射波刀技术介绍瑞康.ppt

* The heart of the image guidance system is the imaging subsystem. This system uses 2 diagnostic X-ray sources mounted to the ceiling paired with amorphous silicon detectors (frequently referred to as “cameras”) to acquire live digital radiographic images of the patient. The patient is imaged at 45 degree LAO (left anterior oblique) and RAO (right anterior oblique) angles to facilitate reconstructing the 2D images into 3D space. The images acquired in this process are compared to the DRRs in the treatment library to calculate the patient’s position in space. The x-ray sources used in the imaging system use low energy kV x-rays as compared to the high energy x-rays produced by the linac. The x-ray sources’ output can be adjusted by the system operator via the user interface, and it is important that the user understand how to adjust the x-ray sources for optimum performance of the system. We will discuss techniques for adjusting the x-ray parameters in later classes. * The amorphous silicon detectors produce the digital radiographic images used for calculating the position of the patient. They are housed in stands that shield them and protect their electronic components from the high energy output of the linear accelerator. The point in the geometric center of the two detectors (the point at which the central axes of the dx beams intersect) is indicated here by the tip of this post, the isopost. The crystal on the end of this marks the position we refer to as “isocenter” or “machine center,” which is used during patient alignment. The crystal is light sensitive and is used for calibration tests for the robot and imaging system (pointing test and camera alignment test). * The couch used by the CK system is unlike the couches used by any other radiotherapy or radiosurgery system. First, it provides a full 5 degrees of freedom, incorporating roll and pitch in addition to the 3 translational directions. It does not support cw/ccw rotation (commonly referred to