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Portal Dosimetry Scripting Application Programming Interface (PDSAPI) for Winston Lutz Test

Y Hao, M Schmidt, Y Wu, M Yaqoub*, N Knutson, Washington University School of Medicine, St Louis, MO


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments require a high degree of accuracy. Mechanical, imaging and radiation isocenter coincidence is especially important. As a common method, the Winston-Lutz test plays an important role. However, weekly or daily Winston-Lutz test can be very time consuming. We developed novel methods using Portal Dosimetry Scripting Application Programming Interface (PDSAPI) to facilitate the test as well as documentation.

Methods: Winston-Lutz PDSAPI was developed and tested on our routine weekly Winston-Lutz imaging. The results were compared against two commercial available software RIT (Radiological Imaging Technology, Colorado Springs, CO) and DoseLab (Varian Medical Systems, Inc. Palo Alto, CA). Two manual methods served as ground truth were used to verify PDSAPI results. Twenty Winston Lutz test image data sets (10 fields per tests, and 200 images in total) were analyzed by these five methods in this study.

Results: More than 99.5% of Winston-Lutz PDSAPI 1D shifts agreed with each of four other methods within ±0.33mm, which is roughly the pixel width of a-Si 1200 portal imager when source to imager distance is at 100cm. For the threshold ±0.22mm and 0.11mm, 1D shifts agree at least 96% and 63% respectively. Same trend was observed for 2D displacement.

Conclusion: Winston-Lutz PDSAPI has corresponding quality as other two commercial software for Winston-Lutz test. This new application can save huge amount of time for data transferring and has the potential to implement daily Winston-Lutz test with reasonable test time. It also provides the data storage capability, enables easy access to imaging and shift data.


Electronic Portal Imaging, Stereotactic Radiosurgery, Software


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