Room: Track 1
Purpose: To report the results of a prospective imaging study of patients who underwent MARS low-dose-rate (LDR) prostate brachytherapy and imaged with an optimized fully balanced steady-state free precession (bSSFP) pulse sequence without using an endorectal coil (ERC).
Methods: 17 patients at a large cancer hospital were imaged on a 3T Prisma MRI scanner, and 1 patient from a community hospital was imaged on a 3T Siemens Skyra MRI scanner. All patients were implanted with radioactive seeds stranded with positive MRI-signal seed markers, and imaged with a fully bSSFP pulse sequence (CISS). Patients were imaged at moderate, high, and/or very high spatial resolution and with 1-3 signal averages (NEX) (Table 1). Multi-NEX acquisitions were accelerated by a factor of 2 to maintain a total scan time between 4-6 minutes. The k-space data of the accelerated acquisitions were reconstructed with an L1-ESPIRiT parallel imaging and compressed sensing (PICS) algorithm. The reconstructed k-space data were processed in the Siemens Image Calculation Environment. Three certified medical dosimetrists (CMDs) performed post-implant quality assessment (QA) using the MRIs without reference to post-implant computed tomography (CT).
Results: All 3 CMDs achieved near perfect precision and recall of the radioactive seeds in the post-implant MRIs (Table 2). Imaging at high spatial resolution was essential to visualize all of the implanted seed markers (Figure 1). Multi-NEX acquisitions enabled by PICS improved SNR over the single NEX acquisitions in a comparable total scan time (Figure 2). The first images acquired at CH were of high quality, enabling all of the implanted radioactive seeds to be identified (Figure 3).
Conclusion: High quality post-implant MRIs can be acquired with fully bSSFP and without an ERC for post-implant QA in MARS LDR prostate brachytherapy, potentially circumventing the need for CT in MARS post-implant QA.
Funding Support, Disclosures, and Conflict of Interest: J.W.S. is supported by a fellowship from the Pauline Altman-Goldstein Foundation. J.W.S. is also partially supported by a sponsored research grant from Siemens Healthineers. A portion of this study was supported by a Pilot Research Program Award from The University of Texas MD Anderson Cancer Center Support Grant.