Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy.
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.
Rehabilitation of sensory and cognitive function typically involves methods for retraining neural pathways or training new neural pathways to regain or improve neurocognitive functioning that have been diminished by disease or trauma. The main objective outcome for rehabilitation is to assist in regaining physical abilities and improving performance. Three common neuropsychological problems treatable with rehabilitation are attention deficit/hyperactivity disorder (ADHD), concussion, and spinal cord injury. Rehabilitation research and practices are a fertile area for clinical neuropsychologists, rehabilitation psychologists, and others.
Myelopathy describes any neurologic deficit related to the spinal cord. The most common form of myelopathy in humans, cervical spondylotic myelopathy (CSM), also called degenerative cervical myelopathy, results from narrowing of the spinal canal ultimately causing compression of the spinal cord. When due to trauma, myelopathy is known as (acute) spinal cord injury. When inflammatory, it is known as myelitis. Disease that is vascular in nature is known as vascular myelopathy.
Blood-oxygen-level-dependent imaging, or BOLD-contrast imaging, is a method used in functional magnetic resonance imaging (fMRI) to observe different areas of the brain or other organs, which are found to be active at any given time.
EEG-fMRI is a multimodal neuroimaging technique whereby EEG and fMRI data are recorded synchronously for the study of electrical brain activity in correlation with haemodynamic changes in brain during the electrical activity, be it normal function or associated with disorders.
Kenneth Kin Man Kwong is a Hong Kong-born American nuclear physicist. He is a pioneer in human brain imaging. He received his bachelor's degree in Political Science in 1972 from the University of California, Berkeley. He went on to receive his Ph.D. in physics from the University of California, Riverside studying photon-photon collision interactions.
In vivo magnetic resonance spectroscopy (MRS) is a specialized technique associated with magnetic resonance imaging (MRI).
Signal enhancement by extravascular water protons, or SEEP, is a contrast mechanism for functional magnetic resonance imaging (fMRI), which is an alternative to the more commonly employed BOLD contrast. This mechanism for image contrast changes corresponding to changes in neuronal activity was first proposed by Dr. Patrick Stroman in 2001. SEEP contrast is based on changes in tissue water content which arise from the increased production of extracellular fluid and swelling of neurons and glial cells at sites of neuronal activity. Because the dominant sources of MRI signal in biological tissues are water and lipids, an increase in tissue water content is reflected by a local increase in MR signal intensity. A correspondence between BOLD and SEEP signal changes, and sites of activity, has been observed in the brain and appears to arise from the common dependence on changes in local blood flow to cause a change in blood oxygenation or to produce extracellular fluid. The advantage of SEEP contrast is that it can be detected with MR imaging methods which are relatively insensitive to magnetic susceptibility differences between air, tissues, blood, and bone. Such susceptibility differences can give rise to spatial image distortions and areas of low signal, and magnetic susceptibility changes in blood give rise to the BOLD contrast for fMRI. The primary application of SEEP to date has been fMRI of the spinal cord because the bone/tissue interfaces around the spinal cord cause poor image quality with conventional fMRI methods. The disadvantages of SEEP compared to BOLD contrast are that it reveals more localized areas of activity, and in the brain the signal intensity changes are typically lower, and it can therefore be more difficult to detect.
Magnetic resonance neurography (MRN) is the direct imaging of nerves in the body by optimizing selectivity for unique MRI water properties of nerves. It is a modification of magnetic resonance imaging. This technique yields a detailed image of a nerve from the resonance signal that arises from in the nerve itself rather than from surrounding tissues or from fat in the nerve lining. Because of the intraneural source of the image signal, the image provides a medically useful set of information about the internal state of the nerve such as the presence of irritation, nerve swelling (edema), compression, pinch or injury. Standard magnetic resonance images can show the outline of some nerves in portions of their courses but do not show the intrinsic signal from nerve water. Magnetic resonance neurography is used to evaluate major nerve compressions such as those affecting the sciatic nerve (e.g. piriformis syndrome), the brachial plexus nerves (e.g. thoracic outlet syndrome), the pudendal nerve, or virtually any named nerve in the body. A related technique for imaging neural tracts in the brain and spinal cord is called magnetic resonance tractography or diffusion tensor imaging.
Tumefactive multiple sclerosis is a condition in which the central nervous system of a person has multiple demyelinating lesions with atypical characteristics for those of standard multiple sclerosis (MS). It is called tumefactive as the lesions are "tumor-like" and they mimic tumors clinically, radiologically and sometimes pathologically.
Preclinical imaging is the visualization of living animals for research purposes, such as drug development. Imaging modalities have long been crucial to the researcher in observing changes, either at the organ, tissue, cell, or molecular level, in animals responding to physiological or environmental changes. Imaging modalities that are non-invasive and in vivo have become especially important to study animal models longitudinally. Broadly speaking, these imaging systems can be categorized into primarily morphological/anatomical and primarily molecular imaging techniques. Techniques such as high-frequency micro-ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) are usually used for anatomical imaging, while optical imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT) are usually used for molecular visualizations.
The physics of magnetic resonance imaging (MRI) concerns fundamental physical considerations of MRI techniques and technological aspects of MRI devices. MRI is a medical imaging technique mostly used in radiology and nuclear medicine in order to investigate the anatomy and physiology of the body, and to detect pathologies including tumors, inflammation, neurological conditions such as stroke, disorders of muscles and joints, and abnormalities in the heart and blood vessels among others. Contrast agents may be injected intravenously or into a joint to enhance the image and facilitate diagnosis. Unlike CT and X-ray, MRI uses no ionizing radiation and is, therefore, a safe procedure suitable for diagnosis in children and repeated runs. Patients with specific non-ferromagnetic metal implants, cochlear implants, and cardiac pacemakers nowadays may also have an MRI in spite of effects of the strong magnetic fields. This does not apply on older devices, and details for medical professionals are provided by the device's manufacturer.
Real-time magnetic resonance imaging (RT-MRI) refers to the continuous monitoring ("filming") of moving objects in real time. Because MRI is based on time-consuming scanning of k-space, real-time MRI was possible only with low image quality or low temporal resolution. Using an iterative reconstruction algorithm these limitations have recently been removed: a new method for real-time MRI achieves a temporal resolution of 20 to 30 milliseconds for images with an in-plane resolution of 1.5 to 2.0 mm. Real-time MRI promises to add important information about diseases of the joints and the heart. In many cases MRI examinations may become easier and more comfortable for patients.
Resting state fMRI is a method of functional magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate regional interactions that occur in a resting or task-negative state, when an explicit task is not being performed. A number of resting-state brain networks have been identified, one of which is the default mode network. These brain networks are observed through changes in blood flow in the brain which creates what is referred to as a blood-oxygen-level dependent (BOLD) signal that can be measured using fMRI.
Functional magnetic resonance spectroscopy of the brain (fMRS) uses magnetic resonance imaging (MRI) to study brain metabolism during brain activation. The data generated by fMRS usually shows spectra of resonances, instead of a brain image, as with MRI. The area under peaks in the spectrum represents relative concentrations of metabolites.
Multiple sclerosis (MS) can be pathologically defined as the presence of distributed glial scars (scleroses) in the central nervous system that must show dissemination in time (DIT) and in space (DIS) to be considered MS lesions.
Sodium MRI is a specialised magnetic resonance imaging technique that uses strong magnetic fields, magnetic field gradients, and radio waves to generate images of the distribution of sodium in the body, as opposed to more common forms of MRI that utilise protons present in water (1H-MRI). Like the proton, sodium is naturally abundant in the body, so can be imaged directly without the need for contrast agents or hyperpolarization. Furthermore, sodium ions play a role in important biological processes via their contribution to concentration and electrochemical gradients across cellular membranes, making it of interest as an imaging target in health and disease.
An MRI sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular image appearance.
An MRI artifact is a visual artifact in magnetic resonance imaging (MRI). It is a feature appearing in an image that is not present in the original object. Many different artifacts can occur during MRI, some affecting the diagnostic quality, while others may be confused with pathology. Artifacts can be classified as patient-related, signal processing-dependent and hardware (machine)-related.
