Submillimeter total-body murine imaging with U-SPECT-I

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Small Animal Imaging

Background:

• U-SPECT-I is a stationary SPECT system designed for small-animal imaging.
• It utilizes a cylinder with 75 gold micropinhole apertures to maximize gamma-photon detection yield.
• Previous resolutions achieved were approximately 0.45 mm and 0.35 mm with 0.6-mm and 0.3-mm pinholes, respectively.

Purpose of the Study:

• To present a combined acquisition and reconstruction strategy for full-body imaging using U-SPECT-I.
• To enable submillimeter-resolution total-body imaging in mice.

Main Methods:

• The scanning focus method (SFM) was employed, involving stepping the bed in axial and transaxial directions.
• A maximum-likelihood expectation maximization algorithm was used for simultaneous reconstruction of all projections.
• Memory for reconstruction was reduced by using a consistent transition submatrix for all bed positions.

Main Results:

• SFM demonstrated significant improvements over methods involving stitching separate reconstructions.
• SFM resulted in reduced noise, streak artifacts, and improper background activity.
• Distinguished radioactively filled capillaries as small as 0.45 mm in a mouse-sized phantom and visualized small bone structures in total-body mouse imaging.

Conclusions:

• Focusing SPECT pinhole systems, like U-SPECT-I, are suitable for submillimeter-resolution total-body imaging of mice.
• The developed SFM strategy enhances the capability of U-SPECT-I for comprehensive small-animal imaging.