Dose the posterior pituitary high signal correspond to the entire posterior pituitary ?

The authors obtained midline sagittal dynamic MR imaging of 12 normal pituitary glands both before and immediately after the injection of Gd-DTPA using a spin-echo sequence with a short repetition time. The images were obtained every minute for six minutes at 1.5 T. A well-defined focal area with a remarkable enhancement was seen in the posterior portion of the pituitary gland on the first image after the injection of Gd-DTPA. These initially enhanced areas of the posterior pituitary (IEPPs) and high signals from posterior pituitary (HSPPs) were compared. The IEPPs were anteriorly convex in eight cases (67%), whereas the HSPPs were anteriorly convex in two (17%). The IEPPs were larger than the HSPPs in eight cases (67%). We believe that IEPPs represents the real posterior lobe because of its direct arterial blood supply. The results support the hypothesis that the HSPP may involve only a portion of the posterior pituitary. (author)