Abstract
To describe the Single Photon Emission Microscope (SPEM), a state-of-the-art instrument for small animal SPECT imaging, and characterize its performance presenting typical images of different animal organs. SPEM consists of two independent imaging devices based on high resolution scintillators, high sensitivity and resolution Electron-Multiplying CCDs and multi-pinhole collimators. During image acquisition, the mouse is placed in a rotational vertical holder between the imaging devices. Subsequently, an appropriate software tool based on the Maximum Likelihood algorithm iteratively produces the volumetric image. Radiopharmaceuticals for imaging kidneys, heart, thyroid and brain were used. The mice were injected with 74 to 148 MBq/0,3mL and scanned for 40 to 80 minutes, 30 to 60 minutes afterwards. During this procedure, the animals remained under ketamine/xilazine anesthesia. SPEM images of different mouse organs are presented, attesting the imaging capabilities of the instrument. SPEM is an innovative technology for small animal SPECT imaging providing high resolution images with appropriate sensitivity for pre-clinical research. Its use with appropriate radiotracers will allow translational investigation of several animal models of human diseases, their pharmacological treatment and the development of potential new therapeutic agents.
Highlights
In the clinical environment, in vivo imaging techniques are considered standard tools used to visualize internal organs and tissues inside the human body
As the small animal organs can be at least 300 times smaller in volume than human ones, two main challenges are faced, which hamper the direct application of those techniques: how to obtain appropriate spatial resolution and sensitivity to image them[1]?
We present the Single Photon Emission Microscope (SPEM), a state-of-the-art molecular imaging single photon emission computed tomography (SPECT) instrument for small animals
Summary
In vivo imaging techniques are considered standard tools used to visualize internal organs and tissues inside the human body. As the small animal organs can be at least 300 times smaller in volume than human ones, two main challenges are faced, which hamper the direct application of those techniques: how to obtain appropriate spatial resolution and sensitivity to image them[1]?. In the specific case of clinical SPECT, planar projections are acquired using parallel hole collimators and are combined by means of the Filtered Backprojection algorithm to produce volumetric reconstructions[2]. This procedure limits the spatial resolution to something around 7mm[3]. Collimators with appropriately distributed, multiple pinholes, in combination with developed software tools, allow the increase of sensitivity without sacrificing spatial resolution
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