Computational simulation of the predicted dosimetric impact of adjuvant yttrium-90 PET/CT-guided percutaneous ablation following radioembolization

Background: 90Y PET/CT post-radioembolization imaging has demonstrated that the distribution of 90Y in a tumor can be non-uniform. Using computational modeling, we predicted the dosimetric impact of post-treatment 90Y PET/CT-guided percutaneous ablation of the portions of a tumor receiving the lowest absorbed dose. A cohort of fourteen patients with non-resectable liver cancer previously treated using 90Y radioembolization were included in this retrospective study. Each patient exhibited potentially under-treated areas of tumor following treatment based on quantitative 90Y PET/CT. 90Y PET/CT was used to guide electrode placement for simulated adjuvant radiofrequency ablation in areas of tumor receiving the lowest dose. The finite element method was used to solve Penne’s bioheat transport equation, coupled with the Arrhenius thermal cell-death model to determine 3D thermal ablation zones. Tumor and unablated tumor absorbed-dose metrics (average dose, D50, D70, D90, V100) following ablation were compared, where D70 is the minimum dose to 70% of tumor and V100 is the fractional tumor volume receiving more than 100 Gy. Results: Compared to radioembolization alone, 90Y radioembolization with adjuvant ablation was associated with predicted increases in all tumor dose metrics evaluated. The mean average absorbed dose increased by 11.2 ± 6.9 Gy. Increases in D50, D70, and D90 were 11.0 ± 6.9 Gy, 13.3 ± 10.9 Gy, and 11.8 ± 10.8 Gy, respectively. The mean increase in V100 was 7.2 ± 4.2%. All changes were statistically significant (P \u3c 0.01). A negative correlation between pre-ablation tumor volume and D50, average dose, and V100 was identified (ρ \u3c − 0.5, P \u3c 0.05) suggesting that adjuvant radiofrequency ablation may be less beneficial to patients with large tumor burdens. Conclusions: This study has demonstrated that adjuvant 90Y PET/CT-guided radiofrequency ablation may improve tumor absorbed-dose metrics. These data may justify a prospective clinical trial to further evaluate this hybrid approach

Endovascular Repair of Thoracic Aortic Aneurysms

Degenerative aneurysms of the thoracic aorta are increasing in prevalence; open repair of descending thoracic aortic aneurysms is associated with high rates of morbidity and mortality. Repair of isolated descending thoracic aortic aneurysms using stent grafts was introduced in 1995, and in an anatomically suitable subgroup of patients with thoracic aortic aneurysm, repair with endovascular stent graft provides favorable outcomes, with decreased perioperative morbidity and mortality relative to open repair. The cornerstones of successful thoracic endovascular aneurysm repair are appropriate patient selection, thorough preprocedural planning, and cautious procedural execution, the elements of which are discussed here

Results of an American College of Radiology-Society of Interventional Radiology Membership Survey on Exclusive Contracts and the Attitudes of Interventional Radiologists.

PURPOSE: To assess the attitudes of interventional radiologists (IRs) and diagnostic radiologists (DRs) toward exclusive contracts and independently practicing IRs who may request privileges at a hospital where an exclusive contract exists with a different group of radiologists. MATERIALS AND METHODS: A total of 22,400 survey instruments were distributed to 4,490 IRs and 17,910 DRs in the United States. Statistical evaluation included multivariate ordinal logistic regression analysis with calculation of the odds ratios and forest plots. RESULTS: Completed surveys were received from 525 (11.69%) IRs and 401 (2.23%) DRs. Given the low response rate of DRs, data analysis was focused on IRs. Early-career IRs and those in outpatient practices had a more positive attitude toward independent IRs who requested admitting and/or procedural privileges. A supermajority of both IRs and DRs who responded to the survey agreed that the importance of IR to hospital and health system contracts will increase. CONCLUSIONS: This survey identified many interrelated and complex variables that significantly affected the attitudes of IRs in various practice settings toward independent IRs requesting hospital admitting and/or procedural privileges. It will benefit independent IRs seeking admitting privileges to better understand some of the factors that impact the potential willingness of the radiology groups and other IRs with exclusive hospital contracts to work toward mutually beneficial practice paradigms, especially as more clinically oriented IRs complete their training in the new, integrated residency programs