4B02b-CT Simulator QA

Ching-Chong Jack  Yang, PhD

Radiation Oncology Dept.

Monmouth Medical Center

300 2nd Ave

Long Branch, NJ  07740

CT has become an important front-end tool for radiation therapy practice and gradually replacing the conventional simulation devices in some clinics. Preparing CT Simulator accepting protocol and QA/QC process in a routine clinic could be a challenge for physicists. CT simulator not only acts as an imaging tool but also performs as a localization device using the associated software and lasers. Therefore, except for the image quality requirement, the geometrical accuracy is the focal point of the QA process.   Quality assurance of a CT simulator should have the following components: 1) Initial acceptance testing; 2) Daily QA protocol; 3) Monthly QA protocol; and 4) Annual QA protocol.  Quality of the acquired CT images are very important for image registration purposes of target and critical structures, however, the geometrical accuracy of coordinate system (isocenter management) is also the key for subsequent treatment planning accuracy. Lasers to correlate patient marking will be addressed and it needs to go through a thorough verification process for clinical implementation. CT number definition is also important for verification if inhomogeneity correction is clinically implemented with 3D planning module. The CT number can be a source for error if not properly calibrated. Using the CT simulation could increase the treatment delivery precision if the QA/QC were performed and maintained properly.