Half-mm resolution SPECT mouse imaging on a clinical SPECT scanner with a 4-degree-of-freedom (4-DOF) scanning path

Objectives We developed a half-mm resolution, high-flexibility, low-cost animal SPECT system based on a clinical SPECT scanner. A stage with 4-DOFs in moving objects was implemented on this system. The goal of this work is to investigate the performance of SPECT mouse imaging on this system and evaluate the benefit of a 4-DOF scanning path.

Methods A single-head SPECT scanner(Beijing Hamamatsu, BHP6601) was used as the base system in this study. A seven-pinhole collimator and a 4-DOF stage were assembled and placed under the detector head. The stage allows translational movements of the imaging object in three orthogonal directions and rotation of the object. The scanning path consisted of 120 positions. In between two neighboring positions, the object was rotated by 3 degree, moved incrementally by 0.33 mm along the axial direction, and shifted by 1.2 mm along one of the two transaxial directions. The sampling completeness, spatial resolution and detection efficiency of this scanning path were evaluated analytically and through Monte Carlo simulation. A 20 gram normal mouse was injected with 103 MBq Tc99m-MDP, euthanized 2.5 hours post-injection and scanned with the scanning path.

Results The 4-DOF scanning path provided increased sampling completeness and better trade-off between spatial resolution and detection efficiency, as compared to conventional single-circular and helical orbits. The ribs and vertebra of the mouse were visually separable in the whole-body image. Continued efforts are underway to investigate the feasibility of other mouse imaging applications, such as cardiac and tumor imaging.

Conclusions Half-mm resolution mouse imaging was achieved on a clinical SPECT system with a multipinhole collimator and a 4-DOF scanning path. The studied technique is attractable for its distinctive characteristics of low cost, high feasibility and reproducibility for existing SPECT users.

Research Support Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP200800031071), National Natural Science Foundation of China(No. 10975086