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

Purpose: 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.

Materials and methods: 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.

Results: 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.

Conclusion: 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.