Accuracy of Attenuation Measurement of Vascular Wall In Vitro on Computed Tomography Angiography: Effect of Wall Thickness, Density of Contrast Medium, and Measurement Point

OBJECTIVES:We sought to assess the effects of measurement point, wall thickness, and intravascular density of contrast material on attenuation measurement of vascular wall. MATERIALS AND METHODS:We used vascular models (actual attenuation value of the wall83 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 254, 325, or 400 HU. The 9 vascular models were fixed in an oil-filled container and scanned with a 16-detector computed tomography. The wall attenuation values were measured at 1 point for 0.5-mm thickness models, 3 for 1.0-mm thickness models, and 5 for 1.5-mm thickness models with the same interval of 0.25 mm. Total 20 measurements were done for each point. RESULTS:For 1.0-mm and 1.5-mm thickness models, wall attenuation progressively increased as the measurement points approached the lumen (P < 0.0001). At all the measurement points for 0.5-mm and 1.0-mm thickness models and the 2 inner measurement points for 1.5-mm thickness models, the densities of contrast material affected the wall attenuations significantly (P < 0.0001). At the midportion for 1.5-mm thickness models, the wall attenuations were not affected by the densities of the contrast material (P = 0.6301), and were 65–68 HU. CONCLUSIONS:The effects of the intravascular density of contrast material, measurement point, and wall thickness should be considered in the attenuation measurement of the wall.