Evaluation of Exponential ADC (eADC) and Computed DWI (cDWI) for the Detection of Prostate Cancer

To directly compare different methods proposed for enhanced conspicuity and discriminability of prostate cancer on diffusion-weighted imaging (DWI) and to compare the results to original DWI images and conventional apparent diffusion coefficient (ADC) maps.

Clinical routine prostate DWI datasets (b = 0, 50, 800 s/mm², acquired at a field strength of 3 T) of 104 consecutive patients with subsequent MR-guided prostate biopsy were included in this retrospective study. For each dataset exponential ADC maps (eADC), computed DWI images (cDWI), and additionally eADC maps for computed b-values of 2000 and 3000 s/mm² were generated (c_eADC). For each of 123 lesions, the contrast (CR) and contrast-to-noise ratio (CNR) were determined. Differences in the CR and CNR of malignant lesions (n = 83) between the different image types and group differences between benign (n = 40), low-risk (n = 53) and high-risk (n = 30) lesions were assessed by repeated measures ANOVA and one-way ANOVA with post-hoc tests. The ability to differentiate between benign and malignant and between low-risk and high-risk lesions was assessed by receiver operating characteristic (ROC) curve analyses.

The CR and CNR were higher for computed DWI and related c_eADC at b = 3000 s/mm² and 2000 s/mm² compared to original DWI, conventional ADC and standard eADC. For differentiation of benign and malignant lesions, conventional ADC and CR of conventional ADC were best suited. For discrimination of low-risk from high-risk lesions, the CR of c_eADC was best suited followed by the CR of cDWI.

Computed cDWI or related c_eADC maps at b-values between 2000 and 3000 s/mm2 were superior to the original DWI, conventional ADC and eADC in the detection of prostate cancer.

· Prostate cancer can appear inconspicuous on original DWI800 images. · Computed DWI images at b = 2000 - 3000 s/mm² improve lesion-to-normal-tissue contrast in prostate cancer. · Contrast in computed DWI is superior to ADC and eADC at b = 800 s/mm².

· Sprinkart AM, Marx C, Träber F et al. Evaluation of Exponential ADC (eADC) and Computed DWI (cDWI) for the Detection of Prostate Cancer. Fortschr Röntgenstr 2018; 190: 758 - 766.