Optimization of dose distributions in moving-strip therapy using a minicomputer

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Dosimetry

Background:

• The moving-strip technique is used in Cobalt-60 (60-Co) radiotherapy to deliver radiation doses.
• Achieving uniform dose distribution is crucial for effective and safe radiotherapy treatment.
• Traditional methods may result in significant dose variations within the patient.

Purpose of the Study:

• To optimize 60-Co dose distributions for the moving-strip technique using a computer program.
• To evaluate the accuracy of the computer program by comparing calculated doses with measured doses.
• To assess the improvement in dose uniformity achieved by the computer optimization method.

Main Methods:

• Calculated optimized 60-Co dose distributions for three patients using a minicomputer program.
• The program incorporated corrections for field obliquity and patient thickness variations.
• Measured beam profiles in a water phantom and midplane doses in a Masonite phantom using thermoluminescent dosimetry (TLD) for validation.

Main Results:

• Computer-calculated midplane doses closely matched experimentally measured doses, validating the program's accuracy.
• The computer optimization technique substantially improved dose uniformity.
• Midplane dose variation was reduced from ±12-13% (unoptimized) to ±3-4% (optimized).

Conclusions:

• Computer-aided optimization is effective in improving dose uniformity for the moving-strip technique.
• The developed program accurately predicts dose distributions, accounting for patient-specific factors.
• Enhanced dose uniformity leads to more precise and potentially safer radiotherapy delivery.