PI-RADS (Prostate Imaging - Reporting and Data System) v2 determination is dependent on whether the lesion is in the peripheral zone (PZ) or transition zone (TZ).
For PZ the primary determining sequence is diffusion-weighted imaging (DWI). That is, the PI-RADS score is determined by DWI appearance, with the exception of PI-RADS 3 lesions, at which further reference is made to the presence or absence of dynamic contrast enhancement (DCE) in an attempt to minimise "indeterminate" lesions.
Conversely, for TZ lesions, the primary determining sequence is T2WI. That is, the PI-RADS score is determined by T2W appearance, with the exception of PI-RADS 3 lesions, at which further reference is made to DWI.
PZ = peripheral zone; TZ = transition zone; DCE = Dynamic Contrast Enhancement