Assessment of ventricular wall thickness in vivo by computed transmission tomography.

Abstract

The potential of computed transmission tomography (CT) scanning for quantitative assessment of interventricular septal wall thickness was studied in living dogs. Seven normal beagles and 7 litter mates with left ventricular hypertrophy were scanned to determine the sensitivity of the method. Left ventricular hypertrophy was created by banding the ascending aorta when the dogs were 6-8 wk old. The operated dogs were followed along with their normal litter mates to the age of 7-9 mo., when CT scanning was performed. The interventricular septum was well visualized using i.v. bolus injections (0.5 ml/kg) of meglumine/sodium diatrizoate. Septal wall thickness was measured using a computer region of interest program that allowed myocardial edge detection. After CT scanning the dogs were sacrificed. The hearts were excised and sectioned at the same levels as the CT scans were obtained. A linear regression for septal wall thickness as measured by CT and by autopsy was calculated. The correlation between CT and autopsy values was excellent although CT consistently underestimated the interventricular septal thickness by 10-20%. The explanation for this underestimation is not clear. Nongated CT scans appeared to represent a composite image of the heart obtained during several heart beats. Systolic and diastolic variation in wall thickness and the method used for boundary detection are potential sources of error in this CT study. CT appears to offer a useful noninvasive method for estimating septal wall thickness and has the potential for providing measurements of total myocardial mass. CT scanning should be readily applicable in the clinical situation.