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A calibration method for patient specific IMRT QA using a single therapy verification film
Arvind Kumar Shukla1, Arun S Oinam1, Sanjeev Kumar2
1Department of Radiotherapy, Post Graduate Institute of Medical Education and Research, 160 012, India.
Summary
A new single film calibration method offers fast and accurate quality assurance for intensity-modulated radiation therapy (IMRT). This technique simplifies daily checks, improving the reliability of IMRT treatments.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Quality Assurance
Background:
- Radiographic films are integral to treatment modality commissioning and treatment planning system (TPS) verification.
- Film-based dosimetry provides absolute 2D dose distribution, valuable for IMRT quality assurance.
- A single verification film offers a rapid and reliable method for IMRT verification.
Purpose of the Study:
- To develop and validate a single film calibration procedure for intensity-modulated radiation therapy (IMRT) quality assurance.
- To establish a reliable method for quantitative dose verification in IMRT.
Main Methods:
- Generated a sensitometric curve using a single Extended Dose Rate (EDR) 2 film, correlating optical density with radiation dose.
- Exposed EDR 2 film with a 6 MV photon beam across nine fields at varying doses (10-362 cGy).
- Verified ten IMRT plans for head and neck carcinoma using the gamma index method against TPS-calculated doses.
Main Results:
- Developed a sensitometric curve for quantitative dose verification in IMRT.
- Observed an exponential decrease in radiation scatter factor with increasing distance from field centers.
- IMRT plan verifications using the calibration curve met acceptable criteria via the gamma index method.
Conclusions:
- The single film calibration method is superior to traditional techniques for IMRT verification.
- This method enables fast daily film calibration, enhancing the accuracy of IMRT verification.
- The validated procedure ensures reliable and efficient quality assurance for IMRT treatments.
