EPR/alanine dosimetry in LDR brachytherapy--a feasibility study

Area of Science:

• Medical Physics
• Oncology
• Radiotherapy

Background:

• Brachytherapy is a crucial treatment for gynecological cancers.
• Accurate dose verification is essential for effective radiotherapy.
• In vivo dosimetry provides direct measurement of radiation dose within the patient.

Purpose of the Study:

• To evaluate the accuracy of in vivo dosimetry using electron paramagnetic resonance (EPR) with L-alanine detectors.
• To compare measured brachytherapy doses with planned doses in patients with gynecological cancers.
• To identify factors influencing dose discrepancies in brachytherapy.

Main Methods:

• Electron paramagnetic resonance (EPR) dosimetry using L-alanine detectors in cellulose capsules.
• In vivo measurements performed on 13 patients undergoing brachytherapy for gynecological cancers.
• Dose determination for Cesium-137 ((137)Cs) and Iridium-192 ((192)Ir) brachytherapy sources.
• Detector positioning verified using orthogonal radiographs and dose calculation via the PLATO (Nucletron) planning system.

Main Results:

• Relative deviations between planned and measured doses ranged from -23% to +14%.
• The mean deviation from the prescribed dose was -5% with a standard deviation of 10%.
• Key sources of discrepancy included uncertainties in detector positioning and intra-treatment position shifts.

Conclusions:

• L-alanine EPR dosimetry offers a viable method for in vivo dose verification in gynecological brachytherapy.
• Detector positioning accuracy is critical for reliable dose measurements.
• Further refinement in positioning techniques can improve the precision of in vivo dosimetry in clinical practice.