Development and Longitudinal Analysis of Plan-Based Streamlined Quality Assurance on Multiple Positioning Guidance...

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Accurate patient positioning is critical in modern radiotherapy.
• Existing quality assurance (QA) methods can be time-consuming and require multiple setups.
• A unified QA approach is needed to efficiently verify diverse patient positioning guidance systems.

Purpose of the Study:

• To propose and validate an efficient, streamlined QA method using a single phantom setup.
• To assess the performance of multiple patient positioning guidance systems, including six-degree-of-freedom (6DoF) couches, various X-ray imaging modalities, optical surface imaging, lasers, and optical distance indicators (ODI).

Main Methods:

• A pseudo-patient treatment plan was developed using an optical surface imaging (AlignRT) cube phantom.
• The phantom's position was initially acquired by AlignRT and cone-beam computed tomography (CBCT).
• Six-degree-of-freedom (6DoF) couch shifts were used to restore the reference position, assessing couch accuracy and tracking performance. Isocenter discrepancies were evaluated using kV-kV, MV-MV, and AlignRT imaging. Laser alignment and ODI were visually inspected. Longitudinal data over 50 weeks were analyzed.

Main Results:

• Six-degree-of-freedom (6DoF) couch motion errors and AlignRT tracking errors were consistently sub-millimeter and sub-degree.
• Isocenter discrepancies between CBCT and kV-kV imaging were negligible.
• Maximal discrepancies between CBCT and MV-MV were 0.4 mm and 0.3 degrees. AlignRT showed high congruence with CBCT and DICOM/SGRT references (<0.6 mm, <0.3 degrees).
• The average QA procedure time decreased to approximately 23 minutes with therapist familiarity.

Conclusions:

• The streamlined QA method is practical and efficient for multipurpose performance checks of patient positioning guidance systems.
• The method fully validates the stability, tracking performance, and isocenter congruence of systems for all image-guided radiotherapy (IGRT) applications.
• This QA approach is suitable even for stringent requirements like stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT).