A study on the effect of detector resolution on gamma index passing rate for VMAT and IMRT QA

Autor: Piyasiri Ekayanake, Jamsari Khalid, Paul B Ravindran, Vikraman S, Yivonne Y.F. Lim, WuiAnn Woon
Rok vydání: 2018
Předmět:
Quality Assurance
Health Care
87.55.dk
87.55.Qr
87.53.Kn
87.56.Fc
IMRT/VMAT
diode arrays
030218 nuclear medicine & medical imaging
03 medical and health sciences
0302 clinical medicine
MLC systematic errors
Histogram
Humans
Radiation Oncology Physics
Radiology
Nuclear Medicine and imaging
Instrumentation
Image resolution
Mathematics
Nasopharyngeal Carcinoma
Radiation
Receiver operating characteristic
business.industry
Radiotherapy Planning
Computer-Assisted
Carcinoma
87.55.km
Resolution (electron density)
Detector
Nasopharyngeal Neoplasms
Radiotherapy Dosage
Prognosis
sensitivity
Multileaf collimator
gamma criteria
Gamma Rays
correlation
030220 oncology & carcinogenesis
Radiotherapy
Intensity-Modulated
business
Nuclear medicine
87.53.Bn
EPID
Sensitivity (electronics)
Quality assurance
Algorithms
Zdroj: Journal of Applied Clinical Medical Physics
ISSN: 1526-9914
DOI: 10.1002/acm2.12285
Popis: The main objectives of this study are to (1) analyze the sensitivity of various gamma index passing rates using different types of detectors having different resolutions and (2) investigate the sensitivity of various gamma criteria in intensity‐modulated radiation therapy (IMRT) and volumetrically modulated arc therapy (VMAT) quality assurance (QA) for the detection of systematic multileaf collimator (MLC) errors using an electronic portal imaging device (EPID) and planar (MapCheck2) and cylindrical (ArcCheck) diode arrays. We also evaluated whether the correlation between the gamma passing rate (%GP) and the percentage dose error (%DE) of the dose–volume histogram (DVH) metrics was affected by the finite spatial resolution of the array detectors. We deliberately simulated systematic MLC errors of 0.25 mm, 0.50 mm, 0.75 mm, and 1 mm in five clinical nasopharyngeal carcinoma cases, thus creating 40 plans with systematic MLC errors. All measurements were analyzed field by field using gamma criteria of 3%/3 mm, 3%/2 mm, 3%/1 mm, and 2%/2 mm, with a passing rate of 90% applied as the action level. Our results showed that 3%/1 mm is the most sensitive criterion for the detection of systematic MLC errors when using EPID, with the steepest slope from the best‐fit line and an area under the receiver operating characteristic (ROC) curve >0.95. With respect to the 3%/1 mm criterion, a strong correlation between %GP and %DE of the DVH metrics was observed only when using the EPID. However, with respect to the same criteria, a 0.75 mm systematic MLC error can go undetected when using MapCheck2 and ArcCheck, with an area under the ROC curve
Databáze: OpenAIRE
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