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3D tomodosimetry using long scintillating fibers: a feasibility study.
Mathieu Goulet1, Louis Archambault, Luc Beaulieu
1Département de Physique, de Génie Physique et d'Optique et Centre de Recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada, and Département de Radio-Oncologie and CRCHU de Quebec, CHU de Québec, 11 Co^te du Palais, Québec, Québec G1R 2J6, Canada.
This study introduces a novel 3D dosimetry system using scintillating fibers in rotating cylinders for precise radiotherapy quality assurance (QA). The tomodosimetry method offers high resolution and accuracy for modern treatment techniques like IMRT.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Dosimetry
Background:
- 3D dosimetry is crucial for patient-specific quality assurance (QA) in advanced radiotherapy.
- Current 3D dosimeters face challenges in clinical implementation due to complex read-out procedures and limitations in accuracy, precision, and sample size.
Purpose of the Study:
- To develop a novel 3D dosimeter based on tomodosimetry using long scintillating fibers.
- To enable accurate QA for modern radiotherapy techniques such as intensity-modulated radiation therapy (IMRT) and intensity-modulated arc therapy (IMAT).
Main Methods:
- Simulated scintillating fibers arranged in concentric cylindrical planes within a water-equivalent phantom.
- Phantom rotation and simulated light acquisitions to reconstruct dose distributions.
- Iterative reconstruction algorithms for 1 mm² resolution in cylindrical planes and 1 mm³ resolution for 3D dose interpolation.
Main Results:
- Straight scintillating fiber patterns with light-tight cuts achieved high accuracy (<0.5 mm distance-to-agreement in gradients, <0.2% dose difference in high-dose regions).
- Achieved precision of <0.9% in high-dose, low-gradient regions for IMRT segments.
- 3D dose interpolation for a clinical IMRT prostate plan showed <1% overall dose difference compared to the reference input.
Conclusions:
- The developed tomodosimetry method using scintillating fibers in rotating cylindrical planes demonstrates potential for high-resolution, precise, and accurate 3D dosimetry.
- The system's water-equivalence and rotational symmetry make it suitable for both treatment QA and machine commissioning.
