MRI is widely used in hospitals and clinics formedical diagnosis,staging and follow-up of disease. Compared to CT, MRI provides bettercontrast in images of soft tissues, e.g. in thebrain 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, although "open" MRI designs mostly relieve this. Additionally,implants 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 avoidnegative associations.[2] Certainatomic nuclei are able to absorbradio frequency (RF) energy when placed in an externalmagnetic field; the resultant evolvingspin polarization can induce an RF signal in a radio frequency coil and thereby be detected.[3] In other words, the nuclear magnetic spin of protons in the hydrogen nuclei resonates with the RF incident waves and emit coherent radiation with compact direction, energy (frequency) and phase. This coherent amplified radiation is easily detected by RF antennas close to the subject being examined. It is a process similar tomasers. In clinical and research MRI,hydrogen atoms are most often used to generate a macroscopic polarized radiation that is detected by the antennas.[3] Hydrogen atoms arenaturally abundant in humans and other biological organisms, particularly inwater andfat. For this reason, most MRI scans essentially map the location of water and fat in the body. Pulses of radio waves excite thenuclear spin energy transition, and magnetic field gradients localize the polarization in space. By varying the parameters of thepulse sequence, different contrasts may be generated between tissues based on therelaxation 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 indiagnostic medicine and biomedical research, it also may be used to form images of non-living objects, such asmummies.Diffusion MRI andfunctional MRI extend 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 withinhealth systems has led to concerns aboutcost effectiveness andoverdiagnosis.[4][5][dubious –discuss]
Schematic of a cylindrical superconducting MR scanner. Top: cross section of the cylinder with primary coil, gradient coils and RF transmit coils. Bottom: longitudinal section of the cylinder and table, showing the same coils and the RF receive coil.
In most medical applications,hydrogen nuclei, which consist solely of aproton, 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 anMRI scanner that forms a strongmagnetic field around the area to be imaged. First, energy from anoscillating magnetic field is temporarily applied to the patient at the appropriateresonance 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 areexcited by aRF pulse and the resultant signal is measured by areceiving 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 usinggradient coils. 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 tomagnetostriction. The contrast between different tissues is determined by the rate at which excited atoms return to theequilibrium state.Exogenouscontrast agents may be given to the person to make the image clearer.[6]
The major components of an MRI scanner are the mainmagnet, which polarizes the sample, theshim coils for correcting shifts in thehomogeneity 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 anduniform to a few parts per million across the scan volume. The field strength of the magnet is measured inteslas – and while the majority of systems operate at 1.5 T, commercial systems are available between 0.2 and 7 T.3T MRI systems, also called 3 Tesla MRIs, have stronger magnets than 1.5 systems and are considered better for images of organs and soft tissue.[7] Whole-body MRI systems for research applications operate in e.g. 9.4T,[8][9] 10.5T,[10] 11.7T.[11] Even higher field whole-body MRI systems e.g. 14 T and beyond are in conceptual proposal[12] or in engineering design.[13] Most clinical magnets aresuperconducting magnets, which requireliquid helium to keep them at low temperatures. Lower field strengths can be achieved with permanent magnets, which are often used in "open" MRI scanners forclaustrophobic patients.[14] Lower field strengths are also used in aportable MRI scanner approved by the FDA in 2020.[15] 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 theLarmor precession fields at about 100 microtesla with highly sensitive superconducting quantum interference devices (SQUIDs).[16][17][18]
Effects of TR and TE on MR signalExamples of T1-weighted, T2-weighted andPD-weighted MRI scansDiagram of changing magnetization and spin orientations throughout spin-lattice relaxation experiment
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 therepetition time (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 forpost-contrast imaging.To create a T2-weighted image, magnetization is allowed to decay before measuring the MR signal by changing theecho time (TE). This image weighting is useful for detectingedema and inflammation, revealingwhite matter lesions, and assessing zonal anatomy in theprostate anduterus.
The information from MRI scans comes in the form ofimage contrasts based on differences in the rate of relaxation ofnuclear spins following their perturbation by an oscillating magnetic field (in the form of radiofrequency pulses through the sample).[19] The relaxation rates are a measure of the time it takes for a signal to decay back to an equilibrium state from either the longitudinal or transverse plane.
Magnetization builds up along the z-axis in the presence of a magnetic field, B0, such that themagnetic dipoles in the sample will, on average, align with the z-axis summing to a total magnetization Mz. This magnetization along z is defined as the equilibrium magnetization; magnetization is defined as the sum of all magnetic dipoles in a sample. Following the equilibrium magnetization, a 90° radiofrequency (RF) pulse flips the direction of the magnetization vector in the xy-plane, and is then switched off. The initial magnetic field B0, however, is still applied. Thus, the spin magnetization vector will slowly return from the xy-plane back to the equilibrium state. The time it takes for the magnetization vector to return to its equilibrium value, Mz, is referred to as the longitudinal relaxation time, T1.[20] Subsequently, the rate at which this happens is simply the reciprocal of the relaxation time:. Similarly, the time in which it takes for Mxy to return to zero is T2, with the rate.[21] Magnetization as a function of time is defined by theBloch equations.
T1 and T2 values are dependent on the chemical environment of the sample; hence their utility in MRI. Soft tissue and muscle tissue relax at different rates, yielding the image contrast in a typical scan.
The standard display of MR images is to represent fluid characteristics inblack-and-white images, where different tissues turn out as follows:
Patient being positioned for MR study of the head and abdomen
MRI has a wide range of applications inmedical diagnosis and around 50,000 scanners are estimated to be in use worldwide.[25] MRI affects diagnosis and treatment in many specialties although the effect on improved health outcomes is disputed in certain cases.[26][27]
Radiologist interpreting MRI images of head and neck
MRI is the investigation of choice in the preoperativestaging ofrectal andprostate cancer and has a role in the diagnosis, staging, and follow-up of other tumors,[28] as well as for determining areas of tissue for sampling in biobanking.[29][30]
The record for the highest spatial resolution of a whole intact brain (postmortem) is 100 microns, from Massachusetts General Hospital. The data was published in NATURE on 30 October 2019.[39][40]
Though MRI is used widely in research on mental disabilities, based on a 2024 systematic literature review and meta analysis commissioned by the Patient-Centered Outcomes Research Institute (PCORI), available research using MRI scans to diagnose ADHD showed great variability.[41] The authors conclude that MRI cannot be reliably used to assist in making a clinical diagnosis of ADHD.[41]
Swallowing movements of the throat and esophagus can cause motion artifacts over the imaged spine. Therefore, a saturation pulse[clarification needed] applied over this region the throat and esophagus can help to avoid these artifacts. Motion artifacts arising due to pumping of the heart can be reduced by timing the MRI pulse according to heart cycles.[47] Blood vessel flow artifacts can be reduced by applying saturation pulses above and below the region of interest.[48]
Hepatobiliary MR is used to detect and characterize lesions of theliver,pancreas, andbile ducts. Focal or diffuse disorders of the liver may be evaluated usingdiffusion-weighted, opposed-phase imaging anddynamic 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 inmagnetic resonance cholangiopancreatography (MRCP). Functional imaging of the pancreas is performed following administration ofsecretin. 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.[49][50][51][52]
Magnetic resonanceangiography (MRA) generates pictures of the arteries to evaluate them forstenosis (abnormal narrowing) oraneurysms (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 aparamagnetic contrast agent (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 alsoFLASH MRI).[53]
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.[54]
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 contrast agents may be givenintravenously,orally, orintra-articularly.[6] Most contrast agents are either paramagnetic (e.g.: gadolinium, manganese, europium), and are used to shorten T1 in the tissue they accumulate in, or super-paramagnetic (SPIONs), and are used to shorten T2 and T2* in healthy tissue reducing its signal intensity (negative contrast agents). The most commonly used intravenous contrast agents are based onchelates ofgadolinium, which is highly paramagnetic.[55] 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%.[56] 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 undergocontrast-enhanced CT.[57]
Gadolinium-based contrast reagents are typicallyoctadentate complexes ofgadolinium(III). The complex isvery stable (log K > 20) so that, in use, the concentration of the un-complexed Gd3+ ions should be below the toxicity limit. The 9th place in the metal ion'scoordination sphere is occupied by a water molecule which exchanges rapidly with water molecules in the reagent molecule's immediate environment, affecting the magnetic resonancerelaxation time.[58]
In December 2017, theFood and Drug Administration (FDA) in theUnited 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.[59]Although gadolinium agents have proved useful for patients with kidney impairment, in patients with severekidney failure requiring dialysis there is a risk of a rare but serious illness,nephrogenic systemic fibrosis, which may be linked to the use of certain gadolinium-containing agents. The most frequently linked isgadodiamide, but other agents have been linked too.[60] Although a causal link has not been definitively established, current guidelines in theUnited States are that dialysis patients should only receive gadolinium agents where essential and thatdialysis should be performed as soon as possible after the scan to remove the agent from the body promptly.[61][62]
In Europe, where more gadolinium-containing agents are available, a classification of agents according to potential risks has been released.[63][64] In 2008, a new contrast agent namedgadoxetate, brand name Eovist (US) or Primovist (EU), was approved for diagnostic use: This has the theoretical benefit of a dual excretion path.[65]
AnMRI sequence is a particular setting of radiofrequency pulses and gradients, resulting in a particular image appearance.[66] TheT1 and T2 weighting can also be described as MRI sequences.
Low signal for fat in standard Spine Echo (SE),[67] though not with Fast Spin Echo/Turbo Spin Echo (FSE/TSE). FSE/TSE is thestandard of care in modern medicine because it is faster. With FSE/TSE, fat has high signal due to disruption ofhyperfineJ-coupling between adjacent fatprotons.[69]
Magnetic labeling of arterial blood below the imaging slab, which subsequently enters the region of interest.[88] It does not need gadolinium contrast.[89]
Magnetic resonance spectroscopy (MRS) is used to measure the levels of differentmetabolites in body tissues, which can be achieved through a variety of single voxel or imaging-based techniques.[96] 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,[97] and to provide information on tumormetabolism.[98]
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 availableSNR), 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).[99] The high procurement and maintenance costs of MRI with extremely high field strengths[100] inhibit their popularity. However, recentcompressed sensing-based software algorithms (e.g.,SAMV[101]) have been proposed to achievesuper-resolution without requiring such high field strengths.
Real-time MRI of a human heart (2-chamber view) at 22 ms resolution[102]Real-time MRI of avocal tract whilesinging, at 40 ms resolution
Real-time magnetic resonance imaging (RT-MRI) refers to the continuous monitoring of moving objects in real time. Traditionally, real-time MRI was possible only with low image quality or low temporal resolution. Aniterative reconstruction algorithm removed limitations. RadialFLASH MRI (real-time) yields a temporal resolution of 20 to 30 milliseconds for images with an in-plane resolution of 1.5 to 2.0 mm.[103] Real-time MRI adds information about diseases of thejoints and theheart. In many cases MRI examinations become easier and more comfortable for patients, especially for the patients who cannot calm their breathing[104] or who havearrhythmia.
The lack of harmful effects on the patient and the operator make MRI well-suited forinterventional radiology, where the images produced by an MRI scanner guide minimally invasive procedures. Such procedures use noferromagnetic instruments.[105]
A specialized growing subset ofinterventional MRI isintraoperative MRI, 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.[106]
In guided therapy,high-intensity focused ultrasound (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 preciseablation 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.[107]
Hydrogen has the most frequently imagednucleus in MRI because it is present in biological tissues in great abundance, and because its highgyromagnetic ratio gives a strong signal. However, any nucleus with a netnuclear spin could potentially be imaged with MRI. Such nuclei includehelium-3,lithium-7,carbon-13,fluorine-19,oxygen-17,sodium-23,phosphorus-31 andxenon-129.23Na and31P are naturally abundant in the body, so they can be imaged directly. Gaseous isotopes such as3He or129Xe must behyperpolarized and then inhaled as their nuclear density is too low to yield a useful signal under normal conditions.17O and19F can be administered in sufficient quantities in liquid form (e.g.17O-water) that hyperpolarization is not a necessity.[108] 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.[109]
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.[110] In principle, heteronuclear magnetization transfer MRI could be used to detect the presence or absence of specific chemical bonds.[111][112]
Multinuclear imaging is primarily a research technique at present. However, potential applications include functional imaging and imaging of organs poorly seen on1H MRI (e.g., lungs and bones) or as alternative contrast agents. Inhaled hyperpolarized3He can be used to image the distribution of air spaces within the lungs. Injectable solutions containing13C or stabilized bubbles of hyperpolarized129Xe 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.[113]
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 10−3mol/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 1.5teslas, 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 andhyperpolarization via optical pumping or dynamic nuclear polarization. There are also a variety of signal amplification schemes based on chemical exchange that increase sensitivity.[114]
To achieve molecular imaging of disease biomarkers using MRI, targeted MRIcontrast agents 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.[115] A new class of gene targeting MR contrast agents has been introduced to show gene action of unique mRNA and gene transcription factor proteins.[116][117] These new contrast agents can trace cells with unique mRNA, microRNA and virus; tissue response to inflammation in living brains.[118] The MR reports change in gene expression with positive correlation to TaqMan analysis, optical and electron microscopy.[119]
It takes time to gather MRI data using sequential applications of magnetic field gradients. Even for the most streamlined ofMRI sequences, 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 mostMRI sequences.
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.[120] The SENSitivity Encoding (SENSE)[121] and Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA)[122] 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.
Most MRI focuses on qualitative interpretation of MR data by acquiring spatial maps of relative variations in signal strength which are "weighted" by certain parameters.[123] Quantitative methods instead attempt to determine spatial maps of accurate tissue relaxometry parameter values or magnetic field, or to measure the size of certain spatial features.
Quantitative MRI aims to increase thereproducibility of MR images and interpretations, but has historically require longer scan times.[123]
Quantitative MRI (or qMRI) sometimes more specifically refers to multi-parametric quantitative MRI, the mapping of multiple tissue relaxometry parameters in a single imaging session.[128]Efforts to make multi-parametric quantitative MRI faster have produced sequences which map multiple parameters simultaneously, either by building separate encoding methods for each parameter into the sequence,[129]or by fitting MR signal evolution to a multi-parameter model.[130][131]
Traditional MRI generates poor images of lung tissue because there are fewer water molecules with protons that can be excited by the magnetic field. Using hyperpolarized gas an MRI scan can identify ventilation defects in the lungs. Before the scan, a patient is asked to inhale hyperpolarizedxenon mixed with a buffer gas of helium or nitrogen. The resulting lung images are much higher quality than with traditional MRI.
MRI is, in general, a safe technique, although injuries may occur as a result of failed safety procedures or human error.[132]Contraindications to MRI include mostcochlear implants andcardiac pacemakers,shrapnel, and metallicforeign bodies in theeyes.Magnetic resonance imaging in pregnancy appears to be safe, at least during the second and thirdtrimesters if done without contrast agents.[133] Since MRI does not use any ionizing radiation, its use is generally favored in preference toCT when either modality could yield the same information.[134] Some patients experience claustrophobia and may require sedation or shorter MRI protocols.[135][136] Amplitude and rapid switching of gradient coils during image acquisition may cause peripheral nerve stimulation.[137]
MRI uses powerful magnets and can therefore causemagnetic materials to move at great speeds, posing a projectile risk, and may cause fatal accidents.[138] However, as millions of MRIs are performed globally each year,[139] fatalities are extremely rare.[140]
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 oflow back pain; theAmerican College of Physicians, for example, recommends against imaging (including MRI) as unlikely to result in a positive outcome for the patient.[26][27]
Motion artifact (T1 coronal study of cervical vertebrae)[142]
AnMRI artifact is avisual artifact, 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.[142]
MRI is used industrially mainly for routine analysis of chemicals. Thenuclear magnetic resonance 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.[1]
Being non-invasive and non-damaging, MRI can be used to study the anatomy of plants, their water transportation processes and water balance.[143] 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.[144]
In palaeontology it is used to examine the structure of fossils.[145]
Forensic imaging provides graphic documentation of anautopsy, which manual autopsy does not. CT scanning provides quick whole-body imaging of skeletal andparenchymal alterations, whereas MR imaging gives better representation of soft tissuepathology.[146] All that being said, MRI is more expensive, and more time-consuming to utilize.[146] Moreover, the quality of MR imaging deteriorates below 10 °C.[147]
In 1971 atStony Brook University,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 journalNature,[148] 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.[1] In the late 1970s, physicistsPeter Mansfield andPaul Lauterbur developed MRI-related techniques, like theecho-planar imaging (EPI) technique.[149]
^abcRinck, Peter A. (2024).Magnetic Resonance in Medicine: A Critical Introduction (14th (ebook) ed.). TRTF – The Round Table Foundation: TwinTree Media."Magnetic Resonance in Medicine".www.magnetic-resonance.org.
^McRobbie DW, Moore EA, Graves MJ, Prince MR (2007).MRI from Picture to Proton. Cambridge University Press. p. 1.ISBN978-1-139-45719-4.
^Sasaki M, Ehara S, Nakasato T, Tamakawa Y, Kuboya Y, Sugisawa M, Sato T (April 1990). "MR of the shoulder with a 0.2-T permanent-magnet unit".AJR. American Journal of Roentgenology.154 (4):777–8.doi:10.2214/ajr.154.4.2107675.PMID2107675.
^Rowayda AS (May 2012). "An improved MRI segmentation for atrophy assessment".International Journal of Computer Science Issues (IJCSI).9 (3).
^Rowayda AS (February 2013). "Regional atrophy analysis of MRI for early detection of alzheimer's disease".International Journal of Signal Processing, Image Processing and Pattern Recognition.6 (1):49–53.
^Nolen-Hoeksema S (2014).Abnormal Psychology (Sixth ed.). New York: McGraw-Hill Education. p. 67.
^Heilbrun MP, Sunderland PM, McDonald PR, Wells TH, Cosman E, Ganz E (1987). "Brown-Roberts-Wells stereotactic frame modifications to accomplish magnetic resonance imaging guidance in three planes".Applied Neurophysiology.50 (1–6):143–52.doi:10.1159/000100700.PMID3329837.
^American College of Radiology; Society of Cardiovascular Computed Tomography; Society for Cardiovascular Magnetic Resonance; American Society of Nuclear Cardiology; North American Society for Cardiac Imaging; Society for Cardiovascular Angiography Interventions; Society of Interventional Radiology (October 2006). "ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging. A report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group".Journal of the American College of Radiology.3 (10):751–71.doi:10.1016/j.jacr.2006.08.008.PMID17412166.
^Aivazoglou, LU; Guimarães, JB; Link, TM; Costa, MAF; Cardoso, FN; de Mattos Lombardi Badia, B; Farias, IB; de Rezende Pinto, WBV; de Souza, PVS; Oliveira, ASB; de Siqueira Carvalho, AA; Aihara, AY; da Rocha Corrêa Fernandes, A (21 April 2021). "MR imaging of inherited myopathies: a review and proposal of imaging algorithms".European Radiology.31 (11):8498–8512.doi:10.1007/s00330-021-07931-9.PMID33881569.S2CID233314102.
^Haacke EM, Brown RF, Thompson M, Venkatesan R (1999).Magnetic resonance imaging: Physical principles and sequence design. New York: J. Wiley & Sons.ISBN978-0-471-35128-3.[page needed]
^Thomsen HS, Morcos SK, Dawson P (November 2006). "Is there a causal relation between the administration of gadolinium based contrast media and the development of nephrogenic systemic fibrosis (NSF)?".Clinical Radiology.61 (11):905–6.doi:10.1016/j.crad.2006.09.003.PMID17018301.
^Henkelman, RM; Hardy, PA; Bishop, JE; Poon, CS; Plewes, DB (September 1992). "Why fat is bright in RARE and fast spin-echo imaging".Journal of magnetic resonance imaging : JMRI.2 (5):533–40.doi:10.1002/jmri.1880020511.PMID1392246.
^Graham D, Cloke P, Vosper M (2011-05-31).Principles and Applications of Radiological Physics E-Book (6 ed.). Elsevier Health Sciences. p. 292.ISBN978-0-7020-4614-8.}
^Turnbull LW (January 2009). "Dynamic contrast-enhanced MRI in the diagnosis and management of breast cancer".NMR in Biomedicine.22 (1):28–39.doi:10.1002/nbm.1273.PMID18654999.S2CID5305422.
^Landheer K, Schulte RF, Treacy MS, Swanberg KM, Juchem C (April 2020). "Theoretical description of modern1 H in Vivo magnetic resonance spectroscopic pulse sequences".Journal of Magnetic Resonance Imaging.51 (4):1008–1029.doi:10.1002/jmri.26846.PMID31273880.S2CID195806833.
^Chakeres DW, Abduljalil AM, Novak P, Novak V (2002). "Comparison of 1.5 and 8 tesla high-resolution magnetic resonance imaging of lacunar infarcts".Journal of Computer Assisted Tomography.26 (4):628–32.doi:10.1097/00004728-200207000-00027.PMID12218832.S2CID32536398.
^S Zhang, M Uecker, D Voit, KD Merboldt,J Frahm (2010a) Real-time cardiovascular magnetic resonance at high temporal resolution: radial FLASH with nonlinear inverse reconstruction. J Cardiovasc Magn Reson 12, 39,[1]doi:10.1186/1532-429X-12-39
^M Uecker, S Zhang, D Voit, A Karaus, KD Merboldt,J Frahm (2010a) Real-time MRI at a resolution of 20 ms. NMR Biomed 23: 986-994,[2]doi:10.1002/nbm.1585
^abUyanik I, Lindner P, Tsiamyrtzis P, Shah D, Tsekos NV, Pavlidis IT (2013). "Applying a Level Set Method for Resolving Physiologic Motions in Free-Breathing and Non-gated Cardiac MRI".Functional Imaging and Modeling of the Heart. Lecture Notes in Computer Science. Vol. 7945. pp. 466–473.doi:10.1007/978-3-642-38899-6_55.ISBN978-3-642-38898-9.ISSN0302-9743.S2CID16840737.
^Brown RA, Venters RA, Tang PP, Spicer LD (1995). "A Test for Scaler Coupling between Heteronuclei Using Gradient-Enhanced Proton-Detected HMQC Spectroscopy".Journal of Magnetic Resonance, Series A.113 (1):117–19.Bibcode:1995JMagR.113..117B.doi:10.1006/jmra.1995.1064.
^Mervak BM, Altun E, McGinty KA, Hyslop WB, Semelka RC, Burke LM (March 2019). "MRI in pregnancy: Indications and practical considerations".Journal of Magnetic Resonance Imaging.49 (3):621–631.doi:10.1002/jmri.26317.PMID30701610.S2CID73412175.
^"iRefer". Royal College of Radiologists. Archived fromthe original on 3 February 2014. Retrieved10 November 2013.
^Murphy KJ, Brunberg JA (1997). "Adult claustrophobia, anxiety and sedation in MRI".Magnetic Resonance Imaging.15 (1). Elsevier BV:51–4.doi:10.1016/s0730-725x(96)00351-7.PMID9084025.
^Giovannetti G, Guerrini A, Salvadori PA (July 2016). "Magnetic resonance spectroscopy and imaging for the study of fossils".Magnetic Resonance Imaging.34 (6). Elsevier BV:730–742.doi:10.1016/j.mri.2016.03.010.PMID26979538.
^abFilograna L, Pugliese L, Muto M, Tatulli D, Guglielmi G, Thali MJ, Floris R (February 2019). "A Practical Guide to Virtual Autopsy: Why, When and How".Seminars in Ultrasound, CT, and MR.40 (1):56–66.doi:10.1053/j.sult.2018.10.011.PMID30686369.S2CID59304740.
Blümer P (1998). Blümler P, Blümich B, Botto RE, Fukushima E (eds.).Spatially Resolved Magnetic Resonance: Methods, Materials, Medicine, Biology, Rheology, Geology, Ecology, Hardware. Wiley-VCH.ISBN978-3-527-29637-8.
Blümich B, Kuhn W (1992).Magnetic Resonance Microscopy: Methods and Applications in Materials Science, Agriculture and Biomedicine. Wiley.ISBN978-3-527-28403-0.
Farhat IA, Belton P, Webb GA (2007).Magnetic Resonance in Food Science: From Molecules to Man. Royal Society of Chemistry.ISBN978-0-85404-340-8.
Fukushima E (1989).NMR in Biomedicine: The Physical Basis. Springer Science & Business Media.ISBN978-0-88318-609-1.
Haacke EM, Brown RF, Thompson M, Venkatesan R (1999).Magnetic resonance imaging: Physical principles and sequence design. New York: J. Wiley & Sons.ISBN978-0-471-35128-3.
Jin (1998).Electromagnetic Analysis and Design in Magnetic Resonance Imaging. CRC Press.ISBN978-0-8493-9693-9.
Kuperman V (2000).Magnetic Resonance Imaging: Physical Principles and Applications. Academic Press.ISBN978-0-08-053570-8.
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