Preclinical SPECT/MR Molecular Imaging System Reduces Radiation Dose

A new preclinical single photon emission tomography and magnetic resonance (SPECT/MR) hybrid molecular imaging system has exceptional molecular imaging capabilities in terms of potential preclinical and clinical applications, cost-effective technologic innovation, and reduction of patient exposure to ionizing radiation.

The technology was presented in June 2013 at the Society of Nuclear Medicine and Molecular Imaging’s (SNMMI) 2013 annual meeting, held in Vancouver (BC, Canada). “We are pioneering simultaneous SPECT and MR imaging technologies now demonstrated in preliminary small animal studies,” said Benjamin M.W. Tsui, PhD, director of the division of medical imaging physics in the department of radiology, and a professor of radiology, electrical and computer, biomedical engineering, and environmental health sciences at Johns Hopkins University (Baltimore, MD, USA). “We have been building the technology with our industrial partner, TriFoil Imaging [Northridge, CA, USA]—formerly the preclinical business of Gamma Medica, Inc.—for the past five years and have sufficient data now to show that it works. This presents a unique multimodality system that images mice down to a spatial resolution of less than1 mm at high detection efficiency.”

SPECT/MR represents a completely different imaging modality from other hybrid systems such as positron emission tomography/ computed tomography (PET/CT) and simultaneous PET/magnetic resonance imaging (PET/MRI) by allowing hybrid imaging with biomarkers labeled with a wide range of radionuclides. SPECT/MRI has a range of possible applications, including but not limited to imaging for cardiovascular and neurologic diseases, cancer, thyroid and other endocrine disorders, trauma, inflammation, and infection.

To generate a SPECT insert that performs in the magnetic field of an MRI system, the developers incorporated 16 x 16 pixel and 1.6-mm pixel pitch cadmium zinc telluride (CZT) solid-state detectors that directly convert incoming photons into electrical signals that are not disturbed by the static magnetic field. The SPECT insert also houses a state-of-the-art “multi-pinhole” collimator that provides both high spatial resolution and capacity for the detection of photons from small animals injected with available or new nuclear medicine biomarkers that use radionuclides to illustrate physiologic functions of the body. Unlike PET imaging, SPECT has the added benefit of being able to identify photons of different energies from multiple radionuclide-labeled biomarkers for fully customized and application-specific multifunctional imaging.

The SPECT/MR system’s key features include the elimination of the radiation dose associated with CT and the much lower cost of building the technology compared to PET/MR, which cost approximately USD 5.5 million for a clinical system. Dr. Tsui noted, however, that the technology is meant not to replace other technologies but instead to further diversify alternatives for biomedical investigators and clinicians to optimize research and patient care. SPECT/MR could roll out into human trials in the not-too-distant future. “We are confident that with sufficient funding we can build a SPECT/MR system for human brain studies in about two years and begin clinical studies by the third year,” Dr. Tsui estimated.

Related Links:
Johns Hopkins University
TriFoil Imaging