A 194-cm-long total-body positron emission tomography/computed tomography (PET/CT) scanner (uEXPLORER), has been constructed to offer a transformative platform for human radiotracer imaging in clinical research and healthcare. Its total-body coverage and exceptional sensitivity provide opportunities for innovative studies of physiology, biochemistry, and pharmacology. The objective of this study is to develop a method to perform ultrahigh (100 ms) temporal resolution dynamic PET imaging by combining advanced dynamic image reconstruction paradigms with the uEXPLORER scanner. We aim to capture the fast dynamics of initial radiotracer distribution, as well as cardiac motion, in the human body. The results show that we can visualize radiotracer transport in the body on timescales of 100 ms and obtain motion-frozen images with superior image quality compared to conventional methods. The proposed method has applications in studying fast tracer dynamics, such as blood flow and the dynamic response to neural modulation, as well as performing real-time motion tracking (e.g., cardiac and respiratory motion, and gross body motion) without any external monitoring device (e.g., electrinjocardiogram, breathing belt, or optical trackers).
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This high temporal resolution tracer imaging technique opens up the opportunity for new applications, such as studying fast pharmacodynamics, using shorter-lived radionuclides (e.g., 82Rb, 13N, and 15O), and performing motion-frozen scans of the heart, lung, and gastrointestinal tract.
PET with high temporal resolution also has potential applications in the characterization of normal and abnormal brain function. Although functional MRI can detect changes associated with cerebral blood flow (CBF), our approach has the potential to directly measure the absolute value of CBF and cerebral metabolic rate of oxygen. The advantage of CBF as determined with diffusible tracers in PET is that it measures blood flow at the nutrient capillary level (not only in large vessels). During the stimulation, parameters derived within a window of a second may show better correlation with postsynaptic activity and less hemodynamic lag. Moreover, these methods could be used for localizing neural activity by correlating it with specific neurotransmitter activity. Furthermore, without the artifacts induced by cardiac and respiratory motion, ultrafast PET may allow analysis of metabolic processes within atherosclerotic plaques and evaluate their distribution and characteristics throughout the cardiovascular system. Finally, high temporal resolution PET together with the TB coverage allows dynamic tracer studies of brain–heart and brain–gut interactions.
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