AIMS: Radiation-induced fibrosis and neuropathy are common in head/neck cancer (HNC) and contribute to late-stage dysphagia. Yet, there is limited evidence for non-invasive tools capable of detecting these tissue changes. Ultrasound with shear-wave elastography shows promise, but no standardised protocol exists. ULTRA Late-RAD aimed to feasibility-test an ultrasound protocol for assessing swallowing-related structures and explore muscle and nerve characteristics. METHODOLOGY: Twenty HNC survivors (75% male, 60% definitive (chemo)RT, mean 7.1y post-treatment) and 12 controls engaged in this exploratory study. B-mode imaging and shear-wave elastography assessed submental, infrahyoid, and cervical muscles and the hypoglossal nerve (CNXII). Feasibility outcomes included image acquisition/quality, protocol adherence, and tolerability. Between-group analyses explored muscle/nerve size, elastography, and echogenicity, with multivariable modelling controlling for sex, age, and BMI. RESULTS: All feasibility benchmarks were met: image acquisition 99.3%, good image quality 98.4%, protocol deviations <3%, and no adverse events. HNC survivors had significantly smaller geniohyoid (bilateral, p=.002) and sternocleidomastoid (SCM) (bilateral, p<.001) muscle sizes, and higher elastography values in the geniohyoid (bilateral, p<.001) and left SCM (p=.009), indicating greater stiffness. Survivors exhibited hyperechoic appearances in the geniohyoid and digastrics, suggesting fibrosis or fat infiltration. CNXII pathology was observed in 20% of the HNC cohort, with hypoechoic nerve appearances (p≤.029). CONCLUSION: Ultrasound with elastography was feasible and well-tolerated, and identified a phenotype in HNC survivors involving reduced muscle size, increased stiffness, and hyperechoic muscle appearance in the geniohyoid and SCM, alongside CNXII pathology in a subset of cases. Findings support the potential of ultrasound for detecting late radiation effects in HNC survivorship care.