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.

635 results found
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Erg (unit)

The erg (symbol, erg, i.e. the same as the unit) is the unit of energy in the cgs system, where one erg represents the work done when a force of one dyne is acting over a distance of one cm and is equivalent to 1 x 10-7 joules. The rad, a legacy unit of absorbed radiation dose, was defined as t...
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Ernst angle

The Ernst angle is the flip angle that maximizes signal in T1-weighted sequences that have a short repetition time (TR). When the TR is very short, the best flip angle to maximize signal can be quite small. Choosing the Ernst angle in this setting can increase signal by several fold. However, i...
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Excitation

Excitation in radiobiology and medical physics refers to excitation of an outer orbital (valence) electron to a higher energy level. By absorbing some energy, but insufficient to cause ionization, the valence electron overcomes the weak attractive force of the nucleus, causing it to move further...
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Exposure

The term exposure refers to the concentration, in air, of x-rays at a specific point and is the ionization produced in a specific volume of air: E = Q / m where E is exposure, Q is the quantity of charge on the ions and m is the unit mass of air. Exposure describes the ability of x-ray photons ...
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Extended reality

Extended reality , sometimes referred to as XR, is term for technologies, such as those that include augmented reality, virtual reality and mixed reality, that allow visualization of three dimensional virtual imaging. Although such technologies have their roots in art and computer gaming, they h...
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Extracellular volume (ECV) - myocardium

Extracellular volume (ECV) refers to the space or volume of a tissue, which is not occupied by cells. Apart from the usual extracellular space, which surrounds the cells of a specific tissue it also includes the intracapillary plasma volume 1,2. It measures the space, which is occupied by the ex...
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F-18 fluorodeoxyglucose

F-18 fluorodeoxyglucose (FDG) is the most common PET radiotracer. Structure The radiopharmaceutical consists of the fluorine-18 radionuclide substituting the hydroxyl group at the C-2 position of glucose. The IUPAC chemical name is 2-deoxy-2-[F-18]fluoroglucose. Production F-18 fluoride ion ...
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FABS position

The FABS position relates to MRI elbow examinations for improved visualization of the distal biceps brachii tendon insertion and is a mnemonic for elbow flexed, shoulder abducted and forearm supinated.
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Factors affecting T1

Factors affecting T1 and T2 relaxation times of different tissues are generally based on molecular motion, size and interactions. The protons giving rise to an NMR signal are mainly those in cell water and lipids (i.e. protons that are free to move), while those in protein and solids usually do...
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Faraday cage

A Faraday cage is a conductive enclosure used to shield the inner space from electromagnetic interference. In MR imaging, this type of structure provides radiofrequency shielding to the scanning room to minimize occurrence of interference-associated imaging artifact. Operation The cage is usua...
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Fast spin echo

Fast or turbo spin echo (FSE/TSE) is an adaptation of conventional spin-echo (SE) acquisition technique designed to reduce imaging time. It has largely supplanted the original spin-echo technique due to vastly improved imaging speed. Basic spin echo sequence In a basic SE sequence, a single ec...
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Fat suppressed imaging

Fat suppression is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue 1. It can be applied to both T1 and T2 weighted sequences.  Due to short relaxation times, fat has a high signal on magnetic resonance images (MRI). This high ...
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Fat-water swapping artifact

Fat-water swapping artifact is seen in a significant proportion of fat/water suppressed sequences using the Dixon method. The artifact follows a computational error in areas of field inhomogeneity resulting in incorrectly determining whether a voxel contains water or fat. The images have geogra...
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Ferromagnetism

Ferromagnetic materials generally contain iron, nickel, or cobalt. These materials include magnets, and various objects that might be found in a patient, such as aneurysm clips, parts of pacemakers, shrapnel, etc.  These materials have a large positive magnetic susceptibility, i.e. when placed ...
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Fetal dosimetry

NB - Please consult original article(s) and discuss with your local radiology department/radiation physicist before making any clinical decision. Although radiation exposure to the gravid uterus is to be avoided whenever possible, and only deliberately performed after careful weighing up of the...
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Fiber assignment by continuous tracking algorithm (FACT)

Fiber assignment by continuous tracking (FACT) algorithms are a commonly used deterministic post-processing algorithm for magnetic resonance tractography studies. In these algorithms, axonal fiber bundles are reconstructed - voxel by voxel - following the direction of the main eigenvector. The ...
Article

Filament circuit

The tungsten cathode needs to be heated for thermionic emission to take place. Thus a 10 voltage potential difference and 3-6 amperes of filament current is supplied, which forms the filament circuit.  This should not be confused with tube current which determines the flow of electrons from the...
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Film dosimeter

Film dosimeters are used to measure radiation exposure to workers to monitor radiation safety and ensuring that they receive doses below the appropriate limit.  Film badges are the cheapest and most common monitoring device. They consist of a small case with a piece of film situated between fil...
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Filtered back projection

Filtered back projection is an analytic reconstruction algorithm designed to overcome the limitations of conventional back projection; it applies a convolution filter to remove blurring. It was, up until recently the primary method in cross-sectional imaging reconstruction.  It utilizes simulta...
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Filters

Filters are metal sheets placed in the x-ray beam between the window and the patient that are used to attenuate the low-energy (soft) x-ray photons from the spectrum. Filtering is the removal of these low energy x-rays from the beam spectrum which would otherwise not contribute to image quality ...
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Fixing solution

Fixing solution is used in the darkroom to fix (i.e. remove unexposed silver) the developed and rinsed x-ray film in conventional radiography. Components fixing agent: sodium/ammonium thiosulfate, dissolves unexposed silver hardener: potassium alum, to harden the gelatin emulsion in film aci...
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FLAIR vascular hyperintensities

FLAIR vascular hyperintensities are hyperintensities encountered on FLAIR sequences within subarachnoid arteries related to impaired vascular hemodynamics 1,2. They are usually seen in the setting of acute ischemic stroke and represent slow retrograde flow through collaterals (and not thrombus) ...
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Flash mode (CEUS)

Flash mode is a technique specific to CEUS-capable ultrasound devices, and in brief is a short ultrasound pulse with a very high mechanical index, resulting in almost complete destruction of the contrast agent microbubbles in the imaging plane.  Physics The microbubbles utilized as contrast ag...
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Flat panel detector

Flat panel detectors (FPD) are used in direct digital radiography (DDR) for the conversion of x-rays to light (indirect conversion) or charge (direct conversion) which is read out using a thin film transistor (TFT) array. Types indirect conversion FPDs outermost layer is scintillator: phospho...
Article

Flip angle

The flip angle is an MRI phenomenon by which the axis of the hydrogen proton shifts from its longitudinal plane (static magnetic field B0) Z axis to its transverse plane XY axis by excitation with the help of radiofrequency (RF) pulses. A RF pulse is sent in at the precise Larmor frequency in re...
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Flow void

Flow voids refer to a signal loss occurring with blood and other fluids, like CSF or urine, moving at sufficient velocity relative to the MRI apparatus. It is a combination of time-of-flight and spin-phase effects usually seen in spin-echo techniques (such as T2-weighted images) 2. Physics Dur...
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Fluid attenuated inversion recovery

Fluid attenuated inversion recovery (FLAIR) is a special inversion recovery sequence with a long inversion time. This removes signal from the cerebrospinal fluid in the resulting images 1. Brain tissue on FLAIR images appears similar to T2 weighted images with grey matter brighter than white mat...
Article

Fluorography

Fluorography is the use of relatively intense (50-1000mA), pulsed x-ray exposures (pulses are of short duration and applied at 1-12 pulses/second) to form an x-ray image.  The resultant images have a relatively high signal to noise ratio (SNR), i.e the images are of better quality than those ac...
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Fluoroscopy

Fluoroscopy is an imaging modality that allows real-time x-ray viewing of a patient with high temporal resolution. It is based on an x-ray image intensifier coupled to a still/video camera. In recent years flat panel detectors (which are similar to the digital radiography used in projection radi...
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Fluoroscopy vs fluorography

Fluoroscopy and fluorography are very similar imaging techniques and, in many instances, can be performed on the same equipment. Fluoroscopy vs fluorography Fluoroscopy low current (0.5-5 mA), continuous or near-continuous x-ray exposures relatively low signal to noise ratio (SNR) prioritis...
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Flying focus tomosynthesis

Flying focus is a technology of image acquisition in digital breast tomosynthesis characterized by a continuous sweep during shooting. Sharpness in digital systems is determined by the modulation transfer function (MTF), which determine contrast transfer as a function of spatial frequency. Sin...
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Focal spot

Focal spot is the area of the anode surface which receives the beam of electrons from the cathode. It is the apparent source of x-rays.  Basic concept Size and shape of the focal spot is determined by the size and shape of the electron beam when it strikes the anode 1. Size and shape of the e...
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Focusing cup

A focusing cup is a negatively charged, shallow depression on the surface of the cathode of an x-ray tube, which concentrates the electron beam towards the focal spot of the anode. It is typically composed of nickel. The negative charge of the focusing cup helps to accelerate the electrons towa...
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Fourier transform

Fourier transform is a mathematical operation which converts a time domain signal into a frequency domain signal. Discussion Fourier transform is integral to all modern imaging, and is particularly important in MRI. The signal received at the detector (receiver coils in MRI, piezoelectric disc...
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Fourier transformation

The Fourier transform is a mathematical formula that converts a signal in time (or spatial) domain t to one in the frequency domain ω. A frequency domain signal F(ω) is obtained by modulating the time domain signal f(t) to a special sinusoidal wave e-jωt across all time (from negative infinity ...
Article

Fractionation (radiation therapy)

Radiation therapy is usually divided or “fractionated” over a treatment course lasting multiple weeks. Fractionation in the context of radiotherapy is the process of dividing a dose of radiation into multiple “fractions”. This practice seeks to maximize the destruction of malignant cells while m...
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Free induction decay

Free induction decay (FID) refers to a short-lived sinusoidal electromagnetic signal which appears immediately following the 90° pulse. It is induced in the receiver coil by the rotating component of the magnetization vector in the x-y plane which crosses the coil loops perpendicularly. It does ...
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Fringe field (MRI)

The fringe field is the peripheral magnetic field outside of the magnet core. It is important because it can cause interference with nearby electronic devices, such as pacemakers. Although the strength of the magnetic fields decreases with distance from the core of the magnet, the effect of the ...
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Functional MRI

Functional magnetic resonance imaging (fMRI) is a technique used to obtain functional information by visualizing cortical activity. fMRI detects subtle alteration in blood flow in response to stimuli or actions. It is used in two broad ways: clinical practice typically in presurgical patients ...
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Gadolinium contrast agents

Molecular complexes containing the rare earth metal gadolinium, chelated to a carrier ligand, form the gadolinium contrast agents (a type of paramagnetic contrast agent) which are the primary class of MRI contrast media. The intravenous route of administration is the commonest. Chemistry The g...
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Gallium-67 scintigraphy

Gallium-67 is a photon-emitting radiotracer used for scintigraphy which is used in the form of various salts like citrate and nitrate. Once administered, imaging may consist of planar (2 dimensional) , SPECT, and SPECT-CT acquisitions. Once injected it binds to plasma proteins (especially transf...
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Gallium-68 DOTATATE

Gallium-68 DOTATATE​​ (or Ga-68 DOTATATE) is a PET radiotracer that is useful for evaluating primary and metastatic well-differentiated neuroendocrine tumors. It is a form of somatostatin-receptor (SSTR) functional imaging and most often combined with cross-sectional imaging in the form of PET-C...
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Gamma-aminobutyric acid (GABA) peak

Gamma-aminobutyric acid (GABA) is the principle inhibitory neurotransmitter in the central nervous system 1 and as such, is one of the compounds examined in MR spectroscopy.  It is present in the human brain at a concentration of about 1 mM, a whole order of magnitude lower than some of the more...
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Gamma camera

Gamma cameras (also called scintillation cameras or Anger cameras) are the predominant nuclear medicine imaging machine currently in use. They permit the acquisition of planar images. They are also central to single photon emission computed tomography (SPECT). Design From the exterior to inter...
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Gamma decay

Gamma decay refers to the release of a gamma (γ) ray photon, a form of high energy electromagnetic radiation, due to radioactive decay of a nucleus. Typically, the energy spectra is in the ~100 keV to ~10 MeV range 1. Gamma decay Gamma decay is a mode of radioactive decay. It differs from alph...
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Gastrointestinal MRI contrast agents

Gastrointestinal MRI contrast agents are varied and can be either positive or negative agents. Acceptance of the use of MRI in abdominal imaging has been limited in part by difficulty in distinguishing bowel from intra-abdominal masses and normal organs. The use of enteric contrast agents can ai...
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Gauss (unit)

The gauss (symbol: G or Gs) is a legacy CGS unit of magnetic flux density, which was superseded by the tesla (T). One gauss is defined as one maxwell per cm2 (Mx/cm2), which equates to 10-4 tesla, and is therefore a small unit. This is one of the reasons for its stubborn persistence in some scie...
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Gibbs and truncation artifacts

Gibbs artifact, also known as truncation artifact or ringing artifact, is a type of MRI artifact. It refers to a series of lines in the MR image parallel to abrupt and intense changes in the object at this location, such as the CSF-spinal cord and the skull-brain interface. The MR image is reco...
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Glutamine-Glutamate peak

Glutamate-Glutamine (Glx) peak is one of the regions assessed on MR spectroscopy, and resonates between 2.2 and 2.4 ppm chemical shift. It overlaps with the GABA peak and cannot be routinely separated from each other.
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Godfrey Hounsfield

Sir Godfrey N Hounsfield (1919-2004) pioneered the CT scanner making him one of the greats in the history of radiology and medicine in general. For his work, he received the Nobel Prize in Physiology or Medicine in 1979. This was remarkable because he had had no previous experience of working in...
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Gradient coils

Gradient coils are used to produce deliberate variations in the main magnetic field (B0). There are three sets of gradient coils, one for each direction. The variation in the magnetic field permits localization of image slices as well as phase encoding and frequency encoding. The set of gradient...
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Gradient echo sequences

Gradient echo sequences (GRE) are an alternative technique to spin-echo sequences, differing from it in two principal points: utilization of gradient fields to generate transverse magnetization flip angles of less than 90° Compared to the spin-echo and inversion recovery sequences, gradient e...
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...
Article

Grids

Grids are placed between the patient and the x-ray film to reduce the scattered radiation reaching the detector (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 ...
Article

Gustav Bucky

Gustav Bucky (1880-1963) was a German-born, American radiologist who pioneered the development of anti-scatter grids in projectional radiography with his invention, the Bucky diaphragm. Early life Gustav Peter Bucky was born in the city of Leipzig, Germany on 3 September 1880 2,3,5. He had a k...
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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. Tp is always a constant for a particular radioactive isotope and is unaffected by changes in surrounding such as temperature or pressure. Biological half-...
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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. ...
Article

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 spike artifact, crisscross artifact, or corduroy artifact, is an MRI artifact related to one or few aberrant data point(s) in k-space. In image space, the regularly spaced stripes resemble the appearance of a fabric with a herringbone pattern. The artifact cov...
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: interstitial lung disease 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

Hip protocol (MRI)

The MRI hip protocol encompasses a set of different MRI sequences for the routine assessment of the single hip joint. Note: This article aims to frame a general concept of an MRI protocol for the assessment of a single hip joint. Protocol specifics will vary depending on MRI scanner type, speci...
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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...
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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...
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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) ...
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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...
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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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Hydrolyzed reduced technetium-99m

Hydrolyzed reduced technetium-99m (HR-Tc-99m) is a secondary product of the radiolabeling process. It is the chemical species of reduced technetium-99m; oxidation states: +5 and +4. It represents one of the possible impurities present in the technetium agents. It does not bind to the carrier mol...
Article

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...
Article

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...
Article

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.
Article

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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Imaging technology

Imaging technology is home to the technical aspects of diagnostic and therapeutic procedures within radiology. Rather than focus on the practical aspect of imaging as seen in imaging in practice, imaging technology pertains to the technical aspect of the equipment and technology used.  See also...
Article

Impact factor

Impact factor is a bibliometric index.  It expresses the "impact" of a publication on the reference scientific community. Specifically, it measures the average number of citations of a scientific article by other researchers. The impact factor was developed in 1961 by the Institute for Scientif...
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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

Incidence

The incidence is an epidemiological term for the number of new cases of a condition (e.g. brain tumors or diabetes), in a given population, during a specified time interval. The formulas for incidence can express it as a rate or a proportion, e.g. x new cases / y population count / z time period...
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...
Article

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...
Article

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

Intermediate weighted images

An intermediate weighted image is acquired by a sequence with a proton-density like long repetition time and a prolonged echo time usually 35-60 ms 1,2. It interconnects the ability to depict the detailed anatomy of a proton density-weighted image with the fluid sensitivity of a T2-weighted sequ...
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...

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