A portable graphite calorimeter for onsite reference dosimetry and beam quality correction factor determination.

Area of Science:

• Medical Physics
• Radiation Oncology
• Metrology

Background:

• Accurate absolute dose calibration is crucial for effective radiation therapy.
• Existing methods for onsite dose measurements can be time-consuming and complex.

Purpose of the Study:

• To develop a portable, reliable, and fast-setup graphite calorimeter for onsite absolute dose measurements.
• To enable accurate determination of beam quality correction factors at clinical sites.

Main Methods:

• Designed and constructed a portable graphite calorimeter with minimal electronics.
• Integrated the system into a water-fillable phantom for user-defined beam quality calibration.
• Optimized operational parameters for rapid thermal equilibrium.
• Validated accuracy against the National Physical Laboratory (NPL) Primary Standard.

Main Results:

• Achieved a 3-hour treatment room occupation time.
• Demonstrated excellent thermal stability (±100 µK) and low temperature drift (60 µK/min).
• Attained a mean relative local deviation of 0.1% compared to NPL standards.
• Successfully measured beam quality correction factors and conducted a hospital measurement campaign.

Conclusions:

• Developed an accurate, portable absolute dosimeter for clinical use.
• The system facilitates efficient determination of beam quality correction factors with minimal disruption.
• The calorimeter enhances onsite quality assurance in radiation therapy centers.