Relative profile and dose verification of intensity-modulated radiation therapy
| Autor: | Jenghwa Chang, C. Clifton Ling, Chen S. Chui, Gikas S. Mageras, Wendell R. Lutz |
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| Rok vydání: | 2000 |
| Předmět: |
Male
Quality Control Normalization (statistics) Cancer Research Sensitivity and Specificity Standard deviation Imaging phantom Physical Phenomena Planned Dose Humans Medicine Dosimetry Radiology Nuclear Medicine and imaging Radiation Phantoms Imaging business.industry Physics Prostatic Neoplasms Reproducibility of Results Isocenter Radiotherapy Dosage Radiotherapy Computer-Assisted Electronics Medical Intensity (physics) Oncology Linear Models business Nuclear medicine Quality assurance Algorithms |
| Zdroj: | International Journal of Radiation Oncology*Biology*Physics. 47:231-240 |
| ISSN: | 0360-3016 |
| DOI: | 10.1016/s0360-3016(99)00555-6 |
| Popis: | Purpose: To develop a quality assurance (QA) procedure to assess the intensity profile and dosimetry for intensity-modulated (IM) treatment fields using electronic portal imaging devices (EPIDs). Methods and Materials: A series of rapidly acquired (∼1/sec) portal images are summed and converted to dose. For relative intensity QA, the intended profile is subtracted point-by-point from the measured profile forming a series of error values. The standard deviation, σ, of the errors, a measure of the goodness of the match, is minimized by applying a normalization and uniform scatter subtraction from the measured profile. For dose verification (dose to isocenter), an empirically determined phantom-correction factor is added to incorporate the effect of patient presence on EPID readings. Seventy prostate treatment fields were used in a phantom study to verify these approaches. Sensitivity was studied by creating artificial mismatches. Results: The average σ for relative profile verification is 3.3% (percentage of average intended intensity) whereas artificial mismatches resulted in σ values from 5% to 27%. The average isocentric dose calculated from EPID readings is 1.001 relative to the planned dose with a standard deviation of 0.018. Conclusions: An EPID can be used for profile verification and absolute isocentric dose measurement for IM fields. |
| Databáze: | OpenAIRE |
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