New Insight and Increased Confidence Using Simultaneous PET/MRI
There is an incredibly complex interplay between various processes within all living subjects. Proving a causal relationship exists between two phenomena can be difficult if each is observed at different times. A single, simultaneous PET/MRI session can measure both molecular and functional changes under identical physiological conditions, allowing more confidence in correlating changes and determining relationships.
In addition, the reduced total scan time compared with sequential scanning keeps anesthesia exposure to a minimum, and can reduce the cumulative stress on sometimes fragile animal models. Since anesthesia impacts many important physiological parameters like cerebral blood flow and glucose metabolism in a dose-dependent way in otherwise healthy animals, less anesthesia exposure can also reduce the risk of spurious experimental outcomes and could reduce the number of animals needed to reach statistically meaningful conclusions.
Parameter maps from PET data overlaid on MRI atlas (upper) and %CBV change from fMRI data by P-value map with P<0.03 (lower).
More Precise Co-Registration, Essential for Quantitation
Image registration errors occur even when an immobilized animal is carefully transported just a few feet from one scanning system to another because in vivo animal models like mice contain so much soft malleable tissue. Experiments performed for applications such as neurology/neuroscience, oncology, and cardiology involve subjects that are breathing or otherwise moving, and activities within the brain that are typically imaged using PET or fMRI can occur rapidly. Having two imaging modalities triggered at exactly the same time is ideal.
More Accurate, Synchronized Data for Your Application
- Brain Receptor Activity: For the first time researchers can correlate changes in brain chemistry with changes in brain activity by using simultaneous PET/fMRI scanning. PET emission data offers high sensitivity and neurochemical specificity, while fMRI offers high spatio-temporal resolution for measuring changes in neurovascular activity.
- Stroke: Ischemic events produce a cascade of rapidly evolving physiological changes that can be highly individualized. Simultaneous PET/MRI can provide complementary information about the evolution of injury and the effect of interventions such as neuroprotective compounds.
- Advanced Tumor Assessment: Tumor characteristics such as hypoxia, acidosis, and angiogenesis are considered related, and simultaneous PET/MRI provides a superior way to study these relationships and provide a “molecular signature” for each phenotype.
- Heart Failure Assessment: Spatially and temporally registered PET/MRI images enable more precise estimations of infarct size and tissue stress, as well as a better understanding of the subject’s hemodynamics. PET data itself can also benefit greatly from MRI-based Partial Volume Correction (PVC) and motion correction, resulting in sharper, higher-resolution detail.
A mixture of 18F-FDG PET agent and MultiHance® MRI agent was injected IV into a flank tumor model of human A549 lung cancer. The large tumor and a small portion of the mouse body are shown in this axial image orientation. Left: Average 18F-FDG PET signal overlaid on an anatomical MR image shows relative glucose uptake. Right: Dynamic Contrast Enhancement (DCE) MRI was used to construct a map of relative vascular permeability. Images courtesy of University of Arizona.