Dynamic computed tomography for the diagnosis of pituitary microadenoma, 1

The purpose of this paper is to evaluate the dynamic CT findings on the normal pituitary gland. Dynamic CT scan was studied in 20 normal pituitary glands. In the anterior lobe, initially the secondary capillary bed ('tuft' by Bonneville) appeared as a high density area located in the midline, beneath the upper surface of the anterior lobe. Subsequently the high density area, located in the secondary capillary bed, spreaded centrifugally into the anterior lobe. Finally, the entire anterior lobe became a homogeneously high density area. Three patterns of the time-density curve were observed in the anterior lobe. Type 1, observed in the midline, beneath the upper surface of the anterior lobe, was a vascular pattern. It corresponded to the tuft topographically. Compared with the other venous system, the peak of the type 1 somewhat delayed. It is considered due to a slower circulation in the hypophyseal portal system. Type 2, observed just below the tuft, represented the extravasation of contrast material in a highly vascular tissue (hypervascular extravasation pattern). Type 3, observed at the bottom of the anterior lobe, represented the extravasation of contrast material in a less vascular tissue (oligovascular extravasation pattern). The posterior lobe appeared as a high density area, in the midline, close to the dorsum sellae. The time-density curve of the posterior lobe had the vascular pattern with the peak time which coincides with arterial one. The ordinary artery-capillary-venouse circulatory system and the blood-brain-barrier in the posterior lobe well explain these facts. (author)