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.

338 results found
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1.5T vs 3T

Comparing 1.5T vs 3T MRI systems identifies a number of differences: increased signal to noise ratio (SNR) increased spatial resolution increased temporal resolution increased specific absorption rate (SAR) increased acoustic noise Signal to noise ratio Theoretically, signal is proportion...
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2-hydroxyglutarate

2-hydroxyglutarate is a metabolite that accumulates in the brains of patients with IDH-1 mutated (IDH-1 positive) brain tumours, particularly diffuse low grade gliomas. Although not in widespread clinical use, it is likely that 2-hydroxyglutarate, which resonates at 2.25 ppm, will be able to be ...
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Absorbed dose

Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of medium, and so has the unit J/kg or gray (Gy) where 1Gy = 1Jkg-1. The absorbed dose is not a good indicator of the likely biological effect. 1 Gy of alpha r...
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Acoustic enhancement

Acoustic enhancement, also called posterior enhancement or enhanced through transmission, refers to the increased echoes deep to structures that transmit sound exceptionally well. This is characteristic of fluid filled structures such as cysts, the urinary bladder and the gallbladder. The fluid...
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Acoustic impedance

Acoustic impedance (Z) is a physical property of tissue. It describes how much resistance an ultrasound beam encounters as it passes through a tissue. Acoustic impedance depends on: the density of the tissue (d, in kg/m3) the speed of the sound wave (c, in m/s) and they are related by: Z = ...
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Acoustic shadowing

Acoustic shadowing on an ultrasound image is characterised by a signal void behind structures that strongly absorb or reflect ultrasonic waves. This happens most frequently with solid structures, as sound conducts most rapidly in areas where molecules are closely packed, such as in bone or stone...
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Acquisition time

The time of acquisition for a conventional spin echo or gradient echo sequence is the product of the repetition time, phase encoding steps, and number of averages (TR x phase steps x NEX). For example, with a one second TR, 128 phase steps, and two averages we would get an acquisition time of ab...
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Air gap

An air gap between the patient and the film-screen will improve contrast of the film by reducing the divergent scattered rays. Also, because of the inverse square law, air gap causes mild reduction in the intensity of primary radiation that comes from target from a larger distance and significan...
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Alanine peak

Alanine is one of the compounds examined in MR spectroscopy. It resonates at 1.48 ppm chemical shift. It is elevated in meningiomas.
Article

Aliasing in MRI

Aliasing in MRI (also known as wrap-around) is a common MRI artifact that occurs when the field of view (FOV) is smaller than the body-part being imaged. The part of the body that lies beyond the edge of the FOV is projected on to the other side of the image. This can be corrected, if necessary...
Article

Alpha decay

All nuclei with the atomic number Z>82, are considered unstable. These are considered “neutron rich” and undergo the decay process by emitting a particle containing two neutrons and two protons. Alpha decay is the process in which an alpha particle (containing two neutrons and two protons) i...
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Anisotropy

Anisotropy is an artifact encountered in ultrasound, notably in muscles and tendons during musculoskeletal ultrasound. In musculoskeletal applications, the artifact may prompt an incorrect diagnosis of tendinosis or tendon tear. When the ultrasound beam is incident on a fibrillar structure as a...
Article

Anode

Anode represents the component in which the X-radiation is produced. It is a piece of metal, shaped in the form of a beveled disk with the diameter between 55 and 100mm, 7mm thick, connected to the positive side of electrical circuit.The anode converts the energy of the electrons into X-radiatio...
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Anode heel effect

Anode heel effect refers to the intensity of the x-ray beam, produced from the x-ray tube, which is not uniform in all portions of the beam. Basic concept In general, the beam consists of a central ray and a diverging beam. The rays towards the cathode end of the tube have more intensity.This ...
Article

Apparent diffusion coefficient

Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (of water molecules) within tissue, and is commonly clinically calculated using MRI with diffusion weighted imaging (DWI) 1.  Basics Diffusion-weighted imaging (DWI) is widely appreciated as an indispensable tool i...
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Arterial spin labelling (ASL) MR perfusion

Arterial spin labelling (ASL) MR perfusion is an MR perfusion technique which does not require intravenous administration of contrast (unlike DSC perfusion and DCE perfusion). Instead it exploits the ability of MRI to magnetically label arterial blood below the imaging slab. The parameter most c...
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As low as reasonably achievable (ALARA)

As low as reasonably achievable (ALARA) is a principle of radioprotection stating that whenever ionizing radiation has to be applied to humans, animals or materials exposure should be as low as reasonably achievable.
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Attenuation

Attenuation is the reduction in power and intensity as the sound travels through the tissue(s).
Article

Attenuation coefficient

Attenuation coefficient is quantified as the measure of how easily a material can be penetrated by the beam. It quantifies how much the beam is "attenuated", i.e., weakened by the material it is passing through.
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Automated full-field volumetric ultrasound

An automatic full-field volumetric breast ultrasound scanner (AFFBUS) is a developing technology which was initiated to overcome the drawback of dense breast and to get a three dimensional view of the breast.  Components scan station view station Scan station Automatic ultrasound imaging ac...
Article

B values

B value measures the degree of diffusion weighting applied, thereby indicating the amplitude (G), time of applied gradients (δ) and duration between the paired gradients (Δ) and is calculated as: b = γ² G² δ² (Δ−δ/3) Therefore, a larger b value is achieved by increasing the gradient amplitude ...
Article

B0

The Bo in MRI refers to the main magnetic field and is measured in Tesla. The majority of MRI systems in clinical use are between 1.5T and 3T. Altering the field strength will affect the Larmour frequency at which the protons precess. See also 1.5T vs 3T
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Beam collimators

Beam collimators are 'beam direction' devices used in the X-ray tube housing, along with an arrangement of mirrors and lights, in such a way that the light and X-ray fields match each other. They are made of lead shutters which completely absorb the photons, and thus reduce patient dose as well ...
Article

Beam width artifact

Ultrasound beam width artifact occurs when a reflective object located beyond the widened ultrasound beam, after the focal zone, creates false detectable echoes that are displayed as overlapping the structure of interest. To understand this artifact, it is important to remember that the ultraso...
Article

Beta decay

Beta particles occurs with either negative or positive charge (β- or β+) and are known to be either electrons or positrons, respectively, therefore beta decay represents the radioactive decay, in which a beta particle is emitted. Kinetic energy of beta particles has continuous spectrum. Beta mi...
Article

Black boundary artifact

Black boundary artifact or india ink artifact is an artificially created black line located at fat-water interfaces such as those between muscle and fat. This results in a sharp delineation of the muscle-fat boundary that is sometimes visually appealing but not an anatomical structure.  Case 1 ...
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Blooming artifact

Blooming artifact is a susceptibility artifact encountered on some MRI sequences in the presence of paramagnetic substances that affect the local magnetic milieux. Most affected sequences are T2*, and in many instances they are designed to exploit this phenomenon to make certain pathologies more...
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BOLD imaging

Blood oxygenation level dependent (BOLD) imaging is the standard technique used to generate images in functional MRI (fMRI) studies, and relies on regional differences in cerebral blood flow to delineate regional activity.  Blood flow in the brain is highly locally controlled in response to oxy...
Article

Bone mineral density

Bone mineral density (BMD) is defined as amount of mineral (calcium hydroxyapatite) per unit of bone. Radiographic features BMD can be measured by various methods: gamma rays: replaced by radiographic methods single-energy photon absorptiometry (SPA) was superseded by the introduction of sin...
Article

Bone scan

Bone scans are a nuclear medicine (scintigraphic) study that makes use of Technetium 99m (commonly Tc99m-methylene diphosphonate (MDP)) as the active agent. The study has three phases which follow intravenous injection of the tracer. Sometimes a fourth (delayed/delayed) phase is performed.  Cl...
Article

Breast imaging and the technologist

Breast screening and diagnostic programmes cannot exist without the technologists. They play an indispensable role in the acquisition of mammogram and ultrasound images  in both screening and diagnostic settings. The mammogram technologist: the primary responsibility of the "mammo tech&quo...
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Breast MRI enhancement curves

Following administration of Gadolinium there can be three possible enhancement kinetic curves for a lesion on breast MRI. These are sometimes termed the Kuhl enhancement curves. type I curve: progressive enhancement pattern typically shows a continuous increase in signal intensity throughout t...
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Breast ultrasound

Breast ultrasound is an important modality in breast imaging. It is the usual initial breast imaging modality in those under 30 years of age in many countries. In assessing for malignancy, is important to remember that one must use most suspicious feature of 3 modalities (pathology, ultrasound,...
Article

Bremsstrahlung

X-rays are basically produced by high-energy electrons bombarding a target, especially targets that have a high proton number (Z). When bombarding electrons penetrate into the target, some electrons travel close to the nucleus due to the attraction of its positive charge and are subsequently inf...
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Cardiac CT

Computed tomography of the heart (or cardiac CT) is routinely performed to gain knowledge about cardiac or coronary anatomy, to detect or diagnose coronary artery disease, to evaluate patency of coronary artery bypass grafts or implanted coronary stents or to evaluate volumetry and cardiac funct...
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Cardiac MRI

Cardiac MRI consists of using MRI to study heart anatomy and pathology. Advantages Main advantages of cardiac MRI in comparison with other techniques are: a better definition of soft tissues use of different types of sequences improves diagnostic accuracy avoid ionising radiation neverthel...
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Cassette

Cassettes are rigid holders used in conventional and computed radiography (CR) for the screen film system and imaging plate respectively.  The back side of the cassette has a rubber or felt for adequate contact between screen film system or with the imaging plate. The front is made of low atomi...
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Cathode

The cathode is part on an x-ray tube and serves to expel the electrons from the circuit and focus them in a beam on the focal spot of the anode. It is a controlled source of electrons for the generation of X-ray beams. The electrons are produced by heating the filament, i.e., a coil of wire made...
Article

Central point artifact

The central point artifact is a focal dot of increased signal in the center of an image. It is caused by a constant offset of the DC voltage in the receiver. After Fourier transformation, this constant offset gives the bright dot in the center of the image as shown in the diagram. The axial MRI...
Article

Cerebral blood flow (CBF)

Cerebral blood flow (CBF) is one of the parameters generated by perfusion techniques (CT perfusion and MR perfusion). CBV is defined as the volume of blood passing through a given amount of brain tissue per unit of time, most commonly milliliters of blood per minute per 100g of brain tissue 1. ...
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Cerebral blood volume (CBV)

Cerebral blood volume (CBV) (often relative CBV - see below) is one of the parameters generated by perfusion techniques (CT perfusion and MR perfusion). CBV is defined as the volume of blood in a given amount of brain tissue, most commonly milliliters of blood per 100 g of brain tissue 1. CBV c...
Article

Characteristic radiation

When a fast moving electron collides with a K-shell electron, the electron in the K-shell is ejected (provided the energy of incident electron is greater than the binding energy of K-shell electron) leaving behind a 'hole'. This hole is filled by an outer shell electron (from the L-shell, M-shel...
Article

Chemical shift artifact

Chemical shift artefact or misregistration is a type of MRI artifact. It is a common finding on some MRI sequences, and used in MRS. Chemical shift is due to the differences between resonance frequencies of fat and water. It occurs in the frequency encode direction where a shift in the detected...
Article

Choline peak

Choline is a precursor of acetylcholine (ACH), a component of cell membranes which is commonly examined in MR spectroscopy. It resonates at 3.2 ppm chemical shift. It is a marker of cellular membrane turnover and therefore elevated in neoplasms, demyelination and gliosis. In the setting of glio...
Article

Chromium labeled red blood cells

Chromium labeled red blood cells is an intravascular MRI contrast agent. The use of 51Cr-labeled RBC's in nuclear medicine suggested the use of paramagnetic Cr(III)-labeled RBC's as an intravascular contrast agent for MRI. In dogs, significant enhancement of the liver and spleen is noted with mi...
Article

Citrate peak

Citrate is a compound examined in MR spectroscopy in the setting of possible prostate carcinoma. Citrate resonates at 2.6 ppm and is decreased in prostate cancer.  For more information go to: MR spectroscopy in prostate cancer
Article

CLEAR

CLEAR, an abbreviation of constant level appearance, is an MR technique to achieve homogeneity correction by using coil sensitivity maps acquired in a reference scan. CLEAR is a term utilised by Philips and is comparable to PURE in Siemens MR scanners.
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Coherent scattering

Coherent scattering (also known as unmodified, classical or elastic scattering) is one of three forms of photon interaction which occurs when the energy of the X-ray or gamma photon is small in relation to the ionisation energy of the atom.  It therefore occurs with low energy radiation. Upon i...
Article

Colour comet-tail artefact

The colour comet-tail artefact is an ultrasonographic sign seen in a number of situations, when colour Doppler scanning is performed. Typically the artefact, which resembles the grey-scale comet-tail artefact, is seen in situation when a small highly refractive (usually calcific) object is inte...
Article

Comet-tail artifact

The comet-tail artifact is a grey-scale ultrasound finding seen when small calcific / crystalline / highly reflective objections are interrogated, and is believed to be a special form of reverberation artifact. It is similar to the colour comet-tail artifact and is seen in similar situations, a...
Article

Compton effect

Compton effect or Compton scatter is one of three principle forms of photon interaction. It is the main cause of scattered radiation in a material. It occurs due to the interaction of the X-ray or gamma photon with the outermost (and hence loosely bound) valence electron at the atomic level. The...
Article

Computed tomographic (CT) colonography

Computed tomographic (CT) colonography, also called virtual colonoscopy (VC), is a powerful minimally invasive technique for colorectal cancer screening. Indications screening test for colorectal carcinoma colon evaluation after incomplete or unsuccessful conventional colonoscopy assessment ...
Article

Computed tomography

Computed tomography (CT) scanning, also known as computerized axial tomography (CAT) scanning, is a diagnostic imaging procedure that uses X-rays in order to present cross-sectional images ("slices") of the body. Cross sections are reconstructed from the measurements of attenuation coe...
Article

Cone beam CT

Cone beam CT (CBCT) is a variant type of computed tomography (CT), and is used particularly in dental and extremity imaging. It differs from conventional CT in that it uses cone-shaped x-ray beam and two dimensional detectors instead of fan-shaped x-ray beam and one dimensional detectors.  Phys...
Article

Congenital cholesteatoma

Congenital cholesteatomas are identical to epidermoid cysts, differing only in name and location.  Pathology They are intraosseous inclusions of ectoderm, and are therefore comprised of keratin debris and cholesterol. Characteristically, they are located at the petrous apex. In contrast middle...
Article

Contrast enhanced mammography

Contrast enhanced mammography (CEM) is a complementary breast imaging modality. A finite number of sequential images are obtained with X-ray beam produced at a high energy, above the K-edge of Iodine, and with an intravenous non-ionic Iodine contrast agent  injected between pre and post contrast...
Article

Contrast enhanced MR angiography

Contrast enhanced MR angiography is a technique involving 3D spoiled gradient-echo (GE) sequences, with administration of Gd-based contrast. It can be utilised to assess vascular structures of almost any part of the body. It's key features are as follows: T1- weighted spoiled gradient-echo sequ...
Article

Contrast enhancement

Contrast enhancement is a ubiquitous term in radiology and can be used in two ways.  Firstly, it may refer to methods of exaggerating the visible difference between adjacent structures on scans by administering contrast agents. This includes differentiating between normal structures. There are ...
Article

Contrast media and breast feeding

Contrast media and breastfeeding is an area of imaging safety that has been investigated for both CT and MRI contrast agents. The current guidelines do not support the cessation of breastfeeding or any special precautions after CT and MRI intravenous contrast media administration. CT contrast a...
Article

Contrast media extravasation

Contrast media extravasation (CMEV) is a well-known complication of contrast-enhanced CT scanning 1. It can also occur in MRI studies, but the complications are rare given the low volume that are used. Epidemiology CT contrast extravasation occurs relatively infrequently, in ~0.5% (range 0.13-...
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Contrast resolution

Contrast resolution in radiology refers to the ability of the imaging modality to distinguish between differences in image intensity. The inherent contrast resolution of a digital image is given by the number of possible pixel values, and is defined as the number of bits per pixel value. See al...
Article

Contrast-enhanced ultrasound

Contrast-enhanced ultrasound (CEUS) involves the administration of intravenous contrast agents containing microbubbles of perfluorocarbon or nitrogen gas. The bubbles greatly affect ultrasound backscatter and increase vascular contrast in a similar manner to intravenous contrast agents used in C...
Article

Contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is the third most common cause of all hospital-acquired acute renal failure, and accounts for ~10% of all cases. There is still an ongoing debate regarding its occurrence after the intravenous contrast administration because most of cases occur after intra-arte...
Article

Coronary MR angiography

Coronary MR angiography (coronary MRA) is a developing approach to imaging the coronary arteries. Advantages of coronary MRA include avoidance of the intravenous iodinated contrast and ionizing radiation used in coronary CT angiography and conventional angiography. A disadvantage of coronary M...
Article

Creatine peak

Creatine is one of the compounds examined in MR spectroscopy. It resonates at 3.0 ppm chemical shift and is found in metabolically active tissues (brain, muscle, heart) where it is important in storage and transfer of energy. It tends to be maintained at a relatively constant level, and is predo...
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Cross-excitation artifact

Cross-excitation artifact is a type of MRI artifact and refers to loss of signal within a slice due to pre-excitation from RF pulse meant for an adjacent slice. The frequency profile of the RF pulse is imperfect; this means that during slice selection there is some degree of excitation of the a...
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CSF flow studies

CSF flow studies are performed using a variety of MRI techniques and are able to qualitatively assess and quantify pulsatile CSF flow. The most common technique used is time resolved 2D phase contrast MRI with velocity encoding.  Note, when referring to CSF flow in the setting on imaging we are...
Article

CT artifacts

CT artifacts are common and can occur for various reasons. Knowledge of these artifacts is important because they can mimic pathology (e.g. partial volume artefact) or can degrade image quality to non-diagnostic levels.  CT artifacts can be classified according to the underlying cause of the ar...
Article

CT cholangiography

CT cholangiography is a technique of imaging the biliary tree with the usage of hepatobiliary excreted contrast. It is very good at delineating biliary anatomy. Indications Second-line test (after ultrasound) when investigating for right upper quadrant pain, obstructive LFTs, etc. It can also ...
Article

CT dose index

CT dose index (CTDI) is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners. In the past CTDI100 (measured over a 100 mm long ionization chamber) and CTDIw (weighted average of dose across a single slice) were...
Article

CT enteroclysis

Computed tomographic (CT) enteroclysis refers to a hybrid technique that combines the methods of fluoroscopic intubation-infusion small-bowel examinations with that of abdominal CT 1. Indications CT enteroclysis is complementary to capsule endoscopy in the elective investigation of small-bowel...
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CT enterography

Computed tomographic (CT) enterography is a non-invasive technique for diagnosis of small bowel disorders. Advantages  evaluates the entire thickness of the bowel wall offers information about the surrounding mesentery, the mesenteric vasculature and the perienteric fat useful in the assessm...
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CT in practice

Computed tomography (CT) is the most commonly used cross sectional imaging tool.  This is a starting page for some general articles about CT: evolution of CT scanners CT protocol standardised reports review areas computed tomography (physics article) high resolution CT dual energy CT Se...
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CT scanner (evolution)

CT scanners were first introduced in 1971 with a single detector for brain study under the leadership of Godfrey Hounsfield, an electrical engineer at EMI (Electric and Musical Industries, ltd). Thereafter, it has undergone several changes with increase in number of detectors and decrease in the...
Article

CT stair-step artifact

The CT stair-step artifact is found in straight structures which are oriented obliquely with respect to movement of the table and appear around the edges of sagittal and coronal reformatted images when wide collimations and non-overlapping reconstruction intervals are used. Solution This can b...
Article

Decibel

The decibel (dB) is a unit that measures the relative difference between two sound intensities. The relationship is logarithmic: dB = 10 log (I2 / I1) dB = relative intensity of the sounds I1 = intensity of sound 1 I2 = intensity of sound 2 Informally, we use decibel as a unit of "loud...
Article

Detective quantum efficiency

Detective quantum efficiency (DQE) is one of the fundamental physical variables related to image quality in radiography and refers to the efficiency of a detector in converting incident x-ray energy into an image signal.  The words "quantum efficiency" have a precise meaning, because ...
Article

Deterministic effects

Deterministic effects describe a cause and effect relationship between radiation and some side-effects. They are also called non-stochastic effects to contrast their relationship with the chance-like stochastic effects, e.g. of cancer induction. Deterministic effects have a threshold below whic...
Article

Developer solution

Developer solution is used in dark room for developing (i.e. converting latent image to visible image) X-ray films used in conventional (screen film) radiography. Components developer: hydroquinone (for high contrast) + metal/phenidone (for low contrast) the developer itself gets oxidised and...
Article

Diamagnetism

Diamagnetism is the property of materials that have no intrinsic atomic magnetic moment, but when placed in a magnetic field weakly repel the field, resulting in a small negative magnetic susceptibility. Materials like water, copper, nitrogen, barium sulfate, and most tissues are diamagnetic. T...
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Diastolic pseudogating

Diastolic pseudogating appears as periodic bright and dark signal in arteries such as the aorta as one progresses through a series of images. Synchronization of the cardiac cycle and the pulse sequence results in high signal in the artery during diastole when blood is relatively stationary and l...
Article

Dielectric effect artifact

Dielectric effect artifact is an MRI artifact encountered most often on body MRI with 3 T units. Artifact At 3 T, the radiofrequency (RF) wavelength measures 234 cm in air, and the speed and wavelength of the RF field is shortened to ~26 cm within the body as a result of dielectric effects. Ho...
Article

Diffusion kurtosis imaging

Diffusion kurtosis imaging (DKI) is an advanced neuroimaging modality which is an extension of diffusion tensor imaging by estimating the kurtosis of water diffusion probability distribution function . It provides high order diffusion of water distribution  and analyses as well as quantifies the...
Article

Diffusion tensor imaging

Diffusion tensor imaging is an extension of diffusion weighted imaging (DWI) that allows data profiling based upon white matter tract orientation DWI is based on the measurement of brownian motion of water molecules. This motion is restricted by membranous boundaries. In white matter, diffusion...
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Diffusion weighted imaging

Diffusion weighted imaging (DWI) is a form of MR imaging based upon measuring the random Brownian motion of water molecules within a voxel of tissue. The relationship between histology and diffusion is complex, however generally densely cellular tissues or those with cellular swelling exhibit lo...
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Diffusion weighted MRI in acute stroke

Diffusion weighted imaging (DWI) is a commonly performed MRI sequence for evaluation of acute ischaemic stroke, and is sensitive in detection of small and early infarcts. Conventional (T1/T2) MRI sequences may not demonstrate an infarct for 6 hours, and small infarcts may be hard to appreciate o...
Article

Diffusion-tensor MRI imaging and fiber tractography

Diffusion-tensor imaging (DTI) is a MRI technique that uses anisotropic diffusion to estimate the axonal (white matter) organisation of the brain. Fiber tractography (FT) is a 3D reconstruction technique to access neural tracts using data collected by DTI. Within cerebral white matter, water mo...
Article

Digital radiography

Digital radiography is based on the use of discrete values in comparison to conventional radiography which uses analogue/continuous values. It removes the requirement of dark room procedures. Types computed radiography (CR) uses photostimulable phosphor plates in cassettes direct digital rad...
Article

Distance measurement

Ultrasound machines perform distance measurement to synthesise images from returning echoes. To generate images for an ultrasound scan, machines need to determine the distance of reflective interfaces from the transducer. Simply, the formula used is: distance = (speed x time)/2 Where: distanc...
Article

Dixon method

The Dixon method is an MRI sequence based on chemical shift and designed to achieve uniform fat suppression. It has been gaining popularity as it has some advantages over other fat suppression techniques, namely:  suppression of fat signal is more uniform and less affected by artifacts than man...
Article

Doppler shift

Doppler shift or Doppler effect is defined as the change in frequency of sound wave due to a reflector moving towards or away from an object, which in the case of ultrasound is the transducer. Doppler equation  F = 2fo(v/c)cos(Q) where: F is doppler frequency shift fo is transmitted frequen...
Article

Doppler waveforms

Doppler waveforms are often misinterpreted and/or overlooked. They can provide great deal of information if carefully understood. Radiographic features Ultrasound Doppler The three basic waveforms are 1,2: triphasic forward flow in systole reverse flow in late systole / early diastole fo...
Article

Double inversion recovery sequence

Double inversion recovery (DIR) is a MRI pulse sequence which suppresses signal from the CSF as well as from the white matter and hence enhances any inflammatory lesion. To obtain such sequence in 3T MRI scanner, two inversion times are required. TI1 which is used for suppression of CSF and usu...

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