Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

511 results found
Article

Gray (SI unit)

The gray (symbol Gy) is the SI unit of absorbed dose and is defined as the absorption of one joule of energy, in the form of ionizing radiation, per kilogram of matter, i.e. one gray = 1 J/kg 2. Terminology One gray is a large unit and is usually used with a prefix, e.g. milligray (mGy), micro...
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Grey scale imaging (ultrasound)

Commonly referred to as B (brightness) mode, the use of grey scale imaging in ultrasound renders a two-dimensional image in which the organs and tissues of interest are depicted as points of variable brightness. The formation of a B-mode image relies on the pulse-echo principle; assuming the spe...
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Grid cutoff

Grid cutoff is an unwanted absorption of x-rays via an x-ray grid, observed when a grid is employed incorrectly, most often seen with parallel grids. The term cutoff stems from the phenomenon in which the primary x-ray beam is 'cut off' by grid lines, leading to an overall decrease in optical de...
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Grids

Grids are placed between the patient and the x-ray film to reduce the scattered radiation (produced mainly by the Compton effect) and thus improve image contrast. They are made of parallel strips of high attenuating material such as lead with an interspace filled with low attenuating material s...
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Gyromagnetic ratio

The gyromagnetic ratio, often denoted by the symbol γ (gamma) is the ratio of the magnetic momentum in a particle to its angular momentum. The SI unit is the radian per second per tesla (rad⋅s−1⋅T−1).  The gyromagnetic ratio of the proton is 2.675 221 900(18) x 108 s-1⋅T-1. Since a proton wil...
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Half-life time

Physical half-life time (Tp) The time interval required for an amount of certain radioactive nuclei to decay to half of its original value. Biological half-life time (Tb)  The time interval required for the body to eliminate 50% of any substance by normal routes of elimination: metabolic turn...
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Half-value layer

Half-value layer (HVL) is the width of a material required to reduce the air kerma of an x-ray or gamma-ray to half its original value. This applies to narrow beam geometry only as broad-beam geometry will experience a large degree of scatter, which will underestimate the degree of attenuation. ...
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Harmonic imaging

Harmonic imaging is a technique in ultrasonography that provides images of better quality as compared with conventional ultrasound technique. Physics Harmonic imaging exploits non-linear propagation of ultrasound through the body tissues. The high pressure portion of the wave travels faster th...
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Helical CT image acquisition

Helical ("spiral") CT image acquisition was a major advance on the earlier stepwise ("stop and shoot") method. With helical CT, the patient is moved through a rotating x-ray beam and detector set. From the perspective of the patient, the x-ray beam from the CT traces a helical path. The helical...
Article

Henry (SI unit)

The henry (symbol: H) is the SI derived unit of electrical inductance.  Terminology As per all other eponymous SI units when the unit is written out in full it is not capitalized, but when shortened to its symbol it is capitalized. History and etymology The henry is named in honor of Joseph ...
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Herringbone artifact

Herringbone artifact, also known as crisscross artifact or corduroy artifact, is an MRI artifact, it mimics a fabric with a herringbone pattern. The artefact is scattered all over the image in a single slice or multiple slices. Causes electromagnetic spikes by gradient coils fluctuating power...
Article

Hertz

The hertz (Hz) is the derived SI unit for frequency. One hertz represents one cycle per second, and thus in base SI units, equates to one per second (1/s). In radiology, it is usually encountered in the context of ultrasound physics. Terminology As for all other eponymous units when the name i...
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High-intensity focused ultrasound

High-intensity focused ultrasound (HIFU) is a promising non-invasive thermal ablation technique. Unlike diagnostic ultrasound, HIFU focuses the ultrasound waves precisely upon a target. In a similar way to how light can be focused to a burning point by a magnifying glass, ultrasound passes thro...
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High-resolution CT

High-resolution CT (HRCT) is a scanning protocol in which thin sections (usually 0.625 to 1.25 mm) are acquired and reconstructed using a sharp algorithm (e.g. bone algorithm). It has been classically used for: lung imaging: HRCT chest  temporal bone imaging
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High voltage generator

X-ray units require a high voltage generator to achieve the necessary power required of an x-ray tube. AC power will supply x-ray units with sinusoidal currents, resulting in 'peaks and troughs', limiting an x-ray tube to produce x-rays only half of the 1/60th of s second cycle.  A single-phase...
Article

Histogram equalization

Histogram equalization is a digital image processing technique used for contrast enhancement across a number of modalities in radiology. In conjunction with other methods, histogram equalization forms one of the key digital image processing techniques utilized in the windowing of images. It is o...
Article

History of ultrasound in medicine

The first written document dealing with the use of waves in spatial orientation dates back to 1794, when an Italian physicist Lazaro Spallanzani (“Opus coli di fisica”), analyzed the basic mechanisms of the navigation of flying bats in the dark, and rightly deduced that bats employed sound rathe...
Article

Hormesis

Hormesis is a controversial concept in toxicology. The proposed concept is that very tiny amounts of a toxin may potentially have beneficial biological effects, rather than deleterious effects. In the context of radiology it refers to a proposed modification to the linear no-threshold theory to...
Article

Hounsfield unit

Hounsfield units (HU) are a dimensionless unit universally used in computed tomography (CT) scanning to express CT numbers in a standardized and convenient form. Hounsfield units are obtained from a linear transformation of the measured attenuation coefficients 1. This transformation (figure 1) ...
Article

HRCT chest

High-resolution CT (HRCT) of the chest, also referred to as HRCT chest or HRCT of the lungs, refers to a CT technique in which thin-slice chest images are obtained and post-processed in a high-spatial-frequency reconstruction algorithm. This technique obtains images with exquisite lung detail, w...
Article

Hunter's angle

Hunter's angle (HA) is a term coined from a neurosurgeon, C Hunter Shelden, at Huntington Medical Research Institutes. He placed his comb on the spectrum at approximately a 45° angle and connected several of the peaks. If the angle and peaks roughly corresponded to the 45° angle, the curve was c...
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Hyperintense on T1-weighted images (mnemonic)

Mnemonics for hyperintense T1-weighted lesions include: My Best Friend is Pretty Cool 3 Fs and 4 Ms Mnemonic My Best Friend is Pretty Cool: M: melanin B: blood (i.e. methemoglobin in subacute hemorrhage) F: fat and slow flow P: protein; paramagnetic substances (e.g. manganese, copper); p...
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Image intensifier

Image intensifiers (II) are utilized to convert low energy x-radiation into visible light images. Frequently the detector portion of an x-ray C-arm used in operating theaters, the image intensifier has a low scatter input portion made of low absorption substances such as titanium or aluminum 1,2...
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Image plate artifact

Image plate artifact is caused by backscatter radiation. Backscatter radiation is transmitted through the back of the cassette to the cassette hinge where the lead coating gets weakened or cracked.  To reduce backscatter, the radiographer should collimate where possible.
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Image reconstruction (CT)

The rapid evolution of mathematical methods of image reconstruction in computed tomography (CT) reflects the race to produce an efficient yet accurate image reconstruction method while keeping radiation dose to a minimum and has defined improvements in CT over the past decade. The mathematical ...
Article

Image reconstruction in CT fluoroscopy

Image reconstruction in CT fluoroscopy requires the computer to provide very fast reconstructions of images in order to provide immediate and accurate spatial and anatomical feedback during a procedure. This is achieved by: use of a small reconstruction matrix – e.g. 256 x 256 (compared with co...
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Important figures in the history of radiology

In the history of radiology, certain important figures stand out for their significant contributions to the development of radiology as a science, medical specialty and major advance in patient care. This list is by necessity arbitrary, although we (the editors) hope that the majority of those l...
Article

Indium-111 OncoScint

Indium-111 OncoScint is a radiopharmaceutical used in SPECT imaging. It is a labeled monoclonal antibody that is directed against TAG-72, which is a tumor-associated antigen associated with ~95% of colorectal carcinomas and 100% of ovarian carcinomas 1,2. Background hepatic uptake limits sensiti...
Article

Indium-111 oxine labeled white blood cell scan

Indium-111 oxine labeled white blood cell (WBC) scan (or In-111 oxine labeled white blood cell scan) is a nuclear medicine test which attempts to localize infection and/or inflammation by injecting the patient's previously extracted and radioactively-labeled white blood cells.  Procedure The p...
Article

Indocyanine green lymphangiography

Indocyanine green (ICG) lymphangiography is an emerging imaging technique used to visualize lymphatic vessels and map their course as they drain to sentinel lymph nodes.  History Indocyanine green is a fluorescent dye discovered by researchers at Kodak working on near-infrared photography in 1...
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In-phase and out-of-phase sequences

In-phase (IP) and out-of-phase (OOP) sequences correspond to paired MRI gradient echo (GRE) sequences obtained with the same repetition time (TR) but with two different echo time (TE) values.  Applications The main application of the IP-OOP sequences is to identify pathological (microscopic) f...
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Intensifying screen

Intensifying screens are used in the x-ray cassette to intensify the effect of the x-ray photon by producing a larger number of light photons. It decreases the mAs required to produce a particular density and hence decreases the patient dose significantly. It also reduces motion blur and x-ray t...
Article

International System of Units

The International System of Units, or the SI units (shortened from the French Système international d'unités) is the globally-adopted system of units of measurement. It is the modern iteration of the metric system. It superseded all prior systems including CGS and MKS, although in certain fields...
Article

International Union of Pure and Applied Chemistry

The International Union of Pure and Applied Chemistry (IUPAC) is the world authority on the nomenclature of chemical elements and compounds. The nomenclature is designed to provide an unambiguous representation of a molecule. However, the systematic names are often not used in scientific or clin...
Article

Intima-media thickness

It is an indirect sonographic assessment of the degree of atheromatous vascular disease of end organs. The thickness of the media and the intima of the vessels changes following many conditions and it can be easily and reliably assessed in B mode of ultrasound imaging in common carotid arteries ...
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Intravascular (blood pool) MRI contrast agents

Intravascular MRI contrast agents normally remain confined to the intravascular space, compared to Gd-DTPA which distributes throughout the extracellular fluid space. This is a result of intravascular agents having a molecular weight of approximately 70,000 and above, compared to a molecular wei...
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Intravenous MRI contrast agents

Intravenous MRI contrast agents include chelates of paramagnetic ions, both ionic and nonionic. The particulates, sequestered in the liver, spleen, and lymph nodes, the intravascular agents, confined to the blood pool, and tumor specific agents are discusses separately (see bottom).  NOTE: This...
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Inverse Fourier transformation

The inverse Fourier transform is a mathematical formula that converts a signal in the frequency domain ω to one in the time (or spatial) domain t. A time domain signal f(t) is obtained by demodulating a frequency domain signal F(ω) using a special sinusoidal wave ejωt across all time (from nega...
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Inverse square law

The inverse square law describes the principle of dose reduction as the distance from the source increases. This assumes a point source. If radiation spreads over a spherical area, as the radius increases, the area over which the dose is distributed increases according to A=4πr^2 where A is the...
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Inversion recovery sequences

Inversion recovery pulse sequences are a type of MRI sequence used to selectively null the signal for certain tissues (e.g. fat or fluid). Inversion recovery can also generate heavily T1-weighted images and was originally developed for this purpose. Physics Basically, an inversion recovery (I...
Article

Iodinated contrast media

Iodinated contrast media are contrast agents that contain iodine atoms used for x-ray-based imaging modalities such as computed tomography (CT), although they are also used in fluoroscopy, angiography and venography, and even occasionally, plain radiography. Although the intravenous route of adm...
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Ionization chamber

Ionization chambers measure exposure by detecting liberated electron charge when x-ray photons ionize the gas within the chamber. The chambers need a high positive voltage applied at the collecting anode to attract the liberated electrons. The electron charge is collected and used to determine t...
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Ionizing radiation

Ionizing radiation is the term given to forms of radiation that are energetic enough to displace orbiting electrons from the atoms in the absorbing medium, thus forming positive ions.  Forms of ionizing radiation Indirect Indirect ionizing radiation involves uncharged particles. X-rays and ga...
Article

Joule heating effect

The Joule heating effect is the physical phenomenon whereby the passage of electric current in a metallic conductor produces heat. The effect is the physical phenomenon on which the heating of the cathode filament of a x-ray tube depends. The electric current flowing through the tungsten filame...
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Kerma

Kerma is a measure of energy transferred from radiation to matter and is an acronym for kinetic energy released to matter. It is related to, but not the same as absorbed dose. Kerma is measured by the SI unit, the gray (joules per kilogram). Kerma measures the amount of energy that is transferr...
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Kernel (image reconstruction for CT)

The kernel, or convolution algorithm, refers to the process used to modify the frequency contents of projection data prior to backprojection 1. This process corrects the image by reducing blurring 1. The kernel affects the appearance of image structures by sharpening the image. Different kernels...
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Key figures in the history of radiology

In the history of radiology certain key figures stand out for their groundbreaking contributions to the establishment and development of radiology as a science, medical specialty and major advance in patient care. This list is by necessity arbitrary, although we (the editors) hope that the major...
Article

Kilovoltage peak

Kilovoltage peak (kVp) is the peak potential applied to the x-ray tube, which accelerates electrons from the cathode to the anode in radiography or computed tomography. Tube voltage, in turn, determines the quantity and quality of the photons generated. An increase in kVp extends and intensifies...
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k-space

k-space is an abstract concept and refers to a data matrix containing the raw MRI data. This data is subjected to mathematical function or formula called a transform to generate the final image. A discrete Fourier or fast Fourier transform 1-3 is generally used though other transforms such as th...
Article

K-trans (MR perfusion)

Ktrans is a measure of capillary permeability obtained using dynamic contrast-enhanced (DCE) MR perfusion. It is calculated by measuring the accumulation of gadolinium-based contrast agent in the extravascular-extracellular space.  Increased permeability of vessels in the brain is seen in a var...
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Lactate peak

Lactate is one of the more important compounds assessed on MR spectroscopy, and resonates at 1.3 ppm chemical shift, with a characteristic double peak at long TEs. It is however superimposed on the lipid band, and using an intermediate TE (e.g. 144ms) will invert only lactate allowing it to be d...
Article

Lanthanum therapy

Lanthanum therapy is used to treat hyperphosphatemia in end-stage renal disease 1. It is taken as oral tablets (usually in the chemical form Lanthanum carbonate) which dissociate in the acidic environment of the stomach. The released trivalent Lanthanum cation has a high affinity for dietary pho...
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LaPlace's law

LaPlace's law is useful in thinking about dilated tubular structures, such as the bowel or vessels (e.g. aortic aneurysms). The relationship between wall tension and radius shows why more dilated regions of a tube develop more wall stress and therefore are at higher risk for perforation: wall t...
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Lateral resolution (ultrasound)

Lateral resolution in ultrasound refers to the ability to discern to separate objects that are lateral to each other. Lateral resolution is roughly four times worse than axial resolution in ultrasound. It is primarily determined by the beam width of the ultrasound beam. Strategies to improve la...
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Law of Bergonié and Tribondeau

The law of Bergonie and Tribondeau is that the radiosensitivity of a biological tissue is directly proportional to the mitotic activity and inversely proportional to the degree of differentiation of its cells. This law underpins the field of radiation-oncology, although such a general law may no...
Article

Lead equivalent personal protection equipment

Lead equivalent personal protection equipment (PPE) should be available in all radiology departments and operating suites. There are three principles for ionizing radiation safety: time, distance, and shielding. It is important to remember that all three principles have a part to play in ensurin...
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Linear array

Ultrasound transducers that produce images via linear array typically contain 256-512 elements, making them the largest assembly. Each element produces a scan line that makes up the ultrasound image. Multiple adjacent elements combine to produce an ultrasound beam that is emitted at 90 degrees ...
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Linear attenuation coefficient

Linear attenuation coefficient (µ) is a constant that describes the fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material 1. It includes all possible interactions including coherent scatter, Compton scatter and photoelectric effect 1. Its complement is ...
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Line focus principle

Line focus principle explains the relationship between the anode surface and the effective focal spot size. Basic concept The focal spot is the area of the target upon which the electron beam impinges. The energy of the electrons in the electron beam is mostly converted into heat (approximatel...
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Lipids peak

Lipids are a collection of related compounds examined in MR spectroscopy. They resonates at 1.3 ppm chemical shift, and are markers of severe tissue damage with liberation of membrane lipids, as is seen in cerebral infarction or cerebral abscesses. It is also encountered in cerebral metastases a...
Article

Longitudinal and transverse magnetization

Longitudinal magnetism and transverse magnetism are components of the net magnetism vector. Longitudinal magnetism Longitudinal magnetization is the component of the net magnetization vector parallel to the magnetic field (z-axis). This is due to a difference in the number of spins in parallel...
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Loopogram

A loopogram is a fluoroscopic study of an ileal conduit, which is a type of urinary diversion. Terminology This procedure is also known is an ileal conduitogram, ileal loopography or ileostoureterography.  Procedure It is a retrograde study in which contrast is injected via the anterior abdo...
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Lymphoscintigraphy

Lymphoscintigraphy is a nuclear medicine technique to visualize regional lymphatic drainage, especially for mapping sentinel lymph nodes, from a site of radiopharmaceutical injection. Radiopharmaceutical Colloidal agents are used as these particles enter lymphatic channels and migrate to lymph...
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Mach bands

Mach bands or the Mach effect refers to an optical phenomenon from edge enhancement due to lateral inhibition of the retina 2. This is an inbuilt edge enhancement mechanism of the retina, where the edges of darker objects next to lighter objects will appear lighter and vice versa, creating a fal...
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Magic angle effect (MRI artifact)

The magic angle is an MRI artifact which occurs on sequences with a short TE (less than 32ms; T1W sequences, PD sequences and gradient echo sequences).  It is confined to regions of tightly bound collagen at 54.74° from the main magnetic field (B0), and appears hyperintense, thus potentially be...
Article

Magnetic dipole

Magnetic dipoles are the magnetic equivalent of an electric dipole, where the two charges are positive and negative, with a flow of electric charge and surrounding electric field. Magnets are bipolar, having two poles: north and south. The term dipole means two charges.  In a magnetic dipole, th...
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Magnetic dipole moment

The magnetic dipole moment is a quantity that represents the strength and orientation of the magnetic dipoles. This can be represented by the torque that a material experiences when added to a magnetic field. The stronger the magnetic moment, the stronger the magnetic field and stronger the torq...
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Magnetic field

The magnetic field describes the influence a magnet has on its surrounding area. Magnets create a magnetic field or line of force running from the magnetic north to the magnetic south pole of the magnet. Magnetic fields are the result of intrinsic magnetic moments and moving electric charges wit...
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Magnetic field gradient

Signal localization for image construction in MR is based on adding a magnetic field gradient onto the main (constant) magnetic field. In 1973, Paul Lauterbur published the idea in Nature of deliberately superimposing linear field gradients on the main magnetic field. Along each gradient, the s...
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Magnetic field homogeneity

One of the key concepts in assessing the quality of a magnet is that of magnetic field homogeneity, as it will relate to image quality and the presence of artifacts.Field homogeneity refers to the uniformity of the main magnetic field when no patient is present, measured in parts per million (pp...
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Magnetic particle imaging

Magnetic particle imaging (commonly abbreviated as MPI) is an emerging cross-sectional imaging technique that in the future may be a new clinical imaging modality offering high resolution, dynamic functional imaging without utilizing ionizing radiation.  Physics MPI is a tracer imaging techniq...
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Magnetic resonance lymphangiography

Magnetic resonance lymphangiography (MRL) is an imaging technique used to visualize and map the lymphatic vessels. The technique is used for treatment planning in supermicrosurgical procedures, including lymphaticovenous anastomosis, lymphaticolymphatic bypass and vascularized lymph node transfe...
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Magnetic resonance neurography

Magnetic resonance neurography (MRN) is a relatively new non-invasive imaging technique for dedicated assessment of peripheral nerves. It is used to assess peripheral nerve entrapments and impingements as well as localization and grading of nerve injuries and lesions. Dedicated high-resolution...
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Magnetic shielding

Magnetic shielding refers to the attempt to isolate or block the magnetic field of the MRI magnet.  This can be done to prevent unwanted interference from the MRI magnet on nearby electronic devices.  This is different from radiofrequency shielding, which is the attempt to prevent the unwanted i...
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Magnetic shimming

Magnetic shimming refers to the process of reducing magnetic field inhomogeneities. It is an important aspect of optimizing image quality. Field inhomogeneities can be the result by both intrinsic magnet properties and the surrounding environment of the MR magnet – such as the presence of nearby...
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Magnetic susceptibility

Magnetic susceptibility is the ability of external magnetic fields to affect the nuclei of an atom. This may also be thought of as the “magnetisability” of a material, or the extent to which a material becomes magnetized when placed in an external magnetic field. Magnetic susceptibility is rela...
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Magnetic susceptibility artifact

Magnetic susceptibility artifacts (or just susceptibility artifacts) refer to a variety of MRI artifacts that share distortions or local signal change due to local magnetic field inhomogeneities from a variety of compounds.  They are especially encountered while imaging near metallic orthopedic...
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Magnetization transfer

Magnetization transfer (MT) imaging is an MRI technique that can be used to exploit contrast between tissues where 1H protons are present in three states1: bound to macromolecules in free water as water in the hydration layer between the macromolecules and the free water To assess MT, an off...
Article

Magnetism

Magnetism is a property of matter that is a result of the orbiting electrons in atoms. The orbiting electrons cause the atoms to have a magnetic moment associated with an intrinsic angular momentum called spin.  Magnetic field strengths are measured in tesla (T), a derived SI unit. The equivale...
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Magnets (types)

Magnets used for MRI are of three types: permanent, resistive and superconductive. Permanent MRI magnets use permanently magnetized iron like a large bar magnet that has been twisted into a C-shape where the two poles are close together and parallel. In the space between the poles the magnetic ...
Article

Mammography

Mammography is a dedicated radiographic technique for imaging the breast. Types of mammography In general terms, there are two types of mammography: screening and diagnostic. Mammography differs significantly in many respects from the rest of diagnostic imaging. Screening mammography  In ge...
Article

Manoel de Abreu

Manoel de Abreu (1892-1962) was a Brazilian radiologist who developed chest photofluorography, which was introduced in 1936. Early life Manoel de Abreu was the son of Julio Antunes de Abreu and Mercedes da Rocha Dias. He was born in São Paulo, Brazil, on 4 January 1892 1. He graduated in 1913 ...
Article

Maximum intensity projection

Maximum Intensity Projection (MIP) consists of projecting the voxel with the highest attenuation value on every view throughout the volume onto a 2D image 1. Such an algorithm is rather simple: for each XY coordinate, only the pixel with the highest Hounsfield number along the Z-axis is represe...
Article

Maxwell (CGS unit)

The maxwell (symbol: Mx) is the CGS unit of magnetic flux and was superseded by the weber, the unit in the SI system.  Terminology As per all other eponymous measurement units when the unit is written out in full it is not capitalized, but when shortened to its symbol it is capitalized. Histo...
Article

Mean transit time (MTT)

Mean transit time (MTT) corresponds to the average time, in seconds, that red blood cells spend within a determinate volume of capillary circulation. It is assessed as part of the CT perfusion protocol, which is basically used in the context of ischemic stroke diagnosis and management, and MR pe...
Article

Mechanical index

The mechanical index (MI) is an attempt to measure part of an ultrasound beam's bioeffects. The MI is found on most ultrasound display screens, along with the thermal index. Mechanical index is proportional to an ultrasound beam's peak negative pressure (or peak rarefaction pressure). It is al...
Article

Meglumine iotroxate (Biliscopin)

Meglumine iotroxate (BiliscopinTM) is an iodinated, intravenous contrast agent that is preferentially excreted into the biliary tree and is used in CT intravenous cholangiography. The typical dose is 100 mL Biliscopin (105 mg meglumine iotroxate/mL; 5.0 g iodine), which is administered via slow...
Article

Metal artifact reduction algorithm

Metal artifact reduction (MAR) algorithms are used to improve CT image quality in patients with metalware, however, can be affected by novel artifacts 1-3. There are a number of commercially-available algorithms (in 2019) 1,3: iterative MAR (iMAR) - Siemens MAR for orthopedic implants (O-MAR) ...
Article

Metal artifact reduction sequence

A metal artifact reduction sequence (MARS) is intended to reduce the size and intensity of susceptibility artifacts resulting from magnetic field distortion. A variety of techniques are used for reducing metal artifacts at MRI, both for addressing artifacts due to the presence of metal in the i...
Article

Microbubbles

Microbubbles are intravenous contrast agents used in contrast-enhanced ultrasound. Microbubble contrast agent is different to the agitated saline contrast agent often used in echocardiographic studies. Microbubbles consist of a gas surrounded by a lipid, lipopolymer, or polymer shell. They rang...
Article

Milliampere-seconds (mAs)

Milliampere-seconds more commonly known as mAs is a measure of radiation produced (milliamperage) over a set amount of time (seconds) via an x-ray tube. It directly influences the radiographic density, when all other factors are constant. An increase in current (mA) results in a higher producti...
Article

Minimum intensity projection (MinIP)

Minimum intensity projection (MinIP) is a data visualization method that enables detection of low-density structures in a given volume. The algorithm uses all the data in a volume of interest to generate a single bidimensional image, in other words, it consists of projecting the voxel with the l...
Article

Mirror image artifact

Mirror image artifact in sonography is seen when there is a highly reflective surface (e.g. diaphragm) in the path of the primary beam. The primary beam reflects from such a surface (e.g. diaphragm) but instead of directly being received by the transducer, it encounters another structure (e.g. ...

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