Using ultrasound sequential images processing to predict radiotherapy-induced sternocleidomastoid muscle fibrosis

The purpose of this study was to evaluate the thickness and biomechanical parameters of the sternocleidomastoid muscle (SCM) before, during, and after radiotherapy using ultrasound elastography to predict radiotherapy-induced muscle fibrosis.

The mean daily absorbed doses of 20 SCMs were determined. To find out the Young and shear modulus, shear wave elastography (SWE) and the B-mode sequential images processing method were implemented. In the B-mode sequential images processing method, by administering dynamic stress, the Young and shear modulus were estimated utilizing the maximum gradient and the block-matching algorithms, respectively. The imaging was done before, during the third and sixth weeks of treatment, and 3 months after radiotherapy.

There was a statistically significant increase in the maximum thickness during the sixth week compared to before radiotherapy (p = .043). However, this parameter did not change significantly 3 months later (p = .095). The Young modulus (p = .611) derived from SWE did not differ significantly throughout any of the weeks of radiotherapy. But Young and shear modulus increased significantly in the B-mode sequential images processing method before and during the third and sixth weeks of treatment (p = .001). The outcomes observed 3 months after radiotherapy revealed a statistically significant increase in both Young modulus (p = .029) and shear modulus (p = .004) compared to pre-radiotherapy.

The Young modulus and shear modulus are introduced as biological markers used to detect the onset of the fibrosis process during the initial radiotherapy fractions.