Patient Positioning in Radiotherapy Using Body Surface Scanning

Sammanfattning: External radiotherapy uses ionising radiation to damage the DNA of the tumour cells and thereby inhibit their uncontrolled proliferation. The technical development regarding imaging and visualisation for radiotherapy has increased considerably during the last decades. By a submillimetre accuracy, a body surface laser scanning (BSLS) system maps the patient body contour in the treatment position by scanning a transversal laser line and detecting its reflection. A treatment plan is created for each patient to find a treatment that delivers a high dose to the tumour whilst keeping the dose to the surrounding normal tissue as low as possible. The setup done for treatment planning must be reproduced in the treatment room. Commonly patient skin-marks are aligned to room lasers to setup the patient in the treatment position. The setup is then verified by the BSLS and a cone-beam CT (CBCT) system. For left-sided-breast cancer patients, the dose to radiosensitive parts of the heart can be decreased by letting the patient take a deep breath and hold it in deep inspiration breath-hold (DIBH) position during treatment. The BSLS system can guide the patient to this position via visual and audial instructions to the patient. The breathing trace of a lung cancer patient can be monitored by the BSLS system to estimate the quality of the images used for treatment planning and also to support the treatment target definition process. The number of application of the BSLS system has increased over the years. Together with its increased accuracy and robustness, surface scanning has now reached a level where it can be used as a primary setup system, replacing skin-marks (paper I), guiding left-sided breast cancer patient to a reproducible DIBH position (paper II) and lung tumour motion can be determined more accurately (paper III and IV).