Brain SPECT with short focal-length cone-beam collimation

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Biomedical Engineering

Background:

• Single-photon emission-computed tomography (SPECT) imaging of deep brain structures is limited by photon attenuation.
• Existing parallel-hole collimators on dual-head SPECT systems cannot optimize sensitivity and spatial resolution simultaneously for central brain regions.

Purpose of the Study:

• To design and evaluate novel collimator pairs for dual-head SPECT systems to enhance sensitivity, particularly for deep and centrally located brain structures.
• To compare the performance of new collimation strategies against existing methods using signal-to-noise ratio (SNRCRB) and image reconstruction.

Main Methods:

• Designed and evaluated cone-beam and fan-beam collimator pairs for dual-head SPECT systems.
• Calculated projections of a brain phantom with spherical lesions to determine ideal signal-to-noise ratios (SNRCRB) based on the Cramer-Rao lower bound.
• Reconstructed images using an ordered-subset expectation-maximization (OS-EM) procedure for visual assessment and artifact detection.

Main Results:

• A combination of a 20 cm focal length cone-beam collimator and a 40 cm focal length fan-beam collimator demonstrated superior performance.
• This optimized pair increased SNRCRB by 1.1 to 3.5 times compared to parallel-parallel collimators across the imaging volume.
• Artifact-free image reconstructions were achieved, showing robustness to positional mismatches.

Conclusions:

• Combining fan-beam and short-focusing cone-beam collimation significantly improves dual-head brain SPECT imaging.
• This approach enhances sensitivity and image quality, especially for imaging deep and centrally located brain structures.
• The developed collimation strategy offers a promising advancement for clinical brain SPECT applications.