Surgeon Radiation Dose during Complex Endovascular Procedures
Melissa L Kirkwood, Jeffrey Guild, Gary Arbique, Jon A Anderson, R. James Valentine, Carlos Timaran
UT Southwestern Medical Center, Dallas, TX
Surgeon radiation dose during complex endovascular procedures (CEPs) has not been well studied. We sought to characterize radiation exposure to surgeons during CEPs based on procedure type, operator position, level of operator training, upper versus lower body exposure and the addition of protective shielding.
Optically stimulable, luminescent nanoDot (Landauer Inc) detectors were used to measure radiation dose prospectively to surgeons during CEPs. Nanodot dosimeters were placed outside the lead apron of the primary and assistant operator at both the left upper chest and left lower pelvis positions. For each case, procedure type, reference air kerma(RAK), kerma area product(KAP), the relative position of the operator, level of training of the fellow and presence or absence of external additional shielding devices were recorded. Three positions were assigned on the right hand side of the patient in decreasing relative proximity to the flat panel detector(FPD) (A,B,C respectively). Position A(main operator) was closest to the FPD. Position D was on the left side of the patient at the brachial access site. NanoDots were read using a Microstar ii medical dosimetry system(Landauer Inc) after every procedure. The nanoDot dosimetry system was calibrated for scattered radiation in an endovascular suite with a NIST traceable solid state radiation detector(Piranha T20, RTI). Comparative statistical analyses of nanodot dose levels between categories was performed using ANOVA with Tukey pairwise comparisons. Bonferroni correction was used for multiple comparisons.
There were 415 nanodot measurements with the following case distribution:16 TEVAR/EVAR,18 FEVARS (fenestrated endovascular aneurysm repairs),13 embolizations,41 lower extremity,10 fistulograms,13 viscerals. The mean operator dose for FEVARs was statistically higher than for other case types(p<.03), 15μSv at position A and 11μSv at position B. For all case types positions A(8.7+/ 2.7μSv) and D(14.4+/-7.8μSv) received statistically higher effective doses than B(3.9+/-2.7μSv)p< 0.001 or C(0mGy). However, the mean operator dose for position D was not statistically different from A. The addition of the lead skirt significantly decreased the lower body dose (33 +/- 3.4 μSv to 6.3 +/- 3.3μSv) but not the upper body dose(6.5+/-3.3μSv, to 5.7+/-2.2μSv). The use of ceiling mounted shielding did not affect nanodot dose. There was no difference in operator dose observed based on level of training when the fellow was in position A. KAP was the better predictor of operator radiation dose compared to RAK. The mean KAP for all cases was 330 Gycm2 and the regression coefficient for operator dose to KAP was 0.021+/-.003 μSv/Gycm2 for position A and 0.015+/-.003μSv/Gycm2 for B.
Surgeon radiation dose during CEPs depends on case type, operator position, and table skirt use; but not on the level of fellow training. Based on this data, the primary operator could perform approximately 12 FEVARs per week and have an annual dose <10mSv which would not exceed lifetime occupational dose limits during a 35 year career. Excluding FEVARs with the above case mix, the primary operator could perform roughly 40 CEPs/week and stay within regulatory limits. With practical case loads, operator doses are relatively low and unlikely to exceed occupational limits.
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