Prostate Cancer: Diffusion-weighted MR Imaging for Detection and Assessment of Aggressiveness—Comparison between Conventional and Kurtosis Models

Abstract

Purpose To compare standard diffusion-weighted (DW) imaging and diffusion kurtosis (DK) imaging for prostate cancer (PC) detection and characterization in a large patient cohort, with attention to the potential added value of DK imaging. Materials and Methods This retrospective institutional review board-approved study received a waiver of informed consent. Two hundred eighty-five patients with PC underwent 3.0-T phased-array coil prostate magnetic resonance (MR) imaging, including a DK imaging sequence (b values 0, 500, 1000, 1500, and 2000 sec/mm) before prostatectomy. Maps of apparent diffusion coefficient (ADC) and diffusional kurtosis (K) were derived by using maximal b values of 1000 and 2000 sec/mm, respectively. Mean ADC and K were obtained from volumes of interest (VOIs) placed on each patient's dominant tumor and benign prostate tissue. Metrics were compared between benign and malignant tissue, between Gleason score (GS) ≤ 3 + 3 and GS ≥ 3 + 4 tumors, and between GS ≤ 3 + 4 and GS ≥ 4 + 3 tumors by using paired t tests, analysis of variance, receiver operating characteristic (ROC) analysis, and exact tests. Results ADC and K showed significant differences for benign versus tumor tissues, GS ≤ 3 + 3 versus GS ≥ 3 + 4 tumors, and GS ≤ 3 + 4 versus GS ≥ 4 + 3 tumors (P < .001 for all). ADC and K were highly correlated (r = -0.82; P < .001). Area under the ROC curve was significantly higher (P = .002) for ADC (0.921) than for K (0.902) for benign versus malignant tissue but was similar for GS ≤ 3 + 3 versus GS ≥ 3 + 4 tumors (0.715-0.744) and GS ≤ 3 + 4 versus GS ≥ 4 + 3 tumors (0.694-0.720) (P > .15). ADC and K were concordant for these various outcomes in 80.0%-88.6% of patients; among patients with discordant results, ADC showed better performance than K for GS ≤ 3 + 4 versus GS ≥ 4 + 3 tumors (P = .016) and was similar to K for other outcomes (P > .136). Conclusion ADC and K were highly correlated, had similar diagnostic performance, and were concordant for the various outcomes in the large majority of cases. These observations did not show a clear added value of DK imaging compared with standard DW imaging for clinical PC evaluation. RSNA, 2017 Online supplemental material is available for this article.

Prostate cancer assessment using MR elastography of fresh prostatectomy specimens at 9.4 T

“…They showed an excellent performance for ADC (AUC, 0.93; sensitivity, 78.5%; specificity, 95.7%), which was even further improved using diffusion kurtosis imaging (AUC, 0.98; sensitivity, 93.3%; specificity, 95.7%). However, in a recent study including 285 patients with PCa, the same group found no clear benefit for diffusion kurtosis imaging (AUC, 0.90) in comparison to standard DWI (AUC, 0.92) . In an ex vivo study, McGrath et al found no significant difference in ADCs between PCa and healthy tissue, although ADC values tended to be lower in PCa .…”

Removing rician bias in diffusional kurtosis of the prostate using real‐data reconstruction

“…Indeed, our simulations in this study indicated uncorrected magnitude data can result in a ~7% increase of true K values in NPZ tissue. This is concerning and may account for the mixed results from earlier studies that compare DKI with DWI for PCa, where often no noise‐correction method is performed at all. Here, we have investigated a real‐data reconstruction approach to noise bias removal from DKI in the prostate.…”

“…One such expanded model is diffusional kurtosis imaging (DKI), which provides an estimate of the apparent diffusional kurtosis ( K ): a dimensionless parameter that quantifies the degree of non‐Gaussian diffusion. Since the first DKI studies, the technique has been applied extensively in neuroimaging and other studies have demonstrated feasibility for body applications, including PCa . Several investigations have compared DKI with standard DWI in PCa, with disagreement over whether DKI brings additional value compared to standard DWI or not .…”

“…Since the first DKI studies, 12,23 the technique has been applied extensively in neuroimaging [24][25][26] and other studies have demonstrated feasibility for body applications, including PCa. [27][28][29][30][31][32][33][34] Several investigations have compared DKI with standard DWI in PCa, [29][30][31][32][33][34] with disagreement over whether DKI brings additional value compared to standard DWI [29][30][31] or not. [32][33][34] However, these findings may be influenced by methodological issues, including the choice of b-values and by whether and how noise compensation (NC) is performed, and this issue has yet to be fully investigated.…”

Diffusion weighted imaging of the prostate—principles, application, and advances

“…This goes along with the results of Roethke et al (67) who did not find a significant benefit of DKI compared with ADC as they used a separate DWI sequence with shorter echo times and lower b -values to calculate ADC maps. Recently, a study comparing the value of DW-MRI and DKI for PCa detection and characterization included a large population of 255 patients to evaluate the potential value of DKI (70). The authors found that ADC and DKI were highly correlated and had a similar diagnostic performance, but did not show a clear added value of DKI compared with standard DW-MRI.…”