Assessing the short-term effects of radiotherapy on the shear modulus of the common carotid artery as a new biomarker of radiation-induced atherosclerosis

Purpose: The purpose of this study was to investigate the incidence of short-term atherosclerosis in the common carotid arteries following radiotherapy. Methods: The mean radiation dose to the arteries was 49.30 +/- 15.83 Gy. A computational ultrasound method was introduced to investigate the elastic modulus. Ultrasonography was performed 2-3 cm inferior to the bifurcation region before and after radiotherapy, and sequential images were extracted from a video of each artery. Instantaneous movement of the arterial wall in the radial and longitudinal directions was extracted by implementing the maximum gradient and block matching algorithms, respectively. Results: There was a significant change in systolic blood pressure after radiotherapy (P=0.008). Irradiated arteries had significantly smaller systolic and end-diastolic diameters than non irradiated arteries (P<0.001). The shear modulus was significantly different between irradiated and non-irradiated arteries (3.10 +/- 2.03 kPa vs. 1.38 +/- 0.98 kPa, P<0.001). The shear and Young moduli of radiation-induced arteries were 2.25 +/- 1.50 and 1.57 +/- 0.59 times higher than those of the pre-irradiation arteries. Conclusion: The arterial shear modulus can be considered as a new biomarker of radiation induced atherosclerosis in the common carotid artery.