Diagnostic evaluation of magnetization transfer and diffusion kurtosis imaging for prostate cancer detection in a re-biopsy population

OBJECTIVE: To evaluate diffusion kurtosis imaging (DKI) and magnetisation transfer imaging (MTI) compared to standard MRI for prostate cancer assessment in a re-biopsy population. METHODS: Thirty-patients were imaged at 3 T including DKI (K(app) and D(app)) with b-values 150/450/800/1150/1500 s/mm(2) and MTI performed with and without MT saturation. Patients underwent transperineal biopsy based on prospectively defined MRI targets. Receiver-operating characteristic (ROC) analyses assessed the parameters and Wilcoxon-signed ranked test assessed relationships between metrics. RESULTS: Twenty patients had ≥ 1 core positive for cancer in a total of 26 MRI targets (Gleason 3+3 in 8, 3+4 in 12, ≥ 4+3 in 6): 13 peripheral (PZ) and 13 transition zone (TZ). The apparent diffusion coefficient (ADC) and D(app) were significantly lower and the K(app) and MT ratio (MTR) significantly higher in tumour versus benign tissue (all p ≤ 0.005); ROC values 0.767-1.000. Normal TZ had: lower ADC and D(app) and higher K(app) and MTR compared to normal PZ. MTR showed a moderate correlation to K(app) (r = 0.570) and D(app) (r = -0.537) in normal tissue but a poor correlation in tumours. No parameter separated low-grade (Gleason 3+3) from high-grade (≥ 3+4) disease for either PZ (p = 0.414-0.825) or TZ (p = 0.148-0.825). CONCLUSION: ADC, D(app), K(app) and MTR all distinguished benign tissue from tumour, but none reliably differentiated low- from high-grade disease. KEY POINTS: • MTR was significantly higher in PZ and TZ tumours versus normal tissue • K (app) was significantly lower and D (app) higher for PZ and TZ tumours • There was no incremental value for DKI/MTI over mono-exponential ADC parameters • No parameter could consistently differentiate low-grade (Gleason 3+3) from high-grade (≥ 3+4) disease • Divergent MTR/DKI values in TZ tumours suggests they offer different functional information ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00330-017-5169-1) contains supplementary material, which is available to authorized users.