Clinical Evaluation of Simultaneous Multi-Slice Diffusion-weighted Magnetic Resonance Imaging of the Prostate
Jakob Weiss1, Jana Taron1, Ahmed E. Othman1, Petros Martirosian1, Sascha Kaufmann1, Ulrich Kramer1, Konstantin Nikolaou1, and Mike Notohamiprodjo1

1Diagnostic and Interventional Radiology, University of Tuebingen, Tuebingen, Germany


To evaluate the clinical performance of simultaneous multi-slice (sms) diffusion-weighted imaging (DWI) of the prostate. A prototype sms-DWI sequence was utilized and compared to conventional DWI sequences. Sms acquisition is based on the recently introduced principle of simultaneously exciting and acquiring multiple slices by a single radiofrequency (RF) pulse, thus accelerating image acquisition directly by the number of simultaneously excited slices (MB-factor). Image analyses revealed similar image quality and lesion detection as compared to conventional DWI sequences at a substantially decreased acquisition time. Sms-DWI seems a valuable alternative to conventional DWI sequences for prostate imaging.


To assess the clinical impact of simultaneous multi-slice (sms) single-shot echo-planar-imaging (EPI) for accelerated diffusion-weighted imaging (DWI) of the prostate.

Material and Methods

43 patients with suspected prostate cancer (PC) were consecutively included in this study. All examinations were performed at 3T (MAGNETOM, Skyra, Siemens Healthcare, Erlangen, Germany). In all patients three DWI sequences with b-values of 50 and 800 s/mm2 were acquired: 1) A prototype sms-DW-EPI sequence (Multi-Band EPI, Release 012, Center for Magnetic Resonance Research, University of Minnesota, MN, USA) was utilized. It is based on the recently introduced principle of simultaneously exciting and acquiring multiple slices by a single radiofrequency (RF) pulse and subsequently unaliasing those using parallel imaging principles [1-3]. Thus, TR can be reduced directly by the number of simultaneously excited slices (MB-factor). Further improvement of this technique could be achieved by introducing the blipped controlled aliasing in parallel imaging technique (blipped CAIPI) and by using time-shifted RF pulses to reduce peak RF power [4, 5]. In this study sms-DW-EPI sequence with MB-factor of 2 and blipped CAIPI with slice shift of FOV phase/4 was utilized. Acquisition time for an average of 28 slices was 1:38 min. 2) Multi-shot-DW-EPI (ms-DW-EPI) sequence is based on dividing the k-space trajectory into multiple readout segments and thus allowing time reduction for TE and encoding-time. Average acquisition time was 6:02 min. 3) Conventional single-shot EPI (ss-DW-EPI); acquisition time 3:29 min. A T2-weigthed turbo-spin-echo sequence in transversal and sagittal planes served as standard of reference for adequate anatomic representation. In all sequences the bipolar diffusion preparation scheme was used to compensate for residual eddy currents and partially reduce the consequent image distortions. All DWI measurements were performed using diffusion gradients applied in three orthogonal directions (three-scan trace) and parallel imaging using GRAPPA technique with an acceleration factor of 2. Diagnostic image quality (overall, anatomic differentiability, lesion detection) and artifacts (noise, distortion) of sms-DW-EPI were assessed qualitatively (5-point Likert scale, 5 = excellent, two independent readers) and quantitatively (signal-to-noise-ratios, ADC values) and compared to ms-DW-EPI and ss-DW-EPI. Statistical analyses were performed using SPSS (Version 22, IMB, Armonk/NY, USA). ANOVA-analysis was calculated for normally distributed data. For qualitative analysis non-parametric Friedman´s ANOVA was performed. Multiple comparisons were accounted by using Bonferroni correction. P-values < 0.05 were assumed to indicate significance.


Scores for overall image quality (p=0.15) and lesion detection (p=0.59) revealed no significant differences among the sequences. See Figure 1 and 2. Anatomic differentiability of the central vs. the peripheral gland was rated significantly higher for sms-DW-EPI as compared to ss-DW-EPI (p<0.01) whereas no differences could be found between sms-DW-EPI and ms-DW-EPI (p=0.08). Noise impairment was rated significantly higher in ms-DW-EPI than in sms-DW-EPI and ss-DW-EPI respectively (p<0.0001). No significant difference could be found regarding distortion artifacts (p=0.24). ADC values for prostate parenchyma and histologically confirmed PC were lowest in sms-DW-EPI and highest in ss-DW-EPI with significant differences between the sequences (p<0.0001). Sms-DW-EPI showed comparable SNR to ss-DW-EPI and significantly higher SNR values than ms-DW-EPI (p<0.05).


In this study we demonstrated that sms acquisition is a valuable new technique for diffusion weighted-MRI of the prostate. The main advantage of sms-DWI is the dramatically decreased acquisition time. This is important, because the number of prostate MRI will increase, resulting in the demand of a higher patient throughput due to the recent implementation of prostate MRI into clinical guidelines [6]. This is reasonable since DWI of the prostate significantly increases sensitivity of PC detection compared to T2-weigthed imaging alone and plays an important role in suspect lesion stratification using the PI-RADS classification system [7, 8]. Usually three b-values are acquired (0, 50 and 800 s/mm2) in standard DW imaging. Recently published studies could even demonstrate the benefit of higher b-values (1000, 1500 or 2000 s/mm2) for improved tumor detection due to higher contrast ratios of tumor to healthy tissue [9]. However, these findings have not yet been implemented into the revised PI-RADS version [8]. Therefore, we acquired our data guideline-conform at the standard b-values. Nevertheless, in preliminary examinations we also acquired images with b-values of 1000 s/mm2 and higher, however the resulting SNR was too low for adequate image interpretation. One possibility to overcome this problem is to use accelerated sms-DW-EPI at standard protocol acquisition time to gain higher SNR.


Simultaneous multi-slice DWI of the prostate is a promising new acquisition technique allowing for substantially reduced examination time with no significant differences in image quality and similar lesion detection compared to conventional DWI sequences.


The authors kindly acknowledge the receipt of the multi-slice DW-EPI sequence used in this study from the University of Minnesota, Center for Magnetic Resonance Imaging. Furthermore, the authors acknowledge Christina Schraml for her helpful comments in the preparation of this study.


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ADC-maps of the prostate of a 63-year old patient with benign prostate hyperplasia (PIRADS II) and a PSA level of 5.5 ng/ml: Example of image quality for sms-DW-EPI (a), ms-DW-EPI (b) and ss-DW-EPI acquisition (c). Image quality was rated excellent for sms-DW-EPI and ss-DW-EPI and good for ms-EPI.

T2-weighted image (a), ADC-maps (b-d) and DW b800 images (e-g) of the same patient: sms-DW-EPI (b), ms-DW-EPI (c) and ss-DW-EPI (c) with hypointense tumor lesion in the left peripheral zone (arrow) and corresponding DW b800 images with slightly hyperintense signal in the corresponding area (sms-DW-EPI (e); ms-DW-EPI (f); ss-DW-EPI (g)).

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)