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Using fast sequential asymmetric fanbeam transmission CT for attenuation correction of cardiac SPECT imaging
E F Hollinger1, S Loncaric, D C Yu
1Department of Diagnostic Radiology and Nuclear Medicine, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612, USA.
Summary
Fast transmission computed tomograms (TCTs) can correct photon attenuation in cardiac single-photon emission computed tomography (SPECT) imaging. This rapid TCT acquisition method improves image uniformity without significantly increasing scan times.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Radiological Physics
Background:
- Photon attenuation in cardiac SPECT imaging reduces image quality and diagnostic accuracy.
- Accurate attenuation correction is crucial for quantitative SPECT analysis.
- Existing methods for attenuation correction can be time-consuming or require specialized equipment.
Purpose of the Study:
- To evaluate the feasibility of using rapid transmission computed tomograms (TCTs) for photon attenuation correction in cardiac SPECT.
- To determine if short-duration TCTs can provide sufficient data for accurate attenuation maps.
- To assess the impact of TCT-based attenuation correction on cardiac SPECT image uniformity.
Main Methods:
- Acquisition of asymmetric fanbeam TCTs using a 99mTc line source immediately after cardiac emission CT on a triple-head SPECT system.
- Reconstruction of TCTs to generate patient-specific attenuation maps.
- Application of an iterative maximum likelihood algorithm for attenuation correction using TCT-derived maps.
- Comparison of results from fast (1-4 min) TCTs with long-duration transmission imaging in phantoms and human studies.
Main Results:
- Fast asymmetric fanbeam TCT-based attenuation correction significantly improved image uniformity in cardiac-thorax phantoms simulating large patients.
- A 4-minute TCT, using a high-activity line source and rapid rotation, yielded a suitable attenuation map for phantom studies.
- Similar improvements in attenuation correction were observed in human patients with thorax widths less than 40 cm.
Conclusions:
- A sequential imaging protocol incorporating fast TCT acquisition is effective for cardiac SPECT attenuation correction.
- This method allows for attenuation correction without substantially increasing overall imaging study duration.
- The proposed TCT approach enables attenuation correction on existing triple-head SPECT systems with minimal hardware modification.