1) Tatelman M: The angiographic evaluation of cerebral arteriosclerosis. Radiology 70: 801-810, 1958. 2) Elkeles A: A comparative study of calcified

8) Limpert JD, Vogelzang RL, Yao JST: Computed tomography of aortoiliac atherosclerosis. J Vasc Surg 5: 814-819, 1987. 9) Herfkens RJ, Higgins CB, Hricak H, Lipton MJ, Crooks LE, Sheldon PE, Kaufman L: 5) Dixon AK, Lawrence JP, Mitchell JRA: Agerelated changes in the abdominal aorta shown sclerotic disease. Radiology 148: 161-166, Nuclear magnetic resonance imaging of athero- by computed tomography. Clin Radiol 35: 1983. 33-37, 1984. 10) Mitchell JRA, Adams JH: Aortic size and 6) Ross R: The pathogenesis of atherosclerosis aoritc calcification. A necropsy study. Atherosclerosis 27: 437-446, 1977. Abstract A New Computed Tomography Method for Quantitative Analysis of Abdominal Aortic Atherosclerosis Hiroshi Ide, Norimitsu Kurihara, Yasuoki Mashima, Kazuo Endou, Munehiko Tanno, Kazuo Chiba and Hideo Yamada Clinical evaluation of aortic atherosclerosis has been most commonly performed by visual analysis of aortic calcification on conventional radiographs or X-ray CT. However, precise evaluation of the degree of calcification or mild changes with increasing age can be difficult by these methods of visual analysis. A new quantitative method of evaluating the abdominal aortic atherosclerosis using CT is reported. Target CT scans of the abdominal aorta were performed at the level of the 1st, 3rd and 4th lumbar vertebrae. Two circular regions of interest (ROI) were selected along the outer margin and inner margin of the abdominal aortic wall on CT images, since it was difficult to precisely trace the aortic wall. Histograms of CT value for each pixel were made from two ROIs. A histogram at the ROI of the outer margin was depicted using class values over the maximum CT Department of Nuclear Medicine and Radiological Sciences, Tokyo Metropolitan Geriatric Hospital value in histogram at the ROI of inner margin which indicated flowing blood. A sum of products of the value in each class by the number in that class was divided by the aortic diameter. The value thus obtained was defined as the atherosclerotic index (S.I.). Forty-five cases were studied with this method. Six cases were excluded because of artifacts. The remaining 39 cases (16 males, 23 females) were analyzed. S.I. increased with aging and was higher in men than in women. However, it increased more rapidly in women (8.68/year) than in men (2.73/year). Because this new method employed the CT value, it is more objectively quantitative than previous methods of visual analysis in evaluating abdominal aortic atherosclerosis. This method has potential for the analysis of slight changes with increasing age or for therapeutic effects in cases of atherosclerosis. key words: atherosclerosis, quantitative analysis, abdominal aorta, histogram, computed tomography (Jpn J Geriat 26: 571-576, 1989)