1. Clinical introduction of a linac head-mounted 2D detector array based quality assurance system in head and neck IMRT
- Author
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Peter C. van der Hulst, Johannes A. Langendijk, Aart A. van 't Veld, Erik W Korevaar, D.J.L. Wauben, Damage and Repair in Cancer Development and Cancer Treatment (DARE), and Guided Treatment in Optimal Selected Cancer Patients (GUTS)
- Subjects
Quality Assurance, Health Care ,DYNAMIC-MODE ,Computer science ,Imaging phantom ,DELIVERY ,Gamma index analysis ,Compass ,RADIATION-THERAPY ,Calibration ,DOSE VERIFICATION ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiometry ,Image resolution ,SPATIAL-RESOLUTION ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Detector ,Reproducibility of Results ,Radiotherapy Dosage ,IMRT QA ,Hematology ,DOSIMETRY ,INTENSITY-MODULATED RADIOTHERAPY ,Oncology ,Head and Neck Neoplasms ,Film dosimetry ,MULTILEAF COLLIMATION ,PIXEL IONIZATION-CHAMBER ,MONITOR UNIT SETTINGS ,Dose reconstruction ,2D ionization chamber array ,Tomography ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,business ,Nuclear medicine ,Tomography, X-Ray Computed ,Quality assurance - Abstract
IMRT QA is commonly performed in a phantom geometry but the clinical interpretation of the results in a 2D phantom plane is difficult. The main objective of our work is to move from film measurement based QA to 3D dose reconstruction in a patient CT scan. In principle, this could be achieved using a dose reconstruction method from 2D detector array measurements as available in the COMPASS system (IBA Dosimetry). The first step in the clinical introduction of this system instead of the currently used film QA procedures is to test the reliability of the dose reconstruction. In this paper we investigated the validation of the method in a homogeneous phantom with the film QA procedure as a reference. We tested whether COMPASS QA results correctly identified treatment plans that did or did not fulfil QA requirements in head and neck (HN) IMRT.A total number of 24 treatments were selected from an existing database with more than 100 film based HN IMRT QA results. The QA results were classified as either good, just acceptable or clinically rejected (mean gamma index0.4, 0.4-0.5 or0.5, respectively with 3%/3mm criteria). Film QA was repeated and compared to COMPASS QA with a MatriXX detector measurement performed on the same day.Good agreement was found between COMPASS reconstructed dose and film measured dose in a phantom (mean gamma 0.83±0.09, 1SD with 1%/1mm criteria, 0.33±0.04 with 3%/3mm criteria). COMPASS QA results correlated well with film QA, identifying the same patients with less good QA results. Repeated measurements with film and COMPASS showed changes in delivery after a modified MLC calibration, also visible in a standard MLC check in COMPASS. The time required for QA reduced by half by using COMPASS instead of film.Agreement of COMPASS QA results with film based QA supports its clinical introduction for a phantom geometry. A standard MLC calibration check is sensitive to1mm changes that could be significant in HN IMRT. These findings offer opportunities to further investigate the method based on a 2D detector array to 3D dose reconstruction in a patient anatomy.
- Published
- 2011