Extracardiac activity complicates quantitative cardiac SPECT imaging using a simultaneous transmission-emission...

Area of Science:

• Nuclear medicine
• Medical imaging
• Image reconstruction

Background:

• Conventional cardiac SPECT imaging is confounded by extracardiac activity.
• Simultaneously acquired transmission-emission (STE) imaging with maximum likelihood (ML) reconstruction and nonuniform attenuation correction (NAC) is proposed to mitigate these effects.
• However, existing methods may not fully correct for increased myocardial counts due to extracardiac activity, potentially causing artifacts.

Purpose of the Study:

• To evaluate the impact of extracardiac activity on STE imaging reconstructed with ML and NAC.
• To assess the effectiveness of STE-NAC in improving image uniformity under varying attenuation and extracardiac activity conditions.

Main Methods:

• Phantoms with uniform and nonuniform attenuation were imaged using STE and conventional SPECT with a triple-headed camera.
• STE acquisitions utilized fanbeam collimation and a 153Gd transmission source.
• Images were reconstructed using ML with and without NAC; short-axis images were quantitated for count profile variability.

Main Results:

• STE with NAC significantly improved image uniformity in a nonuniform phantom.
• The benefit of STE-NAC on uniformity decreased with increasing extracardiac activity.
• In a uniform phantom, STE with NAC improved uniformity only when extracardiac activity was present.

Conclusions:

• Attenuation correction in STE-ML reconstruction has complex effects when extracardiac activity is present.
• The outcome depends on the extent of extracardiac activity and the pattern of attenuation.
• Further investigation is needed to fully understand and mitigate artifacts caused by extracardiac activity in SPECT imaging.