Elsevier

European Journal of Radiology

Volume 107, October 2018, Pages 125-133
European Journal of Radiology

Research article
Diagnostic efficacy of b value (2000 s/mm2) diffusion-weighted imaging for prostate cancer: Comparison of a reduced field of view sequence and a conventional technique

https://doi.org/10.1016/j.ejrad.2018.08.028Get rights and content

Abstract

Objectives

To compare high b value (2000 s/mm2) reduced field-of-view (rFOV) diffusion-weighted imaging (DWI) with a conventional DWI sequence in terms of image quality, as well as diagnostic performance concerning prostate cancer (PCa) detection and tumor staging at 3 T.

Methods

Sixty-one patients underwent rFOV DWI and conventional DWI due to clinical suspicious of PCa were retrospectively recruited. Imaging qualities were evaluated qualitatively and quantitatively by two blinded radiologists. Thirty-two subjects with detailed pathology reports were further analyzed for diagnostic efficacy using the Prostate Imaging Reporting and Data System (PI-RADS) version 2. The PCa detection rate, sensitivity, specificity, and PI-RADS staging changes were compared between the DWI sequences.

Results

Qualitative evaluation regarding image quality was significantly better in rFOV DWI than in the conventional DWI (all P < 0.05). ADC contrast with rFOV DWI was rated significantly higher than the conventional DWI in both peripheral zone (PZ) and transition zone (TZ) (P = 0.001 for PZ, and P =  0.003 for TZ). Regarding diagnostic efficacy, rFOV DWI yielded higher tumor detection, sensitivity and the area under the curve (AUC) than the conventional DWI (all P < 0.05), except the AUC in the PZ for one reader (P = 0.262). Conventional DWI achieved slightly higher specificity for the PZ and TZ but with no significant difference except for one reader in the PZ (P = 0.009).

Conclusion

The rFOV DWI could offer improved image quality and yielded better diagnostic performance in terms of higher tumor detection rate and relatively precise staging for PCa compared to the conventional sequence.

Introduction

Diffusion-weighted imaging (DWI) is a dominant sequence of multiparametric magnetic resonance imaging (mpMRI) for prostate cancer (PCa) evaluation [[1], [2], [3], [4], [5]]. Despite advantages such as demonstrating high contrast between the tumor and healthy tissue and the ability to provide a parametric map of the apparent diffusion coefficient (ADC) [6], DWI based on single-shot echo-planar imaging (ss-EPI) may suffer from geometry distortion, relatively poor spatial resolution and artifacts that can affect the image quality and diagnostic performance, especially combined with high b values at 3 T [[7], [8], [9]]. Small foci or lesions abutting the capsule may also be missed with the conventional DWI techniques.

Recently, reduced field-of-view (rFOV) based two dimensional selective excitation (2D RF) pulse DWI was introduced to compensate for these defects, yielding improved spatial resolution and reduced image blurring, geometric distortions, and artifacts [[10], [11], [12], [13], [14], [15]]. Additionally, scan time could also be reduced. Researches concerning image quality based on phantom and healthy volunteers had been reported [16,17], applications of rFOV DWI in detecting and accurately staging of PCa for cancer patients was still worth exploring. The purpose of this study was to qualitatively and quantitatively compare the image quality and diagnostic efficacy of the rFOV DWI and the conventional DWI technique in patients with suspected prostate cancer at 3 T MRI.

Section snippets

Patients

This retrospective study was approved by the local ethics committee with a waiver of informed consent. Between July 2015 and September 2015, 86 consecutive patients with suspected PCa due to an elevated serum prostate-specific antigen (PSA) level and/or suspicious digital rectal examination were enrolled and underwent prostate MR examination. The patient selection flowchart is presented in Fig. 1. The patients were recruited using the following criteria: (a) complete MRI data of rFOV DWI and

Qualitative evaluation

The evaluation scores in Table 3 showed the items of the qualitative image quality were rated significantly higher on rFOV DWI than conventional DWI (P < 0.05, for all). Inter-reader agreement was substantial for both DWI sequences (κ = 0.76 and κ = 0.72, respectively, for tissue contrast resolution; κ = 0.75 and κ = 0.76, respectively, for demarcation; κ = 0.75 and κ = 0.72, respectively, for susceptibility artifacts; κ = 0.77 and κ = 0.76, respectively, for geometric distortion; κ = 0.79 and κ

Discussion

The present study investigated two DWI sequences for their image quality and ability to detect PCa at 3 T. Significantly higher image quality and diagnostic efficacy were demonstrated in the rFOV DWI sequence than in the conventional technique.

Regarding the image quality, optimized DWI techniques reported in recent studies have shown the ability to reduce distortion of targeted objects (i.e., kidney, liver and pancreas) and to restrain artifacts of surrounding tissues, leading to a high spatial

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    These authors contributed equally to this work.

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