Applying the N-isopropylacrylamide gel dosimeter to quantify dynamic dose effects: A feasibility study

Area of Science:

• Medical Physics
• Radiotherapy
• Dosimetry

Background:

• Gel dosimeters serve as chemical and relative measurement tools.
• Accurate dose assessment is crucial in radiotherapy, especially for moving targets.

Purpose of the Study:

• To assess the viability of N-isopropylacrylamide (NIPAM) gel dosimeters for observing dynamic dose effects.
• To quantify respiratory motion's impact on radiation dose and inform safety margin calculations.

Main Methods:

• NIPAM gel dosimeter and a dynamic phantom simulated lung/abdominal tumor radiotherapy.
• Simulated respiration rate of 4 sec/cycle with a 2 cm motion range.
• MRI for data acquisition and MATLAB for analysis, using a 3%/3 mm gamma passing rate >95% as a benchmark.

Main Results:

• Comparison with Treatment Planning System (TPS) fields showed varying gamma passing rates (74.32% for 4x5 cm2).
• Gamma mapping indicated dose distribution alignment with a 4x4 cm2 TPS field.
• A 96.49% gamma passing rate was achieved when comparing the >60% dose curve region with TPS.

Conclusions:

• NIPAM gel dosimeters are feasible for dynamic dose measurement in simulated respiratory motion.
• The method effectively quantifies dynamic dose effects, aligning with clinical evaluation standards.