Patient radiation dose from x-ray guided endovascular aneurysm repair: a Monte Carlo approach using voxel phantoms and detailed exposure information

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.

Potential risks of cardiovascular and cerebrovascular disease and cancer due to cumulative doses received from diagnostic CT scans?

“…Reports of high doses from interventional procedures on adults include endovascular aortic aneurysm repair (EVAR), a life-saving procedure. Doses reported for EVAR include median cumulative doses to organs in the trunk of 190-270 mGy [35], and median heart doses of 84 mGy with some cases reaching several 100 mGy [36]. The body CT scans received by a proportion of patients in this study are likely to either precede or be ancillary to interventional procedures and the summation of doses from the two types of procedure could result in some patients receiving doses above 500 mGy.…”

Through the Smoke Screen Clearly

“…The planning and completion of endovascular AAA repair (the predominant mode of repair in the United States) ranges from 47 to 74 mSv, depending on the complexity of the procedure. 4 This range is from 7 to 11× the annual radiation dose of US citizens (6.7 mSv), and the radiation burden increases further if computed tomography scans are used for surveillance. There is also radiation scatter from fluoroscopy, which has been demonstrated by studies of clinicians performing endovascular AAA repair, leading to many organs being vulnerable to radiation exposure and DNA damage.…”

Neutron Radiobiology and Dosimetry

“…Such in vitro studies could be conducted more efficiently, but may require a modified exposure profile, perhaps guided by computational studies, to reflect the actual exposure the specific organ would receive after the neutron component has interacted with other tissues surrounding the organ. Computational human phantoms, created by the National Cancer Institute (NCI; Bethesda, MD), can be used to estimate external exposures, organ depth distributions and dose estimation (85)(86)(87). Perhaps this technology can be adapted to help with neutron dosimetry, and researchers can learn from the valuable contributions of the radiotherapy community.…”