Shear-wave ultrasound elastography for tissue-specific quantification of radiation-induced cervical fibrosis

Background and purpose: Radiation-induced cervical fibrosis is a common late effect following radiotherapy for head and neck cancer, potentially leading to reduced tissue compliance and functional impairment. Objective assessment, however, remains challenging in clinical practice. Therefore, this study aimed to evaluate the feasibility of shear-wave ultrasound elastography (SWE) for quantitative, tissue-specific assessment of radiation-induced cervical fibrosis. Materials and methods: Sixteen patients after bilateral cervical lymphatic irradiation were compared with sixteen age-, sex-, and body mass index-matched controls without prior head and neck irradiation. SWE was used to quantify stiffness of muscle, fascia, and subcutaneous tissue of the sternocleidomastoid muscle. Ultrasound-based thickness measurements and assessment of cervical range of motion were additionally performed. Results: Mean muscle stiffness was significantly higher in irradiated patients compared with controls (left: 46.98 vs. 28.10 kPa; right: 46.75 vs. 21.52 kPa). Comparable increases were observed in the fascia (left: 46.41 vs. 25.47 kPa; right: 44.28 vs. 22.69 kPa), whereas differences in subcutaneous tissue were less pronounced. Muscle and skin thickness were significantly reduced after radiotherapy. Cervical range of motion did not differ significantly between groups, although a non-significant reduction of approximately 5° in cervical rotation was observed. Negative correlations between muscle stiffness and cervical range of motion were observed but did not reach statistical significance. Conclusion: Shear-wave elastography enables reliable, tissue-specific quantification of radiation-induced cervical fibrosis, predominantly affecting muscle and fascia. Despite increased tissue stiffness and reduced thickness, cervical range of motion remained largely preserved, suggesting a dissociation between structural tissue alterations and functional impairment.