14. Radiation Therapy Planning for Skin Cancer: Using 3D Surface Scanning to Localize Tumour

Abstract


 Orthovoltage radiation therapy (ORT) is a non‑invasive treatment often used for patients with skin cancer, which is characterized by shallow tumours visible at the surface of the skin. Currently there is no commercially available treatment planning system for ORT. The first step of treatment planning is localizing the tumour in a computed tomography (CT) scan of the patient. We propose using 3D surface scanning to obtain a coloured and textured image of the patient, from which the tumour can be identified. The contour of the tumour can then be overlaid onto the CT image, for planning delivery of radiation therapy. This process was demonstrated using a male mannequin model, with a red sticker on the nose representing a skin tumour. A coloured and textured image of the face was obtained using a handheld 3D surface scanner [Figure 1]. The surface scan was aligned to a CT image of the mannequin head using a two‑step registration process, with a resulting error of 0.25mm. The tumour could then be easily segmented from the coloured surface scan by following the outline of the lesion. The tumour contour was extended in depth to 1cm, to encompass subdermal cancerous tissue in the treatment volume, and saved with the CT image for treatment planning [Figure 2]. This workflow is the first step to an open-source treatment planning system for ORT, which will allow physicians to deliver more precise treatment using ORT. This project was done in collaboration with the Kingston General Hospital.