Explanation of the MR imaging appearance of the periprostatic and uterovaginal venous plexus

On MR images, the prostrate, cervix, and vagina are frequently observed to be surrounded by a venous plexus that is characterized by intermediate signal intensity on T1-weighted images and extreme hyperintensity on T2-weighted images. This appearance is usually ascribed to slowly flowing blood. Phase imaging and normalized intensity measurements on single-section multiecho images (0.5 and 1.5 T) of periprostatic and uterovaginal venous plexus failed to demonstrate evidence of flow-induced phase changes or even echo rephasing. Thus, the flow in these vascular structures is too slow to be detected with standard MR imaging techniques and should not influence the appearance of the images. Rather, the signal intensity of these regions reflects the intermediate T1 and relatively prolonged T2 relaxation times of unclotted stagnant blood