DOSIMAP: a high-resolution 2-D tissue equivalent dosemeter for linac QA and IMRT verification

Area of Science:

• Medical Physics
• Radiation Oncology
• Detector Technology

Background:

• Advanced radiation therapy techniques like Intensity-Modulated Radiation Therapy (IMRT) demand precise dose verification.
• Current methods struggle with the high spatial resolution and accuracy required for multi-leaf collimator (MLC) positioning verification.
• Need for real-time, tissue-equivalent dosimetry with high spatial resolution in radiation therapy.

Purpose of the Study:

• To present a new 2-D tissue-equivalent dosemeter for high spatial resolution dose measurements in radiation therapy.
• To demonstrate its capability for real-time dose mapping and verification of IMRT fields.
• To validate the dosemeter's performance against standard ionization chamber measurements.

Main Methods:

• Utilized a plastic scintillator sheet sandwiched between polystyrene cubes, with light detection via a high-resolution camera.
• Implemented a patented procedure to distinguish scintillation light (dose-proportional) from Cerenkov radiation.
• Acquired images at 10 frames per second for quasi real-time dose rate and accumulated dose mapping.
• Ensured tissue equivalence (ICRU-44) using identical phantom and detector materials for electrons and photons.

Main Results:

• Achieved high spatial resolution mapping of dose rate and accumulated dose in quasi real-time.
• Demonstrated tissue equivalence and broad applicability to both electron and photon beams without complex adjustments.
• Reported simple calibration independent of irradiation conditions.
• Presented dose depth profiles comparable to standard ionization chamber measurements in polystyrene.

Conclusions:

• The developed 2-D scintillator dosemeter meets the stringent requirements for accurate dose measurements in modern radiation therapy, particularly for IMRT.
• Its tissue equivalence, real-time capabilities, and simple calibration offer significant advantages for quality assurance in radiation oncology.
• The detector shows promise for precise verification of complex radiation fields and patient-specific dose distributions.