Fig. 13

A 55-year-old patient with low-volume Gleason score 3 + 3 = 6 tumour at TRUS biopsy in the left apical PZ underwent MRI prior to consideration for potential AS. Axial T2W TSE image (a) demonstrates a low T2 SI focus in the left apical PZ (white arrow). Axial ADC map displayed with automatic windowing/levelling shows minimal decreased SI (black arrow in b). These findings could be considered typical for a 3 + 3 = 6 cancer. With modified display of the ADC map using previously validated settings (width = 1.650 and level = 1.675 × 10–6 mm²/s) the nodule (black arrow in c) is noted to be of lower SI than initially displayed in (b). Using quantitative data, the ADC value obtained within the tumour (d) was 1.462 × 10⁻³ mm²/s, which would also be considered to be of low (Gleason score 6) grade using previously reported thresholds. Comparing ADC values across systems is challenging due to a lack of standardization, and an ADC ratio has been previously proposed as a better metric to compare ADC. An ADC value from the contralateral normal PZ obtained at the same level was 2.000 × 10⁻³ mm²/s, which yields an ADC ratio of 0.73, which would be compatible with a Gleason score ≥7 tumour based on previously published thresholds. Corresponding DCE image (e) from the same level demonstrated a focal enhancing nodule with a type III contrast curve. Based on the imaging findings, a repeat TRUS-guided biopsy was performed, which demonstrated Gleason pattern 4 in the left apical PZ