Design and evaluation of a highly accurate optical setup for backscatter analysis

In modern radiation therapy the interest in optical tracking systems has increased sincethey provide the possibility of non-invasive real-time patient localization. The target of our work is toimprove the tradeoff between comfort and accuracy provided by current systems such as thermoplasticmasks. Although the accuracy of optical systems has been improved in recent years markerless opticaltracking suffers from the influence of skin elasticity which has not been considered yet. To take theseeffects into account it is necessary to study this influence. For this purpose we performed initial MonteCarlo simulations [6] of light-tissue interactions to specify our hardware requirements. These are mainlygiven by a wavelength of 850 nm and an in-beam setup for the camera to laser position. This study aimsat developing an appropriate experimental setup to validate our results and to apply our knowledge fromthe simulations. Therefore, we present our hardware design and all relevant calibration steps for reliabledata acquisition. After a general overview we focus on the optical part and a laser/effector calibration.Finally, we evaluate our setup regarding the accuracy of the calibration and the laser positioning on agiven pattern.