Enhanced calibration method for wall-mounted RGSC cameras: Mitigating baseline drift caused by CT couch sagging

Area of Science:

• Medical Imaging Physics
• Radiotherapy Technology
• Image-Guided Therapy

Background:

• CT couch sagging introduces noise into respiratory signals, affecting tumor motion management accuracy.
• Accurate respiratory gating relies on precise tracking of patient motion during CT scans.

Purpose of the Study:

• To present an enhanced calibration method for the wall-mounted Respiratory Gating for Scanner (RGSC) camera.
• To reduce calibration uncertainty and mitigate baseline drift caused by CT couch sagging.

Main Methods:

• A 70kg weight simulated patient load on the CT table.
• Reflector blocks were precisely positioned using a laser alignment system and CT console.
• Calibration measurements were performed at nine points across lateral and longitudinal positions, with Varian's method used for comparison.

Main Results:

• Block positioning uncertainty was reduced to the sub-millimeter level.
• Residual baseline drift was significantly mitigated from 2.84 ± 0.22 mm to 0.64 ± 0.06 mm (p<0.001).

Conclusions:

• The proposed calibration method robustly minimizes positioning uncertainty and reduces baseline drift from CT couch sagging.
• This enhances the repeatability and accuracy of wall-mounted camera calibration.
• The method's versatility supports both wall- and ceiling-mounted cameras, expanding clinical utility.