Timing offset calibration for TOF PET using stationary line source scans at multiple positions

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Physics

Background:

• Accurate timing offset calibration is critical for Time-of-Flight Positron Emission Tomography (TOF PET) to reduce image artifacts and enhance quantitative accuracy.
• Existing calibration methods are often complex, time-consuming, and require expensive equipment or specialized sources.

Purpose of the Study:

• To present a novel, cost-effective method for TOF PET timing offset calibration.
• To eliminate the need for costly equipment, phantoms, short-half-life sources, and precise source positioning.

Main Methods:

• Channel timing offsets were estimated using stationary scans of a germanium-68 (⁶⁸Ge) line source at three non-coplanar positions.
• Line source positions were determined using reconstructed images, enabling precise arrival time difference calculations.
• Timing offsets were calculated by solving a least squares problem, validated with phantom and patient data.

Main Results:

• Calibration using a minimum of three positions corrected offsets (-500 ps to 500 ps) and achieved <1% discrepancy compared to 12 positions.
• Significant improvements observed in image quality phantom: 14% increase in contrast recovery, 61% reduction in background variability, 90% reduction in residual error.
• Patient data showed improved lesion detection (14-55% SUVmax increase for 6-14 mm lesions), enhanced contrast, and elimination of artifacts.

Conclusions:

• The proposed method offers a fast, user-friendly, and cost-effective solution for TOF PET timing offset calibration.
• This calibration significantly enhances lesion detection and diagnostic accuracy in TOF PET imaging.
• The method effectively reduces image artifacts and improves quantitative accuracy without specialized requirements.