Characterization of artifact simulating aortic dissection in computed tomography imaging.

An artifact simulating aortic dissection has been seen in computed tomography (CT) and reported in numerous journals. The purpose of this study is to determine the origin. A phantom was constructed to simulate the motion of the ascending aorta during the cardiac cycle. Technique factors such as scan time, slice thickness, pitch, and reconstruction algorithms were examined for their effect on the simulated dissection appearance. Change in the angle of the simulated aorta with respect to the scanner axis was also studied. CT images displaying the simulated aortic dissection are obtained reproducibly. The amplitude of the artifact is more pronounced for increased scan time. The artifact amplitude is proportional to the displacement of the phantom. The simulated aortic dissection seems to be more pronounced when the scan time is comparable to the cycling time of aortic motion.

Measurement of skin entrance exposure with a dose-area-product meter at chest radiography.

Skin entrance exposure measurements obtained with a dose-area-product meter and thermoluminescent dosimeters were compared at posteroanterior and lateral chest radiography in 52 adult male patients. In a linear regression analysis of data collected in both views, values of 1.23 +/- 0.02 and 1.26 +/- 0.01 (r = .98 and .99) were found for the ratios of thermoluminescent-dosimeter and dose-are-product exposures, respectively. Skin entrance exposures from 16 mR (4.13 microC/kg) to 150 mR (38.7 microC/kg) in the posteroanterior view and 24 mR (6.19 microC/kg) to 475 mR (123 microC/kg) in the lateral view were found. Dose-area-product meters offer a rapid and accurate means to measure skin entrance exposure when the radiography field size is known.