Medical Physics

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Browsing Medical Physics by Subject "Cancer -- Radiotherapy -- South Africa"

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    A multi-institutional quantitative survey of multi-leaf collimator accuracy using a digital picket fence test with sub-millimetre detection capabilities.
    (Stellenbosch : Stellenbosch University, 2022-04) Boonzaier, Willem Petrus Engelbrecht; Trauernicht, C. J.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Medical Physics.
    ENGLISH SUMMARY: When patients are treated with modern radiotherapy, multi-leaf collimators (MLC) are used to shape treatment fields. With recent advances in technology, MLCs have also been used to modulate dose in certain areas inside patients to obtain better treatment outcomes. For the desired treatment outcomes to be valid, the equipment used to deliver the radiotherapy must function optimally. This study was aimed at creating software that can measure the accuracy of the MLC independently with routine picket fence test measurements. With this in place, the software was used to conduct a national survey of the accuracy of MLC systems on various medical linear accelerators in South Africa. Using on-board imaging and the in-house created software, MLC position and width errors could be found efficiently and with a very low degree of user input. When the results from the software were validated with measurements, other commercial software, and log files from linear accelerators, the average errors found agreed within 0.27mm, 0.49mm and 0.11mm for the measurements, commercial software and log file comparisons respectively. A national survey could be done with data from participating volunteer centres. A distinction could be made between units with more advanced capabilities such as VMAT and SRS capabilities by including picket fence tests acquired during arc delivery and picket fence tests done as a measure of the performance of the MLC for VMAT and SRS applications. The results showed that the software was easy and non-costly to compile. Results indicate that the software is robust enough to be used across a multitude of vendor types but sensitive enough to detect MLC errors in the order of 1 pixel of the onboard detector used. The software indicated that all units that participated in this study met the national standards of 2mm MLC accuracy. SRS capable units all had MLC accuracies under 1mm.