Abstract No. 160 MR Susceptibility-Weighted Imaging During Transurethral Prostate Sono-Ablation Procedures for Guidance of Device Placement to Counter Effect of Intra-Prostatic Calcifications

Men seeking MRI-guided transurethral ultrasound ablation (TULSA) for treatment of prostate cancer (PCa) are screened calcifications. Large calcifications can block (US) and cause inadequate heating. Smaller (≤3 mm) be accommodated by aligning the applicator (UA) with between transducer elements. We compare calcification detection size measurement using susceptibility-weighted MRI (SWI) vs. computed tomography (CT). also assess impact on coverage benchmarked against a previously published pivotal trial. Pre-TULSA screening (calcs) was performed CT 17 men. The mean (range) slice thickness 1.6 (0.6-5.0) mm. When relevant calcs were detected, intraprocedural SWI (1.0-mm slices) used to guide positioning UA elements respect calcs. Calcification in-plane through-plane diameters measured SWI, their assessed MR thermometry. Maximum temperature thermal dose maps from thermometry segmented in 90-degree quadrants across active elements, presence based magnitude phase images. 25 prostatic identified All visible SWI. In 4 men, images differentiate iron. Mean diameter 3.8 (1.4-10.4) mm 4.0 (2.2-10.8) larger median 22% at least one dimension all men 42/50 measurements overall. With SWI-guided placement 9 (IQR) proportion target volume reaching boiling (2-8.0) % 3.0 (0-7.0) sectors without Adequate achieved calcs: 98 (93-100) vs (95-100) %. trial 115 patients, which did not have placement, 93% (90-98%) reached adequate compared (93-100)% overall 6 (1-9)% had approaching 0 (0-5) Intraprocedural detected CT-identified calcifications, tending overestimate but guiding effective device positioning. remains gold standard pre-TULSA screening, further studies warranted optimize protocols, correlate predict coverage.