Geometric characterization of multi-axis multi-pinhole SPECT.

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Biomedical Engineering

Background:

• Accurate calibration is essential for high-resolution single photon emission computed tomography (SPECT) imaging.
• Traditional SPECT systems often integrate pinhole collimators with detectors, limiting independent movement.
• Advanced geometric modeling is needed for novel SPECT configurations, particularly for small animal studies.

Purpose of the Study:

• To develop and validate a geometric model and calibration process for a multi-pinhole, multi-axis SPECT system.
• To enable independent rotation of pinhole collimators and detectors in a SPECT setup.
• To assess the calibration accuracy's impact on spatial resolution in small animal SPECT.

Main Methods:

• Developed a novel geometric model accommodating detached and independently rotating pinhole collimators and detectors.
• Applied the model to a prototype small animal SPECT device with 22 pinholes and dual detectors.
• Estimated model parameters using point source calibration scans with varying numbers of sources and rotation angles.

Main Results:

• A full calibration using four point sources and 360-degree rotation accurately estimated 95 free parameters.
• A rapid calibration using two point sources and 180-degree rotation estimated 22 repositioning parameters.
• Experimental validation showed residual coordinate differences with 0.8 mm FWHM, contributing 0.12 mm RMS to spatial resolution.

Conclusions:

• The developed geometric model and calibration process are highly accurate for multi-pinhole SPECT systems.
• The calibration accuracy is sufficient for high-resolution small animal SPECT imaging, with minimal impact on spatial resolution.
• This method offers a robust solution for calibrating advanced SPECT systems with independent collimator and detector movement.