Yoshiro Furuya

Determinations of organ doses and effective dose equivalents from computed tomographic examination

The organ or tissue doses were determined with a phantom measurement for 12 types of CT scanners widely used in Japan. Two types of thermoluminescent dosimeters were used for the dose determinations in a Rando woman phantom. The effective dose equivalents recommended by the International Commission on Radiological Protection were calculated using the measured organ or tissue doses. It was found that the CT scanners currently available give quite different organ or tissue doses. When selecting the optimum technical factors for scanning, therefore, it is important to take into consideration the balance of the image quality and the radiation exposure to patients.

CT of calcified chronic aortic dissection simulating atherosclerotic aneurysm

Calcification along the outermost aspect of the aorta usually means atherosclerotic aneurysm. On occasion, however, this peripheral type calcification is seen in chronic aortic dissection and leads to a misdiagnosis. Conventional chest roentgenography and CT of 50 cases of chronic dissection proven by angiography were reviewed. Four of these cases (8%) showed calcification in the outermost wall of the affected portion of the aorta. Two cases were Stanford type A and the other two cases were type B. In type A cases chest roentgenography showed calcification in the wall of the dilated ascending aorta closely mimicking aneurysm. In type B cases, calcification was in the outer wall of a localized hump in the descending aorta. Computed tomography clearly demonstrated that this peripheral calcification was located in the outermost wall of the false lumen. Review of the pathologic literature shows sporadic reports of such phenomenon and a theory of endothelialization of the false lumen. It is presumed that the endothelialized false lumen may develop atheromatous changes much more rapidly than the true lumen since two of four cases showed calcification only in the wall of the false lumen with the intimal flap and the wall of the true lumen remaining noncalcified.

CT evaluation of invasive trophoblastic disease

We report the use of dynamic CT for the evaluation of trophoblastic disease of the uterus. In five cases showing evidence of persistent trophoblastic disease after evacuation of a molar gestation, contrast enhancement of the myometrium demonstrated several hypodense foci surrounded by highly enhanced areas. These observations were not found in two cases of successfully evacuated hydatidiform mole without sequela. A case of choriocarcinoma showed a large central nonenhanced lesion with peripheral contrast enhancement. Filling defects in a markedly contrast enhanced lesion probably represent hydatids penetrating the myometrium and should suggest invasive mole.

Acetazolamide-enhanced MR angiography of intracranial aneurysms

The purpose of our study was to evaluate the enhancing effect of acetazolamide in three-dimensional time-of-flight magnetic resonance angiography (MRA) for the diagnosis of intracranial aneurysms. MRA obtained at 1.5 T before and after acetazolamide administration was compared in a group of five patients without aneurysms and another group of seven patients with seven aneurysms. In each patient, distal arterial branches were more clearly demonstrated on MRA with the administration of acetazolamide than without. Four of the seven aneurysms (mean diameter, 9.0 mm) were better depicted after the acetazolamide infusion. In the remaining three aneurysms (mean diameter, 4.7 mm), no significant change was noted. This method improves the visualisation of distal small arteries and provides better images of relatively large aneurysms.

Biliary tract system

Data obtained on the biliary tract in initial clinical experience with the computed radiography (CR) system are presented in this chapter. In drip infusion cholecystocholangiography (DIC) combined with tomography, CR produced better images than the screen film; even in the case of low-dose exposure, CR was thought to be sufficiently usable for clinical diagnosis. In simultaneous multisection tomography, CR could probably present even better images if the exposure conditions were improved.

Intravenous digital subtraction angiography

Computed radiography (CR) is a general-purpose diagnostic system developed for application to various kinds of radiography by means of unique imaging plates. We have so far used this system for angiography, taking advantage of one of the features of CR, namely that it allows easy subtracton because it performs analog to digital conversion in the course of processing [1, 2]. Another type of digital angiography is digital fluorography (DF) using an imaging intensifier (II). Since the DF system was originally developed for angiography, there are naturally fundamental differences between the two systems. In routine angiography, however, the two systems have already been widely used, currently for the same purposes in most cases. This chapter includes a comparison of the two systems.