What can be done to reduce artefacts from hip endoprosthesis?
Use lower magnet strength e.g. 1.5 T instead of 3 T, short echo spacing and high TSE factor, small water fat shift, increase bandwidth during slice selection and readout, high matrix and thin slices (usually not a problem in prostate MRI), use metal artefact reduction sequence (MARS).
How should a focal lesion look on diffusion-weighted images to be assessed as a PI-RADS 4 lesion?
Focal markedly hypointense on ADC and markedly hyperintense on high b-value DWI and/or focal hypointense on ADC and/or focal hyperintense on high b-value DWI with focal and early enhancement on DCE. It should be <15 mm in the greatest dimension.
What is the difference between PI-RADS 4 and PI-RADS 5 lesions?
PI-RADS 5 lesions have similar signal characteristics to PI-RADS 4 lesions, but they are larger in dimension (≥15 mm) and/or show definite signs of extraprostatic extension. As per definition, PI-RADS 5 is more likely to be clinically significant cancer.
Key findings:
The suspect lesion is depicted.
The axial images are all in the same plane, which is illustrated on the sagittal image (blue dotted line). The focal lesion can be seen in the b1400 and corresponding ADC images and can be also seen in sagittal and coronal T2w images, but it is rather difficult to see the focus on the axial T2w images.