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Isotropic reconstruction of SPECT data using OSEM3D: correlation with CT
Wolfgang Römer1, Nicky Reichel, Hans A Vija
1Clinic of Nuclear Medicine, University of Erlangen/Nürnberg, Schlossplatz 4, D-91054 Erlangen, Germany. wolfgang.roemer@nuklear.imed.uni-erlangen.de
Academic Radiology
|March 24, 2006
Summary
The iterative OSEM3D reconstruction algorithm accurately preserves SPECT lesion shape in the z-direction, unlike OSEM2D. This improved axial fidelity is crucial for precise SPECT/CT hybrid imaging.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Image Reconstruction
Background:
- Iterative reconstruction algorithms like OSEM are vital for SPECT imaging.
- Accurate lesion characterization requires precise representation of lesion dimensions.
- Previous methods (OSEM2D) may introduce axial distortions.
Purpose of the Study:
- To evaluate the axial shape fidelity of a novel 3D OSEM algorithm (OSEM3D).
- To compare OSEM3D's performance against a standard 2D OSEM algorithm (OSEM2D).
- To assess the impact on lesion dimensions in SPECT/CT hybrid imaging.
Main Methods:
- SPECT and CT imaging were performed on phantoms and 22 neuroendocrine tumor patients using In-111.
- Three-dimensional lesion extensions (dx, dy, dz) and an index of eccentricity (IE) were measured.
- OSEM3D and OSEM2D reconstructions were compared to CT reference values.
Main Results:
- OSEM2D showed significant axial elongation (dz) in phantom and patient data (P < .05).
- OSEM3D reconstructions demonstrated significantly improved axial shape fidelity, with IE not differing from 1.
- Patient data revealed OSEM2D overestimated dz by ~15.5% compared to OSEM3D and CT.
Conclusions:
- OSEM3D effectively prevents deformation of SPECT hot lesions in the z-direction.
- This enhanced axial accuracy is particularly important for SPECT/CT hybrid imaging.
- OSEM3D facilitates a more precise spatial correlation between SPECT and CT data.