A Noninvasive Body Setup Method for Radiotherapy by Using a Multimodal Image Fusion Technique

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image-Guided Therapy

Background:

• Accurate patient positioning is crucial in radiotherapy to minimize radiation dose to healthy tissues.
• Mismatches between the patient's surface and immobilization systems introduce setup errors, impacting treatment accuracy.
• Noninvasive methods for patient setup are essential to reduce interfraction uncertainties.

Purpose of the Study:

• To develop and evaluate a noninvasive patient setup method for minimizing mismatch errors in tumor localization.
• To improve the precision of patient positioning for pelvic tumors during radiotherapy.

Main Methods:

• A point set registration method integrating computed tomography (CT) scans and optical surface landmarks was employed.
• Validation involved phantom studies to quantify mismatch errors and patient studies for pelvic tumors.
• Performance was compared against two other similar patient positioning systems.

Main Results:

• Phantom verification demonstrated mismatch error estimation with a precision of less than 0.22 mm.
• For pelvic tumors, the method achieved average tumor location errors of 1.303 mm (LR), 2.602 mm (AP), and 1.684 mm (SI).
• Comparative analysis indicated superior positioning accuracy for pelvic tumor location compared to existing systems.

Conclusions:

• The developed noninvasive method effectively reduces interfraction uncertainty caused by patient-surface/immobilization mismatches.
• This technique enhances patient positioning precision, particularly for pelvic tumor radiotherapy.
• The method offers a promising advancement in image-guided radiotherapy for improved treatment outcomes.