Temperature dependent operation of PSAPD-based compact gamma camera for SPECT imaging

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Detector Physics

Background:

• Position Sensitive Avalanche Photodiodes (PSAPDs) are crucial for small animal Single Photon Emission Computed Tomography (SPECT) gamma cameras.
• Current systems often require nitrogen gas cooling for PSAPDs to minimize dark current shot noise, leading to complex setups.
• Operating PSAPDs at higher temperatures could enable more compact and simpler cooling solutions.

Purpose of the Study:

• To investigate the impact of PSAPD temperature on image quality in a small animal SPECT gamma camera.
• To determine the feasibility of operating PSAPDs at a higher temperature (e.g., 5°C) without compromising essential diagnostic information.
• To evaluate the trade-offs between temperature, cooling requirements, and imaging performance.

Main Methods:

• PSAPD temperature was varied from -40°C to 20°C using controlled nitrogen gas flow.
• Point Spread Function (PSF) and its Full-Width-Half-Maximum (FWHM) were measured at different temperatures.
• Scintillator segmentation visibility and mouse heart phantom imaging were assessed at -25°C and 5°C using 99mTc-pertechnetate.

Main Results:

• PSAPD temperature variations affected the PSF's FWHM.
• Scintillator segmentation visibility was maintained across the tested temperature range.
• Mouse heart phantom imaging at 5°C showed slightly degraded but still clear visualization of defects and structures compared to -25°C.

Conclusions:

• Operating PSAPDs for SPECT imaging at 5°C is feasible, offering a simplified cooling system without nitrogen gas.
• While image quality shows some degradation at higher temperatures, it remains diagnostically useful for small animal imaging.
• This finding supports the development of more compact and cost-effective SPECT systems.