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Updated: Jun 11, 2026
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Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition
Published on: March 11, 2021
IMRT implementation and patient specific dose verification with film and ion chamber array detectors
S Sathiyan1, M Ravikumar, C Varatharaj
1Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore, India. ssathiyan@rediffmail.com
The Gulf Journal of Oncology
|July 6, 2010
Summary
This study validated Intensity Modulation Radiotherapy (IMRT) delivery using a dynamic multileaf collimator (dMLC) and patient-specific dose verification. Results show acceptable accuracy for clinical implementation, emphasizing regular quality assurance for precise radiation therapy.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Quality Assurance
Background:
- Intensity Modulation Radiotherapy (IMRT) requires precise delivery of radiation doses.
- Dynamic multileaf collimators (dMLC) are crucial components for IMRT beam shaping.
- Rigorous quality assurance (QA) is essential for verifying IMRT accuracy and patient safety.
Purpose of the Study:
- To implement and verify Intensity Modulation Radiotherapy (IMRT) using a 120-leaf Millennium dynamic multileaf collimator (dMLC).
- To assess the mechanical, electrical, and dosimetric performance of the dMLC for IMRT.
- To evaluate patient-specific dose verification using film, I'mariXX, and ion chambers against Treatment Planning System (TPS) calculations.
Main Methods:
- Performed mechanical and electrical commissioning tests, including leaf position accuracy and repeatability.
- Conducted picket fence and garden fence tests for dMLC stability and gap reproducibility.
- Executed dosimetric checks (output stability, leaf transmission, leaf separation) and pretreatment patient dose verification for 50 patients.
Main Results:
- Output variation with gravity was within 0.9%; average leaf transmission was 1.6% (6 MV) and 1.8% (18 MV).
- Dosimetric leaf separation was 2.2 mm (6 MV) and 2.3 mm (18 MV); weekly dynalog file analyses showed good agreement.
- Patient dose verification showed variations within acceptable criteria, with 86% of patients achieving >95% gamma pixel match (3% DD, 3 mm DTA).
Conclusions:
- The dMLC commissioning and QA for IMRT are time-consuming but critical for accurate dose delivery.
- Regular weekly and monthly checks are necessary to ensure dMLC stability and precision.
- Patient-specific pretreatment verification is vital; individual Monitor Unit (MU) checks are recommended before treatment delivery.
