Precise positioning of patients for radiation therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Precise patient positioning is critical for effective radiation therapy.
• Intratreatment movement can compromise radiation dose delivery and increase toxicity.
• Existing immobilization techniques may lack the necessary precision for certain treatments.

Purpose of the Study:

• To develop and evaluate novel immobilization schemes for precise daily patient positioning in radiation therapy.
• To quantify intratreatment movement in various patient positions using advanced imaging.
• To assess the reproducibility of patient setup using laser alignment and radiographic verification.

Main Methods:

• Development of thermoplastic immobilization devices for supine, seated, and decubitus positions.
• Analysis of pretreatment and post-treatment radiographs to measure intratreatment patient movement.
• Evaluation of day-to-day position reproducibility using laser alignment and radiographic verification.

Main Results:

• Mean intratreatment movement was consistently below 1 mm across different positions.
• Seated position with bite block and mask showed minimal movement (0.5 mm +/- 0.3 mm).
• Supine position with neck hyperextension had slightly higher movement (1.4 mm +/- 0.9 mm).
• Laser alignment achieved positioning within 2.2 mm +/- 1.4 mm of the intended position.

Conclusions:

• Rigid immobilization devices significantly improve patient positioning precision in radiation therapy.
• These enhanced precision techniques offer advantages for tumor coverage and normal tissue sparing.
• The developed immobilization schemes are practical, utilizing readily available materials.