Initiation of multi-leaf collimator conformal radiation therapy

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Conformal radiotherapy utilizes advanced techniques for precise tumor targeting.
• Traditional field shaping in radiotherapy often involves lead alloy blocks.

Purpose of the Study:

• To evaluate the clinical acceptability and dosimetric performance of computer-controlled multi-leaf collimators (MLCs) in conformal radiotherapy.
• To compare MLC field shaping with conventional lead alloy blocking systems.

Main Methods:

• Quantitative dosimetry and treatment planning studies were conducted.
• Sixteen patients with multiple tumor sites received treatments using both blocking systems.
• Penumbra characteristics of shaped beams were measured and analyzed.
• Three-dimensional treatment planning was employed for dose distribution comparisons.

Main Results:

• MLCs demonstrated clinical acceptability for most field shapes and disease sites.
• MLC penumbra matched conventional blocking for straight edges perpendicular to leaf travel.
• Penumbra widened by approximately 4 mm at a 45-degree angle of approach compared to divergent blocks.
• Equivalent dose distributions were achievable with both MLC and block systems.

Conclusions:

• Computer-controlled MLCs are effective and efficient for treating various disease sites in conformal radiotherapy.
• MLCs are particularly advantageous for complex treatment fields involving multiple shaped beams.
• MLCs provide clinically acceptable blocking, comparable to traditional methods, with specific considerations for angled contours.