Comparison of single-shot EPI and multi-shot EPI in prostate DWI at 3.0 T

Abstract

In prostate MRI, single-shot EPI (ssEPI) DWI still suffers from distortion and blurring. Multi-shot EPI (msEPI) overcomes the drawbacks of ssEPI DWI. The aim of this article was to compare the image quality and diagnostic performance for clinically significant prostate cancer (csPC) between ssEPI DWI and msEPI DWI. This retrospective study included 134 patients with suspected PC who underwent 3.0 T MRI and subsequent MRI-guided biopsy. Three radiologists independently assessed anatomical distortion, prostate edge clarity, and lesion conspicuity score for pathologically confirmed csPC. Lesion apparent diffusion coefficient (ADC) and benign ADC were also calculated. In 17 PC patients who underwent prostatectomy, three radiologists independently assessed eight prostate regions by DWI score in PI-RADS v 2.1. Anatomical distortion and prostate edge clarity were significantly higher in msEPI DWI than in ssEPI DWI in the three readers. Lesion conspicuity score was significantly higher in msEPI DWI than in ssEPI DWI in reader 1 and reader 3. Regarding discrimination ability between PC with GS ≤ 3 + 4 and PC with GS ≥ 4 + 3 using lesion ADC, AUC was comparable between ssEPI DWI and msEPI DWI. For diagnostic performance of csPC using DWI score, AUC was comparable between msEPI DWI and ssEPI DWI in all readers. Compared with ssEPI DWI, msEPI DWI had improved image quality and similar or higher diagnostic performance.

Figure 1

Region of interest (ROI) placement for signal intensity and ADC measurements of prostate cancer region in left peripheral zone and benign prostatic region in right peripheral zone and for signal intensity measurement of left internal obturator muscle region. The ROIs for PC region, benign prostatic region, and internal obturator muscle region in one of these four MR images was copy-and-pasted into the other three MR images [ssEPI DWI (a), ssEPI DWI ADC map (b), msEPI DWI (c), and msEPI DWI ADC map (d)].

Figure 2

An 83-year-old man with prostate cancer (PSA level, 6.60 ng/mL; Gleason score, 3 + 4) in the left peripheral zone. A homogeneous hypointense lesion is seen on T2-weighted imaging (a) (arrow). A focal hyperintensity is depicted clearly on ssEPI DWI (b) and msEPI DWI (c) (arrow). The clarity of the prostate edge is better in msEPI DWI (c) compared with ssEPI DWI (b). PSA prostate-specific antigen, ssEPI single-shot echo-planar imaging, DWI diffusion-weighted imaging, msEPI multi-shot echo-planar imaging.

Figure 3

A 73-year-old man with prostate cancer (PSA level, 8.34 ng/mL; Gleason score, 3 + 3) in the right peripheral zone. A heterogeneous hypointense lesion with mass effect is seen on T2-weighted imaging (a) (arrow). A focal hyperintensity is depicted clearly on msEPI DWI (c) (arrow). Lesion clarity in ssEPI DWI (b) is impaired by distortion induced by rectal gas (arrow). However, SNR is higher in ssEPI DWI (b) than in msEPI DWI (c). PSA prostate-specific antigen, SNR signal-to-noise ratio, ssEPI single-shot echo-planar imaging, DWI diffusion-weighted imaging, msEPI multi-shot echo-planar imaging.

Figure 4

A 58-year-old man with prostate cancer (PSA level, 9.43 ng/mL; Gleason score, 4 + 3) in the left peripheral zone. A homogeneous hypointense lesion is seen on T2-weighted imaging (a) (arrow). A focal hyperintensity is depicted clearly on msEPI DWI (c) (arrow). Lesion conspicuity is lower in ssEPI DWI (b) than in msEPI DWI (c) (arrow). PSA prostate-specific antigen, msEPI multi-shot echo-planar imaging, DWI diffusion-weighted imaging, ssEPI single-shot echo-planar imaging.

Figure 5

A 77-year-old man with prostate cancer (prostate-specific antigen level, 5.10 ng/mL; Gleason score, 4 + 3) in the apex of the left peripheral zone and the left transition zone (not shown). SsEPI DWI (a) and ADC map in ssEPI DWI (b) show lesions corresponding to a DWI/ADC map score of 3 on the anterior middle regions of the bilateral peripheral zones (arrows). However, the same regions were diagnosed with a DWI/ADC map score of 1 in msEPI DWI (c) and ADC map in msEPI DWI (d). MsEPI DWI (c) and ADC map in msEPI DWI (d) show a lesion corresponding to a DWI/ADC map score of 2 in the posterior middle region of the right peripheral zone (arrow). Prostatectomy specimens confirmed a diagnosis of benign prostatic condition for the three middle regions in the right and left peripheral zones. Thus, for the bilateral middle peripheral zone lesions, ssEPI DWI gave a false-positive result and msEPI DWI showed a true-negative result. PSA prostate-specific antigen, ssEPI single-shot echo-planar imaging, DWI diffusion-weighted imaging, ADC apparent diffusion coefficient, ssEPI single-shot echo-planar imaging.