High frequency ultrasound – Use in the Photo Dynamic Therapy Clinic

Colin Swift, The Christie NHS Foundation Trust

Basal cell carcinomas (BCC) are the most common form of skin cancer and make up more than 80% of skin cancers seen in the UK. They are primarily caused by exposure to ultraviolet light from the sun or sunbeds but also seen in individuals with certain genetic disorders such as Gorlin syndrome. Several treatment options for this condition are available including surgery, cryotherapy, radiotherapy, and Photodynamic Therapy (PDT). PDT has been shown to be an effective treatment having high clearance rates and excellent cosmetic outcomes. For PDT to be successful the depth of the tumour should ideally be less than approximately 3mm, to ensure both sufficient penetration of the photosensitizing drug, and penetration of the activating light. High frequency ultrasound (HFUS) at 35MHz has been used extensively within the PDT clinic to determine the extent of such tumours. BCCs are clearly defined on such scans having a different echogenicity to the normal surrounding tissue. Depth measurements of BCCs to be determined are an important factor as it will influence clinical decisions as to whether PDT is a suitable mode of treatment or if other treatment options may be more suitable.

HFUS scans have been undertaken in multiple sites (up to 11) on 213 patients in the last year. The majority (184) were treated for BCCs, 18 for Bowen’s disease and 11 for actinic keratosis. The HFUS scans have proven to be very useful in the monitoring of the effectiveness of the treatment and additionally tumour shrinkage should repeat treatments be required. Its use in further applications in skin oncology in the Christie clinic is being explored.

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