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Magnetic resonance imaging (MRI) is a
medical imaging Medical imaging is the technique and process of imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materi ...
technique used in
radiology Radiology is the medical discipline that uses medical imaging Medical imaging is the technique and process of imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the form ...

radiology
to form pictures of the
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It ...

anatomy
and the
physiological Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
processes of the body. MRI scanners use strong
magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in the plane can be visualised as a collection of arrows with ...

magnetic field
s, magnetic field gradients, and
radio wave Radio waves are a type of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...
s to generate images of the organs in the body. MRI does not involve
X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Moti ...

X-rays
or the use of
ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of s or s that have sufficient to s or s by detaching s from them. The particles generally travel at a speed that is greater than 1% of , and the electromagnetic w ...
, which distinguishes it from
CT
CT
and
PET scan Positron emission tomography (PET) is a functional imaging Functional imaging (or physiological imaging), is a medical imaging technique of detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption ...

PET scan
s. MRI is a
medical application
medical application
of
nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon A phenomenon (; plural phenomena) is an observable In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ...
(NMR) which can also be used for imaging in other
NMR applications
NMR applications
, such as
NMR spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic Spectroscopy is the study of the interaction between matter and Electromagnetism, electromagnetic ra ...
. MRI is widely used in hospitals and clinics for
medical diagnosis Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and medical sign, signs. It is most often referred to as diagnosis with the medicine, medical context being implic ...
, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft-tissues, e.g. in the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tis ...
or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube. Additionally,
implants Implant can refer to: Medicine *Implant (medicine), or specifically: **Brain implant **Breast implant **Buttock augmentation, Buttock implant **Cochlear implant **Contraceptive implant **Dental implant **Fetal tissue implant **Implantable cardiove ...
and other non-removable metal in the body can pose a risk and may exclude some patients from undergoing an MRI examination safely. MRI was originally called NMRI (nuclear magnetic resonance imaging), but "nuclear" was dropped to avoid negative associations. Certain
atomic nuclei The atomic nucleus is the small, dense region consisting of proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutr ...
are able to absorb
radio frequency Radio frequency (RF) is the oscillation Oscillation is the repetitive variation, typically in time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparently irreversible p ...
energy when placed in an external
magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in the plane can be visualised as a collection of arrows with ...

magnetic field
; the resultant evolving
spin polarization Spin polarization is the degree to which the spin, i.e., the intrinsic angular momentum In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational equivalent of linear momentum. It is an important quanti ...
can induce a RF signal in a radio frequency coil and thereby be detected. In clinical and research MRI,
hydrogen atoms
hydrogen atoms
are most often used to generate a macroscopic polarization that is detected by antennae close to the subject being examined. Hydrogen atoms are naturally abundant in humans and other biological organisms, particularly in
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...
and
fat In nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided ...
. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite the
nuclear spin In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model is a nuclear model, model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The f ...
energy transition, and magnetic field gradients localize the polarization in space. By varying the parameters of the
pulse sequence In Fourier transform NMR spectroscopy and imaging, a pulse sequence describes a series of radio frequency pulses applied to the sample, such that the free induction decay is related to the characteristic frequencies of the desired signals. After ...
, different contrasts may be generated between tissues based on the relaxation properties of the hydrogen atoms therein. Since its development in the 1970s and 1980s, MRI has proven to be a versatile imaging technique. While MRI is most prominently used in diagnostic medicine and biomedical research, it also may be used to form images of non-living objects.
Diffusion MRI Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is the use of specific MRI sequence An MRI sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular i ...
and
Functional MRI 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 ...

Functional MRI
extends the utility of MRI to capture neuronal tracts and blood flow respectively in the nervous system, in addition to detailed spatial images. The sustained increase in demand for MRI within
health system A health system, also known as health care system or healthcare system, is the organization An organization, or organisation (Commonwealth English The use of the English language English is a West Germanic languages, West Germa ...
s has led to concerns about
cost effectiveness Cost-effectiveness analysis (CEA) is a form of economic financial analysis, analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which ...
and
overdiagnosis Overdiagnosis is the diagnosis of "disease" that will never cause symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower tempe ...
.


Mechanism


Construction and physics

In most medical applications,
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
nuclei, which consist solely of a
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
, that are in tissues create a signal that is processed to form an image of the body in terms of the density of those nuclei in a specific region. Given that the protons are affected by fields from other atoms to which they are bonded, it is possible to separate responses from hydrogen in specific compounds. To perform a study, the person is positioned within an
MRI scanner 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 ...
that forms a strong
magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in the plane can be visualised as a collection of arrows with ...

magnetic field
around the area to be imaged. First, energy from an
oscillating Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of Mechanical equilibrium, equilibrium) or between two or more different states. The term ''vibration'' is precisely used to describ ...

oscillating
magnetic field is temporarily applied to the patient at the appropriate
resonance Resonance describes the phenomenon of increased amplitude The amplitude of a Periodic function, periodic Variable (mathematics), variable is a measure of its change in a single Period (mathematics), period (such as frequency, time or Wavelen ...

resonance
frequency. Scanning with X and Y gradient coils causes a selected region of the patient to experience the exact magnetic field required for the energy to be absorbed. The atoms are excited by a
radio frequency Radio frequency (RF) is the oscillation Oscillation is the repetitive variation, typically in time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparently irreversible p ...
(RF) pulse and the resultant signal is measured by a receiving coil. The RF signal may be processed to deduce position information by looking at the changes in RF level and phase caused by varying the local magnetic field using . As these coils are rapidly switched during the excitation and response to perform a moving line scan, they create the characteristic repetitive noise of an MRI scan as the windings move slightly due to
magnetostriction Magnetostriction (cf. electrostriction) is a property of magnet, magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field ...
. The contrast between different tissues is determined by the rate at which excited atoms return to the equilibrium state.
Exogenous In a variety of contexts, exogeny or exogeneity () is the fact of an action or object originating externally. It contrasts with endogeneity or endogeny, the fact of being influenced within a system. Economics In an economic An economy (; ) ...
contrast agent A contrast agent (or contrast medium) is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, any ...
s may be given to the person to make the image clearer. The major components of an MRI scanner are the main
magnet A magnet is a material or object that produces a magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a ve ...

magnet
, which polarizes the sample, the shim coils for correcting shifts in the
homogeneity Homogeneity and heterogeneity are concepts often used in the sciences and statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a sc ...
of the main magnetic field, the gradient system which is used to localize the region to be scanned and the RF system, which excites the sample and detects the resulting NMR signal. The whole system is controlled by one or more computers. MRI requires a magnetic field that is both strong and
uniform A uniform is a variety of clothing A kanga, worn throughout the African Great Lakes region Clothing (also known as clothes, apparel, and attire) are items worn on the body. Typically, clothing is made of fabrics or textiles, but over ti ...
to a few parts per million across the scan volume. The field strength of the magnet is measured in teslas – and while the majority of systems operate at 1.5 T, commercial systems are available between 0.2 and 7 T. Most clinical magnets are
superconducting Superconductivity is a set of physical properties observed in certain materials where Electrical resistance and conductance, electrical resistance vanishes and magnetic field, magnetic flux fields are expelled from the material. Any material exh ...

superconducting
magnets, which require
liquid helium Liquid helium is a physical state of helium, at very low temperatures if it is at standard atmospheric pressures. Liquid helium may show superfluidity. At standard pressure, the chemical element Image:Simple Periodic Table Chart-blocks.svg, ...

liquid helium
to keep them very cold. Lower field strengths can be achieved with permanent magnets, which are often used in "open" MRI scanners for
claustrophobic Claustrophobia is the fear of confined spaces. It can be triggered by many situations or stimuli, including elevator An elevator (North American English) or lift (Commonwealth English) is a type of wire rope, cable-assisted, roller-track a ...

claustrophobic
patients. Lower field strengths are also used in a portable MRI scanner approved by the FDA in 2020. Recently, MRI has been demonstrated also at ultra-low fields, i.e., in the microtesla-to-millitesla range, where sufficient signal quality is made possible by prepolarization (on the order of 10–100 mT) and by measuring the Larmor precession fields at about 100 microtesla with highly sensitive superconducting quantum interference devices (
SQUID Squid are cephalopod A cephalopod is any member of the mollusca Mollusca is the second-largest phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is ...

SQUID
s).


T1 and T2

Each tissue returns to its equilibrium state after excitation by the independent relaxation processes of T1 ( spin-lattice; that is, magnetization in the same direction as the static magnetic field) and T2 ( spin-spin; transverse to the static magnetic field). To create a T1-weighted image, magnetization is allowed to recover before measuring the MR signal by changing the
repetition time The physics of magnetic resonance imaging (MRI) concerns fundamental Physics, physical considerations of Magnetic resonance imaging, MRI techniques and technological aspects of MRI devices. MRI is a medical imaging technique mostly used in radiolo ...
(TR). This image weighting is useful for assessing the cerebral cortex, identifying fatty tissue, characterizing focal liver lesions, and in general, obtaining morphological information, as well as for post-contrast imaging. To create a T2-weighted image, magnetization is allowed to decay before measuring the MR signal by changing the echo time (TE). This image weighting is useful for detecting
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a ...

edema
and inflammation, revealing white matter lesions, and assessing zonal anatomy in the
prostate The prostate is both an accessory gland of the male reproductive system The male reproductive system consists of a number of sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual repr ...

prostate
and
uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

uterus
. The standard display of MRI images is to represent fluid characteristics in
black and white Black-and-white (B/W or B&W) images combine black and white in a continuous spectrum In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is ...

black and white
images, where different tissues turn out as follows:


Diagnostics


Usage by organ or system

MRI has a wide range of applications in
medical diagnosis Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and medical sign, signs. It is most often referred to as diagnosis with the medicine, medical context being implic ...
and more than 25,000 scanners are estimated to be in use worldwide. MRI affects diagnosis and treatment in many specialties although the effect on improved health outcomes is disputed in certain cases. MRI is the investigation of choice in the preoperative staging of
rectal The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction, the end of the sig ...
and
prostate cancer Prostate cancer is cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumor A benign tumor is a mass of cells Cell most o ...

prostate cancer
and has a role in the diagnosis, staging, and follow-up of other tumors, as well as for determining areas of tissue for sampling in biobanking.


Neuroimaging

MRI is the investigative tool of choice for neurological cancers over CT, as it offers better visualization of the
posterior cranial fossa The posterior cranial fossa is part of the cranial cavity The cranial cavity, also known as intracranial space, is the space within the skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biolog ...
, containing the
brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and anima ...

brainstem
and the
cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain The hindbrain or rhombencephalon is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and ce ...

cerebellum
. The contrast provided between
grey Grey or gray (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Eng ...
and
white matter White matter refers to areas of the central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anato ...
makes MRI the best choice for many conditions of the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
, including
demyelinating disease A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This damage impairs the conduction of signals in the affected nerves. In turn, the reduction in conduction ability causes deficienc ...
s,
dementia Dementia manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or ...
,
cerebrovascular disease Cerebrovascular disease includes a variety of Medicine, medical conditions that affect the blood vessels of the brain and the cerebral circulation. Arteries supplying oxygen and nutrients to the brain are often Angiopathy, damaged or deformed in ...
,
infectious diseases An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxin A toxin is a harmful substance produced within living cells ...
,
Alzheimer's disease Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of . The most common early symptom is difficulty in . As the disease advance ...
and
epilepsy Epilepsy is a group of non-communicable neurological disorder A neurological disorder is any disorder of the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates i ...

epilepsy
. Since many images are taken milliseconds apart, it shows how the brain responds to different stimuli, enabling researchers to study both the functional and structural brain abnormalities in psychological disorders. MRI also is used in guided
stereotactic surgery Stereotactic surgery is a minimally invasive form of surgery, surgical intervention that makes use of a three-dimensional coordinates, coordinate system to locate small targets inside the body and to perform on them some action such as ablation, ...
and
radiosurgery Radiosurgery is surgery using radiation, that is, the destruction of precisely selected areas of tissue (biology), tissue using ionizing radiation rather than excision with a blade. Like other forms of radiation therapy (also called radiotherapy), ...
for treatment of intracranial tumors, arteriovenous malformations, and other surgically treatable conditions using a device known as the
N-localizer The N-localizer or N-bar is a device that enables guidance of stereotactic surgery Stereotactic surgery is a minimally invasive form of surgical intervention that makes use of a three-dimensional coordinate system to locate small targets insid ...
. New
Artificial intelligence in healthcare Artificial intelligence in healthcare, known also as Deep Medicine, is an overarching term used to describe the use of machine-learning algorithms and software, or artificial intelligence (AI), to mimic human cognition in the analysis, presentation ...
tools have demonstrated higher image quality and morphometric analysis in
neuroimaging Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly Medical imaging, image the neuroanatomy, structure, function, or pharmacology of the nervous system. It is a relatively new discipline within medicine ...
with the application of a denoising system.


Cardiovascular

Cardiac MRI is complementary to other imaging techniques, such as
echocardiography An echocardiography, echocardiogram, cardiac echo or simply an echo, is an ultrasound Ultrasound is s with higher than the upper audible limit of human . Ultrasound is not different from "normal" (audible) sound in its physical properties ...
, cardiac CT, and
nuclear medicine Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include children (paediatrics Pediatrics (American and Briti ...
. It can be used to assess the structure and the function of the heart. Its applications include assessment of myocardial ischemia and viability, cardiomyopathies,
myocarditis Myocarditis, also known as inflammatory cardiomyopathy, is inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is ...
,
iron overload Iron overload or haemochromatosis (spelled ''hemochromatosis'' in American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language nat ...
, vascular diseases, and
congenital heart disease A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps b ...
.


Musculoskeletal

Applications in the musculoskeletal system include , assessment of
joint A joint or articulation (or articular surface) is the connection made between bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various organs of th ...

joint
disease, and soft tissue tumors. Also, MRI techniques can be used for diagnostic imaging of systemic muscle diseases including genetic muscle diseases.


Liver and gastrointestinal

Hepatobiliary MR is used to detect and characterize lesions of the
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
,
pancreas The pancreas is an Organ (anatomy), organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...

pancreas
, and
bile duct A bile duct is any of a number of long tube-like structures that carry bile, and is present in most vertebrates. Bile, required for the digestion of food, is secreted by the liver into passages that carry bile toward the hepatic duct, which ...
s. Focal or diffuse disorders of the liver may be evaluated using diffusion-weighted, opposed-phase imaging and dynamic contrast enhancement sequences. Extracellular contrast agents are used widely in liver MRI, and newer hepatobiliary contrast agents also provide the opportunity to perform functional biliary imaging. Anatomical imaging of the bile ducts is achieved by using a heavily T2-weighted sequence in magnetic resonance cholangiopancreatography (MRCP). Functional imaging of the pancreas is performed following administration of
secretin Secretin is a hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and / or behavior. Hor ...
. MR enterography provides non-invasive assessment of inflammatory bowel disease and small bowel tumors. MR-colonography may play a role in the detection of large polyps in patients at increased risk of colorectal cancer.


Angiography

Magnetic resonance
angiography Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. This is traditionally done by ...
(MRA) generates pictures of the arteries to evaluate them for
stenosis A stenosis (from Ancient Greek στενός, "narrow") is an abnormal narrowing in a blood vessel or other tubular Organ (anatomy), organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture) ...
(abnormal narrowing) or
aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the ca ...
s (vessel wall dilatations, at risk of rupture). MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs (called a "run-off"). A variety of techniques can be used to generate the pictures, such as administration of a
paramagnetic Paramagnetism is a form of magnetism Magnetism is a class of physical attributes that are mediated by magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, a ...
contrast agent (
gadolinium Gadolinium is a chemical element with the Symbol (chemistry), symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with ...

gadolinium
) or using a technique known as "flow-related enhancement" (e.g., 2D and 3D time-of-flight sequences), where most of the signal on an image is due to blood that recently moved into that plane (see also FLASH MRI). Techniques involving phase accumulation (known as phase contrast angiography) can also be used to generate flow velocity maps easily and accurately. Magnetic resonance venography (MRV) is a similar procedure that is used to image veins. In this method, the tissue is now excited inferiorly, while the signal is gathered in the plane immediately superior to the excitation plane—thus imaging the venous blood that recently moved from the excited plane.


Contrast agents

MRI for imaging anatomical structures or blood flow do not require contrast agents since the varying properties of the tissues or blood provide natural contrasts. However, for more specific types of imaging,
exogenous In a variety of contexts, exogeny or exogeneity () is the fact of an action or object originating externally. It contrasts with endogeneity or endogeny, the fact of being influenced within a system. Economics In an economic An economy (; ) ...
contrast agents may be given
intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that delivers fluids, medications and nutrition directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrition ...
, , or intra-articularly. The most commonly used intravenous contrast agents are based on
chelate Chelation is a type of bonding of ions An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascrib ...
s of
gadolinium Gadolinium is a chemical element with the Symbol (chemistry), symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with ...

gadolinium
. In general, these agents have proved safer than the iodinated contrast agents used in X-ray radiography or CT. Anaphylactoid reactions are rare, occurring in approx. 0.03–0.1%. Of particular interest is the lower incidence of nephrotoxicity, compared with iodinated agents, when given at usual doses—this has made contrast-enhanced MRI scanning an option for patients with renal impairment, who would otherwise not be able to undergo contrast-enhanced CT. Gadolinium-based contrast reagents are typically octadentate complexes of . The complex is very stable (log K > 20) so that that, in use, the concentration of the un-complexed Gd3+ ions should be below the toxicity limit. The 9th place in the metal ion's
coordination sphere ''cis''- +_The_NH3_and_Cl_groups_form_a_coordination_sphere_around_the_central_cobalt.html" ;"title="oCl2(NH3)4sup>+ The NH3 and Cl groups form a coordination sphere around the central cobalt">oCl2(NH3)4sup>+ The NH3 and Cl groups form a coordinatio ...
is occupied by a water molecule which exchanges rapidly with water molecules in the reagent molecule's immediate environment, affecting the magnetic resonance
relaxation time In the physical sciences, relaxation usually means the return of a perturbed system into thermodynamic equilibrium, equilibrium. Each relaxation process can be categorized by a relaxation time tau, τ. The simplest theoretical description of rela ...
. For details see
MRI contrast agent MRI contrast agents are contrast agent A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging Medical imaging is the technique and process of imaging the ...
. In December 2017, the
Food and Drug Administration The United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, st ...
(FDA) in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
announced in a drug safety communication that new warnings were to be included on all gadolinium-based contrast agents (GBCAs). The FDA also called for increased patient education and requiring gadolinium contrast vendors to conduct additional animal and clinical studies to assess the safety of these agents. Although gadolinium agents have proved useful for patients with kidney impairment, in patients with severe
kidney failure Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys are functioning at less than 15% of normal levels. Kidney failure is classified as either acute kidney failure, which develops rapidly and may res ...
requiring dialysis there is a risk of a rare but serious illness,
nephrogenic systemic fibrosis Nephrogenic systemic fibrosis is a rare syndrome that involves fibrosis of skin, joints, eyes, and internal organs. NSF is caused by exposure to gadolinium in gadolinium-based MRI contrast agents (GBCAs) in patients with impaired kidney function. ...
, which may be linked to the use of certain gadolinium-containing agents. The most frequently linked is
gadodiamide Gadodiamide is a gadolinium-based MRI contrast agent, used in Magnetic resonance imaging, MR imaging procedures to assist in the visualization of blood vessels. It is commonly marketed under the trade name Omniscan. Uses Gadodiamide is a drug ...

gadodiamide
, but other agents have been linked too. Although a causal link has not been definitively established, current guidelines in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
are that dialysis patients should only receive gadolinium agents where essential and that
dialysis In medicine, dialysis (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximate ...

dialysis
should be performed as soon as possible after the scan to remove the agent from the body promptly. In Europe, where more gadolinium-containing agents are available, a classification of agents according to potential risks has been released. In 2008, a new contrast agent named , brand name Eovist (US) or Primovist (EU), was approved for diagnostic use: This has the theoretical benefit of a dual excretion path.


Sequences

An
MRI sequence 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. A multiparametric MRI is a combination of two or more sequences, and/or including ...
is a particular setting of radiofrequency pulses and gradients, resulting in a particular image appearance. The T1 and T2 weighting can also be described as MRI sequences.


Other specialized configurations


Magnetic resonance spectroscopy

Magnetic resonance spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei The atomic nucleus is the small, de ...
(MRS) is used to measure the levels of different
metabolites In biochemistry, a metabolite is an intermediate or end product of metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabo ...

metabolites
in body tissues, which can be achieved through a variety of single voxel or imaging-based techniques. The MR signal produces a spectrum of resonances that corresponds to different molecular arrangements of the isotope being "excited". This signature is used to diagnose certain metabolic disorders, especially those affecting the brain, and to provide information on tumor
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
. Magnetic resonance spectroscopic imaging (MRSI) combines both spectroscopic and imaging methods to produce spatially localized spectra from within the sample or patient. The spatial resolution is much lower (limited by the available SNR), but the spectra in each voxel contains information about many metabolites. Because the available signal is used to encode spatial and spectral information, MRSI requires high SNR achievable only at higher field strengths (3 T and above). The high procurement and maintenance costs of MRI with extremely high field strengths inhibit their popularity. However, recent
compressed sensing Compressed sensing (also known as compressive sensing, compressive sampling, or sparse sampling) is a signal processing technique for efficiently acquiring and reconstructing a Signal (electronics), signal, by finding solutions to Underdetermined s ...
-based software algorithms (''e.g.'', SAMV) have been proposed to achieve
super-resolution Super-resolution imaging (SR) is a class of techniques that enhance (increase) the resolution of an imaging system. In optical SR the diffraction limit , who approximated the diffraction limit of a microscope as d=\frac, where ''d'' is the resolv ...
without requiring such high field strengths.


Real-time MRI

Real-time MRI refers to the continuous imaging of moving objects (such as the heart) in real time. One of the many different strategies developed since the early 2000s is based on radial FLASH MRI, and
iterative reconstruction Iterative reconstruction refers to Iteration, iterative algorithms used to reconstruct 2D and 3D reconstruction, 3D images in certain Digital imaging, imaging techniques. For example, in computed tomography an image must be reconstructed from proj ...
. This gives a temporal resolution of 20–30 ms for images with an in-plane resolution of 1.5–2.0 mm. Balanced steady-state free precession (bSSFP) imaging has a better image contrast between the blood pool and myocardium than the FLASH MRI, yet it will produce severe banding artifact when the B0 inhomogeneity is strong. Real-time MRI is likely to add important information on diseases of the heart and the joints, and in many cases may make MRI examinations easier and more comfortable for patients, especially for the patients who cannot hold their breathings or who have arrhythmia.


Interventional MRI

The lack of harmful effects on the patient and the operator make MRI well-suited for
interventional radiology Interventional radiology (IR) is a medical subspecialty that performs various minimally-invasive procedures using medical imaging guidance, such as Fluoroscopy, x-ray fluoroscopy, CT scan, computed tomography, magnetic resonance imaging, or ultra ...

interventional radiology
, where the images produced by an MRI scanner guide minimally invasive procedures. Such procedures use no
ferromagnetic Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), formi ...
instruments. A specialized growing subset of interventional MRI is
intraoperative MRI Intraoperative magnetic resonance imaging (iMRI) refers to an operating room configuration that enables surgeons to image the patient via an Magnetic resonance imaging, MRI scanner while the patient is undergoing surgery, particularly brain surgery. ...
, in which an MRI is used in surgery. Some specialized MRI systems allow imaging concurrent with the surgical procedure. More typically, the surgical procedure is temporarily interrupted so that MRI can assess the success of the procedure or guide subsequent surgical work.


Magnetic resonance guided focused ultrasound

In guided therapy,
high-intensity focused ultrasound High-intensity focused ultrasound (HIFU) is a non-invasive therapeutic technique that uses non-ionizing ultrasonic waves to heat or ablate tissue. HIFU can be used to increase the flow of blood or lymph, or to destroy tissue, such as tumors ...
(HIFU) beams are focused on a tissue, that are controlled using MR thermal imaging. Due to the high energy at the focus, the temperature rises to above 65 °C (150 °F) which completely destroys the tissue. This technology can achieve precise
ablation Ablation is removal or destruction of material from an object by vaporization, chipping, or other erosion, erosive processes. Examples of ablative materials are described below, and include spacecraft material for ascent and atmospheric reentry, ...
of diseased tissue. MR imaging provides a three-dimensional view of the target tissue, allowing for the precise focusing of ultrasound energy. The MR imaging provides quantitative, real-time, thermal images of the treated area. This allows the physician to ensure that the temperature generated during each cycle of ultrasound energy is sufficient to cause thermal ablation within the desired tissue and if not, to adapt the parameters to ensure effective treatment.


Multinuclear imaging

Hydrogen has the most frequently imaged
nucleus ''Nucleus'' (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA ...
in MRI because it is present in biological tissues in great abundance, and because its high
gyromagnetic ratio In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through Spa ...
gives a strong signal. However, any nucleus with a net
nuclear spin In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model is a nuclear model, model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The f ...
could potentially be imaged with MRI. Such nuclei include
helium-3 Helium-3 (3He see also helion) is a light, stable isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons A proton is a subatomic particle, symbol or , with a positive electric charge Ele ...

helium-3
,
lithium-7 Naturally occurring lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the Symbol (chemistry), symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pr ...

lithium-7
,
carbon-13 Carbon-13 (13C) is a natural, stable isotope The term stable isotope has a meaning similar to stable nuclide Stable nuclides are nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by ...

carbon-13
,
fluorine Fluorine is a chemical element with the Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard conditions for temperature and pressure, standard conditions as a highly toxic, pale yellow Diatomic molecule ...

fluorine
-19,
oxygen-17 Oxygen-17 (17O) is a low-abundance, natural, stable A stable is a building in which livestock Livestock are the domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a signif ...

oxygen-17
,
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
-23,
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
-31 and
xenon-129 Naturally occurring xenon Xenon is a chemical element with the Symbol (chemistry), symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas found in Atmosphere of Earth, Earth's atmosphere in trace amounts. Altho ...
. 23Na and 31P are naturally abundant in the body, so they can be imaged directly. Gaseous isotopes such as 3He or 129Xe must be hyperpolarized and then inhaled as their nuclear density is too low to yield a useful signal under normal conditions. and 19F can be administered in sufficient quantities in liquid form (e.g. -water) that hyperpolarization is not a necessity. Using helium or xenon has the advantage of reduced background noise, and therefore increased contrast for the image itself, because these elements are not normally present in biological tissues. Moreover, the nucleus of any atom that has a net nuclear spin and that is bonded to a hydrogen atom could potentially be imaged via heteronuclear magnetization transfer MRI that would image the high-gyromagnetic-ratio hydrogen nucleus instead of the low-gyromagnetic-ratio nucleus that is bonded to the hydrogen atom. In principle, hetereonuclear magnetization transfer MRI could be used to detect the presence or absence of specific chemical bonds. Multinuclear imaging is primarily a research technique at present. However, potential applications include functional imaging and imaging of organs poorly seen on 1H MRI (e.g., lungs and bones) or as alternative contrast agents. Inhaled hyperpolarized 3He can be used to image the distribution of air spaces within the lungs. Injectable solutions containing 13C or stabilized bubbles of hyperpolarized 129Xe have been studied as contrast agents for angiography and perfusion imaging. 31P can potentially provide information on bone density and structure, as well as functional imaging of the brain. Multinuclear imaging holds the potential to chart the distribution of lithium in the human brain, this element finding use as an important drug for those with conditions such as bipolar disorder.


Molecular imaging by MRI

MRI has the advantages of having very high spatial resolution and is very adept at morphological imaging and functional imaging. MRI does have several disadvantages though. First, MRI has a sensitivity of around 10−3 mol/L to 10−5 mol/L, which, compared to other types of imaging, can be very limiting. This problem stems from the fact that the population difference between the nuclear spin states is very small at room temperature. For example, at 1.5 teslas, a typical field strength for clinical MRI, the difference between high and low energy states is approximately 9 molecules per 2 million. Improvements to increase MR sensitivity include increasing magnetic field strength and hyperpolarization via optical pumping or dynamic nuclear polarization. There are also a variety of signal amplification schemes based on chemical exchange that increase sensitivity. To achieve molecular imaging of disease biomarkers using MRI, targeted MRI
contrast agent A contrast agent (or contrast medium) is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, any ...
s with high specificity and high relaxivity (sensitivity) are required. To date, many studies have been devoted to developing targeted-MRI contrast agents to achieve molecular imaging by MRI. Commonly, peptides, antibodies, or small ligands, and small protein domains, such as HER-2 affibodies, have been applied to achieve targeting. To enhance the sensitivity of the contrast agents, these targeting moieties are usually linked to high payload MRI contrast agents or MRI contrast agents with high relaxivities. A new class of gene targeting MR contrast agents has been introduced to show gene action of unique mRNA and gene transcription factor proteins. These new contrast agents can trace cells with unique mRNA, microRNA and virus; tissue response to inflammation in living brains. The MR reports change in gene expression with positive correlation to TaqMan analysis, optical and electron microscopy.


Parallel MRI

It takes time to gather MRI data using sequential applications of magnetic field gradients. Even for the most streamlined of
MRI sequence 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. A multiparametric MRI is a combination of two or more sequences, and/or including ...
s, there are physical and physiologic limits to the rate of gradient switching. Parallel MRI circumvents these limits by gathering some portion of the data simultaneously, rather than in a traditional sequential fashion. This is accomplished using arrays of radiofrequency (RF) detector coils, each with a different ‘view’ of the body. A reduced set of gradient steps is applied, and the remaining spatial information is filled in by combining signals from various coils, based on their known spatial sensitivity patterns. The resulting acceleration is limited by the number of coils and by the signal to noise ratio (which decreases with increasing acceleration), but two- to four-fold accelerations may commonly be achieved with suitable coil array configurations, and substantially higher accelerations have been demonstrated with specialized coil arrays. Parallel MRI may be used with most
MRI sequence 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. A multiparametric MRI is a combination of two or more sequences, and/or including ...
s. After a number of early suggestions for using arrays of detectors to accelerate imaging went largely unremarked in the MRI field, parallel imaging saw widespread development and application following the introduction of the SiMultaneous Acquisition of Spatial Harmonics (SMASH) technique in 1996–7. The SENSitivity Encoding (SENSE) and Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) techniques are the parallel imaging methods in most common use today. The advent of parallel MRI resulted in extensive research and development in image reconstruction and RF coil design, as well as in a rapid expansion of the number of receiver channels available on commercial MR systems. Parallel MRI is now used routinely for MRI examinations in a wide range of body areas and clinical or research applications.


Safety

MRI is, in general, a safe technique, although injuries may occur as a result of failed safety procedures or human error.
ContraindicationsIn medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their inj ...
to MRI include most
cochlear implant A cochlear implant (CI) is a surgically implanted neuroprosthesis that provides a person who has bilateral moderate-to-profound sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss Hearing loss is a partial or ...

cochlear implant
s and cardiac pacemakers,
shrapnel Shrapnel may refer to: Military * Shrapnel shell, explosive artillery munitions, generally for anti-personnel use * Shrapnel (fragment), a hard loose material Popular culture *Shrapnel (Radical Comics), ''Shrapnel'' (Radical Comics) Charac ...
, and metallic
foreign bodies A foreign body (FB) is any object originating outside the body of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, pr ...

foreign bodies
in the
eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized as parenchyma Parenchyma () is th ...
. Magnetic resonance imaging in pregnancy appears to be safe, at least during the second and third if done without contrast agents. Since MRI does not use any ionizing radiation, its use is generally favored in preference to CT when either modality could yield the same information. Some patients experience claustrophobia and may require sedation or shorter MRI protocols. Amplitude and rapid switching of gradient coils during image acquisition may cause peripheral nerve stimulation. MRI uses powerful magnets and can therefore cause magnetic materials to move at great speeds, posing a projectile risk, and may cause fatal accidents. However, as millions of MRIs are performed globally each year, fatalities are extremely rare.


Overuse

Medical societies issue guidelines for when physicians should use MRI on patients and recommend against overuse. MRI can detect health problems or confirm a diagnosis, but medical societies often recommend that MRI not be the first procedure for creating a plan to diagnose or manage a patient's complaint. A common case is to use MRI to seek a cause of
low back pain Low back pain (LBP) or lumbago is a common musculoskeletal disorders, disorder involving the muscles, nerves, and bones of the back, inbetween the lower edge of the ribs and the lower fold of the buttocks. Pain can vary from a dull constant ache ...

low back pain
; the
American College of Physicians The American College of Physicians (ACP) is a national organization of internists, who specialize in the diagnosis, treatment, and care of adults.Sokanu "What is an Internist?" Retrieved 20 October 2014 With 154,000 members, ACP is the largest medi ...
, for example, recommends against this procedure as unlikely to result in a positive outcome for the patient.


Artifacts

An
MRI artifactAn MRI artifact is a visual artifact (an anomaly seen during visual representation) 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, ...
is a
visual artifact Visual artifacts (also artefacts) are anomalies apparent during visual representation as in digital graphics and other forms of image File:TEIDE.JPG, An Synthetic aperture radar, SAR radar imaging, radar image acquired by the SIR-C/X-SAR ra ...
, that is, an anomaly during visual representation. Many different artifacts can occur during magnetic resonance imaging (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.


Non-medical use

MRI is used industrially mainly for routine analysis of chemicals. The
nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon A phenomenon (; plural phenomena) is an observable In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ...
technique is also used, for example, to measure the ratio between water and fat in foods, monitoring of flow of corrosive fluids in pipes, or to study molecular structures such as catalysts. Being non-invasive and non-damaging, MRI can be used to study the anatomy of plants, their water transportation processes and water balance. It is also applied to veterinary radiology for diagnostic purposes. Outside this, its use in zoology is limited due to the high cost; but it can be used on many species. In palaeontology it is used to examine the structure of fossils.
Forensic Forensic science, also known as criminalistics, is the application of science to Criminal law, criminal and Civil law (legal system), civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards ...
imaging provides graphic documentation of an
autopsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination Examination may refer to: * Physical examination, a medical procedure * Questioning and more speci ...
, which manual autopsy does not. CT scanning provides quick whole-body imaging of skeletal and
parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the Ancient G ...

parenchyma
l alterations, whereas MRI imaging gives better representation of soft tissue
pathology Pathology is the study of the causesCauses, or causality, is the relationship between one event and another. It may also refer to: * Causes (band), an indie band based in the Netherlands * Causes (company), an online company See also * Cau ...
. But MRI is more expensive, and more time-consuming to utilize. Moreover, the quality of MR imaging deteriorates below 10 °C.


History

In 1971 at
Stony Brook University The State University of New York at Stony Brook (SUNY at Stony Brook), more commonly known as Stony Brook University (SBU), is a public university, public research university in Stony Brook, New York. It is one of four university centers of the S ...
, Paul Lauterbur applied magnetic field gradients in all three dimensions and a back-projection technique to create NMR images. He published the first images of two tubes of water in 1973 in the journal ''Nature'', followed by the picture of a living animal, a clam, and in 1974 by the image of the thoracic cavity of a mouse. Lauterbur called his imaging method zeugmatography, a term which was replaced by (N)MR imaging. In the late 1970s, physicists
Peter Mansfield Sir Peter Mansfield (9 October 1933 – 8 February 2017) was an English physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, ar ...
and
Paul Lauterbur Paul Christian Lauterbur (May 6, 1929 – March 27, 2007) was an American chemist who shared the Nobel Prize in Physiology or Medicine in 2003 with Peter Mansfield for his work which made the development of magnetic resonance imaging Magne ...
developed MRI-related techniques, like the echo-planar imaging (EPI) technique. Advances in
semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric curre ...
technology were crucial to the development of practical MRI, which requires a large amount of computational power. This was made possible by the rapidly increasing number of
transistors file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A ...
on a single
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
chip. Mansfield and Lauterbur were awarded the 2003
Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly , native_name_lang = , image = Nobel Assembly at Karolinska Institutet.jpeg , size = , motto = , formation = 190113 March 1978(as a forma ...
for their "discoveries concerning magnetic resonance imaging".


See also

*
Physics of magnetic resonance imaging The physics of magnetic resonance imaging (MRI) concerns fundamental Physics, physical considerations of Magnetic resonance imaging, MRI techniques and technological aspects of MRI devices. MRI is a medical imaging technique mostly used in radiol ...
* Amplified magnetic resonance imaging *
Electron paramagnetic resonance Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy Spectroscopy is the study of the interaction Interaction is a kind of action that occurs as two or more objects have an effect upon one another. The idea of ...
* High-definition fiber tracking *
High-resolution computed tomography High-resolution computed tomography (HRCT) is a type of computed tomography (CT) with specific techniques to enhance image resolution Image resolution is the detail an image An SAR radar imaging, radar image acquired by the SIR-C/X-SAR ...
* History of neuroimaging * International Society for Magnetic Resonance in Medicine * Jemris *
List of neuroimaging software Neuroimaging Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly Medical imaging, image the neuroanatomy, structure, function, or pharmacology of the nervous system. It is a relatively new discipline wit ...
*
Magnetic immunoassay Magnetic immunoassay (MIA) is a type of diagnostic immunoassay An immunoassay is a biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organism In biology, an organism (fro ...

Magnetic immunoassay
*
Magnetic particle imaging Magnetic particle imaging (MPI) is an emerging non-invasive Tomography, tomographic technique that directly detects Superparamagnetic Iron Oxide Nanoparticles, superparamagnetic nanoparticle tracers. The technology has potential applications in diag ...
* Magnetic resonance elastography * ''Magnetic Resonance Imaging'' (journal) * Magnetic resonance microscopy * Nobel Prize controversies – Physiology or medicine *
Rabi cycle Rabi oscillations, showing the probability of a two-level system initially in , 1\rangle to end up in , 2\rangle at different detunings Δ. In physics, the Rabi cycle (or Rabi flop) is the cyclic behaviour of a two-level quantum system Quant ...
* Robinson oscillator *
Sodium MRI Sodium MRI (also known as 23Na-MRI) is a specialised magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and ...
* Virtopsy


References


Further reading

* * * * * * * * * * * * * * * * * *


External links

*
A Guided Tour of MRI: An introduction for laypeople
National High Magnetic Field Laboratory
The Basics of MRI
''Underlying physics and technical aspects''.

from the Institute for Magnetic Resonance Safety, Education, and Research (IMRSER)
Royal Institution Lecture – MRI: A Window on the Human Body


* ttps://www.howequipmentworks.com/mri_basics/ How MRI works explained simply using diagrams
Real-time MRI videos: Biomedizinische NMR Forschungs GmbH
* Paul C. Lauterbur
Genesis of the MRI (Magnetic Resonance Imaging) notebook, September 1971
(all pages freely available for download in variety of formats from
Science History Institute The Science History Institute is an institution that preserves and promotes understanding of the history of science. Located in Philadelphia, Pennsylvania, it includes a library, museum, archive, research center and conference center. It was fo ...
Digital Collections a
digital.sciencehistory.org
{{DEFAULTSORT:Magnetic Resonance Imaging 1973 introductions American inventions Articles containing video clips Cryogenics Radiology Discovery and invention controversies 20th-century inventions Biomagnetics