Towards a fractioned treatment in conformal radiotherapy using 3D-multimodal data registration

The combination of conformal radiotherapy and fractioned radiotherapy is a very useful tool against cancer. Meanwhile, this combination is only interesting if the patient positioning method is accurate and non invasive. This paper presents an algorithm fulfilling the latter conditions. The method was developed for tumors located in the head and does not need any patient dedicated device. Homologous structures, acquired with a computer tomograph and with a sensor fixed in the treatment room, are used to register two 3D-surfaces. The registration scheme is notably based on the directed Hausdorff distance. The registration, together with a calibration of the 3D-sensor in the therapy room, leads to a mean positioning error of 0.77 mm. Tests performed with a phantom deliver also a maximal error of 1.6 mm.