Pros and Cons of High-Performance Gradient Enabled Short-TE Prostate DWI: A Prospective Study.

Objectives: Recent advances in high-performance gradient technology have enabled shorter echo times (TEs) for diffusion-weighted prostate MRI. Short TE may improve the conspicuity of the usually T2 hypointense lesions but may also influence the diagnostic performance of the apparent diffusion coefficient (ADC) due to a changed weighting of subcompartments, including prostate fluid and tissues. The purpose of this study was to evaluate the influence of TE on prostate diffusion-weighted images with respect to lesion conspicuity and diagnostic performance of the ADC.

Materials and methods: This institutional review board-approved prospective monocentric study included n = 55 (mean age 69 ± 9 years) patients undergoing clinically indicated prostate MRI on two 3 T MRI scanners with high-performance gradients. Diffusion-weighted imaging (DWI) was performed with an echo-planar sequence at 2 different TEs, 41 ms and 70 ms, with b-values of 50 s/mm2 and 800 s/mm2. Computed DWI was generated for a b-value of 1400 s/mm2. The lesion conspicuity and image quality were rated by 3 independent readers with a 5-point Likert scale and tested with the Wilcoxon rank sum test. Lesion ADCs were recorded, and their ability to detect significant lesions (Gleason score >6) was assessed with a receiver operator curve analysis.

Results: Among the participants, n = 24 had clinically significant prostate cancer. The image quality at b = 1400 s/mm2 was rated significantly higher at TE = 41 ms than at TE = 70 ms (mean Likert score ± standard deviation for TE = 41 ms vs TE = 70 ms: R1: 4.06 ± 0.68 vs 3.02 ± 0.59; R2: 4.09 ± 0.82 vs 3.26 ± 0.67; R3: 4.16 ± 0.71 vs 3.18 ± 0.70; for all P's < 0.001). The lesion conspicuity at b = 1400 s/mm2 was rated higher at TE = 41 ms than at TE = 70 ms (mean Likert score ± standard deviation for TE = 41 ms vs TE = 70 ms: R1: 4.55 ± 0.66 vs 4.46 ± 0.72, P = 0.17; R2: 4.64 ± 0.59 vs 4.53 ± 0.63, P = 0.03; R3: 4.53 ± 0.66 vs 4.28 ± 0.80, P = 0.01). However, the ADC-based area under the curve for lesion characterization decreased from 0.80 at TE = 70 ms to 0.70 at TE = 41 ms (P = 0.07).

Conclusions: Shortening TE to 41 ms in prostate DWI increases lesion conspicuity on high b-value images; however, it negatively impacts the diagnostic performance of the ADC.