Molecular Imaging Branch
GOALS. Established by the NIMH in 2000, the Molecular Imaging Branch (MIB) uses a variety of neuroimaging techniques to explore molecular and chemical mechanisms associated with neural function in health and disease. The overall goal of the Branch is to further elucidate pathophysiological mechanisms associated with neuropsychiatric disorders, with the expectation that such knowledge will ultimately decrease the burden of these illnesses by helping to guide the development and evaluation of improved therapeutics for these disorders.
METHODS. The primary methods used by investigators in this Branch are PET (positron emission tomography) and NMR (nuclear magnetic resonance). New PET radiotracers are synthesized for use as in vivo ligands to measure many different molecular targets, including membrane-bound receptors, proteins associated with intracellular signal transduction, and ones that reflect gene expression. Several NMR methods are also studied to measure molecular targets (magnetic resonance spectroscopy (MRS)), local neuronal activity (functional MRI or fMRI), and structure of the brain (structural MRI).
COMPONENTS. This Branch has three sections, each headed by a tenured scientist:
- Section on PET Radiopharmaceutical Sciences: Chief, Victor Pike, PhD
- Section on PET Neuroimaging Sciences: Chief, Robert Innis, MD, PhD
- Section on Magnetic Resonance Spectroscopy: Chief, Jun Shen, PhD
The first two Sections on Radiopharmaceuticals and Neuroimaging are almost exclusively oriented to PET, with a smaller effort in SPECT (single photon emission computed tomography). These two sections include a strong methodological orientation, with state-of-the-art facilities to develop, evaluate, and then apply new radiotracers for in vivo imaging. New radiotracers are synthesized and then rigorously evaluated in animals (rodents and primates) to assess their utility to localize, quantify, and measure the functional status of their targets. Promising candidate radiotracers are extended to human subjects, first in healthy subjects and then in relevant patient populations.
The Neuroimaging Section applies both PET and NMR imaging technologies to investigate the neurobiological bases of mood and anxiety disorders. Because different imaging technologies have distinct capabilities, strengths, and limitations, studies are designed so that the same subjects are iteratively studied using multiple techniques to provide complementary information about pathophysiology.
The Section on Magnetic Resonance Spectroscopy (MRS) develops and applies both high-resolution and in vivo nuclear MRS and imaging techniques. In vivo MRS is a fundamentally new method for non-invasive assessment of the homeostasis and dynamics of important endogenous metabolically active compounds and neurotransmitters in the brain. This Section develops and applies both high-resolution and in vivo nuclear MRS and imaging techniques. Working with high-field magnetic resonance spectrometers this Section develops novel NMR methods and applies them to the study of neurotransmission and neurometabolism, with significant opportunities available for multi-modal collaborative imaging using MRS, MRI, and PET.
PET RADIOCHEMISTRY FACILITY. The new NIMH PET radiochemistry facility is directed by Victor Pike, PhD. This laboratory is fully equipped for medicinal chemistry and radiochemistry, including six hot cells, extensive HPLC, LC-MS, GC-MS, 400 MHz NMR, three 11C and one 18F automated synthesis apparatus. Each hot cell is connected to each of three cyclotrons located in an adjacent vault.
PET IMAGING. The NIH PET Department has three GE Advance PET cameras and a Siemens High Resolution Research Tomograph. In addition, a rodent PET device (ATLAS) constructed in-house by Mike Green is available for in vivo imaging of rats and mice at the NIH Mouse Imaging Facility (MIF) . NIMH recently purchased two new PET cameras to image rodents (Siemens microPET Focus 120) and monkeys (Siemens microPET Focus 220). The branch receives a full range of support, from personnel to equipments, from the Clinical Center .
MR IMAGING. Most MRI/fMRI studies will be carried out on the 3 Tesla magnet at the 3T Functional Neuroimaging Facility. Some studies may also be performed on the NIH MRI Research Facility . A 7-Tesla small animal MR scanner is also available at the MIF.