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TrueFISP for Single Sequence MR-Only Post-Implant Dosimetry of Prostate Brachytherapy

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J Sanders

J Sanders*, S Frank , A Venkatesan , T Bathala , J Szklaruk , P Blanchard , R Kudchadker , J Ma , UT MD Anderson Cancer Center, Houston, TX


MO-L-GePD-I-3 (Monday, July 31, 2017) 1:15 PM - 1:45 PM Room: Imaging ePoster Lounge

Purpose: To develop a single sequence protocol for magnetic resonance-based post-implant prostate brachytherapy dosimetry.

Methods: Twenty-two prostate cancer patients were included in this study. All studies were conducted on a Siemens 1.5T Aera MR scanner. An endorectal coil with a rigid two-channel design in combination with two 18-channel external pelvic arrays were used. Patients underwent prostate brachytherapy with radioactive seeds and positive MR-signal markers and were scanned on the same day. Each study consisted of a 3D FLASH sequence for T1-weighted imaging and a 3D SPACE sequence for T2-weighted imaging, which were optimized for visualization of the markers and the anatomical structures, respectively. In addition, a 3D trueFISP sequence (constructive interference in steady state, or CISS) was used to acquire images with combined T1 and T2 contrast. The acquisition parameters are shown in Table I.

Results: Representative T1 FLASH, T2 SPACE, and T1/T2 CISS images from a patient are shown in Figure 1. FLASH imaging delineated the markers as focal hyperintensities (arrows). However, intra- and extra-prostatic anatomical structures were not well defined. SPACE imaging demonstrated sufficient delineation of the anatomical structures, but produced no signal from the markers. In comparison, CISS imaging provided excellent delineation of both anatomical structures and markers in a single sequence. Furthermore, the CISS images exhibited higher SNR compared to the FLASH and SPACE images.

Conclusion: CISS imaging of the prostate after brachytherapy provided excellent visualization of the prostate (including the dominant intraprostatic tumors), the seed markers, and locoregional anatomy in a single sequence. In contrast to FLASH and SPACE, CISS offered combined T1 and T2 contrast and exhibited higher SNR. These findings demonstrated that high quality images of the seed markers as well as prostate and surrounding anatomy can be obtained with a single MR sequence, potentially enabling efficient and accurate post-implant prostate brachytherapy dosimetry.

Funding Support, Disclosures, and Conflict of Interest: Steven J. Frank, C4 Imaging

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