Initial experience with a system for automated patient positioning

Conformal radiation therapy promises to deliver high tumor doses while sparing nearby tissue. Full realization of this promise, however, requires accurate and convenient patient positioning. Methods for positioning cranial targets rely on the rigidity of this body region. This work investigates a novel approach for positioning extracranial targets based on the location of IR reflective markers attached to the patient’s skin. Both phantom and volunteer tests assess the accuracy and reproducibility of the system. Volunteer tests suggest that in addition to positioning the patient, the system might also track his breathing cycle for gating of the linear accelerator. The system promises to strengthen the weak link in the chain of conformal radiation therapy, patient positioning. While conventional accuracy is between 5–10 mm1, this system positions a target to within 2–3 mm of the isocenter.