<unk> /CT-System with 16-slice CT; the ceiling mounted device is an injection pump for CT contrast agent<unk>  is both a medical and research tool used in pre-clinical and clinical settings. It is used heavily in the imaging of tumors and the search for metastases within the field of clinical oncology, and for the clinical diagnosis of certain diffuse brain diseases such as those causing various types of dementias.<unk>  is a valuable research tool to learn and enhance our knowledge of the normal human brain, heart function, and support drug development.<unk>  is also used in pre-clinical studies using animals. It allows repeated investigations into the same subjects over time, where subjects can act as their own control and substantially reduces the numbers of animals required for a given study. This approach allows research studies to reduce the sample size needed while increasing the statistical quality of its results. Physiological processes lead to anatomical changes in the body. Since<unk>  is capable of detecting biochemical processes as well as expression of some proteins,<unk>  can provide molecular-level information much before any anatomic changes are visible.<unk>  scanning does this by using radiolabelled molecular probes that have different rates of uptake depending on the type and function of tissue involved. Regional tracer uptake in various anatomic structures can be visualized and relatively quantified in terms of injected<unk>  emitter within a<unk>  scan.<unk>  imaging is best performed using a dedicated<unk>  scanner. It is also possible to acquire<unk>  images using a conventional dual-head gamma camera fitted with a coincidence detector. The quality of gamma-camera<unk>  imaging is lower, and the scans take longer to acquire. However, this method allows a low-cost on-site solution to institutions with low<unk>  scanning demand. An alternative would be to refer these patients to another center or relying on a visit by a mobile scanner. Alternative methods of medical imaging include single-photon emission computed<unk>  (SPECT), x-ray computed<unk>  (CT), magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI), and ultrasound. SPECT is an imaging technique similar to<unk>  that uses radioligands to detect molecules in the body. SPECT is less expensive and provides inferior image quality than<unk> . Oncology Whole-body<unk>  scan using 18F-FDG. The normal brain and kidneys are labeled, and radioactive urine from breakdown of the FDG is seen in the bladder. In addition, a large metastatic tumor mass from colon cancer is seen in the liver.<unk>  scanning with the tracer 18F-FDG is widely used in clinical oncology. FDG is a glucose analog that is taken up by glucose-using cells and phosphorylated by hexokinase (whose mitochondrial form is significantly elevated in rapidly growing malignant tumors). Metabolic trapping of the radioactive glucose molecule allows the<unk>  scan to be utilized. The concentrations of imaged FDG tracer indicate tissue metabolic activity as it corresponds to the regional glucose uptake. 18F-FDG is used to explore the possibility of cancer spreading to other body sites (cancer metastasis). These 18F-FDG<unk>  scans for detecting cancer metastasis are the most common in standard medical care (representing 90% of current scans). The same tracer may also be used for the diagnosis of types of dementia. Less often, other radioactive tracers, usually but not always labelled with fluorine-18, are used to image the tissue concentration of different kinds of molecules of interest inside the body. A typical dose of FDG used in an oncological scan has an effective radiation dose of 7.6 mSv. Because the hydroxy group that is replaced by fluorine-18 to generate FDG is required for the next step in glucose metabolism in all cells, no further reactions occur in FDG. Furthermore, most tissues (with the notable exception of liver and kidneys) cannot remove the phosphate added by hexokinase. This means that FDG is trapped in any cell that takes it up until it decays, since phosphorylated sugars, due to their ionic charge, cannot exit from the cell. This results in intense radiolabeling of tissues with high glucose uptake, such as the normal brain, liver, kidneys, and most cancers, which have a higher glucose uptake than most normal tissue due to the Warburg effect. As a result,<unk>  can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin lymphoma, non-Hodgkin lymphoma, and lung cancer. A 2020 review of research on the use of<unk>  for Hodgkin lymphoma found evidence that negative findings in interim<unk>  scans are linked to higher overall survival and progression-free survival; however, the certainty of the available evidence was moderate for survival, and very low for progression-free survival. A few other isotopes and radiotracers are slowly being introduced into oncology for specific purposes. For example, 11C-labelled metomidate (11C-metomidate) has been used to detect tumors of adrenocortical origin. Also, FDOPA<unk> /CT (or F-18-DOPA<unk> /CT) has proven to be a more sensitive alternative to finding and also localizing pheochromocytoma than the MIBG scan. Neuroimaging Neurology<unk>  scan of the human brainPET imaging with oxygen-15 indirectly measures blood flow to the brain. In this method, increased radioactivity signal indicates increased blood flow which is assumed to correlate with increased brain activity. Because of its 2-minute half-life, 15O must be piped directly from a medical cyclotron for such uses, which is difficult.<unk>  imaging with 18F-FDG takes advantage of the fact that the brain is normally a rapid user of glucose. Standard 18F-FDG<unk>  of the brain measures regional glucose use and can be used in neuropathological diagnosis. Brain pathologies such as Alzheimer's disease greatly decrease brain metabolism of both glucose and oxygen in tandem. Therefore 18F-FDG<unk>  of the brain may also be used to successfully differentiate Alzheimer's disease from other dementing processes, and also to make early diagnoses of Alzheimer's disease. The advantage of 18F-FDG<unk>  for these uses is its much wider availability. Some 18F based radioactive tracers used for Alzheimer's include florbetapir, flutemetamol, PiB and florbetaben, which are all used to detect amyloid-beta plaques (a potential biomarker for Alzheimer's) in the brain.<unk>  imaging with FDG can also be used for localization of seizure focus. A seizure focus will appear as hypometabolic during an interictal scan. Several radiotracers (i.e. radioligands) have been developed for<unk>  that are ligands for specific neuroreceptor subtypes such as 11C raclopride, 18F fallypride and 18F desmethoxyfallypride for dopamine D2/D3 receptors, 11C McN 5652 and 11C DASB for serotonin transporters, 18F Mefway for serotonin 5HT1A receptors, 18F Nifene for nicotinic acetylcholine receptors or enzyme substrates (e.g. 6-FDOPA for the AADC enzyme). These agents permit the visualization of neuroreceptor pools in the context of a plurality of neuropsychiatric and neurologic illnesses.<unk>  may also be used for the diagnosis of hippocampal sclerosis, which causes epilepsy. FDG, and the less common tracers flumazenil and MPPF have been explored for this purpose. If the sclerosis is unilateral (right hippocampus or left hippocampus), 18F-FDG uptake can be compared with the healthy side. Even if the diagnosis is difficult with MRI, it may be diagnosed with<unk> . The development of a number of novel probes for noninvasive, in vivo<unk>  imaging of neuroaggregate in human brain has brought amyloid imaging close to clinical use. The earliest amyloid imaging probes included 2-(1-{6-(2-18Ffluoroethyl)(methyl)amino-2-naphthyl}ethylidene)malononitrile (18FFDDNP) developed at the University of California, Los Angeles and N-methyl-11C2-(4'-methylaminophenyl)-6-hydroxybenzothiazole (termed Pittsburgh compound B) developed at the University of Pittsburgh. These amyloid imaging probes permit the visualization of amyloid plaques in the brains of Alzheimer's patients and could assist clinicians in making a positive clinical diagnosis of AD pre-mortem and aid in the development of novel anti-amyloid therapies. 11CPMP (N-11Cmethylpiperidin-4-yl propionate) is a novel radiopharmaceutical used in<unk>  imaging to determine the activity of the acetylcholinergic neurotransmitter system by acting as a substrate for acetylcholinesterase. Post-mortem examination of AD patients have shown decreased levels of acetylcholinesterase. 11CPMP is used to map the acetylcholinesterase activity in the brain, which could allow for pre-mortem diagnoses of AD and help to monitor AD treatments. Avid Radiopharmaceuticals has developed and commercialized a compound called florbetapir that uses the longer-lasting radionuclide fluorine-18 to detect amyloid plaques using<unk>  scans. Neuropsychology or cognitive neuroscience To examine links between specific psychological processes or disorders and brain activity. Psychiatry Numerous compounds that bind selectively to neuroreceptors of interest in biological psychiatry have been radiolabeled with C-11 or F-18. Radioligands that bind to dopamine receptors (D1, D2 receptor, reuptake transporter), serotonin receptors (5HT1A, 5HT2A, reuptake transporter) opioid receptors (mu and kappa) cholinergic receptors (nicotinic and muscarinic) and other sites have been used successfully in studies with human subjects. Studies have been performed examining the state of these receptors in patients compared to healthy controls in schizophrenia, substance abuse, mood disorders and other psychiatric conditions. Stereotactic surgery and radiosurgery<unk> -image guided surgery facilitates treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions. Cardiology Cardiology, atherosclerosis and vascular disease study: 18F-FDG<unk>  can help in identifying hibernating myocardium. However, the cost-effectiveness of<unk>  for this role versus SPECT is unclear. 18F-FDG<unk>  imaging of atherosclerosis to detect patients at risk of stroke is also feasible.
Positron emission tomography
Neutron stimulated emission computed tomography
Single-photon emission computed tomography
Molecular imaging
Mediastinoscopy
PET-CT
Neutron imaging
Kinetic imaging