Quality Assurance of Pinnacle Treatment Planning System for External Beam Radiotherapy
Introduction: A quality assurance (QA) program for two Pinnacle version 7.0 workstations was developed and implemented.
Materials and methods: The program consisted of periodic test procedures which were designed according to the IAEA recommendations for treatment planning system (TPS) quality assurance. The TPS features tested were hardware, transferred CT images, and critical software functions. The hardware tested was CPU, digitizer, printer, and backup devices. Consistency of CT images of 3d01a and CIRS phantoms transferred to Pinnacle was examined, i.e. patient orientation, image geometry, tissue density, and contour dimensions. The aspects of Pinnacle software evaluated were monitor unit and dose calculation, plan printout data and electronic plan transfer. Photon dose calculations were verified against doses measured with a Farmer chamber. For electron beams, Pinnacle and manual calculations were compared.
Results: Test results for hardware functionality were satisfactory. Patient orientation was properly represented in CT images in Pinnacle. Image geometry and contour dimensions were acceptable. However, the reported densities in Pinnacle differed from the actual density values by more than 0.02 g/cm3 for low (ρ ≤0.28 g/cm3) and high-density (ρ ≥1.362 g/cm3) inserts of the 3d01a phantom. Similar discrepancies were observed in the lung, adipose, solid water, and bone inserts of the CIRS phantom. Moreover, calculated doses in Pinnacle exceeded tolerance in some points in the CIRS phantom.
Discussion: Erroneous tissue densities in Pinnacle most likely contributed to the discrepancies in calculated doses. Thus the CT number-density calibration curve must be corrected and dose measurements repeated to resolve the dose calculation inaccuracies. Electron dose calculations also need to be verified with measurements. Initial implementation of the QA program verified the capabilities of Pinnacle and was a marked improvement on the overall treatment planning process. Periodic testing would have to be followed to ensure that the Pinnacle workstations consistently meet the desired quality.
Keywordstreatment planning quality assurance
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