Accelerated Segmented Diffusion-Weighted Prostate Imaging for Higher Resolution, Higher Geometric Fidelity, and Multi-b Perfusion Estimation

Purpose The aim of this study was to improve the geometric fidelity and spatial resolution of multi-b diffusion-weighted magnetic resonance imaging of the prostate. Materials and Methods An accelerated segmented diffusion imaging sequence was developed and evaluated in 25 patients undergoing multiparametric magnetic resonance imaging examinations of the prostate. A reduced field of view was acquired using an endorectal coil. The number of sampled diffusion weightings, or b-factors, was increased to allow estimation of tissue perfusion based on the intravoxel incoherent motion (IVIM) model. Apparent diffusion coefficients measured with the proposed segmented method were compared with those obtained with conventional single-shot echo-planar imaging (EPI). Results Compared with single-shot EPI, the segmented method resulted in faster acquisition with 2-fold improvement in spatial resolution and a greater than 3-fold improvement in geometric fidelity. Apparent diffusion coefficient values measured with the novel sequence demonstrated excellent agreement with those obtained from the conventional scan (R2 = 0.91 for bmax = 500 s/mm2 and R2 = 0.89 for bmax = 1400 s/mm2). The IVIM perfusion fraction was 4.0% ± 2.7% for normal peripheral zone, 6.6% ± 3.6% for normal transition zone, and 4.4% ± 2.9% for suspected tumor lesions. Conclusions The proposed accelerated segmented prostate diffusion imaging sequence achieved improvements in both spatial resolution and geometric fidelity, along with concurrent quantification of IVIM perfusion. Received for publication July 20, 2018; and accepted for publication, after revision, October 15, 2018. Conflicts of interest and sources of funding: Financial support from NIH grants R01 CA160902, R01 EB010195, R01 CA149342, R25 CA89017, and P41 EB015898 as well as TUBITAK 116C024, ALFGBG-727661, and CAN 2017/558 is acknowledged. Correspondence to: Stephan E. Maier, MD, PhD, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA 02115. E-mail: stephan@bwh.harvard.edu. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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