Dual-layer collimator for improved spatial resolution in SPECT with CZT camera: an analytical and Monte Carlo study

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Detector Physics

Background:

• Current SPECT imaging relies on hole matching pixel detectors (HMPD) with either one hole per pixel (1HMPD) or four holes per pixel (4HMPD) configurations.
• Optimizing collimator design is crucial for improving SPECT imaging performance, especially for low- and medium-energy gamma emitters.

Purpose of the Study:

• To assess the performance of a novel dual-layer collimator (1H/4HMDP) combining 1HMPD and 4HMPD configurations.
• To evaluate its efficacy for low- and medium-energy gamma emitters in SPECT imaging.

Main Methods:

• Derivation of analytical equations for geometrical efficiency and full width at half maximum (FWHM).
• Development of a dedicated Monte Carlo (MC) code to simulate collimator performance, including point spread function and planar/SPECT acquisitions.
• Optimization of dual-layer collimator dimensions (hole lengths) for spatial resolution and geometrical efficiency.

Main Results:

• Analytical equations and MC simulations showed good agreement (within 3%) for efficiency and FWHM.
• An optimized 1H/4HMDP collimator (20 mm + 13 mm hole lengths) was derived.
• This optimized collimator demonstrated superior spatial resolution compared to 1HMPD and 4HMPD collimators at equal geometrical efficiency and source-collimator distances > 5 cm.
• Improved resolution was confirmed in phantom simulations (bar, hot rods, Jaszczak).

Conclusions:

• The dual-layer 1H/4HMDP collimator offers enhanced spatial resolution for SPECT imaging.
• It is a promising advancement for CZT SPECT imaging of low- and medium-energy gamma emitters.