4C-5 Combining High Frequency Ultrasound Reflex Transmission Imaging and Imaging Spectrophotometry for the Diagnosis of Skin Cancer

We have developed novel ultrasound (US) and optical non-invasive methods suitable for use in combination, to determine whether a hybrid multivariate approach may eventually be able to provide an objective aid to skin cancer diagnosis in primary care. A high frequency 3D US scanner was modified for C-scan, surface echo tracking and reflex transmission imaging. The images were co-registered with colour photographs and with images from a purpose-built spectrophotometric camera. The US system was used to scan 87 suspicious pigmented skin lesions referred from primary care. Nine were also examined using the imaging spectrophotometer. US regions of interest were drawn using the pigmented lesion boundaries on co- registered photographs, and numerical US characteristics were extracted for each lesion, providing a relative measure of US surface reflectance, intra-lesional US reflectance, total US attenuation, and the relative homogeneity of each characteristics. Quantitative differences between melanoma, seborrheic keratosis and benign naevi provided discrimination that was sufficient to potentially reduce the referral of benign tumours by 65% without missing melanoma. The extent and nature of the visual correspondence between optical spectral images of various wavelength and US C-scans at various depths varied with pigmented lesion type so as to suggest that there may indeed be value in combining spectrophotometric and US imaging in pigmented lesion diagnosis.