Assessment of neck tissue fibrosis using an ultrasound palpation system: afeasibility study

Fibrotic change in the soft tissue of the neck is a common side-effect afte r radiotherapy treatment for cancers of the head and neck region. The devel opment of a quantitative approach for the assessment of neck tissue stiffne ss using an ultrasound palpation system (UPS) is reported. A testing protoc ol was established with the participation of eight normal subjects and four patients who had neck fibrosis after previous radiotherapy to the neck. Si x reference sites were assessed on each side of the neck in each subject Si te-dependence, inter-observer variability and infra-observer variability we re further evaluated by measurement of sites 1 cm anterior, posterior, supe rior and inferior to two of the reference sites on each side of the neck, a nd by repeating measurements using a second observer on the same occasion a nd using the same observer one week afterwards. The mean tissue Young's mod ulus for normal subjects was 12.8+/-3.9 kPa, and that of the radiotherapy-t reated patients ranged from 46.4 to 108.3 kPa. The modulus shows limited va riation among anatomical sub-sites within the neck. For a confidence level of 95%, there was a variation of +/- 14.2% for site-dependence, +/- 15.2% f or inter-observer, and +/- 7.2% for intra-observer tests for the group of n ormal subjects. The variation in the patients was +/-13.6% for site-depende nce, and +/- 13.1% for the inter-observer test.