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A Self-Checking Treatment Couch Coordinate Calculation System in Radiotherapy

P Tsai*, C Liu , J Li , B Lu , G Yan , University of Florida, Gainesville, FL


(Tuesday, 7/16/2019) 9:00 AM - 10:00 AM

Room: Pins Room | Hall 2

Purpose: Traditionally, the treatment couch coordinates (TCC) for patients undergoing radiotherapy can only be determined at the time of treatment, placing pressure on the treating therapists and leaving several pathways for errors such as wrong-site treatment. The purpose of this work is to propose an accurate, robust, and streamlined system that calculates TCC in advance.

Methods: The proposed system combined the advantages of two different calculation methods that used indexed immobilization device. The first method used an array of reference ball bearings (BBs) embedded on the CT scanner’s couch-top. To obtain the patient-specific TCC, the spatial offset of the treatment planning isocenter from the reference BB was used to adapt the reference couch coordinates (the couch position that places reference BB at treatment room isocenter). The second method performed calculation using the one-to-one mapping relationship between the CT Scanner’s DICOM (Digital Imaging and Communications in Medicine) coordinate system and the TCC system. Both methods were used to calculate TCC and the results were checked against each other, creating an integrated workflow via automated self-checking. The accuracy of the calculation system was retrospectively evaluated with 275 patients, where the actual treatment position determined with cone-beam CT was used as references.

Results: An efficient workflow transparent to the therapists at both CT simulation and treatment was created. It works with any indexed immobilization devices and can be universally applied to all treatment sites. The two methods had comparable accuracy with 95% of the calculations within 3 mm. The inter-fraction variation was within ±1.0 cm for 95% of the coordinates across all treatment sites.

Conclusion: A robust, accurate, and streamlined system was implemented to calculate TCC in advance across all treatment sites. It eases the pressure on the treating therapists, reduces patient setup time and enhances patient safety by preventing setup errors.


Setup Errors


IM/TH- Formal quality management tools: General (most aspects)

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