Dual-photopeak joint image reconstruction for pinhole SPECT, PET and PET-SPECT

Area of Science:

• Nuclear medicine
• Medical imaging
• Radiochemistry

Background:

• Many SPECT and PET radionuclides emit multiple gamma rays, complicating image reconstruction.
• Current methods often use only one energy peak or sum counts, potentially reducing image quality, especially in low-count scenarios.

Purpose of the Study:

• To investigate and compare different dual-photopeak joint reconstruction (JR) methods for multi-energy emitting radionuclides.
• To evaluate the effectiveness of Single-Band JR (SB-JR), mixed Multi-Band JR (mMB-JR), and Multi-Band JR (MB-JR) in improving image quality.

Main Methods:

• Monte Carlo simulations were used to generate Derenzo phantom projections for radionuclides like 225Ac, 226Ac, and 89Zr on a VECTor PET-SPECT system.
• Three JR methods (SB-JR, mMB-JR, MB-JR) were applied, utilizing different combinations of energy windows and system matrices.
• Quantitative analysis was performed using contrast-to-noise ratio (CNR) on reconstructed images.

Main Results:

• The MB-JR method demonstrated superior visual image quality and achieved the highest CNRs across all tested radionuclides and activity concentrations.
• CNR improvements with MB-JR over single-photopeak reconstruction ranged from 20% to 65% for the smallest phantom structures.
• Other methods showed variable CNR changes: mMB-JR ranged from -16% to 61%, and SB-JR from -21% to 51%.

Conclusions:

• Multi-band joint reconstruction (MB-JR) is a highly effective method for improving SPECT, PET, and combined PET-SPECT imaging.
• This technique enhances the utilization of multiple gamma emissions from radionuclides, leading to significant improvements in image quality and diagnostic potential.