A dual-modality imaging device for the scanning of small laboratory animals is proposed. The device is a combination of single-photon emission computed tomography (SPECT), which is a nuclear medicine instrument, and a high-field magnetic resonance imager (MRI). Dual-modality imaging has experienced the most commercial success of new innovations in the medical imaging field during the past 10 years. The successful combinations have been nuclear (SPECT and PET) combined with computed tomography (CT). The success of the multi-modality products extends to the small animal laboratory, where Gamma-Medica-Ideas, the originator of this proposal, has installed dozens of SPECT/CT devices and recently introduced and sold several PET/CT combinations. Although the CT images provide sufficient resolution to depict anatomical detail, there remain drawbacks to this approach that cannot be easily addressed. Acquisition speed, soft tissue contrast, and the ability to image functional, dynamic, and targeted molecular interactions are all limitations to the CT modality. The use of MR provides the anatomical information of CT but also addresses the above limitations. An addition, longitudinal experiments, i.e., multiple measurements of the same animal over a long time period, can be especially affected in CT by what can be a fractionated radiation therapy dose. MR does not influence the experiment through the addition of high levels of radiation dose. Gamma Medica-Ideas is applying for Fast-Track Phase I/II SBIR grant to fund the development of the SPECT/MRI device. The technological challenges of this combination exceed those that involve CT, mainly because of the cross-contamination that occurs when the two modalities are put in proximity: the MR field precludes the use of photomultiplier tubes (PMTs) and motion associated with SPECT; and the presence and electro-magnetic emissions from the SPECT instrument can possibly change the MR and RF fields and cause MR image degradations. Gamma Medica has a unique position in having developed a clinical product based upon the semiconductor CZT. CZT material has been shown to be minimally affected by strong magnetic fields. Phase I of the project aims to evaluate and document the effects on CZT image quality when operated in close proximity and within strong magnetic fields up to 4.7 Tesla (T). Other aims of the Phase I proposal involve the determination of tomographic image quality of stationary, multi-pinhole, multi-detector CZT SPECT and the selection of a 4.7 T, actively shielded superconducting magnet to be purchased (with internal, non-governmental GMI investment) for the Phase II prototype. During Phase II the fabrication of the SPECT chassis and its integration with the MRI system will take place. At the conclusion of Phase I/II, Gamma Medica will be ready to create a pilot SPECT/ MRI product. Stationary tomographic nuclear imaging in a high-magnetic field is the project's primary innovation. The Dual-Modality SPECT-MRI for in vivo small animal imaging project is a challenging next step in the development of multi-modality imaging devices of living subjects. The complementary nature of nuclear and computed tomography imaging has resulted in synergistic understanding of biological processes and reduction in unnecessary clinical procedures. The rich dynamic, chemical, spectroscopic, and dynamic image data of MRI combined with the molecularly-targeted imaging of SPECT can be expected to provide even more fruitful results. This application describes an innovative nuclear imaging technology that uniquely can be engineered to be compatible with MRI.
