page_title: Preclinical imaging
section_title: Combined SPECT-MR
hierarchical_section_title: Preclinical imaging / Combined SPECT-MR
caption_attribution_description: English: A preclinical imaging system with clip-on SPECT
context_page_description: Preclinical imaging is the visualization of living animals for research purposes, such as drug development. Imaging modalities have long been crucial to the researcher in observing changes, either at the organ, tissue, cell, or molecular level, in animals responding to physiological or environmental changes. Imaging modalities that are non-invasive and in vivo have become especially important to study animal models longitudinally. Broadly speaking, these imaging systems can be categorized into primarily morphological/anatomical and primarily molecular imaging techniques. Techniques such as high-frequency micro-ultrasound, magnetic resonance imaging and computed tomography are usually used for anatomical imaging, while optical imaging, positron emission tomography, and single photon emission computed tomography are usually used for molecular visualizations.
  These days, many manufacturers provide multi-modal systems combining the advantages of anatomical modalities such as CT and MR with the functional imaging of PET and SPECT. As in the clinical market, common combinations are SPECT/CT, PET/CT and PET/MR.
context_section_description: Principle: The new SPECT-MR for small animal imaging is based on multi-pinhole technology, allowing high resolution and high sensitivity. When coupled with cryogen-free MRI the combined SPECT-MR technology dramatically increases the workflow in research laboratories whilst reducing laboratory infrastructure requirements and vulnerability to cryogen supply.
  Strengths: Research facilities no longer need to purchase multiple systems and may choose between different system imaging configurations. The SPECT or MRI equipment can each be used as a standalone device on a bench, or sequential imaging can be carried out by clipping the SPECT module on to the MRI system. The animal translates automatically from one modality to the other along the same axis. By inserting a SPECT module inside the MRI magnet simultaneous acquisition of SPECT and MRI data is possible. The workflow of the laboratory can be increased by acquiring multiple modalities of the same subject in one session or by operating the SPECT and MRI systems separately, imaging different subjects at the same time. SPECT-MR is available in different configurations with different trans-axial field of views, allowing imaging from mice to rats. 
  Weaknesses: As this is a combination of imaging systems the weaknesses associated with one or other imaging modality are no longer applicable. In sequential SPECT-MR, the operator needs to allow a little time to transfer the subject between the SPECT and MR acquisition positions. This is negated in simultaneous SPECT-MR. However, for sequential SPECT-MR, when the SPECT module is clipped on it is easy to clip-on or off and transfer between rooms. The researcher has to have sufficient knowledge to interpret two different system outputs and would require training for this.
  Cancer research: The combination of MRI, which is used as a non-invasive imaging technique, and SPECT provide results far more quickly when compared to using one technique at a time. Images from the two modalities may also be registered far more precisely, since the time delay between modalities is limited for sequential SPECT-MR systems, and effectively non-existent for simultaneous systems. This means that there is little to no opportunity for gross movement of the subject between acquisitions. With separate, independent operation of the MRI and SPECT systems workflow can easily be increased.
caption: A preclinical imaging system with clip-on SPECT
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