Characterization of carotid artery plaque components on magnetic resonance imaging using signal intensity of the...

To evaluate the properties of plaque by the use of magnetic resonance imaging (MRI), it is necessary to use a material with stable signal intensity (eg, muscle or submandibular gland) as a reference. However, there may be differences between individuals. Therefore, we used a small phantom set on the circumference of the neck as a reference. The signal intensity ratio (SIR) methods using the phantom as a reference were reviewed for discrimination of the properties of plaque in the carotid artery.

Three phantoms (phantom 1: water; phantom 2: 5 μmol gadopentetate dimeglumine; and phantom 3: 2.5 μmol gadopentetate dimeglumine) were set around the neck. SIR was calculated for each region of interest and compared according to pathological grade.

The method using a phantom as a reference reduced the standard deviations of tissue ratios to 0.16 from 0.27 in comparison with the method using muscle and showed a close correlation with pathological grade. In addition, the agreement rates with pathological grade and grades from each SIR using signal intensity of the phantom as a reference were higher than using signal intensity of the muscle as a reference to 0.86 from 0.63 for two-dimensional images and to 0.86 from 0.71 for three-dimensional images.

The method described here reduced error compared to the method using muscle as a reference, and the results were closely correlated with pathological grade.