Ultra-High Resolution Brain PET Scanner Offers Potential for Early Diagnosis of Neurological Conditions

By MedImaging International staff writers
Posted on 03 Jul 2023

Image: Brain images of a 59-year-old woman acquired using UHR scanner (top) and Discovery MI scanner (bottom) (Photo courtesy of University of Sherbrooke)

While PET (Positron Emission Tomography) has been instrumental in studying neurological phenomena and diagnostics, its potential has been somewhat restricted due to the subpar spatial resolution of existing PET systems. Now, amidst the technological improvements in PET instrumentation and a global initiative to enhance brain PET imaging capabilities, scientists have designed and built a novel ultra-high resolution (UHR) brain PET scanner that offers unmatched resolution, paving the way for more precise brainstem studies.

The new UHR-dedicated brain PET system developed by researchers at the University of Sherbrooke (Québec, Canada) could potentially characterize previously unidentifiable brain regions known to contribute to Alzheimer's disease, depressive disorders, visual attention disorders, tinnitus, and other conditions. In contrast to conventional PET scanners, this UHR scanner boasts truly pixelated detectors and achieves a 1.25 mm isotropic spatial resolution. This represents a two-fold improvement over the High Resolution Research Tomograph (HRRT) scanner, the previous gold standard for brain PET imaging for the last two decades. This advancement enables visualization of the radiotracer uptake in the human brain in the range of a few tens of microliters for the first time.

To demonstrate the UHR scanner's ability to delineate small cerebral structures and accurately quantify in vivo tracer concentration, researchers compared it to a whole-body PET scanner. Three patients prescribed an 18F-FDG PET scan underwent their clinical examination on the whole-body PET scanner followed by a brain scan on the UHR scanner. Images from both scanners were compared, and region identification was performed. Standardized uptake values relative to the cerebellum were also calculated. Several brain regions, especially in the brainstem, were readily identifiable visually in UHR images but were not visualized by the whole-body PET scanner. The inferior and superior colliculi, the subthalamic nuclei, and the red nuclei were clearly delineated in the UHR images.

Furthermore, the thalamus, usually seen as a whole in standard PET images, could be visually segmented into smaller nuclei using the UHR scanner. Hypermetabolic regions of the cortex were also noticeable in the UHR images but barely perceivable with the whole-body PET scanner. The first UHR prototype is fully operational and in use for research applications at the Sherbrooke Molecular Imaging Center. In the coming months, additional UHR units will be deployed to brain research centers across North America, and progress will be made toward obtaining necessary regulatory approvals for clinical imaging. The performance of a second UHR model, featuring new detectors to improve the overall resolution across the field of view, will also be tested shortly.

“The UHR scanner is a quantum leap for PET image resolution,” said Vincent Doyon, a master’s student in Radiation Sciences and Biomedical Imaging at the University of Sherbrooke. “Proper visualization of brainstem nuclei will provide the ability to detect early changes associated with many diseases and offer a potential avenue for early diagnosis. This will impact both research and clinical settings.”

Related Links:
University of Sherbrooke