Resolving signal drift in the wall-mounted camera of the RGSC system

Area of Science:

• Medical Physics
• Radiotherapy Technology

Background:

• Respiratory Gating for Scanner (RGSC) systems are crucial for motion management in radiotherapy.
• Table sagging in CT systems can cause signal drift, leading to inaccuracies in gating and radiation delivery.
• Wall-mounted camera RGSC systems are susceptible to errors caused by couch deformation.

Purpose of the Study:

• To introduce a modified calibration method to mitigate signal drift caused by table sagging in RGSC systems.
• To enhance the precision of radiation delivery in motion-managed radiotherapy.
• To address systematic errors in systems utilizing wall-mounted cameras.

Main Methods:

• A modified calibration procedure was developed using approximately 70 kg of solid water phantoms on the CT couch.
• Calibration measurements were taken at nine points across extended lateral and longitudinal positions relative to the CT isocenter.
• The efficacy of the new calibration method was validated in two distinct hospital settings.

Main Results:

• The modified calibration method significantly reduced signal drift during Deep Inspiration Breath Hold (DIBH) scans to within 1 mm from 3 mm.
• The extended calibration positions demonstrated consistent drift reduction across both tested hospitals.
• The results highlight the robustness and potential for widespread application of the method.

Conclusions:

• The proposed calibration technique effectively minimizes systematic errors in radiation delivery for patients undergoing motion management.
• This solution is particularly beneficial for wall-mounted camera RGSC systems, especially when used with bariatric CT couchtops.
• The method offers improved accuracy and reliability for radiotherapy treatments requiring precise motion control.