above studies also, the effects of varying exposure parameters, beam field size and patient size on occupational exposure were not investigated. In comparison to corresponding data reported by Theocharopoulos et al. for the specific FGCC electrophysiology procedure considered in that study, effective dose estimated using current data for an operating physician standing next to the patient table wearing 0.35 or 0.5 mm Pb lead apron was found to differ by less than 17% and 3%, respectively, despite the deviations in position definition between the two studies. Besides, Stratakis et al. [20] provided data on normalized air-kerma distributions from commonly used projections in fluoroscopy guided percutaneous transhepatic biliary procedures. Reported scatter exposure rates for AP, LAO and RAO projections at the position of the operator differ by less than 15% compared to corresponding results estimated using data of the present study. According to ICRP recommendations [21] ‘Pregnant medical radiation workers may work in a radiation environment as long as there is reasonable assurance that the fetal dose can be kept below 1 mSv during the course of pregnancy’. The 2-d maps of exposure at the waist level, provided here, may also be used for the estimation of cumulative radiation dose to the conceptus of a pregnant operator involved in FGCC procedures. It is noted that the radiation exposure to the abdominal surface of a pregnant operator obtained from Eqs. (1) and (3) shall be converted to conceptus dose using previously reported conversion factors [22]. Moreover, scatter exposure charts provided here may aid optimization of working practices of pregnant operators and assessing maximum permissible workload to ensure a cumulative conceptus dose below 1 mSv. The most efficient means to suppress radiation exposure of operators involved in FGCC procedures is the use of radioprotective garments. Transmission factors shown in Table 2 are comparable with previously published data [23] and confirm that wearing common lead apron-collar and lead goggles may reduce effective dose and eye lens dose to an operator involved in FGCC procedures by more

than 90%. It is noted, however, that transmission factors shown in Table 2 may deviate considerably from the dose reduction factor achieved through lead protection, especially for the eye lens if the operator employs lead glasses without lateral protection or/and worn leaving gaps between cheeks and goggles, which is the recommended practice for operators involved in FGCC procedures. Also, scatter exposure rate at any position around the patient was found to be significantly increased with fluoroscopy beam field size. Changing beam field size from 10 × 10 cm2 to 12.5 × 12.5 cm2 increased scatter exposure by more than 30%. Apparently, keeping fluoroscopy beam field size as low as reasonably achievable may allow for considerable reduction of scatter radiation exposure to medical personnel, which is accompanied with an also considerable reduction of patient radiation burden. Given that scatter exposure follows the inverse square law of distance from the scatterer, moving away from the patient during fluoroscopic guidance is another efficient method to significantly reduce occupational exposure during FGCC procedures. However, the close proximity of operating physician or/and other medical staff members to the patient during fluoroscopic guidance may be demanded by the procedural needs. Since scatter exposure strongly depends on the position around the table, especially for steep projections, positions associated with low levels of scatter exposure should be preferred if possible. Scatter exposure maps shown in Fig. 2 may aid training operators how to identify low exposure positions around the patient for the specific fluoroscopic projections employed. As a general rule for oblique projections, positions closer to image intensifier rather than x-ray tube should be preferred. Also, fluoroscopic guidance along steep oblique projections should be avoided or at least minimized, since they are involved with higher exposure parameters due to the increased volume of patient tissues to be penetrated and therefore produce higher scatter exposure. This is clearly shown in the example described in Table 3, where the main contribution to physician’s radiation burden comes from the LAO40/CRA25 projection despite PA projection is associated with two times higher KAP. In accordance to above reasoning, scatter exposure around the patient was found to be significantly increased with patient size. Operators involved in FGCC procedures performed in overweight patients should have increased alert regarding radiation protection and strictly adhere to basic radiation protection measures such as being ungenerous in the use of fluoroscopic guidance and using any available radioprotective garments or devices available. There are several uncertainties regarding absorbed radiation dose estimates for occupationally exposed workers in the cardiac catheterization lab derived using data and methods provided in this study. First, there is an uncertainty in the acquisition of scatter exposure data originating from the positioning error and recording inaccuracies of detectors. This uncertainty is guesstimated to be below 15%. Second, there might be angulation deviation between fluoroscopy projections used in clinical practice and these investigated here. Data were collected for 17 different projections to ensure that any projection selected in clinical practice closely resembles to one of those investigated here. It is also noted that the scatter exposure data uncertainty introduced by variations in beam angulation ±10°or in table height by ±10 cm was found to be minor in convergence to previously reported data [24]. Third, the detector size of the fluoroscopy suit used in a cardiac catheterization lab may be different than the detector size of the system employed in the present study. However, associated inaccuracies are expected to be minor. Also, measuring instruments employed were not calibrated for different pulse rates of pulsed fluoroscopy mode. In the current study, scatter exposure data were obtained for fluoroscopic guidance in the chest area. During a FGCC procedure, however, a brief fluoroscopic guidance is occasionally spent to guide the catheter from the groin to the heart, but this is only a small fraction of the total fluoroscopy time [25]. Nevertheless, data provided here may be also used to approximate-

Please cite this article in press as: Kostas Perisinakis, Georgia Solomou, John Stratakis, John Damilakis, Data and methods to assess occupational exposure to personnel involved in cardiac catheterization procedures, Physica Medica (2016), doi: 10.1016/j.ejmp.2016.02.006

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ly estimate occupational radiation burden from fluoroscopic guidance in the pelvic/abdominal areas given that operator’s position is defined with respect to beam entrance skin surface. Finally, cumulative effective dose estimates for occupationally exposed medical staff derived using current data and methods are conservative. The operator’s body angulation was assumed antero-posterior with respect to patient body throughout the procedure which corresponds to the worst case scenario. For different operator’s body orientations, which may occur during a FGCC procedure, the resulting effective dose is expected to be less. Moreover, effective dose estimates for the occupationally exposed personnel rely on scatter exposure data measured at the waist level. Scatter exposure rate may vary from operator’s feet to head level but for the most frequently used projections, such as PA and oblique projections with moderate angulations, the higher value is expected to occur close to the waist level. In addition, current scatter exposure data were obtained for a fluoroscopy suit without any radioprotective table mountable shields or ceiling suspended barriers in order to represent the worst case scenario. However, this was a one-way approach since data acquisition for every type, geometry and combination of such radioprotective devices is practically not feasible. Conclusions Despite the main means to reduce occupational exposure during FGCC procedures is the use of radioprotective garments, appropriate selection of the position relative to patient thorax and orientation/ size of fluoroscopic beam may further moderate radiation burden to operators involved. Presented projection-specific scatter exposure data charts and methods may be used to derive reliable estimates of cumulative radiation burden to medical staff involved in any FGCC procedure either prospectively or retrospectively. Apart, from assessment of maximum workloads, provided data may contribute to familiarization of involved medical staff to good radiation protection practice and optimization of working habits in the cardiac catheterization lab. Acknowledgement This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ‘Education and Lifelong Learning’, ARISTIA #1628 (Research project: CONCERT). Appendix Supplementary material Supplementary data to this article can be found online at doi:10.1016/j.ejmp.2016.02.006. References [1] Agarwal S, Parashar A, Ellis SG, Heupler FA, Lau E, Tuzcu EM, et al. Measures to reduce radiation in a modern cardiac catheterization laboratory. Circ Cardiovasc Interv 2014;7:447–55. [2] Heidbuchel H, Wittkampf FHM, Vano E, Ernst S, Schilling R, Picano E, et al. Practical ways to reduce radiation dose for patients and staff during device implantations and electrophysiology procedures. Europace 2014;16:946–64.

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Please cite this article in press as: Kostas Perisinakis, Georgia Solomou, John Stratakis, John Damilakis, Data and methods to assess occupational exposure to personnel involved in cardiac catheterization procedures, Physica Medica (2016), doi: 10.1016/j.ejmp.2016.02.006