Abstract
Endovascular aneurysm repair (EVAR) is a well-established minimally invasive technique that relies on x-ray guidance to introduce a stent through the femoral artery and manipulate it into place. The aim of this study was to estimate patient organ and effective doses from EVAR procedures using anatomically realistic computational phantoms and detailed exposure information from radiation dose structured reports (RDSR). Methods: Lookup tables of conversion factors relating kerma area product (PKA) to organ doses for 49 different beam angles were produced using Monte Carlo simulations (MCNPX2.7) with International Commission on Radiological Protection (ICRP) adult male and female voxel phantoms for EVAR procedures of varying complexity (infra-renal, fenestrated/branched and thoracic EVAR). Beam angle specific correction factors were calculated to adjust doses according to x-ray energy. A MATLAB function was written to find the appropriate conversion factor in the lookup table for each exposure described in the RDSR, perform energy corrections and multiply by the respective exposure PKA. Using this approach, organ doses were estimated for 183 EVAR procedures in which RDSRs were available. A number of simplified dose estimation methodologies were also investigated for situations in which RDSR data are not available. Results: Mean estimated bone marrow doses were 57 (range: 2–247), 86 (2–328) and 54 (8–250) mGy for infra-renal, fenestrated/branched and thoracic EVAR, respectively. Respective effective doses were 27 (1–208), 54 (1–180) and 37 (5–167) mSv. Dose estimates using non-individualised, average conversion factors, along with those produced using the alternative Monte Carlo code PCXMC, yielded reasonably similar results overall, though variation for individual procedures could exceed 100% for some organs. In conclusion, radiation doses from x-ray guided endovascular aneurysm repairs are potentially high, though this must be placed in the context of the life sparing nature and high success rate for this procedure.
Highlights
Aortic aneurysms occur when a section of the blood vessel wall weakens, allowing a balloon-like cri pt bulge to develop
We used the reference adult male and female voxel phantoms published by the International Commission on Radiological Protection (ICRP) [19]
This resulted in Monte Carlo (MC) simulation statistical uncertainties of well below 5% for all in-field and beam bordering organs considered in this study and for all organs making a meaningful contribution to effective dose
Summary
Aortic aneurysms occur when a section of the blood vessel wall weakens, allowing a balloon-like cri pt bulge to develop. The procedure relies on the use of x-ray guidance to introduce and manipulate the stent graft within the aorta. As experience with this technique has increased, so has the complexity of repairs performed, some involving the use of multiple stent components during procedures lasting an several hours. This has recently focused attention on the possible deleterious effects of the consequent radiation exposure, including studies that have suggested an increased risk of malignancy in patients after EVAR, but this evidence is by no means conclusive [2, 3]
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