First results from the high-resolution mouseSPECT annular scintillation camera

Abstract

High-resolution single-photon emission computed tomography (SPECT) imaging in small animals tends to use long imaging times and large injected doses due to the poor sensitivity of single pinhole gamma cameras. To increase sensitivity while maintaining spatial resolution, we designed and constructed a multipinhole collimator array to replace the parallel hole collimators of a Ceraspect human SPECT brain scanner. The Ceraspect scanner is composed of an annular NaI(TI) crystal within which the eight pinhole collimators (1-mm-diameter holes) rotate while projecting nonoverlapping images of the object onto the stationary annular crystal. In this manner, only one-eighth of a collimator rotation is required to acquire a full circle orbit tomographic data set. The imaging field of view (FOV) has a diameter of 25.6 mm in the transverse direction, which is sufficient to encompass a mouse in the transverse direction. The axial FOV is 25.6 mm at the center of the FOV and 13.9 mm at the edge of the transverse FOV. Data are currently acquired in step-and-shoot mode; however, the system is capable of list mode acquisition with the collimator continuously rotating. Images are reconstructed using a cone-beam ordered subsets expectation maximization method. The reconstructed spatial resolution of the system is 1.7 mm and the sensitivity at the center of the FOV is 13.8 cps/microCi. A whole-body bone scan of a mouse injected with [Tc-99 m]MDP clearly revealed skeletal structures such as the ribs and vertebral bodies. These preliminary results suggest that this approach is a good tradeoff between resolution and sensitivity and, with further refinement, may permit dynamic imaging in living animals.

Physiological imaging of the lung: single-photon-emission computed tomography (SPECT)

“…Another recent development is the construction of SPECT systems dedicated for the functional studies of small animals (11,17,28). Application of pin-hole collimator techniques and the proximity of the imaging field to the camera result in a spatial resolution that allows imaging of radiotracer distributions even in small objects.…”

Preclinical positron emission tomography scanner based on a monolithic annulus of scintillator: initial design study

“…Application of this paradigm has been reduced over the last two decades with the introduction of high-resolution scanners designed for imaging of small animals. [1][2][3][4][5][6][7][8] It is now possible to perform longitudinal studies on relatively small cohorts of animals. The application of radiopharmaceutical-based molecular imaging techniques is of particular interest to investigators due to the ability to track and quantify physiologic processes.…”

Theoretical Bounds and System Design for Multipinhole SPECT

“…The sensitivity equivalent aperture diameter in the center of the FOV as derived in [23] is given by (10) where is the linear attenuation coefficient for the knife edge material. The sensitivity, including penetration effects, for a single pinhole is (11) and for the whole system (12) The resolution equivalent aperture can, in the same manner, be used to take into account the penetration effects on the resolution. The resolution equivalent aperture diameter in terms of the FWHM is given by [24] and can be computed as (13) hence the geometric resolution in this case becomes (14) We use the penetration formulas for computing and evaluating our example systems, but do not include them in the optimization.…”