Articles

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

511 results found
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Radiation protection

Radiation protection is based on the three fundamental principles of justification of exposure, keeping doses (of ionizing radiation) as low as reasonably achievable (optimization) and the application of dose limits. The International Commission on Radiological Protection (ICRP) is responsible f...
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Radiofrequency coils

Radiofrequency coils (RF coils) are the "antennae" of the MRI system, broadcasting the RF signal to the patient and/or receiving the return signal. RF coils can be receive-only, in which case the body coil is used as a transmitter; or transmit and receive (transceiver). Surface coils are the si...
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Radiofrequency receiver

Radiofrequency coils are the radiofrequency receivers (as well as sometimes the transmitters) of the electromagnetic signal used in MRI. Radiofrequency coils can be either receive-only, or both receivers and transmitters of the radiofrequency signal. The receiver coils detect the electromagnetic...
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Radiofrequency shielding

Radiofrequency or RF shielding is a technique for creating electromagnetic (EM) isolation, which is critical during the acquisition of MR images. RF shielding serves to both prevent external EM interference from contaminating the target tissue signal, and to ensure that signals generated by MR i...
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Radiofrequency transmitter

The radiofrequency (RF) transmitter is the generator of the radiofrequency current which is delivered to the transmitting coil. This creates a signal which is used to excite protons in the imaging field. Radiofrequency coils can be both transmitters and receivers of the radiofrequency signal or ...
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Radiograph (terminology)

Radiograph (or plain radiograph although the word 'plain' is strictly superfluous) is the radiologist's preferred term for the static image generated following the passage of x-rays through the patient. Non-imaging clinicians and the lay population generally use the term "x-ray" to refer to a ra...
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Radioisotope spills

Radioisotope spills are classified as major or minor Examples of major spills include quantities equal to or larger than: 1mCi I-131 100 mCi Tc-99m or Tl-201 10 mCi Ga-67, In-111, or I-123
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Radiological image artifact

Most artifacts in radiology refer to something seen on an image that are not present in reality but appear due to a quirk of the modality itself. Artifact is also used to describe findings that are due to things outside the patient that may obscure or distort the image, e.g. clothing, external c...
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Radiopharmaceuticals

Radiopharmaceuticals are drugs that are bound to radioactive substances.  The pharmaceutically active portion determines the activity that will be measured and the radioactive portion emits radiation that can be measured by the scanner. A number of radiopharmaceuticals are used in human imaging...
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RadLex

RadLex is a lexicon of radiological information that has been produced by the Radiological Society of North America (RSNA).  It is an ontological system whose principle aim is to develop a useful vocabulary for radiologists.  In the words of the RSNA "As images, imaging reports, and medical re...
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Raymond V Damadian

Raymond V Damadian (1936-fl.2020) is a pioneer in the field of MRI and inventor of one of the first MRI scanners. Early life Raymond Vahan Damadian was born on 16 March 1936 in New York City and was a child prodigy. He studied violin at the Juilliard School of music for eight years, did his fi...
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Receiver operating characteristic curve

The receiver operating characteristic (ROC) curve is a statistical relationship used frequently in radiology, particularly with regards to limits of detection and screening. The curves on the graph demonstrate the inherent trade-off between sensitivity and specificity: y-axis: sensitivity x-a...
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Rectal cancer protocol (MRI)

MRI protocol for rectal cancer is a group of MRI sequences put together for imaging staging of primary tumors of the rectum.  Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and r...
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Reflection

Reflection of a sound wave occurs when the wave passes between two tissues of different acoustic speeds and a fraction of the wave 'bounces' back. This forms one of the major principles of ultrasound imaging as the ultrasound probe detects these reflected waves to form the desired image. Angle ...
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Refraction

Refraction of a sound wave occurs if it travels between tissues with different propagation speeds. As the incident pulse or returning echo strikes an interface of different density or elasticity and therefore a different propagation speed, the direction of the wave changes according to Snell’s l...
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Refraction artifact

Refraction artifact can occur when a transmitted ultrasound pulse strikes an interface at a non-perpendicular angle. The difference in propagation speeds between the two tissues can cause refraction to occur. Should the refracted incident sound wave strike a reflector and cause an echo to return...
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Relaxation

Relaxation is the process in which spins release the energy received from a radiofrequency pulse. MRI signal is influenced, among other factors, by different types of relaxation: T1 relaxation (spin-lattice or longitudinal relaxation) T2 relaxation (spin-spin or transverse relaxation) T2* rel...
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Relaxometry

Relaxometry is measurement of relaxation times from MR images. T1, T2 and T2* can be estimated using the appropriate pulse sequence and parameters. T2 relaxometry has found useful in quantitating signal changes on T2-weighted images as in evaluating mesial temporal sclerosis. Details T2 relaxo...
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Rem (unit)

The rem (an acronym for roentgen equivalent man) was the cgs unit of effective dose and was officially replaced by the sievert many years ago.  One rem was a large quantity of radiation, and therefore for practical day to day use the millirem (mrem), representing one-thousandth of a rem, was us...
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Renal intraparenchymal acceleration time

Renal intraparenchymal acceleration time is a parameter used in assessing renal arterial stenosis on Doppler ultrasound. It is the time taken from the start of systole to peak systole.  normal range: a value of usually < 0.07 seconds is taken as being within normal limits 1.
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Repetition time

The repetition time (TR) is the time from the application of an excitation pulse to the application of the next pulse. It determines how much longitudinal magnetization recovers between each pulse. It is measured in milliseconds.
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Resonance and radiofrequency

Protons in a magnetic field have a microscopic magnetization and act like tiny toy tops that wobble as they spin.The rate of the wobbling or precession is the resonance or Larmor frequency. In the magnetic field of an MRI scanner at room temperature, there is approximately the same number of pro...
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Reticuloendothelial MRI contrast agents

Reticuloendothelial MRI contrast agents can best be discussed in terms of those used for liver and spleen imaging and those for lymph node imaging. Liver and spleen The use of Gd-DTPA with routine imaging sequences of the liver is unsatisfactory. Particulate contrast agents targeted to the ret...
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Reverberation artifact

Reverberation artifact occurs when an ultrasound beam encounters two strong parallel reflectors. When the ultrasound beam reflects back and forth between the reflectors ("reverberates"), the ultrasound transducer interprets the sound waves returning as deeper structures since it took longer for...
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RF overflow artifact

RF overflow artefact cause a nonuniform, washed-out appearance to an image. This artifact occurs when the signal received by the scanner from the patient is too intense to be accurately digitized by the analog-to-digital converter. Autoprescanning usually adjusts the receiver gain to prevent thi...
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Ring artifact

Ring artifacts are a CT phenomenon that occur due to miscalibration or failure of one or more detector elements in a CT scanner. Less often it can also be caused by insufficient radiation dose, or contrast material contamination of the detector cover 2. They occur close to the isocenter of the s...
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Ring down artifact

Ring down artifact is a special type of resonance artifact. Its appearance is similar to the ladder-like reverberation of comet-tail artifact, but it is produced by a completely different mechanism. The artifact is only associated with gas bubbles, and occurs when an ultrasound pulse encounters...
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Roentgen (unit)

The roentgen (symbol R) or röntgen (in German) is a legacy unit to measure radiation exposure. It was defined as the quantity of x-rays that produce 2.580 × 10-4 coulombs of charge collected per unit mass (kilograms) of air at standard temperature and pressure (STP): 1 R = 0.000258 coulombs per ...
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Rutherford (unit)

The rutherford (symbol Rd) is an obsolete unit of radioactivity which was superseded by the introduction of the becquerel in 1975. One rutherford was equivalent to 1,000,000 nuclear disintegrations per second, or alternatively one becquerel equated to one microrutherford (μRd).  Terminology As...
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Samarium-153

Samarium-153 (Sm-153) is a radioisotope used in metabolic radiotherapy for the treatment of pain from bone metastases. It is produced in nuclear reactors, by neutron irradiation of samarium-152 (Sm-152 Sm2O3). Samarium-153 decays by emitting both beta minus particles and gamma photons with a ch...
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Saturation recovery sequences

Saturation recovery (SR) sequences are rarely used for imaging now. Their primary use at this time is as a technique to measure T1 times more quickly than an inversion recovery pulse sequence. Saturation recovery sequences consist of multiple 90 degree RF pulses at relatively short repetition ti...
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Scattering (ultrasound)

Scattering occurs when a sound wave strikes a structure with a different acoustic impedance to the surrounding tissue and which is smaller than the wavelength of the incident sound wave. Such structures are known as “diffuse reflectors,” with examples being red blood cells and non-smooth surface...
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SeHCAT

SeHCAT™ (23-seleno-25-homo-tauro-cholic acid or tauroselcholic acid) is a radiopharmaceutical used in the investigation of bile salt malabsorption, which is a cause of chronic diarrhea.  Characteristics physical half-life: 118 days Uses, dosage and timings A capsule containing SeHCAT is inge...
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Sensitivity

Sensitivity of a test/investigation is defined as the ability of the test to identify true positive cases of the disease under question. Calculation Sensitivity = true positives detected by test / total cases of the disease where, total cases with the disease = true positive + false negative
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Sensitivity and specificity

Sensitivity and specificity are fundamental characteristics of diagnostic imaging tests. The two characteristics derive from a 2x2 box of basic, mutually exclusive outcomes from a diagnostic test (Figure 1): true positive (TP): an imaging test is positive and the patient has the disease/condit...
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Sensitivity and specificity of multiple tests

Sensitivity and specificity of multiple tests is a common statistical problem in radiology because frequently two tests (A and B) with different sensitivities and specificities are combined to diagnose a particular disease or condition. These two tests can be interpreted in an "and" or an "or" ...
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Shading artifact

Shading artifact in MRI refers to loss of signal intensity in one part of the image, leading to dark shading in this portion of the image. Causes uneven excitation of nuclei within the field; due to RF pulses applied at flip angles other than 90 and 180 degrees abnormal loading of coil or cou...
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Shear wave elastography

Shear wave elastography is a developing variation of ultrasound imaging. The concept is similar to strain elastography, but instead of using transducer pressure to compare a shift in an ultrasound A-line (thereby measuring changes in strain), a higher intensity pulse is transmitted to produce s...
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Short tau inversion recovery

Short tau inversion recovery (STIR), also known as short TI inversion recovery, is a fat suppression technique with an inversion time TI = ln(2)·T1fat,where the signal of fat is zero. This equates to approximately 140 ms at 1.5 T. To distinguish two tissue components with this technique, their ...
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Side lobe artifact

Side lobe artifacts occur where side lobes reflect sound from strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam. Ultrasound transducer crystals expand and contract to produce primary ultrasound beams in th...
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Sievert (SI unit)

The sievert (symbol Sv) is the SI unit of dose equivalent and is dimensionally-equivalent to one joule per kilogram. The sievert represents the stochastic effects of ionizing radiation as adjusted by a tissue weighting factor to account for differing responses of different human tissues to ioniz...
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Signal-to-noise ratio

Signal-to-noise ratio (SNR) is a generic term which, in radiology, is a measure of true signal (i.e. reflecting actual anatomy) to noise (e.g. random quantum mottle). A lower signal-to-noise ratio generally results in a grainy appearance to images.  Each modality has its own source(s) of noise ...
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Size specific dose estimate

Size specific dose estimate (SSDE) measured in mGy, is a method of estimating CT radiation dose that takes a patient's size into account.  CTDIvol and DLP are common methods to estimate a patient's radiation exposure from a CT procedure. The exposures are the same regardless of patient size, bu...
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Slew rate

Slew rate refers to the speed at which a gradient can be turned on and off, and is defined as the maximum gradient strength of the gradient divided by the rise time.  MR imaging is a product of magnetic field gradients which are created by magnetic gradient coils. The quality and performance of...
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Space charge

Space charge refers to the collection of electrons which are emitted from the metal surface, after the application of tube current, at a short distance away from the metal surface. These electrons collect and form a cloud of negative charge around the metal surface. This space charge repels and...
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Spatial resolution

Spatial resolution in radiology refers to the ability of the imaging modality to differentiate two objects. Low spatial resolution techniques will be unable to differentiate between two objects that are relatively close together. See also spatial resolution (CT) spatial resolution (MRI) axia...
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Spatial resolution (CT)

Spatial resolution in CT is the ability to distinguish between object or structures that differ in density. A high spatial resolution is important for one to discriminate between structures that are located within a small proximity to each other.  Factors affecting CT spatial resolution field...
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Spatial resolution MRI

Spatial resolution determines how "sharp" the image looks. Low resolution will give either fuzzy edges, or a pixelly appearance to the image. In MRI, spatial resolution is defined by the size of the imaging voxels. Since voxels are three dimensional rectangular solids, the resolution is frequen...
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Specific absorption rate

Specific absorption rate (SAR) is the rate that electromagnetic energy in the radiofrequency is absorbed by tissues during MR image acquisition represented as watts per kilogram (W/kg).  Both the International Electrotechnical Commission and the USA's Food and Drug Administration limit the amoun...
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Specificity

Specificity of a test/investigation is the ability of a test to be correctly negative (true negative) in persons without the disease in question. Calculation Specificity = true negatives detected by test / total cases without the disease where, total cases without the disease = true negative ...
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Speckle artifact

Speckle artifact may be encountered in ultrasound. It is caused by the scattering of waves from the surface of small structures within a certain tissue. The artifact produces a textured appearance. See also ultrasound artifacts
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Speckle tracking echocardiography

Speckle tracking echocardiography describes the semi-automated analysis of grey scale (B-mode) echocardiographic studies in which the spatial translocation of derived functional units (speckles) allows quantitative analysis of myocardial function. Speckle tracking constitutes a subset of deform...
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Spectral Doppler (ultrasound)

Utilizing automated Fourier analysis to convert returning sound waves into a series of individual frequencies, spectral Doppler refers to ultrasound modalities which yield graphical representations of flow velocity over time.  Terminology The frequency of the sound waves returned to an ultraso...
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Speed displacement artifact

Speed displacement artifact,  also known as propagation velocity artifact, is a gray scale ultrasound finding that can be identified as an area of focal discontinuity and displacement of an echo deeper than that its actual position in an imaged structure. Depth determination by an ultrasound mac...
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Spin echo sequences

Spin-echo pulse sequences are one of the earliest developed and still widely used (in the form of fast spin-echo) of all MRI pulse sequences. The pulse sequence timing can be adjusted to give T1-weighted, proton density, and T2-weighted images. Dual echo and multiecho sequences can be used to ob...
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Spiral pulse sequences

Spiral scanning in MRI is unlike spiral scanning in CT where the x-ray tube is continuously rotating and data is continuously being acquired. In MRI the word "spiral" refers to the pattern of sampling k-space. In conventional imaging sequences including spin echo and gradient echo and in fast im...
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Spoiled gradient echo MRI

Spoiled gradient echo MRI (also known as incoherent gradient echo) is an MRI technique which destroys residual transverse magnetization at the end of each excitation cycle.  Vendor-specific examples T1 FFE (Philips) SPGR (GE) FLASH (Siemens)
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Standard triangle language

Standard triangle language (STL), is one of many file formats used for 3D printing. For biomedical 3D printing from DICOM files, DICOM files must undergo image post-processing including segmentation and then be turned into an appropriate file format for printing. Currently (2019) STL is the most...
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Standard uptake value

The standard uptake value (SUV), also known as standardized uptake value, is a simple way of determining activity in PET imaging, most commonly used in fluorodeoxyglucose (FDG) imaging. It is also known as the dose uptake ratio (DUR). As the name suggests it is a mathematically derived ratio of ...
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Steady-state free precession MRI

Steady-state free precession MRI (SSFP) is a type of gradient echo MRI pulse sequence in which a steady, residual transverse magnetization (Mxy) is maintained between successive cycles. The sequence is noted for its superiority in dynamic/cine assessment of cardiac function. Discussion To unde...
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Step-and-shoot tomosynthesis (breast)

Step-and-shoot is a technology of image acquisition in digital breast tomosynthesis characterized by stop scanning at every single angle during images acquisition. Step-and-shoot technology allows advantages in microcalcifications conspicuity, spatial resolution, signal-to-noise Ratio improveme...
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Stochastic effects

Stochastic effects occur by chance and can be compared to deterministic effects which result in a direct effect. Cancer induction and radiation induced hereditary effects are the two main examples of stochastic effects. Models Cancer induction as a result of exposure to radiation is thought by...
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Strain elastography

Strain elastography (also known as tissue strain elastography/static elastography/compression elastography) is a developing form of ultrasound that assesses tissues' macroscopic structure through the strain modulus. This is different from normal B-mode grayscale ultrasound which characterizes a ...
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Structure of the atom

The structure of the atom is key to the majority of the techniques used in radiology, and a general understanding of atomic structure is worthwhile. The following is a simplified overview of the structure of the atom. Nucleus The composition of an atom is - in classical physics - principally ...
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Superb microvascular imaging (ultrasound)

Superb microvascular imaging (SMI) is a recently developed ultrasound imaging technique that aims to visualize low velocity and small diameter blood vessel flow. Unlike conventional color and power Doppler imaging, SMI can suppress noise caused by motion artifacts without removing the weak signa...
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Superparamagnetic iron oxide

Superparamagnetic iron oxides (SPIO) are a class of MR contrast agents composed of nanoparticles of iron oxide crystals coated in carbohydrates. They are used to image vasculature and the liver via shortening T1 and T2/T2* relaxation times. The main agent currently used is ferumoxytol (Feraheme...
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Superparamagnetism

Superparamagnetic materials consist of individual domains of elements that have ferromagnetic properties in bulk. Their magnetic susceptibility is between that of ferromagnetic and paramagnetic materials.  The figure illustrates the effect of a superparamagnetic material (grey circle) on the ma...
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Surface coil

Surface coils are a type of receive-only radiofrequency coil used in MRI to receive the radiofrequency signal (transmitted by the body coil). Surface coils are small and are shaped so that they can be placed near the part of anatomy being imaged. By their nature, surface coils have good signal-t...
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Susceptibility weighted imaging

Susceptibility weighted imaging (SWI) is an MRI sequence that is particularly sensitive to compounds which distort the local magnetic field and as such make it useful in detecting blood products, calcium, etc. Physics SWI is a 3D high-spatial-resolution fully velocity corrected gradient-echo M...
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Synthetic MRI

Synthetic MRI is a technique that generates contrast weighted images based on measurements of tissue properties from a single acquisition. Basic principles With synthetic MRI, different contrast weighted images can be obtained based on quantifications of a single multiple dynamic and multiple...
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T1 rho

T1 rho, also known as T1ρ or "spin lock" ('ρ' is the symbol for the Greek letter rho), is an MRI sequence that is being developed for use in musculoskeletal imaging. At the moment it is mostly investigational and does not yet have widespread clinical use. The "rho" in the sequence name refers t...
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T1 values (1.5 T)

T1 values are a few hundred milliseconds (ms) for most tissues examined. The following are approximate T1 values (ms) of several tissues for B0 = 1.5 T fat = 260 liver = 500 muscle = 870 brain white matter = 780 brain grey matter = 920 CSF = 2500 Tissues that will have high signal in T1-...
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T1 weighted image

T1 weighted image (also referred to as T1WI or the "spin-lattice" relaxation time) is one of the basic pulse sequences in MRI and demonstrates differences in the T1 relaxation times of tissues. A T1WI relies upon the longitudinal relaxation of a tissue's net magnetization vector (NMV). Basicall...
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T2 relaxation

T2 relaxation, also known as spin-spin relaxation or transverse relaxation, refers to the progressive dephasing of spinning dipoles resulting in decay in the magnetization in the transverse plane (Mxy). Following a radiofrequency pulse, this form of relaxation occurs with the time constant T2. T...
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T2* relaxation

T2* decay refers to an exponential decrease in Mxy  (i.e. signal strength) following the initial excitation pulse as a function of time constant T2*. A picture of the signal or free induction decay (FID) is shown on the right, occurring immediately after a 90o RF excitation pulse in a liquid pha...
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T2 shine through

T2 shine-through refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which 'shines through' to the DWI image. T2 shine through occurs because of long T2 decay time in some normal tissue. This is most often seen with subacute infarctions due ...
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T2 washout

T2 washout is a phenomenon encountered on diffusion weighted imaging (DWI) which results in DWI images (e.g. B = 1000) appearing normal despite abnormal ADC maps.  For the phenomenon to occur a particular combination of ADC and T2 signal intensity is required.  increased T2 signal facilitated...
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T2 weighted image

T2 weighted image (T2WI) is one of the basic pulse sequences in MRI. The sequence weighting highlights differences in the T2 relaxation time of tissues. Summary repetition time (TR): long echo time (TE): long flip angle: less important than with T1 weighting fat: intermediate-bright fluid:...
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Tc-99m HMPAO labeled WBC

Tc-99m HMPAO (hexamethylpropyleneamine oxime) labeled WBC is one of the technetium radiopharmaceuticals used in WBC imaging. There are three potential radiochemical impurities in the 99mTc-HMPAO: a hydrophilic secondary complex, the free pertechnetate and the reduced 99mTc-hydrolyzate. 1The min...
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Tc-99m labeled RBC

Tc-99m labeled RBC is one of the technetium radiopharmaceuticals used in the assessment of GI bleeding. Characteristics photon energy: 140 KeV physical half life: 6 hours biological half life:  normal distribution: heart, vessels, spleen miscellaneous facts: threshold for detection is 0.0...
Article

Tc-99m MAG3

Tc-99m MAG3 (mercaptoacetyltriglycine) is one of the technetium radiopharmaceuticals used in renal imaging. Characteristics photon energy: 140 KeV physical half life: 6 hours biological half life: 4 hours normal distribution: kidneys (100%) pharmacokinetics: uptake by tubular secretion (9...
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Tc-99m pertechnetate

Tc-99m pertechnetate (Na+ 99mTc O4-) is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach. Technetium (99mTc) has eight oxidation states 6, from -1 to +7; specifically, the oxidation state of technetium in the pertechnetate anion (99mTcO4-) is +7....
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Tc-99m sulfur colloid

Technetium-99m sulfur colloid is one of the technetium radiopharmaceuticals. Characteristics photon energy: 140 keV physical half-life: 6 hours biological half-life normal distribution: liver: 85% spleen: 10% bone marrow: 5% excretion: hepatic target organ: liver, spleen pharmacokinet...
Article

Technetium 99m-methyl diphosphonate

Technetium 99m-methyl diphosphonate (99mTc MDP) is a radiotracer used in nuclear medicine especially for bone scans. Any disease process which results in extracellular fluid expansion will lead to accumulation of this tracer. Radionuclide profile photon energy: 140 keV physical half life: 6 h...
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Temporal resolution

Temporal resolution relates to the duration of time for acquisition of a single frame of a dynamic process, i.e., cine imaging. Discussion The concept of temporal resolution is fundamental to cardiac CT and MRI, in which a rapidly beating heart is imaged over the order of milliseconds into mul...
Article

Tesla (SI unit)

The tesla (symbol T) is the derived SI unit of magnetic flux density, which represents the strength of a magnetic field. One tesla represents one weber per square meter. The equivalent, and superseded, cgs unit is the gauss (G); one tesla equals exactly 10,000 gauss. Most current medical magnet...
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Texture analysis

Texture analysis is a non-invasive, mathematical method assessing the spatial heterogeneity of regions of interest in medical imaging, its primary application is in the assessment of tumors. Although not a new topic of research, the past decade has seen a significant resurgence of texture analys...
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Thallium-201 chloride

Thallium-201 chloride (TlCl) is a radiopharmaceutical used primarily in cardiac imaging. Thallium-201 is an analog of potassium; it is produced in cyclotron by bombarding thallium-203 with protons. Characteristics thallium is a monovalent cation photon energy: 80 keV physical half life: 73 h...
Article

Thermal index

The thermal index (TI) is intended as a measure of an ultrasound beam's thermal bioeffects. It is often displayed on ultrasound screens (along with the mechanical index). Absorption of sound waves may cause heating in tissue. The thermal index depends on: a measure of time-averaged acoustic po...
Article

Thermionic emission

Thermionic emission is the emission of electrons from a heated metal (cathode). This principle was first used in the Coolidge tube and then later in the modern day x-ray tubes. Before the discovery of the principle, gas tubes were used for x-ray production. The cathode has its filament circuit ...
Article

Thermoluminescent dosimeter

Thermoluminescent dosimeter (TLD) is a passive radiation detection device that is used for personal dose monitoring or to measure patient dose.  Parts plastic holder nickel-coated aluminum card with TLD discs the discs are made of a thermoluminescent material, commonly calcium sulphate doped...
Article

Thomas Edison

Thomas Edison (1847-1931) was a prolific inventor, considered by many to be the greatest inventor in American history. Edison holds over one thousand US patents; however, this article will focus on his work on fluoroscopy.  Early life and career Thomas Alva Edison was born on 11 February 1897 ...
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Thorotrast

Thorotrast is a suspension of radioactive thorium dioxide first produced in Germany in 1928 and used as a contrast agent until the 1950s. Its principal use was for cerebral angiography: 90% of the estimated 50,000-100,000 patients treated received it for this purpose. Umbrathor was another thori...

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