Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study

Area of Science:

• Medical Imaging
• Radiology
• Nuclear Medicine

Background:

• Hybrid imaging combines SPECT/PET with CT, leading to cumulative radiation exposure.
• Optimization efforts focus on diagnostic applications and radiation dose reduction.
• The study investigates the impact of iterative CT reconstruction (ASIR) on low-dose CT image quality.

Purpose of the Study:

• To evaluate the influence of the Adaptive Statistical Iterative Reconstruction (ASIR) algorithm on low-dose CT image quality in hybrid SPECT-CT systems.
• To assess the trade-offs between reduced radiation dose and image quality metrics.

Main Methods:

• SPECT-CT scans were performed using reduced X-ray tube currents.
• CT image quality was analyzed using iterative reconstruction (ASIR) and compared to filtered back-projection (FBP).
• Impact on SPECT attenuation maps and image quality was assessed using phantoms.

Main Results:

• ASIR reduced image noise and improved contrast-to-noise ratio (CNR) compared to FBP at similar tube currents.
• HU values showed good correlation with FBP (R2 ≥ 0.88), but shifts occurred at low tube currents (≤ 60 mA).
• Attenuation-corrected SPECT images showed HU value shifts at very low tube currents (≤ 20 mA).

Conclusions:

• Decreasing X-ray tube current (up to 30 mA) with ASIR reduces CT radiation dose.
• This dose reduction is achieved without significant degradation of CT image quality.
• ASIR offers a viable strategy for optimizing radiation dose in low-dose CT protocols for hybrid imaging.