 I am Dr. Steven Pomerance, welcome to MRIOnline's review of PIRAD's 2.1 Changes and Designations for Assessment of Prostate MR. Let's start with a review of the changes we're going to be describing and breaking down. First, image data acquisition, technical specifications, now the T2 weighted image, it's recommended to perform the T2 in either a straight, axial, orthogonal plane, and at least one additional plane, and we'll drill into that a little further what we mean by one additional plane. Diffusion weighted imaging, clarification of B values, four purposes of diffusion weighted imaging acquisition, and for ADC map calculation. Third, DCE or Dynamic Contrast Enhanced MRI, where you have to put an IV in the patient and inject, temporal resolution should be no greater than 15 seconds. In our personal practice, it's about 7 to 8 seconds per image, per location. So less than 15 seconds per dynamic is advised. 3D T1 GRE is preferred. Clarifications in Interpretation Criteria, further description of assessment of lesions in the CZ and anterior fibromuscular stroma is one of the biggest and most important changes, for you'll see in our experience, the overwhelming majority of lesions in the TZ have been overcalled. Revision and criteria for T2 weighted imaging scores for score one and score two in the TZ area, which further contributes to our analysis of TZ lesions. Clarification and determination of overall assessment of what we're going to call aggressive, intermediate, or non-aggressive in the TZ area. Revision and criteria for diffusion weighted imaging scores of two and three. Clarification of the distinction between positive and negative enhancement on DCE MRI, clarification and measurement of the prostate volume, and revision of the sector map. And finally, a discussion of bi-parametric MRI. What is bi-parametric MRI? Well, in order to understand that, you've got to know what multi-parametric MRI is. Multi-parametric MRI revolves around T2, diffusion weighted imaging, spectroscopy, and dynamic contrast enhanced MRI. In bi-parametric MRI, you're relying on two important criteria. The T2 weighted imaging and the diffusion weighted characteristics of the lesion has evidenced on the diffusion weighted series and the ADC map.