[The usefulness of prolonged high dose delayed contrast computed tomography for the diagnosis of intracranial angiographically occult vascular malformations].

It is difficult to diagnose angiographically occult vascular malformations. When conventional CT (plain & contrast enhancement) can not demonstrate the lesions, it was impossible to diagnose in the past. We developed a new technique which enabled us to diagnose them. Materials and methods; Seven cases of spontaneous intracerebral hemorrhage, in which no abnormality was detected by repeated magnified serial angiography with subtraction technique and prolonged injection technique, were examined. In each case, conventional CT (plain & enhancement using 100 ml of 60% meglumine iothalamate) was performed first, which was immediately followed by the administration of 220 ml of 30% meglumine iothalamate for one hour. CT is taken at the end of the infusion. It, we call, is prolonged high dose delayed contrast CT: PHDD-CT. Total dose of iodine used in this technique was 59.22 gI (1.0 gI/kg body weight: BW). Results; Contrast enhancement effect of PHDD-CT was much better than that of conventional CT in all the cases. In three cases, the lesions were more clearly delineated in PHDD-CT. In four cases, only PHDD-CT could demonstrate the lesions. No side effect was observed. Comments; Several techniques for better enhancement have been reported, however they used large volume of contrast medium such as 1.5 or 2.0 gI/kg BW. Our technique can be performed with more security. Based on our good results, we recommend to use this PHDD-CT technique for the diagnosis of angiographically occult vascular malformations.