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.

393 results found
Article

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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Lead apron

Lead aprons are one of the key parts of personal radiation protection equipment along with lead gloves, lead glasses, and thyroid shields. In medical imaging, there are two main types 1: 0.25 mm lead equivalence weighs 1-5 kg ("lightweight apron") attenuates 75% of the x-ray beam at 5...
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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 coefficent (µ) is a constant that describes the the fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material. Its complement is the transmitted portion of the beam. It is expressed numerically in units of cm-1. Calculating µ The intens...
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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...
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Longitudinal and transverse magnetisation

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

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...
Article

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...
Article

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...
Article

Magnetic field gradient

Signal localisation 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 resonance neurography

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

Magnetic shimming refers to the process of reducing magnetic field inhomogeneities. It is an important aspect of optimising 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 magnetised when placed in an external magnetic field. Magnetic susceptibility is rela...
Article

Magnetic susceptibility artifact

Magnetic susceptibility artifacts (or just susceptibility artifact) 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 ...
Article

Magnetisation transfer

Magnetisation 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...
Article

Magnets (types)

Magnets used for MRI are of three types: permanent, resistive and superconductive. Permanent MRI magnets use permanently magnetised 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

Maximum intensity projection (MIP)

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 capitalised, but when shortened to its symbol it is capitalised. 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 ischaemic stroke diagnosis and management, and MR p...
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...
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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 than the agitated saline contrast agent often used in echocardiographic studies. Microbubbles consist of a gas surrounded by a lipid, lipopolymer, or polymer shell. They ra...
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, its consists of projecting the voxel with the ...
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. ...
Article

Modulation transfer function

The modulation transfer function (MTF) is the spatial frequency response of an imaging system or a component. It is the contrast at a given spatial frequency relative to low frequencies. On the radiogram, objects having different sizes and opacity are displayed with different gray-scale values....
Article

Moiré fringes

Moiré fringes are an interference pattern most commonly seen when acquiring gradient echo images using the body coil. Because of lack of perfect homogeneity of the main magnetic field from one side of the body to the other, aliasing of one side of the body to the other results in superimpositio...
Article

Molecular tumbling rate effects on T1 and T2

The average rate at which molecules tumble (and therefore T1 and T2 time) is related to the molecular size. Small molecules (e.g. water/CSF) have a broad distribution of motional frequencies with poor matching with the Larmor frequency and therefore have long T1 values. Medium sized molecules (e...
Article

Motion artifact

Motion artifact is a patient-based artifact that occurs with voluntary or involuntary patient movement during image acquisition. Misregistration artifacts, which appear as blurring, streaking, or shading, are caused by patient movement during a CT scan.  Blurring also occurs with patient moveme...
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MR angiography

MR angiography (MRA) is an alternative to conventional angiography and CT angiography, eliminating the need for iodinated contrast media and ionising radiation. It has evolved into several techniques with different advantages and applications: contrast enhanced MR angiography non-contrast enha...
Article

MR enterography

MR enterography is a non-invasive technique for diagnosis of small bowel disorders. Indications The most common indication is to evaluate patients with Crohn disease (CD). Other less common indications would include coeliac disease, postoperative of adhesions, radiation enteritis, scleroderma,...
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MR fingerprinting

MR fingerprinting (MRF) is a relatively recent approach to the acquisition and evaluation of MRI data aimed at generating quantitative multiparametric data from a single acquisition.  The underlying process is acquiring data in a pseudorandom manner resulting in a unique pattern of signal evolu...
Article

MRI artifacts

MRI artifacts are numerous and give an insight into the physics behind each sequence. Some artifacts affect the quality of the MRI exam while others do not affect the diagnostic quality but may be confused with pathology. When encountering an unfamiliar artifact, it is useful to systematically ...
Article

MRI contrast agents

MRI contrast agents have become an indispensable part of modern magnetic resonance imaging. Although MRI was initially hoped to provide a means of making definitive diagnoses non-invasively, it has been found that the addition of contrast agents in many cases improves sensitivity and/or specific...
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MRI contrast agent safety

Though considered safer than the frequently used iodinated contrast agents used in x-ray and CT studies, there are safety issues with MRI contrast agents as well. Paramagnetic metal ions suitable as MRI contrast agents are all potentially toxic when injected IV at or near doses needed for clinic...
Article

MRI electronics and data processing

As an introduction to the electronics and data processing of the MRI scanner, a schematic diagram has been provided (figure 1). Starting from the right hand side, we have the computer that directs all of the action in the MRI acquisition and acquires and processes the data. The computer tells t...
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MRI physics

The basic process The way MR images are generated is complicated and is much harder to understand than plain radiography, CT and ultrasound. It has strong underpinnings in physics which must be understood before any real sense of 'how it works' is gained.  What follows is a very abbreviated, '...
Article

MRI pulse sequence abbreviations

This article contains a list of commonly and less commonly used MRI pulse sequence abbreviations and their meaning. If available, an explanation is included in a separate article. spin echo sequences (SE) T1: T1 weighted IR: inversion recovery T2 : T2 weighted RARE: rapid acquisition with r...
Article

MRI pulse sequences

An MRI pulse sequence is a programmed set of changing magnetic gradients. Each sequence will have a number of parameters, and multiple sequences are grouped together into an MRI protocol.  Parameters A pulse sequence is generally defined by multiple parameters, including: time to echo (TE) t...
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MRI safety

MRI scanners, although free from potentially cancer-inducing ionising radiation found in plain radiography and CT, have a host of safety issues which must be taken very seriously. MRI safety can be divided into: main magnetic field varying magnetic (gradient) fields radiofrequency NOTE: This...
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MRI sequence parameters

Listed in the table below are the most common acquisition parameters for commonly used MRI pulse sequences (in msec). For a general introduction to these sequences please refer to MRI sequences (basic). The specific parameters for any given study varies from one manufacturer to another, and fr...
Article

MRI sequences (overview)

An MRI sequence is a number of radiofrequency pulses and gradients that result in a set of images with particular appearance. This article presents a simplified approach to recognising and thinking about common MRI sequences, but does not concern itself with the particulars of each sequences. F...
Article

MR liver iron quantification

MR liver iron quantification is a non-invasive means of measuring liver iron concentration, a key indicator in the management of patients with haemochromatosis (primary or secondary). Advantages Apart from being non-invasive, sampling occurs in a large cross-section of the liver, as opposed to...
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MR perfusion weighted imaging

Perfusion weighted imaging is a term used to denote a variety of MRI techniques able to give insights into the perfusion of tissues by blood.  There are three techniques in wide use to derive one or more perfusion values:  ​techniques ​dynamic susceptibility contrast (DSC) MR perfusion dynam...
Article

MR spectroscopy

MR spectroscopy (MRS) allows tissue to be interrogated for the presence and concentration of various metabolites. Grossman and Yousem said "If you need this to help you, go back to page 1; everything except Canavan has low NAA, high choline" 1. This is perhaps a little harsh, however it is fair ...
Article

Myoinositol peak

Myoinositol is one of the compounds images with MR spectroscopy (MRS) at both 1.5 T and 3 T and is seen to resonate at 3.5 ppm chemical shift (right of the choline peak).  Myoinositol is a precursor of both phosphatidylinositol (the major inositol-containing phospholipid) and of phosphatidylino...
Article

N-acetylaspartate (NAA) peak

N-acetylaspartate (NAA) is one of the more important compounds assessed on MR spectroscopy, and resonates at 2.0 ppm chemical shift.  NAA is the acetylated form of the amino acid, aspartate, which is found in high concentrations in neurons and is a marker of neuronal viability. It is therefore ...
Article

Negative enhancement integral

The negative enhancement integral in MR perfusion is used to calculate the relative cerebral blood volume (rCBV).  It represents the area described by the baseline and the signal loss due to passage of contrast bolus in tissue. 
Article

Noise

Noise is present in all electronic systems, and originates from a number of sources including electronic interference. It appears as irregular granular pattern in all images and degrades image information. It may be inapparent or render images non-diagnostic, depending on the severity. Radiogra...
Article

Non contrast enhanced MR angiography

Non contrast enhanced MR angiography is performed in several ways including: time of flight angiography phase contrast angiography three-dimensional (3D) electrocardiograph-triggered half-Fourier fast spin echo Generally, these techniques are time-consuming as compared with contrast enhanced...
Article

Nuclear magnetic resonance

Nuclear magentic resonance is a powerful technique which involves placing nuclei within an external magnetic field enabling thus them to undergo precession. The 'resonance' part of the names implies the fact that a second (usually perpendicular) radiofrequency pulse tuned to the precessional fre...
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Nuclear magnetisation

Nuclear magnetisation refers to the magnetic moment of an atomic nucleus. Magnetic resonance imaging (MRI) makes use of nuclear magnetic resonance (NMR). Some nuclei may have nuclear magnetisation depending on their nuclear charge distribution and the spin of its protons and neutrons. Nuclei wit...
Article

Octreotide scintigraphy

Octreotide scintigraphy uses 111In-labelled octreotide which is a somatostatin analog; it is also known as an OctreoscanTM, a brand name for 111In-labelled pentetreotide; pentetreotide is a DTPA-conjugated form of octreotide, originally manufactured by Mallinckrodt Nuclear Medicine LLC, which no...
Article

Ontology

Ontology is the study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology deals with questions concerning what entities exist or can be ...
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Pair production

Pair production (PP), like the photoelectric effect, results in the complete attenuation of the incident photon. Pair production can only occur if the incident photon energy is at least 1.022 MeV. As the photon interacts with the strong electric field around the nucleus it undergoes a change of ...
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Paramagnetism

Paramagnetic materials include oxygen and ions of various metals like Fe (iron), Mg (magnesium), and Gd (gadolinium). These ions have unpaired electrons, resulting in a positive magnetic susceptibility. The magnitude of this susceptibility is less than 0.1% of that of ferromagnetic materials. T...
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Partial volume averaging (CT artifact)

Partial volume artifact occurs when tissues of widely different absorption are encompassed on the same CT voxel producing a beam attenuation proportional to the average value of these tissues.  The last generation of CT scanners and its reduction in the volume of a voxel has substantially reduc...
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Paul Lauterbur

Paul C Lauterbur (1929-2007) is remembered as one of the co-developers of MRI, for which he was co-awarded the Nobel Prize for Medicine or Physiology in 2003, with Peter Mansfield. Early life Paul Christian Lauterbur was born on May 6th 1929 in Sidney, Ohio.In 1951 he graduated with a bachelor...
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PD weighted spin-echo images

Proton-density weight images are related to the number of nuclei in the area being imaged (number of hydrogen protons), as opposed to the magnetic characteristics of the hydrogen nuclei. They are produced from the first echo. PD weight images result when the contribution of both T1 and T2 contra...
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Pelvic cervical carcinoma protocol (MRI)

A dedicated pelvic MRI protocol is very useful for imaging assessment of cervical carcinoma. Although the FIGO is a clinical staging, the 2009 revised FIGO staging encourages the use of MRI to complement clinical staging. Preparation Imaging is optimally performed after three hours of fasting...
Article

Peter Mansfield

Sir Peter Mansfield (1933-2017) was an English physicist best known for his research into, and development of MRI, for which he was awarded the Nobel Prize in Physiology or Medicine in 2003 1. Early life Peter Mansfield was born on the 9th October, 1933 in Lambeth, London. His father, Sidney w...
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Phase contrast imaging

Phase contrast imaging is an MRI technique that can be used to visualise moving fluid. It is typically used for MR venography as a non-IV-contrast requiring technique.  Spins that are moving in the same direction as a magnetic field gradient develop a phase shift that is proportional to the vel...
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Phased array

A phased array ultrasound transducer is typically 2-3 cm long, consisting of 64-128 elements. It is a smaller assembly than a sequential array and can be either linear or curvilinear. A sector field of view is produced by all elements firing to create a single waveform. Small delays in element ...
Article

Phase-encoded motion artifact

Phase-encoded motion artifact is one of many MRI artifacts occurring as a result of tissue/fluid moving during the scan. It manifests as ghosting in the direction of phase-encoding, usually in the direction of the short axis of the image (i.e left to right on axial or coronal brains, and anterio...
Article

Photoelectric effect

Photoelectric effect, or photoelectric absorption (PEA) is a form of interaction of X-ray or gamma photon with the matter. A low energy photon interacts with the electron in the atom and removes it from its shell. The probability of this effect is maximum when the energy of the incident photon...
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Photon

A photon is, in simple terms, an elementary particle. It has a zero mass (rest mass) and travels at the speed of light. It is defined as stable with no electric charge and exhibits both wavelike and particle-like properties. For the sake of this article, a photon refers to an uncharged particle ...
Article

Photon starvation

Photon starvation is one source of streak artifact which may occurs in CT. It is seen in high attenuation areas, particularly behind metal implants. Because of high attenuation insufficient photons reach the detector surface resulting in characteristic artifact. During reconstruction process, th...
Article

Photostimulable phosphors

Photostimulable phosphors (PSP) are materials that store absorbed energy within excited electrons and release it in the form of light on exposure to laser energy. The process can be broken up as follows 1: an x-ray or gamma photon interacts with the PSP and releases high energy secondary elect...
Article

Physical principles of ultrasound

Medical ultrasound is based on the use of high-frequency sound to aid in the diagnosis and treatment of patients. Ultrasound frequencies range from 2 to approximately 15 MHz, although even higher frequencies may be used in some situations. The ultrasound beam originates from mechanical oscillat...
Article

Physics and imaging technology: CT

Knowledge of the physics and imaging technology involved in the production of CT scans is vitally important for medical imaging specialists. See also physics and imaging technology: x-ray physics and imaging technology: ultrasound physics and imaging technology: CT physics and imaging techn...
Article

Physics and imaging technology: MRI

Knowledge of the physics and imaging technology involved in the production of MRI scans is vitally important for medical imaging specialists. See also physics and imaging technology: x-ray physics and imaging technology: ultrasound physics and imaging technology: CT physics and imaging tech...
Article

Physics and imaging technology: nuclear medicine

Knowledge of the physics and imaging technology involved in the production of nuclear medicine scans is vitally important for medical imaging specialists. See also physics and imaging technology: x-ray physics and imaging technology: ultrasound physics and imaging technology: CT physics and...
Article

Physics and imaging technology: ultrasound

Knowledge of the physics and imaging technology involved in the production of ultrasound (US) scans is vitally important for medical imaging specialists. See also physics and imaging technology: x-ray physics and imaging technology: ultrasound physics and imaging technology: CT physics and ...
Article

Physics and imaging technology: x-ray

Knowledge of the physics and imaging technology involved in the production of X-rays is vitally important for medical imaging specialists. See also physics and imaging technology: X-ray physics and imaging technology: Ultrasound physics and imaging technology: CT physics and imaging technol...
Article

Physics curriculum

The physics curriculum is one of our curriculum articles and aims to be a collection of articles that represent core physics and imaging technology knowledge: physics and imaging technology: X-ray physics and imaging technology: Ultrasound physics and imaging technology: CT physics and imagi...
Article

Picture archiving and communication system

Picture archiving and communication system (PACS) is a modality of imaging technology which helps in image transmission from the site of image acquisition to multiple physically-disparate locations. This technology not only is economical (film-less department), but also convenient to access mult...
Article

Piezoelectric effect

The Piezoelectric effect converts kinetic or mechanical energy, due to crystal deformation, into electrical energy. This is how ultrasound transducers receive the sound waves. The same effect can be used in reverse – inverse piezoelectric effect – whereby the application of an electric field to...
Article

Pitch

Pitch (P) is a term used in helical CT. It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3. Single slice CT (SSCT) The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2....
Article

Pixel

A pixel (or pel or picture element) may refer to either the smallest discrete element of the physical display or to the smallest element of the image. Voxel is its 3-dimensional equivalent, as employed in CT and other cross-sectional imaging modalities. History and etymology The history of the...
Article

Portosystemic shunt ratio

The portosystemic shunt ratio is a measure performed using ultrasound to quantify the abnormal flow of portal venous blood that is shunted away from the hepatic sinusoidal circulation in the context of a congenital portosystemic shunt 1. Ultrasound The ratio is determined using the following e...
Article

Positron emission tomography

Positron emission tomography (PET) is a modern non-invasive imaging technique for quantification of radioactivity in vivo. It involves the intravenous injection of a positron-emitting radiopharmaceutical, waiting to allow for systemic distribution, and then scanning to detect and quantification ...
Article

Power Doppler

Power Doppler is a technique that uses the amplitude of Doppler signal to detect moving matter. Power Doppler: is independent of velocity and direction of flow, so there is no possibility of signal aliasing is independent of angle, allowing detection of smaller velocities than colour Doppler, ...
Article

Production of radioactive nuclei

Naturally occurring radioactive nuclei have a physical half life time of  about 108 to 1010 years which makes them unsuitable for use in medical imaging. Thus radioactive nuclei used in medical practice are artificially made. Production of these nuclei involve bombarding stable nuclei with prot...
Article

Propagation speed

The propagation speed of sound waves through tissue is an important element of ultrasound scans. Ultrasound machines assume sound waves travel at a speed of 1540 m/sec through tissue 1. In reality, the speed of sound is affected by the density and elasticity of the medium through which it is tr...
Article

Pseudoenhancement

Pseudoenhancement is an artifact in postcontrast CT evaluation of renal cysts. The distinction between cystic and solid lesions visualised in CT is primarily made on the basis of whether the lesion enhances with contrast administration. A renal cystic lesion is considered "enhancing" when there...

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