Quantifying upright positioning accuracy with optical surface tracking in radiotherapy.

Area of Science:

• Radiotherapy
• Medical Physics
• Oncology

Background:

• Upright radiotherapy offers potential benefits but requires precise patient positioning.
• Accurate patient setup is crucial for effective radiation delivery and minimizing side effects.
• Immobilization techniques significantly influence setup accuracy in radiotherapy.

Purpose of the Study:

• To quantify inter- and intra-fractional setup accuracies in the upright posture.
• To compare setup accuracies among different immobilization methods for abdominal and head and neck (HN) cancers.
• To assess the impact of immobilization devices on upright patient positioning.

Main Methods:

• Evaluated two setups for abdominal and four for HN cancer treatments using volunteers.
• Assessed inter-fractional setup errors and intra-fractional displacements with various immobilization devices (masks, leg devices, backrests).
• Utilized 3D surface marker tracking via camera images to monitor patient and mask positions.

Main Results:

• Thermoplastic masks reduced inter-fractional setup errors in abdominal treatments (6.6±3.3 mm to 3.9±1.7 mm).
• Upright HN setups with leg immobilization and backrest attachments achieved the highest accuracy (2.9±1.7 mm).
• Immobilization devices reduced intra-fractional displacements in both abdominal (1.9±1.1 mm) and HN (1.8±1.5 mm) setups.

Conclusions:

• Thermoplastic masks enhance upright setup accuracy for abdominal radiotherapy.
• Leg immobilization devices and backrest attachments are optimal for upright head and neck cancer treatment accuracy.
• Findings support expanding upright radiotherapy applications across various cancer types.