A filtered backprojection algorithm for pinhole SPECT with a displaced centre of rotation

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Image Reconstruction

Background:

• High-resolution pinhole collimation in single-photon-emission computed tomography (SPECT) is sensitive to small center-of-rotation displacements.
• Mechanical shift (MS) introduces artifacts, degrading image quality and resolution in SPECT.
• Accurate image reconstruction is vital for quantitative analysis and diagnostic accuracy in SPECT.

Purpose of the Study:

• To demonstrate the importance of correcting small center-of-rotation displacements in SPECT.
• To develop and evaluate a filtered backprojection (FBP) algorithm for pinhole SPECT with a displaced center-of-rotation.
• To assess the algorithm's ability to correct artifacts and restore system resolution.

Main Methods:

• Derivation of a filtered backprojection (FBP) algorithm tailored for pinhole geometry with a displaced center-of-rotation.
• Characterization of center-of-rotation displacement (mechanical shift) by its orthogonal components (eta and tau).
• Evaluation of the algorithm using a three-line source and a micro-SPECT cold rod phantom.

Main Results:

• The developed pinhole FBP algorithm effectively corrects center-of-rotation displacement.
• The algorithm successfully corrects 'doughnut'-type artifacts caused by mechanical shift.
• Restoration of the expected system resolution was achieved with the proposed correction method.

Conclusions:

• A fast and direct FBP algorithm for pinhole SPECT with mechanical shift correction has been developed.
• This method significantly improves image quality by eliminating artifacts in SPECT.
• The findings highlight the necessity of precise center-of-rotation correction for accurate high-resolution SPECT imaging.