Digital image verification for clinical quality assurance in radiation therapy

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(1) For basic research of 'setup error', we investigated the 6 dimensional (X, Y, Z, pitch, roll, yaw) detection ability of an inspection by watching. We use the simulation films and portal films of a head phantom. Rotations were more difficult to be detected than Shifts. And in rotations, yawing was comparatively easy to be detected than other to rotation, because it's axis of rotation was a perpendicular line of film plane.(2) We study the way of appropriate image-processing for simulation films and portal films to detect landmark of skeletal structures. The defferences of basical bias because of soft tissues were eliminated by Fourier transformation and high-pass filter. We use small metal marker for calibration of correction of magnification by fan-beam projection.(3) We discuss the landmark of skeletal structures as reference point to determine the fields of irradiation. In side-view ( left-right), auditory canals were usefull as skeletal landmark to detect the setup errors of rolling and yawing. If both auditory canals were recognized, they were usefull as well as metal markers.(4) Finally, for clinical use, we measured setup errors about fifteen clinical cases who were whole brain irradiated, through simulation films and portal films. It was sometimes difficult to recognize the landmarks of skeletal structures by human. And to detect setup errors were more difficult for machine recognize without some metal markers.