MRI Abbreviations
Here is a list of commercial-product MRI abbreviations. Error corrections are welcome!
Notes: This table is sortable by clicking on column headings; press shift if you want to sort by more than one column.
| Abbrev. | Meaning | Abbreviation seen used by | Comment | ||
|---|---|---|---|---|---|
| Philips | Siemens | GE | |||
| Abbrev. | Meaning | Philips | Siemens | GE | Comment |
| ACQ | ACQuisitions | ✔ | Number of repetitions of data acquisition, for signal averaging. Cf NSA, NEX | ||
| ADC | Apparent Diffusion Coefficient | ✔ | ✔ | ✔ | Apparent average diffusion-freedom of water molecules, implying organisation of tissue structure |
| ADC | Analogue to Digital Converter | ✔ | ✔ | ✔ | A device that converts a continuous signal to a series of discrete digital numbers |
| AFOV | Asymmetric Field-Of-View | ✔ | see RFOV | ||
| AIF | Arterial Input Function | ✔ | ✔ | ✔ | The characteristics (duration, variation of flow) of the injection of contrast agent bolus |
| AIT | Available Imaging Time | ✔ | Time between the end of a trigger delay and the beginning of the next trigger window, during which data acquisition may occur | ||
| AP | Anterior-to-Posterior | ✔ | ✔ | ✔ | Front to back direction, normal to the coronal plane |
| APA | Adaptive Phase Array | ✔ | Prescan function to test for ghosting from elements beyond the prescribed FOV, by assessing signal levels; where ghosting is found those elements are switched off during data acquisition | ||
| APS | Automatic PreScan | ✔ | Automatic adjustment of centre frequency, transmit gain and receiver gain | ||
| AR | Arrhythmia Rejection | ✔ | ✔ | Rejection and subsequent re-measuring of data acquired in R-R intervals deemed too short or too long | |
| ARC | Auto-calibrating Reconstruction for Cartesian sampling | ✔ | A self-calibrated parallel imaging method. GRAPPA-based with improved computational efficiency allowing higher reconstruction accuracy | ||
| ART | Acoustic Reduction Technology | ✔ | Pulse sequence modification technique for quieter pulse sequences | ||
| ART | Advanced Retrospective Technique | ✔ | Automatic motion correction. 3D data is shifted, rotated and interpolated to correspond to a reference data set | ||
| ASL | Arterial Spin Labelling | ✔ | ✔ | ✔ | Use of spins as an endogenous contrast agent by means of magnetic labeling (e.g. inversion). Two images are acquired; one with labeled inflowing arterial blood, and one without the labeling (control image). Control image minus labeled image = signal proportional to blood flow, used in the calculation of a perfusion estimate |
| ASSET | Array Spatial Sensitivity Encoding Technique | ✔ | Parallel imaging method, based on sensitivity encoding. Calculations to unwrap aliasing are made in the image domain | ||
| AVE | Advanced Viewing Environment | ✔ | Dedicated environment for image viewing and analysis on the MR scanner console | ||
| AW | Advantage Workstation | ✔ | Image reviewing and analysis computer / software | ||
| AWSO | Automated Water Suppression Optimisation | ✔ | ✔ | In spectrocopy: A prescan during which suppression parameters to be used in the following scan are optimised to maximise suppression of the water peak | |
| B0 | main, static magnetic field | ✔ | ✔ | ✔ | The always-on strong magnetic field, e.g. 1.5 Tesla, 3.0 Tesla |
| B1 | magnetic field oscillating at radio frequency (RF pulses: excitation, refocusing, etc) | ✔ | ✔ | ✔ | "RF pulse" and "B1 field" are synonymous. This field is referred to as a "pulse" simply because it is turned on only a brief moment |
| BAM | Bulk Acquisition Memory | ✔ | Data storage memory, before and during image reconstruction | ||
| BASING | BAnd Selective INversion with Gradient dephasing | ✔ | ✔ | ✔ | Frequency-selective suppression of water and/or fat. A bipolar gradient pair surrounds a frequency-selective 180° pulse; spins affected by the inversion are not rephased |
| BB | Black Blood | ✔ | A non-selective inversion followed by a slice-selective inversion. The slice to be imaged is therefore returned to equilibrium. Inverted blood flows into the slice and and an image is acquired at the null point of blood magnetisation recovery (no signal from blood: "black" blood) | ||
| BEAT | not an acronym (?) | ✔ | Data acquisition tool for cardiac MRI exams | ||
| BFFE | Balanced Fast Field Echo | ✔ | see bSSFP | ||
| BH | Breath Hold | ✔ | Temporary suspension of chest-wall movement, to prevent motion artefacts propagating across the phase encoding direction of an MR image. Particularly important in cardiac MRI | ||
| BLADE | not an acronym (?) | ✔ | see PROPELLER | ||
| BLAST | (k-t) Broad-use Linear Acquisition Speed-up Technique | ✔ | Method for acceleration of dynamic imaging. Low-resolution temporal training data are used to undo aliasing from a temporally undersampled (i.e. accelerated) acquisition, in cine or dynamic imaging. Acquisition of the training data may be interleaved or in a separate scan. Suitable for quasi-periodic motion. A multiple-element receiver coil is not required | ||
| BLISS | BiLateral Imaging in Sagittal view with SENSE | ✔ | 3D fat-suppressed spoiled turbo gradient-echo with parallel imaging, isotropic voxels, and SPAIR fat suppression, for use in DCE breast studies. 4D-BLISS denotes use of Keyhole and CENTRA for faster dynamic scan times. Cf VIBRANT, VIEWS | ||
| BOLD | Blood Oxygen Level Dependent [effect] | ✔ | ✔ | ✔ | Reduction of T2* in tissues due to build up of deoxyhaemoglobin (which is paramagnetic) during high oxygen demand. Resultant signal loss can be related to perfusion |
| BPM | (heart) Beats Per Minute | ✔ | ✔ | ✔ | Units of heart rate (cardiac frequency). E.g. 60 bpm |
| BRACE | BReast Acquisition CorrEction | ✔ | Offline, 3D correction for motion artifacts during dynamic imaging in MR mammography. A non-rigid body / warping registration | ||
| BRAVO | BRAin VOlume imaging | ✔ | Fast IR-prepared 3D gradient echo, high isotropic resolution | ||
| BREASE | BREAst Spectroscopy Exam | ✔ | A TE-averaged, single-voxel PRESS spectroscopy acquisition | ||
| bSSFP | balanced Steady State Free Precession | Generic name for balanced gradient echo sequence in which both SSFP-FID and SSFP-echo signals are measured. The integral of the gradient area in each TR interval must be the zero, or banding in images results from overlapping (and interference) of the SSFP-FID and SSFP-echo. Additional requirements include TR ≤ T2, and RF excitation pulses must be phase coherent (or sign-alternated). Contrast weighting is according to the ratio T2/T1. Also known as BFFE, FIESTA, TrueFISP | |||
| BTFE | Balanced Turbo Field Echo | ✔ | see bSSFP | ||
| B-TRANCE | Balanced TRiggered Angiography Non Contrast Enhanced | ✔ | Peripheral MRA using triggered 3D balanced turbo gradient echo, no contrast agent used | ||
| BW | BandWidth | ✔ | a range of frequencies, may be referring to transmit bandwidth (range of frequencies in RF pulse) or receiver bandwidth (range of frequencies deemed to be on-resonance in signal reception) | ||
| BWA | Body Wrap Around coil | ✔ | |||
| CARE | Combined Applications to Reduce Exposure | ✔ | Used in 'CARE Bolus' in CE-MRA, in which the centre of k-space is sampled as quickly as possible (3D elliptic-centric k-space ordering) immediately after contrast reaches a region of interest (monitored on rapid 2D scans) | ||
| CASL | Continuous Arterial Spin Labeling | ✔ | See ASL; Inversion of arterial blood occurs continuously. Can result in high energy deposition and SAR limitation may be a problem, and so long rectangular RF pulses can be substituted for a series of short hard RF pulses. The control image is acquired with a tag distal to the imaging slice (it's proximal in the tagged image) to have no tagging effect but to provide the same eddy currrent conditions and magnetisation transfer effects. Also known as steady-state ASL, or flow driven ASL | ||
| CCOMP | Cardiac COMPensation | ✔ | Use of ECG timing to adjust phase encoding to minimise pulsatile motion artfacts | ||
| CE | Contrast Enhanced | ✔ | ✔ | ✔ | Use of exogenous contrast agent. E.g. in CE-MRA, the T1 shortening effect of a bolus of contrast agent is used to provide contrast in flowing blood |
| CENTRA | Contrast ENhanced Timing Robust Angiography | ✔ | ky-kz space is divided into a central and a peripheral sector. A random profile order is used in the central sector first, to coincide with contrast arrival, followed by a low-high profile order in the peripheral sector. Data from the peripheral sector is copied back to dynamics in which only the central sector was acquired | ||
| CF | Cardiac Frequency, in beats/minute | ✔ | Heart rate. See also BPM | ||
| CHARM | CHunk Acquisition and Reconstruction Method | ✔ | A 3D inflow technique for MRA to see small/tortuous vessels. The 3D volume is divided into overlapping sub-volumes (or chunks), which are temporally interleaved for acquisition. The borders of the chunks are merged during reconstruction into one total volume | ||
| CHESS | CHEmical Shift Selective pulses | ✔ | ✔ | ✔ | RF pulses tailored to excite protons in a particular resonant frequency range. This range can be narrowed so that the RF pulse affects only water, or only fat. This works better at higher field strengths where these resonant frequencies are more separated. Good magnet (B0) homogeneity is required to make this frequency-selective excitation effective, and so techniques based on frequency-selective excitation are more effective over smaller fields-of-view |
| CIET | Clinical Image Extraction Tool | ✔ | Tool on the MR console, which creates a directory from which a remote manufacturer-engineer may pull images for analysis. Notes may be added by the user | ||
| CISS | Constructive Interference in Steady State | ✔ | A technique generically known as multi-acquisition SSFP, used to suppress banding artefact at the cost of doubling scan time. Two sequential acquisitions, one with sign alternation of RF excitation pulses and one without; band locations are shifted between the images by one-half of the period of the banding and so a maximum-intensity combination of the images removes the banding. Also known as FIESTA-C | ||
| CL | CLassic fat suppression | ✔ | Fat suppression by centering on the water peak. See CHESS | ||
| CLEAR | Constant LEvel AppeaRance | ✔ | Homogeneity correction using coil sensitivity maps acquired in a reference scan. Cf PURE (or on Siemens, 'Prescan Normalize') | ||
| CLIQ | Clinical Image Quality | ✔ | |||
| CMSMP | Cycled MultiSlice MultiPhase | ✔ | |||
| CNR | Contrast-to-noise ratio | ✔ | ✔ | ✔ | The difference between the signal between two (selected) tissues in an image, divided by the noise in the image. Important for clinical utility |
| CNS | Central nervous system | ✔ | ✔ | ✔ | The central nervous system (CNS) is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the body. It contains the majority of the nervous system and consists of the brain and the spinal cord |
| COSMIC | Coherent Oscillatory State acquisition for the Manipulation of Imaging Contrast | ✔ | bSSFP-based sequence, with modified elliptic-centric k-space filling, and oscillatory flip angle sweeps before and after data acquisition to move in and out of the steady state quickly to allow T1 recovery periods. Provides mixed (T2/T1)-weighted and T2-weighted contrast | ||
| CP | Circularly Polarized | ✔ | ✔ | Circularly polarized light consists of two perpendicular electromagnetic plane waves of equal amplitude and 90° difference in phase. To illustrate: Hold a piece of string. Move the end of the string in a circle. The resulting wave is said to be circularly polarized. Each bit of the string moves in a transverse circle, but the wave still moves down the string | |
| CR | Corrected Real | ✔ | Image created from the real part of the complex image data (Re, Im), corrected for phase changes. T1 contrast is increased using IR, if the sign of the (recovering) longitudinal magnetisation can be preserved after the excitation pulse. However, due to a variety of factors, as soon as the excitation pulse rotates longitudinal magnetisation into the transverse plane, phase errors accumulate and the phase which could have been used to determine the polarity of the longitudinal magnetisation is obscured. Phase-sensitive techniques allow the recovery of the original polarity, and hence the whole dynamic range of signal (∝2*M0) can be used, enhancing T1 contrast. See also PSIR | ||
| CRM | Cardiac Resonance Module | ✔ | |||
| CS | Chemical Shift | ✔ | In the frequency-encode direction, the MRI scanner uses the (precessional) frequency of the MR signal to indicate spatial position in the frequency encoding direction. The different electron (i.e. chemical) environments of molecules in which resonant protons reside can shield (or deshield) the external magnetic field. If protons experience changing magnetic fields, their frequency of precession will change (cf. the Larmor equation). This is chemical shift | ||
| CS | Contiguous Slice | ✔ | Slices with no gaps between them | ||
| CSA | Chemical Saturation Amplitude | ✔ | Allows the flip angle of a tissue saturation pulse to be altered (as a percentage). Part of the manual prescan | ||
| CSF | CerebroSpinal Fluid | ✔ | ✔ | ✔ | A clear bodily fluid that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord |
| CSF | Chemical Saturation Frequency | ✔ | Allows the frequency of a tissue saturation pulse to be altered. Part of the manual prescan | ||
| CSI | Chemical Shift Imaging | ✔ | ✔ | ✔ | Multi-voxel spectroscopy; phase encoding in 2D (no frequency encoding) |
| C-SPAMM | Complementary SPAtial Modulation of Magnetisation | ✔ | Improves on the SPAMM method in cardiac MRI, to prevent fading of the black tagging lines (from T1 recovery) through the cardiac cycle. Uses more than one NSA and image subtraction. See SPAMM | ||
| CSTun | Chemical Saturation Tuning | ✔ | A prescan function for a CHESS pulse (see CSF, CSA) | ||
| CT | Cardiac Triggering | ✔ | Synchonisation of data acquisition to a point in the cardiac cycle, by a consistent measurement delay after each R-wave (trigger delay) | ||
| CTL | Cervical Thoracic Lumbar | ✔ | Different regions (curvatures) of the vertebral column | ||
| Cube | not an acronym | ✔ | See SPACE. Cf also VISTA | ||
| CV | Control Variable | ✔ | Pulse sequence parameter which allows a finer control over protocol behaviour. Often used in research applications | ||
| DCE | Dynamic Contrast Enhanced | ✔ | ✔ | ✔ | Temporal change of the MR signal using contrast agent introduced into the body |
| DDAS | DisableD AcquisitionS | ✔ | Dummy acquisitions in echo trains that allow time for magnetisation to evolve closer to to a steady state condition | ||
| DE | Driven Equilibrium | ✔ | Extra T2-weighting using a 90°[x] 180°[y] 90°[-x] preparation pulse | ||
| DE | Dual Echo | ✔ | In-phase and out-of-phase images from one acquisition / breath hold (water-only and fat-only images are not calculated) | ||
| DESS | Double Echo Steady State | ✔ | As bSSFP, but with a very long readout gradient which separates the SSFP-FID and SSFP-echo such that they do not interfere with each other. The two echoes can be used to form separate images, or combined. Not the same as dual-echo gradient-echo, which refocuses the same FID twice | ||
| DFOV | Display Field-of-View | ✔ | |||
| DICOM | Digital Imaging and Communications in Medicine | ✔ | ✔ | ✔ | A standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol |
| Dixon | not an acronym | ✔ | Implementation of Dixon's method of acquiring in-phase and out-of-phase images (i.e. 2 echoes) and calculating water-only and fat-only images. Cf mDIXON, LAVA-Flex, VIBRANT-Flex, IDEAL | ||
| Dot | Day Optimizing Throughput | ✔ | Guidance for workflows, customisable automated protocol selection, some automated parameter prescription | ||
| DRIVE | DRIVen Equilibrium | ✔ | Fast return of transverse magnetisation to the longitudinal direction in a spin echo pulse sequence. Quickens return to equilibrium magnetisation. Also known as Fast Recovery (FR). Allows T2-weighted imaging with shorter TR (and shorter scan time), increasing signal when TR is much less than T1. Cf also FRFSE, RESTORE. (Driven equilibrium for gradient echo is a different method, employing a 90°[x] 180°[y] 90°[-x] T2-preparation pulse.) | ||
| DS | Dynamic Scan | ✔ | Repeated scanning in order to synchronise data acquisition with a physiological motion or process, or to capture evolution of signal changes (e.g. contrast uptake) | ||
| DSC | Dynamic Susceptibility Contrast imaging | ✔ | ✔ | ✔ | Observation of signal intensity changes over time due to arrival and washout or contrast agent |
| DSE | Dual Spin Echo | ✔ | Spin echo with two 180° refocusing pulse to acquire two echoes per excitation. Data from the second echo are separately stored and reconstructed to form a separate image with a longer TE. Crusher gradients around the second refocusing RF pulse must differ from those around the first, to avoid stimulated echo artefacts | ||
| DSV | Diameter of Spherical Volume | ✔ | ✔ | ✔ | Volume over which field homogeneity may be specified (cm); the field homogeneity is usually quoted in ppm using VRMS |
| DTI | Diffusion Tensor Imaging | ✔ | ✔ | ✔ | First see DWI. If multiple diffusion weighted images are acquired with the diffusion gradients oriented in a different direction for each DWI image (to sample the diffusion in multiple directions), a 3D picture of diffusion at a particular point in tissue can be created. This information is called the diffusion tensor (think of an ellipsoid, the shape of which describes the probability of the position to which molecule at that location will diffuse). DTI information can be summarised in parametric maps and can be used to infer connectivity between parts of the brain |
| DTP | Dense Temporal Packaging | ✔ | |||
| DVD | Digital Versatile Disc | ✔ | ✔ | ✔ | You know, a DVD. Optical recordable media |
| DW | Diffusion Weighted | ✔ | ✔ | ✔ | See DWI |
| DWI | Diffusion Weighted Imaging | ✔ | ✔ | ✔ | Application of a strong gradient causes dephasing of spins. Application of an identical gradient opposite to the first reverses that dephasing, except where motion along the gradient direction has occurred. This causes signal loss, and an image acquired with these strong gradients turned on prior to data acquisition is a diffusion weighted image. In apparently stationary tissue, diffusion of water molecules along the direction of the diffusion gradients causes signal loss, seen on a diffusion weighted image |
| DWIBS | Diffusion Weighted whole body Imaging with body Background signal Suppression | ✔ | Multi-station whole-body DWI with STIR fat suppression | ||
| ECG | ElectroCardioGram | ✔ | ✔ | ✔ | A transthoracic interpretation of the electrical activity of the heart over time captured and externally recorded by skin electrodes |
| EMC | ElectroMagnetic Compatibility | ✔ | Used in reference to compliance with relevant international and national law and standards on electromagnetic compatibility for MRI equipment when used as intended | ||
| EPI | Echo Planar Imaging | ✔ | ✔ | ✔ | Rapid changes of frequency-encoding gradient polarity to refocus the MR echo many times after a single RF spin excitation, with a small change in phase encoding for each echo. One of the fastest methods of acquiring MRI k-space data. If all data for an image is acquired after one RF excitation, it is single-shot EPI, in which each slice is acquired in one TR |
| EPIC | Environment for Pulse programming In C | ✔ | General Electric's pulse programming environment for research use | ||
| ERD | Examination Room Display | ✔ | The LCD display in the magnet room (often on the magnet), for display of VCG trace and other information for in-room monitoring and limited scanner operation (e.g. for cardiac pharmacological stress) | ||
| ESP | Echo Spacing | ✔ | Temporal spacing between consecutive echo acquisitions in an echo train | ||
| ET | Echo-Train | ✔ | Multiple refocused echoes after a single RF excitation (i.e. in one TR) | ||
| eTHRIVE | Enhanced T1 High Resolution Isotropic Volume Excitation | ✔ | See THRIVE. eTHRIVE provides improved SNR, CNR and sharpness over THRIVE by adjusting the k-space profile order and using partial Fourier in kz. Asymmetric profile order is used which leads to improved fat suppression and better contrast timing | ||
| ETL | Echo-Train Length | ✔ | Number of refocused echoes after a single RF excitation (i.e. in one TR) | ||
| FAIR | Flow-sensitive Alternating Inversion Recovery | ✔ | See ASL. An ASL method in which the labelled image employs a slice selective 180° on the imaging slice, and the control image employs a non-selective 180° pulse. There is virtually no sensitivity to arterial inflow in the control image. Several variations on the basic FAIR technique have been developed | ||
| FATSAT | FAT SATuration | ✔ | ✔ | ✔ | See SPIR |
| FC | Flow Compensation | ✔ | See GMN | ||
| FE | Field Echo | ✔ | Gradient echo | ||
| FFE | Fast Field Echo | ✔ | See SSFP-FID | ||
| FFT | Fast Fourier Transform | ✔ | ✔ | ✔ | An efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse. A DFT decomposes a sequence of values (e.g. a digitised MR signal) into components of different frequencies |
| FGRE | Fast GRadient Echo | ✔ | As TurboFLASH but without RF spoiling | ||
| FH | Foot-to-Head direction | ✔ | ✔ | ✔ | Along the bore of the magnet, normal to the transverse plane |
| FID | Free Induction Decay | ✔ | ✔ | ✔ | An oscillating decaying MRI signal in the transverse plane, which will induce a voltage in appropriately placed receiver equipment |
| FIESTA | Fast Imaging Employing Steady sTate Acquisition | ✔ | see bSSFP | ||
| FIESTA-C | Fast Imaging Employing Steady sTate Acquisition with phase Cycling | ✔ | see CISS | ||
| FISP | Fast Imaging with Steady-state Precession | ✔ | See SSFP-FID | ||
| FLAG | FLow Adjusted Gradients | ✔ | Flow compensation. See FC | ||
| FLAIR | FLuid Attenuated Inversion Recovery | ✔ | ✔ | ✔ | Inversion recovery (IR) with a long inversion time (TI), at the null point of fluid (no signal from fluid). See IR |
| FLASH | Fast Low Angle SHot | ✔ | Gradient echo with RF-spoiling (by phase cycling) and gradient spoiling, and with low flip angles. As SSFP-FID with additional RF spoiling. Also known as T1-FFE, SPGR | ||
| FMP | Fast MultiPlanar | ✔ | Multi-slice sequence. E.g. "FMP GRE" | ||
| fMRI | functional Magnetic Resonance Imaging | ✔ | ✔ | ✔ | Detection of brain activation via the BOLD effect. Oxygenation levels at the site of brain activity are modulated (using a paradigm, e.g. finger tapping and resting), and signal changes may be correlated. Signal changes due to activation are only a few percent |
| FOS | Fold-over Suppression | ✔ | Prevention of aliasing from tissue outside of the FOV wrapping into the image. Regional saturation (REST) is used for NSA=1, phase oversampling is used for NSA>1 | ||
| FOV | Field Of View | ✔ | ✔ | ✔ | The area or volume to be imaged |
| FRFSE | Fast Recovery Fast Spin Echo | ✔ | See DRIVE. Cf also RESTORE | ||
| FS | Fat Saturated | ✔ | ✔ | A fat-saturation method has been applied | |
| FSE | Fast Spin Echo | ✔ | see RARE | ||
| FSPGR | Fast SPoiled GRASS | ✔ | See FLASH | ||
| FT | Full echo Train | ✔ | All echoes are acquired after one RF excitation. A single shot | ||
| FWHM | Full Width Half Maximum | ✔ | ✔ | ✔ | An expression of the extent of a function, given by the difference between the two extreme values of the independent variable (x-axis) at which the dependent variable (on the y-axis) is equal to half of its maximum value |
| G | Gauss (e.g. 0.5mT = 5G) | ✔ | The cgs unit of measurement of a magnetic field B (magnetic flux density). In SI units, tesla is used. One tesla is equal to 104 gauss | ||
| GBP | Global Bolus Plot | ✔ | Display of signal curve created by contrast bolus along a time axis, in dynamic perfusion imaging | ||
| GE | General Electric | ✔ | MR system manufacturer | ||
| GE | Gradient Echo | Basic pulse sequence in which signal is dephased and refocused by a gradient only. GRE is commonly used instead to avoid confusion with an MR system manufacturer. See SSFP-FID | |||
| GEM | Geometry Embracing Method | ✔ | Flexible receive surface-coils | ||
| GEM | General Encoding Matrix | ✔ | Parallel imaging reconstruction method. Uses variable-density k-space sampling for auto-calibration | ||
| GLM | General Linear Model | ✔ | fMRI (BOLD) data analysis method. Parameter estimates are made indicating the strength of activation (according to a defined paradigm) and strength of confounds. A statistical parameter mapping method | ||
| GMN | Gradient Moment Nulling | ✔ | Application of binomial gradient waveforms to reduce flow effects. Also known as gradient moment rephasing (GMR), or simply flow compensation. Zeroth-order GMN rephases static spins after the application of a gradient. First-order GMN is velocity compensation. Second-order GMN is acceleration compensation. The appropriateness of flow compensation (i.e. first-order GMN with higher orders optional) depends on the application. E.g. in CE-MRA a shorter TE is more important | ||
| GMR | Gradient Motion Rephasing | ✔ | See GMN | ||
| GRACE | GeneRAlized breast speCtroscopy Exam | ✔ | Single volume spectoscopy in breast | ||
| GRAPPA | Generalized Autocalibrating Partial Parallel Acquisition | ✔ | Parallel imaging method. Self-calibrating. Calculations to unwrap image aliasing are made in the k-space domain. Part of iPAT | ||
| GRASE | GRadient And Spin Echo | ✔ | A turbo spin echo sequence, in which the collection of one line of k-space after each 180-degree refocusing pulse is replaced by a short EPI echo train. More echoes are collected per unit time. GRASE overcomes some of the limitations of TSE and EPI, but also inherits many of the problems of both | ||
| GRASS | Gradient Recalled Acquisition in the Steady State | ✔ | See SSFP-FID | ||
| GRE | Gradient Echo | ✔ | ✔ | Basic pulse sequence in which signal is dephased and refocused by a gradient only. Uses a low excitation flip angle and the TR may be very short. See SSFP-FID | |
| GS | Gated Sweep | ✔ | A special k-space order: a sweep through k-space in only part of the cardiac cycle (during a "gate"). Used in gated phase-contrast angiography | ||
| GSP | Graphical Slice Positioning | ✔ | |||
| HASTE | Half-Fourier Acquired Single-shot Turbo spin Echo | ✔ | All k-space lines acquired in a single shot TSE. Echo spacing is minimised (e.g. increased receiver bandwidth, shorter 180° pulses (lower than 180° or a degraded slice profile)), and partial ("half") Fourier is used to reduce the number of k-space lines to be acquired, reducing the shot length. Used for T2-weighted imaging of the abdomen (e.g. MRCP), freezing abdominal motion (e.g. bowel). Cf SSFSE, SSh | ||
| HBI | Heart Beat Interval | ✔ | The time between two R peaks in an ECG trace. The R-R interval. Equal to 60000/(heart rate) (ms) | ||
| HC | Hard Copy | ✔ | Print-out of MR images, usually to plain film | ||
| HC | Homogeneity Correction | ✔ | Optional image post-processing function which compensates for gradually decreasing contrast changes across the FOV. Multiple parameters are available allowing the selection of the type of homogeneity correction (using surface coil sensitivity maps (see CLEAR) or not), or to turn homoeneity correction off | ||
| HD | High Definition | ✔ | Marketing term alluding to improved image resolution | ||
| HF | Head-to-Foot direction | ✔ | ✔ | ✔ | Direction normal to an axial (transverse) slice through the patient |
| HFO | High-Field Open | ✔ | General purpose large aperture magnet with a vertical field (allowing higher efficiency surface coils than traditional phased array coils). E.g. 160cm wide aperture, 1.0T. Every anatomy can be placed at isocentre due to the larger space. May be preferred by anxious/claustrophobic/large patients | ||
| HIFU | High Intensity Focused Ultrasound | ✔ | Use of focused ultrasound waves to heat tissue deep inside the body without damaging intervening tissue (e.g. the treatment of uterine fibroids on an outpatient basis). When combined with MRI, the HIFU system is embedded in the MRI bed and is activated whilst the patient is in the MRI scanner, and MRI can provide real-time visual feedback of the progress of the tissue ablation. Cf also MRgFUS | ||
| HIS | Hospital Information System | ✔ | ✔ | ✔ | An integrated information system designed to manage the administrative, financial and clinical aspects of a hospital |
| HOS | Higher Order Shimming | ✔ | The static magnetic field (B0) is distorted by the presence of a patient. Fine adjustment of the magnetic field is performed to restore B0 homogeneity and maximise the signal received. This is B0 shimming. The complexity of the shimming performed is in the shape of the magnetic field gradients which are used to correct the B0 field (this is a separate process from frequency- and phase-encoding). The simplest shimming gradient is a linear gradient in the x, y or z direction. However more complicated gradients can be applied in which gradient curves are used, described by more complicated equations with higher (polynomial) order terms, such as second-order z2, x2-y2, zy, zx, 2xy. This is HOS, used in higher field systems (3T+). At very high field (e.g. 7T), 3rd order B0 shimming is used | ||
| HR | High Resolution | ✔ | |||
| HS | HalfScan | ✔ | A partial Fourier method in which just over half of k-space is acquired (in the k dimension in which halfscan is applied: ky or kz). More than half of k-space is acquired because the centre of k-space must be fully sampled to provide reliable correction for phase errors. Conjugate symmetry of k-space is used to synthesise unacquired k-space lines. Scan time is reduced, resolution is maintained, SNR is reduced. Aka Half Fourier. Cf 0.5 NEX | ||
| Hz | Hertz | ✔ | ✔ | ✔ | The SI unit of frequency defined as the number of cycles per second of a periodic phenomenon |
| IA | Infusion Angiography | ✔ | Marketing name for fluoroscopic contrast arrival method in which imaging is started after signal passes a threshold in a user-defined ROI. See MRA | ||
| IA | InterActive | ✔ | Real-time scanning user interface, in which fast real-time images may be continuously acquired which respond immediately to changes in planning geometry | ||
| ICE | Image Calculation Environment | ✔ | Siemens' image production/reconstruction environment for research use | ||
| IDEA | Integrated Development Environment for Applications | ✔ | Siemens' pulse programming environment for research use | ||
| IDEAL | Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation | ✔ | 3-echo Dixon technique for fat and water separation with focus on noise performance. Can be used with gradient echo-based and spin-echo based methods. Cf Dixon, mDIXON, LAVA/VIBRANT-Flex | ||
| IDEAL IQ | see IDEAL | ✔ | As IDEAL but with improved water-fat (triglyceride) separation by (i) estimating and correcting for T2* decay between echoes, (ii) more accurately modelling the spectral profile of triglyceride fat with multiple peaks rather than a single peak. A low excitation flip angle is used to reduce T1 effects. Fat fraction and T2* maps are produced in addition to images produced with IDEAL | ||
| IEC | International Electrotechnical Commission | ✔ | ✔ | ✔ | A global organization that publishes consensus-based International Standards and manages conformity assessment systems for electric and electronic products, systems and services |
| IP | In Phase | ✔ | No difference between two points in the time of a cyclical motion or process | ||
| IPA | Integrated Panorama Array | ✔ | Marketing term referring to the simultaneous connection of multiple coils on the patient table, and the manual selection of particular coil elements from those coils (see IPP), to reduce the need for receiver-coil changes in multi-exam studies | ||
| iPAT | integrated Parallel Accquisition Techniques | ✔ | iPAT denotes parallel imaging, but it is not a specific parallel imaging method. Instead, within iPAT the parallel imaging method is chosen (GRAPPA, mSENSE) | ||
| iPAT2 | integrated Parallel Accquisition Techniques in 2 dimensions | ✔ | Parallel imaging acceleration in two phase encoding directions of a 3D acquisition. See iPAT | ||
| IPP | Integrated Panoramic Positioning | ✔ | Remote selection of individual coil elements from the user interface. See IPA | ||
| IR | Inversion Recovery | ✔ | ✔ | ✔ | A 180° preparation pulse which inverts longitudinal magnetisation. Magnetisation recovers according to the (different) T1s of tissues. Imaging then occurs after the inversion delay time (TI). The TI may be set at the null point of a specific tissue (short for fat, long for fluid), or to maximise contrast between two tissues. Note that due to the fact that partial recovery will have occurred for most tissues at TI, image contrast is modified |
| IRM | Inversion Recovery Magnitude | ✔ | A magnitude reconstruction of an inversion recovery image, (as opposed to real image, corrected-real image (see PSIR), phase image, etc | ||
| IROI | Irregular Region Of Interest | ✔ | User-defined shape for a ROI | ||
| IS | Inferior-to-Superior direction | ✔ | ✔ | ✔ | Direction normal to an axial (transverse) slice through the patient, from foot up to head |
| ISIS | Image Selected In vivo Spectroscopy | ✔ | 3D single voxel localisation scheme usually used in 31P spectroscopy. Subtractions between 8 acquisition setups are used to determine the FID of a 3D voxel | ||
| ISO | ISOtropic voxels | ✔ | Same size in all three orthogonal axes | ||
| IVI | Interactive Vascular Imaging | ✔ | Post-processing tool used to create MIPs from MRA acquisitions | ||
| k-t | K-space domain and Time domain | ✔ | e.g. k-t BLAST | ||
| LAVA | Liver Acquisition with Volume Acceleration | ✔ | 3D spoiled fast/turbo gradient echo with partial Fourier in kz. Used in abdomen and pelvis (not just liver). Cf eTHRIVE, VIBE | ||
| LAVA-XV | Liver Acquisition with Volume Acceleration - eXtended Volume | ✔ | LAVA with parallel imaging, see GEM. Cf eTHRIVE, VIBE | ||
| LAVA-Flex | Liver Acquisition with Volume Acceleration | ✔ | LAVA with 2-echo Dixon water-fat separation, see LAVA and see Dixon). Uses ARC parallel imaging. Cf Dixon, mDIXON, IDEAL | ||
| LOLO | LOcal LOok | ✔ | Small-FOV technique in TSE, in which orthogonal slice selection for the 90° spin excitation and 180° refocusing pulses is used. No spin echo is formed from the rest of the anatomy because it doesn't receive both RF pulses. Sometimes called ZOOM imaging, originally called inner volume imaging | ||
| LOTA | Long Term Averaging | ✔ | |||
| LP | Linearly Polarized | ✔ | ✔ | Confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. See also CP | |
| LPC | Local Phase Correction | ✔ | Background offset correction applied to phase images used to measure flow. Phase errors due to residual eddy currents are addressed. Uses an optimized spatial low pass filter. Concomitant field corrections are not part of the LPC (they are applied separately) | ||
| LPH | Left-Posterior-Head | ✔ | |||
| LR | Left-to-Right direction | ✔ | ✔ | ✔ | Direction normal to an sagittal slice through the patient |
| M2D | Multiple (sequential) 2D slices | ✔ | 2D slices acquired sequentially, data acquisition not interleaved | ||
| MAP | Multi-Angle Projection | ✔ | |||
| MART | Modulated Angle Refocusing Train | ✔ | |||
| MAST | Motion Artifact Suppression Technique | ✔ | |||
| MAVRIC SL | Multi-Acquisition with Variable Resonances Image Combination, SLab selection | ✔ | Method to mitigate image arefacts caused when imaging in the presence of metal implants. Multiple acquisitions are acquired with different frequency offsets, and the resultant range of off-resonance images are summed at each slice location. See blog post on metal artefact reduction sequences | ||
| MC | MultiChunk | ✔ | |||
| MC | MultiConnect | ✔ | |||
| MDDW | Multi Directional Diffusion Weighting | ✔ | |||
| MDE | Myocardial Delayed Enhancement | ✔ | |||
| mDIXON | modified DIXON | ✔ | A 3D spoiled turbo gradient echo method, using 2-echo Dixon water and fat separation, with modifications which allow more flexibility in selection of TEs than standard Dixon methods. CF Dixon, LAVA-Flex, VIBRANT-Flex, IDEAL | ||
| ME | Myocardial Evaluation | ✔ | |||
| MEDIC | Multi-Echo Data-Image Combination | ✔ | ✔ | ||
| MEGA | Mescher-Garwood | ✔ | |||
| MEMP | Multi-Echo Multi-Planar | ✔ | |||
| MENSA | Multi-Echo iN Steady-state Acquisition | ✔ | |||
| MEPPS | Morphology Enhanced Probabilistic Plaque Segmentation | ✔ | |||
| MERGE | Multi-Echo Recombined Gradient Echo | ✔ | |||
| MID | Multiple Image Display | ✔ | |||
| MIP | Maximum Intensity Projection | ✔ | ✔ | ✔ | |
| mIP | Minimum Intensity Projection | ✔ | |||
| MNS | Multi-Nuclear Spectroscopy | ✔ | ✔ | ✔ | |
| MOD | Magnetic Optical Disk | ✔ | ✔ | ✔ | |
| MOIST | Multiple Optimizations Insensitive Suppression Train | ✔ | |||
| MOTSA | Multiple Overlapping Thin Slab Angiography | ✔ | ✔ | ||
| MP | Magnetisation Prepared | ✔ | |||
| MPGR | Multi-Planar Gradient Recalled | ✔ | |||
| MPPS | Modality Performed Procedure Step | ✔ | |||
| MPR | Multi-Planar Reformat | ✔ | ✔ | ✔ | |
| MP-RAGE | Magnetization Prepared RApid Gradient Echo Imaging | ✔ | |||
| MPS | Manual PreScan | ✔ | Allows manual adjustment of centre frequency, transmit gain and receiver gain | ||
| MPS | Measurement/Phase/Slice | ✔ | Encoding directions in the image frame of reference | ||
| MPVR | Multi-Projection Volume Reconstruction | ✔ | |||
| MR | Magnetic Resonance | ✔ | ✔ | ✔ | |
| MRA | MR Angiography | ✔ | ✔ | ✔ | Visualisation of blood flow within vessels by using the flow sensitivity of MRI. See TOF, PC, CE |
| MRCP | Magnetic Resonance Cholangio-Pancreatography | ✔ | ✔ | ✔ | An examination of the bile ducts and pancreas using MRI |
| MRgFUS | MR Guided Focused Ultrasound | ✔ | See HIFU | ||
| MRI | Magnetic Resonance Imaging | ✔ | ✔ | ✔ | |
| MRS | MR spectroscopy | ✔ | ✔ | ✔ | |
| MRSI | Magnetic Resonance Spectroscopic Imaging | ✔ | |||
| MS | Multiple (temporally interleaved) Slices | ✔ | |||
| MSE | Modified Spin Echo | ✔ | |||
| mSENSE | modified SENSitivity Encoding | ✔ | Sensitivity encoding (see SENSE) variant using additional autocalibration k-space lines instead of a dedicated scan to acquire coil sensitivity information | ||
| MSh-TSE | MultiShot Turbo Spin Echo | ✔ | |||
| MSMA | Multi-Slice Multi-Angle | ✔ | |||
| MSMG | Multi-Slice Multi-Group | ✔ | |||
| MSMP | MultiSlice MultiPhase | ✔ | |||
| MST | Multiple Stack | ✔ | |||
| MT | Moving Table | ✔ | |||
| MTC | Magnetisation Transfer Contrast | ✔ | ✔ | ✔ | |
| MTR | Magnetisation Transfer Ratio | ✔ | |||
| MTT | Mean Transit Time | ✔ | ✔ | ✔ | |
| MultiVane | not an acronym | ✔ | see PROPELLER | ||
| Mxy | Magnetisation in the x-y plane | ✔ | ✔ | ✔ | Vector component of net magnetisation in a plane orthogonal to the direction of the main magnetic field |
| Mz | Magnetisation in the z direction | ✔ | ✔ | ✔ | Vector component of net magnetisation in the direction of the main magnetic field |
| NATIVE | Non-contrast MRA of ArTerIes and VEins | ✔ | |||
| NEMA | National Electrical Manufacturers Association | ✔ | ✔ | ✔ | |
| NEX | Number of Excitations | ✔ | When NEX > 1, NEX denotes the number of repetitions of data acquisition, for signal averaging (cf ACQ, NSA). Non-integer NEX > 1 is also allowed, e.g. 1.5 NEX means all of k-space and then the centre 50% again. When NEX < 1, NEX denotes partial Fourier in the in-plane phase encoding direction (a separate parameter on other systems, e.g. Halfscan, Half Fourier), e.g. 0.5 NEX | ||
| NIBP | Non-Invasive Blood Pressure | ✔ | |||
| NMR | Nuclear Magnetic Resonance | ✔ | ✔ | ✔ | |
| NOE | Nuclear Overhauser Effect | ✔ | ✔ | ✔ | |
| NPW | No Phase Wrap | ✔ | |||
| NSA | Number of Signals Averaged | ✔ | Number of repetitions of data acquisition, for signal averaging. Cf ACQ, NEX | ||
| og | Gradient overplus | ✔ | |||
| OP | Out-of-Phase | ✔ | |||
| OVS | Outer Volume Suppression | ✔ | |||
| PA | Post-Acquisition | ✔ | |||
| PA | Posterior-to-Anterior direction | ✔ | ✔ | ✔ | Back to front direction, normal to the coronal plane |
| PA | Pulse-Acquire (spectroscopy) | ✔ | |||
| PACC | Prostate Analytical Coil Correction | ✔ | |||
| PACE | Prospective Acquisition CorrEction | ✔ | Cf PMC | ||
| PACS | Picture Archiving and Communications System | ✔ | ✔ | ✔ | |
| PARADISE | Philips Advanced Research And Development Integrated Sequence-programming Environment | ✔ | Philips' pulse programming environment for research use | ||
| PB | Pencil Beam | ✔ | |||
| PBP | Percentage of Baseline at Peak | ✔ | |||
| PC | Phase Correct | ✔ | |||
| PC | Phase Contrast | ✔ | ✔ | ✔ | Detection of flowing blood using the change of phase introduced by blood moving along a magnetic field gradient. Takes longer than TOF-MRA because multiple scans with different directional flow sensitivity must be acquired and then combined. Cf also MRA, TOF |
| PCA | Phase Contrast Angiography | ✔ | See PC | ||
| PD | Preparation pulse Delay time | ✔ | |||
| PD | Proton Density | ✔ | ✔ | ✔ | |
| PE | Partial echo | ✔ | |||
| PEAR | Phase Encoded Artifact Reduction | ✔ | |||
| PERFORM | Precision-Enhanced RF Optimisation, Regulation and Management | ✔ | |||
| PET/MR | Positron Emmission Tomography / Magnetic Resonance | ✔ | Combination of PET and MR in one system, for a composite picture of PET and MR soft tissue signal data | ||
| PFOV | Phase Field-Of-View | ✔ | see RFOV | ||
| PG | Peripheral Gating | ✔ | |||
| PH | Philips Healthcare | ✔ | |||
| PIQT | Periodic Image Quality Test | ✔ | |||
| Pixel | PIcture ELement | ✔ | ✔ | ✔ | |
| PMC | Prospective Motion Correction | ✔ | Cf PACE | ||
| PMS | Philips Medical Systems (depreciated, see PH) | ✔ | |||
| PNS | Peripheral Nerve Stimulation | ✔ | ✔ | ✔ | |
| PP | Peripheral Pulse | ✔ | |||
| PP | Preparation Pulse | ✔ | |||
| PP | Preset Procedure | ✔ | |||
| ppm | Parts Per Million | ✔ | ✔ | ✔ | Pseudo units to describe small proportions. Just as per cent means out of a hundred, parts per million means out of a million |
| PPNS | Potential Peripheral Nerve Stimulation | ✔ | |||
| PPU | Peripheral Pulse Unit | ✔ | |||
| PRESS | Point RESolved Spectroscopy | ✔ | ✔ | ✔ | |
| PRESTO | PRinciples of Echo Shifting with a Train of Observations | ✔ | |||
| PRIDE | Philips Research Image Development Environment | ✔ | |||
| PRIME | Proton Regional Imaging of MEtabolites | ✔ | |||
| PROBE-P | PROton Brain Exam using PRESS | ✔ | |||
| PROBE-S | PROton Brain Exam using STEAM | ✔ | |||
| PROPELLER | Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction | ✔ | Non-Cartesian k-space data acquisition, in small groups of parallel lines through the centre of k-space, the groups rotated with respect to one-another (imagine a rotating propeller blade). MultiVane and BLADE are similar sequences. May be used for motion correction in TSE sequences. The centre of k-space is sampled in every blade: this allows the low-resolution images from individual blades to be compared for in-plane rotation and translation (which can then be corrected) and through-plane motion (which motivates re-acquisition of that blade of data). A final high-resolution image is constructed once all the blades of data are acquired | ||
| PROSE | proton PROState Exam | ✔ | |||
| ProSet | PRinciple Of Selected Excitation Technique | ✔ | Composite RF pulses; can be used to produce a signal from only water (or only fat) protons by making use of the dephasing of fat and water. They are RF pulses made up of a series of shorter RF pulses with small delays between them. They can be quite complicated, but here is a simple example to explain the method. First, a 45° excitation pulse flips both fat and water. Then after a short time, fat and water are exactly out of phase (both still at 45°, but with opposing transverse components of magnetisation, and thus have a 90° angle between them). Another 45° RF pulse is then applied which flips the fat net magnetisation back to Mz, and puts the water magnetisation in the x-y plane, providing a fat-suppressed signal | ||
| PSD | Pulse Sequence Definition | ✔ | |||
| PSIF | (FISP, read backwards) | ✔ | see SSFP-echo | ||
| PSIR | Phase-Sensitive Inversion Recovery | ✔ | ✔ | PSIR enables the large dynamic range of signal change which IR affords whilst keeping the observed signal intensity change of tissues monotonic with increasing TI. In cardiac MRI PSIR can used for delayed enhancement (viability); one implementation uses two-beat-IR: the first R-R interval for data acquisition, the second for acquisition of data for use as a phase reference to correct the data acquired in the previous heartbeat. Phase-corrected real images (real as opposed to imaginary or magnitude, etc) are produced. In neuro MRI, PSIR provides stronger GM and WM contrast, which is required for e.g. migration disorder in neonates. See also CR | |
| PURE | Phased array UnifoRmity Enhancement | ✔ | Homogeneity correction using coil sensitivity maps acquired in a reference scan. Cf CLEAR (or on Siemens, 'Prescan Normalize') | ||
| PV | Peripheral Vascular | ✔ | |||
| Q | Quality factor (of the RF-coil) | ✔ | ✔ | ✔ | |
| QA | Quality Assurance | ✔ | ✔ | ✔ | |
| QBC | Quadrature Body Coil | ✔ | |||
| QF/QFlow | Quantitative Flow | ✔ | |||
| R1 | Relaxation rate for T1: 1/T1 | ✔ | ✔ | ✔ | |
| R2 | Relaxation rate for T2: 1/T2 | ✔ | ✔ | ✔ | |
| RADIANT | RADial Imaging Around Nipple or Tumor | ✔ | |||
| RAL | ROI, Annotation, Line | ✔ | |||
| RARE | Rapid Acquisition with Relaxation Enhancement | ||||
| RAS | Right-Anterior-Superior | ✔ | Coordinate system for reference to anatomy | ||
| rBW | receiver BandWidth | ✔ | |||
| RC | Respiratory Compensated | ✔ | |||
| RC | Respiratory Control | ✔ | |||
| ref | REFerence scan | ✔ | |||
| REPP | REsearch PrePulse | ✔ | |||
| REST | REgional Saturation Technique | ✔ | |||
| RESTORE | not an acronym | ✔ | See DRIVE. Cf also FRFSE | ||
| REVEAL | not an acronym (?) | ✔ | |||
| RF | Radio Frequency | ✔ | ✔ | ✔ | |
| RFA | Reduced Flip Angle | ✔ | |||
| RFE | Refocussed Field Echo | ✔ | Spin echo | ||
| RFOV | Rectangular Field-Of-View | ✔ | An increase of line spacing in k-space, meaning the same k-space extent is covered (keeping the resolution the same) with fewer phase encode lines (so faster, but reduces SNR). AKA: Asymmetric FOV, Phase FOV | ||
| RF-SMART | Radio Frequency Superior Management ARrchiTecture | ✔ | |||
| RIS | Radiology Information System | ✔ | ✔ | ✔ | An integrated information system designed to manage the administrative, financial and clinical aspects of a radiology department |
| RL | Right-to-Left direction | ✔ | ✔ | ✔ | Direction normal to an sagittal slice through the patient |
| ROI | Region Of Interest | ✔ | ✔ | ✔ | |
| ROPE | Respiratory Ordered Phase Encoding | ✔ | |||
| RR-INT | R-top to R-top interval | ✔ | The time between two R peaks in an ECG trace. The R-R interval. Equal to 60000/(heart rate) (ms) | ||
| RSL | Relative Signal Level | ✔ | |||
| RT | Real-Time | ✔ | |||
| RT | Respiratory Triggering | ✔ | |||
| Rx | prescription | ✔ | |||
| SAGE | Spectroscopy Analysis by General Electric | ✔ | |||
| SAR | Specific energy Absorption Rate | ✔ | ✔ | ✔ | |
| SAT | SATuration | ✔ | |||
| SC | Secondary Capture | ✔ | |||
| SCIC | Surface Coil Intensity Correction | ✔ | |||
| SCT | SCan Time, scan duration | ✔ | |||
| SE | Spin Echo | ✔ | ✔ | ✔ | Basic pulse sequence in which signal is dephased and refocused by a gradient only. Uses a low excitation flip angle and the TR may be very short |
| SENSE | SENSitivity Encoding | ✔ | Parallel imaging method for accelerating image acquisition. A reference scan is acquired prior to clinical data acquisition to measure coil sensitivity profiles. Accelerated data acquisition follows (lines in k-space are more spaced out; fewer lines are acquired) causing aliasing in images. Unwrapping of the aliasing is performed in the image-domain (as opposed to on the k-space data before FFT) using the sensitivity data from the reference scan | ||
| SER | Signal Enhancement Ratio | ✔ | |||
| SHARK | SHifting Artefacts Reordering K-space | ✔ | |||
| SI | Superior-to-Inferior direction | ✔ | ✔ | ✔ | Direction normal to an axial (transverse) slice through the patient, from head down to foot |
| SLD | Stereotactic Localisation Device | ✔ | |||
| SLINKY | SLiding INterleaved ky | ✔ | |||
| SMART | Serial Motion Artifact Reduction Technique | ✔ | |||
| SMASH | SiMultaneous Acquisition of Spatial Harmonics | ||||
| SMC | Synergy MultiConnect | ✔ | |||
| SMS | Sliding Multi Slice | ✔ | |||
| SNR | Signal-to-Noise Ratio | ✔ | ✔ | ✔ | The ratio of signal power to the noise power corrupting the signal |
| SPACE | Sampling Perfection with Application optimized Contrasts using different flip angle Evolution | ✔ | 3D fast spin echo which uses a train of non-selective refocusing RF pulses with variable flip angles which reduces SAR and stores magnetisation for later in the echo train, allowing an extended echo train. Used for isotropic volumetric imaging. Cf also Cube, VISTA | ||
| SPAIR | SPectral Attenuated Inversion Recovery | ✔ | As SPIR but with a 180° adiabatic CHESS preparation pulse making it insensitive to B1 (flip angle) inhomogeneity. Spoiler gradients follow the preparation which ensure any magnetisation in the transverse plane is dephased | ||
| SPAIR | Spectrally Adiabatic Inversion Recovery | ✔ | As SPIR but with a 180° adiabatic CHESS preparation pulse making it insensitive to B1 (flip angle) inhomogeneity. Spoiler gradients follow the preparation which ensure any magnetisation in the transverse plane is dephased | ||
| SPAMM | SPAtial Modulation of Magnetisation | ✔ | Two RF pulses with a gradient in between. The first (e.g.) 90° pulse puts spin isochromats into the transverse plane. The gradient causes phase dispersion which depends on position along the gradient. Then another 90° pulse rotates the lot; if that pulse rotates around the x-axis (for example), magnetisation along x is unaffected whereas magnetisation along y is rotated into z. Since the magnetisation along y depended on the position along the tagging gradient, that magnetisation (now in z) has an amplitude which is spatially modulated (lines across the resultant image). The x magnetisation decays away or is spoiled. SPAMM can be performed in two directions to produce a grid pattern. An imaging sequence follows the SPAMM magnetisation preparation | ||
| SPECIAL | SPECtral Inversion At Lipid | ✔ | Spectral fat suppression method. A fat-selective CHESS preparation pulse; imaging occurs when fat reaches the null point. | ||
| SPGR | SPoiled GRASS | ✔ | see FLASH | ||
| SPIDER | Steady-state Projection Imaging with Dynamic Echo-train Readout | ✔ | |||
| SPIR | Spectral Presaturation Inversion Recovery | ✔ | Spectral fat suppression method. A fat-selective CHESS preparation pulse; imaging occurs when fat reaches the null point. The CHESS pulse angle is reduced to closer to 90° so that the inversion time is as short as possible, which saves imaging time | ||
| SPL | Sound Pressure Level | ✔ | |||
| SPM | Statistical Parametric Map | ✔ | |||
| SPT | System Perfomance Test | ✔ | |||
| SR | Slew Rate | ✔ | |||
| SSD | Shaded Surface Display | ✔ | |||
| SSFP | Steady State Free Precession | Do you mean the balanced SSFP method? See bSSFP | |||
| SSFP-FID | Steady State Free Precession Free Induction Decay | Generic name for (the most common form of) gradient echo; gradient-recalled echo is measured after excitation, before gradient spoiling of the SSFP-echo. Not RF spoiled. Gradient area within each TR interval must be the same, TR ≤ T2, and RF excitation pulses must be phase coherent (or sign-alternated). So-called S-plus (forward gradient waveform) sequence. Also known as FFE, FISP, GRASS | |||
| SSFP-echo | Steady State Free Precession echo | Generic name for (a less common form of) gradient echo, measured after gradient spoiling of the SSFP-FID. This means that the first excitation rotates magnetisation into the transverse plane as normal. The second excitation acts a spin-echo partial-refocusing pulse, but also produces more excitation and an associated FID. That FID is spoiled away, allowing the the spin echo from the two consecutive RF excitations to be measured (the SSFP-echo), before the next RF excitation arrives. Not RF spoiled. Gradient echo of a stimulated Spin Echo is measured (i.e. the refocussed signal of two excitation pulses earlier). Gradient area in each TR interval must be the same, TR ≤ T2, and RF excitation pulses must be phase coherent (or sign-alternated). So-called S-minus (reversed gradient waveform) sequence. Also known as T2-FFE, PSIF. Not generally used because bSSFP produces more signal and has less sensitivity to flow dephasing | |||
| SSFSE | Single-Shot Fast Spin Echo | ✔ | See HASTE, SSh | ||
| SSGR | Slice-Selection Gradient Reversal | ✔ | Fat suppression in spin echo: inversion of the polarity of the slice selection gradient associated with the 180° refocusing pulse. SSGR relies on through-plane chemical shift being in opposite directions for the 90° and the 180° pulses, so that the shifted fat doesn’t receive both RF pulses and therefore no spin echo is formed from the fat. Appropriate at higher field where chemical shift between fat and water is larger. Effective over large FOV | ||
| SSh | Single-Shot | ✔ | All echoes are acquired after one RF excitation. One (full) echo train. E.g. SSh TSE | ||
| SSMP | Single Slice Multiple Phase | ✔ | |||
| SSRF | Spatial-Spectral Radio Frequency | ✔ | |||
| STAR | Signal Targeting with Alternating Radiofrequency | ✔ | ASL technique in which the magnetisation transfer effects are kept the same between the label and the control by performing one adiabatic pulse during the labeling phase (e.g. 180°), and two consecutive adiabatic pulses of half RF power during the control (e.g. 180° + 180° in the same location as the label tag). The labeling sequence is preceded with a WET pre-saturation scheme and followed by a single 90°-dephasing pulse to ensure identical timing between both labeling and control experiments | ||
| STE | STimulated echo | ✔ | |||
| STEAM | STimulated Echo Acquisition Method | ✔ | ✔ | ✔ | |
| STIR | Short TI Inversion Recovery | ✔ | ✔ | ✔ | A fat suppression method suitable for large FOVs or regions of magnetic susceptibility variation. A 180° inversion prepulse is used to invert all magnetisation. Then imaging proceeds after a delay, when the longitudinal recovery of fat magnetisation has reached the null point, when there is no fat magnetisation to flip into the x-y plane. Tissues with a T1 relaxation time different to fat have a signal, because they either have not yet reached the null point, or have recovered past it |
| SVQ | Single Voxel Quantitative spectroscopy | ✔ | |||
| SVS | Single Voxel Spectroscopy | ✔ | ✔ | ✔ | Used to determine a spectrum of metabolic information from a single volume of interest |
| SWAMP | Sequence for Water suppression with Adiabatic Modulated Pulses | ✔ | |||
| SWAN | t2-Star Weighted ANgiography | ✔ | 3D multi-echo gradient echo, with weighted combination of echoes and further reconstruction (cf SWI) | ||
| SWI | Susceptibility Weighted Imaging | ✔ | ✔ | Magnitude images multiplied by a filter determined from corresponding phase images, providing contrast by reducing signal where susceptibility effects are more significant | |
| SWIFT | SWItch on the Fly Technique | ✔ | |||
| T/R | Transmit/Receive | ✔ | ✔ | ||
| T0 | Time to arrival | ✔ | |||
| T1-FFE | T1-weighted Fast Field Echo | ✔ | See FLASH | ||
| T2-FFE | T2-weighted Fast Field Echo | ✔ | See SSFP-echo | ||
| TA | Time to Acquisition | ✔ | |||
| TD | Trigger Delay time | ✔ | ✔ | ✔ | |
| TE | Echo Time | ✔ | ✔ | ✔ | |
| TEA | TE Averaged | ✔ | |||
| TEeff | EFFective Echo Time | ✔ | ✔ | ✔ | |
| TF | Turbo spin echo Factor | ✔ | |||
| TF | Time of Flight | ✔ | Referenced in the context of PET/MR, TF refers to measurement of the time difference between the detections of a positron-electron annihilation event to more accurately identify the origin of the annihilation. For time-of-flight in MRI, see TOF | ||
| TFE | Turbo Field Echo | ✔ | see TurboFLASH | ||
| TG | Transmit Gain | ✔ | |||
| THRIVE | T1 High Resolution Isotropic Volume Excitation | ✔ | 3D spoiled turbo gradient echo, with SPAIR fat suppression and SENSE acceleration. Used for single breath hold, isotropic voxel, contrast enhanced studies (e.g. liver, small bowel, pancreas). Suitable for calculation of MIPs and MPRs. 4D-THRIVE denotes addition of keyhole and CENTRA for a fast dynamic scan (e.g. breast). Cf LAVA, VIBE. See also eTHRIVE | ||
| TI | Inversion Time | ✔ | ✔ | ✔ | Delay time after inversion preparation RF pulse. See IR |
| TID | Time Intensity Diagram | ✔ | |||
| TID | Time intensity diagram | ✔ | |||
| TILT | Transfer-Insensitive Labeling Technique | ✔ | |||
| Tim | Total Imaging Matrix | ✔ | |||
| TimCT | Tim Continuous Table move | ✔ | |||
| TIR | True Inversion Recovery | ✔ | |||
| TIR | Turbo Inversion Recovery | ✔ | |||
| TIRM | True Inversion Recovery Magntiude | ✔ | |||
| TOF | Time Of Flight | ✔ | ✔ | ✔ | The effect on image contrast of flowing blood: high velocity signal loss (causes black blood in spin echo), and flow related enhancement (contributes to bright blood in gradient echo, along with the absence of high velocity signal loss). Flow related enhancement can affect spin echo too if the flow is slow. Cf also MRA, PC |
| TONE | Tilt Optimized Nonsaturating Excitation | ✔ | ✔ | Reduces the saturation of blood in a 3D MRA volume. The flip angle is varied linearly across the excited volume; as blood magnetisation is more and more saturated as it passes through the volume experiencing excitation pulses, the excitation pulse angle increases to maintain signal response | |
| TP | Trigger Point | ✔ | |||
| tPAT | Temporal Parallel Acquisition Technique | ✔ | Autocalibrating parallel imaging for dynamic scans, in which a fully sampled k-space zone for coil sensitivity estimation (TSENSE) or k-space weights (TGRAPPA) is synthesised from adjacent temporal frames. Unlike iPAT methods, each individual frame has no fully sampled zone in its corresponding k-space | ||
| TPS | Transceiver Processing and Storage | ✔ | |||
| TR | Repetition Time | ✔ | ✔ | ✔ | |
| TRAK | Time-Resolved Angiography using Keyhole | ✔ | CE-MRA method (cf TRICKS, TWIST). E.g. 4D-TRAK. Uses a modified CENTRA-based k-space trajectory. Dynamic frame rate is determined by the frequency of acquisition of central ky-kz space data, with the most recent acquisition of remaining k-space data filling in the rest of k-space | ||
| TRANCE | TRiggered Angiography Non Contrast Enhanced | ✔ | Peripheral MRA using triggered 3D turbo spin echo, no contrast agent used | ||
| TRAPS | TRAnsition into static Pseudo Steady state | ✔ | |||
| TReff | EFFective Repetition Time | ✔ | |||
| TrF | Tailored Radio Frequency | ✔ | |||
| TRICKS | Time-Resolved Imaging of Contrast Kinetics | ✔ | CE-MRA method (cf TRAK, TWIST). ky-kz space is divided into a central sector (e.g. 'A') and multiple concentric peripheral sectors (e.g. concentric rings of increasing diameter in ky-kz space 'B', 'C', 'D'). Data acqusition alternates between central and peripheral sectors, with frequent reacquisition of the central sector (e.g. ABCDABACADABACAD etc). Dynamic frame rate is determined by the frequency of acquisition of the central sector, with the most recent acquisitions of the peripheral sectors filling in the rest of k-space | ||
| TrueFISP | True Fast Imaging with Steady-state Precession | ✔ | See bSSFP. (Original 'FISP' was modified for practical imaging, and the original FISP was renamed TrueFISP) | ||
| TS | Saturation time | ✔ | |||
| TS | Time Series | ✔ | |||
| TSE | Turbo Spin Echo | ✔ | ✔ | see RARE | |
| TSI | Turbo Spectroscopic Imaging | ✔ | |||
| TTP | Time To Peak | ✔ | ✔ | ✔ | |
| TTR | Table Top Release | ✔ | |||
| TTS | Travel-To-Scanplane | ✔ | |||
| TurboFLASH | Turbo Fast Low Angle Shot | ✔ | |||
| TurboGSE | Turbo Gradient Spin Echo | ✔ | |||
| TW | Trigger Window | ✔ | |||
| TWIST | Time-resolved angiography WIth Stochastic Trajectories | ✔ | CE-MRA method (cf TRAK, TRICKS). ky-kz space is divided into a central and a peripheral sector. Data acquisition alternates between the sectors. When the central sector is acquied it is fully sampled. The peripheral sector is randomly sampled and may not be fully acquired; data can borrowed from temporally neighboring peripheral sector acquisitions. Dynamic frame rate is determined by the frequency of acquisition of the central sector, with the most recent acquisition of the peripheral sector data filling in the rest of k-space | ||
| TX | Transmit | ✔ | |||
| USPIO | Ultra Small Super paramagnetic Iron Oxide nano-particles | T2*-reducing contrast agent | |||
| UTE | Ultrashort Echo Time | ✔ | ✔ | ✔ | |
| UTSE | Ultrashort TSE | ✔ | |||
| VAST | VAriable Sampling in Time | ✔ | |||
| VCG | Variable Coil Geometry | ✔ | |||
| VCG | VectorCardioGram | ✔ | ✔ | ||
| VEF | Volume ejection fraction | ✔ | |||
| VENC | Velocity ENCoding | ✔ | ✔ | ✔ | |
| VERSE | VariablE-Rate Selective Excitation | ✔ | ✔ | Variable gradient amplitude during an RF pulse. Can be used for SAR reduction in turbo spin echo by reducing RF amplitude; flip angle is maintained by stretching the pulse duration | |
| VIBE | Volume Interpolated Breathhold Examination | ✔ | 3D spoiled turbo gradient echo, with fat saturation, and with partial Fourier or zero filling in kz. Used for abdominal and pelvic imaging including contrast enhanced studies. Cf LAVA, eTHRIVE | ||
| VIBRANT | Volume Imaging for BReast AssessmeNT | ✔ | Bilateral 3D spoiled turbo gradient echo breast imaging. Uses SPECIAL fat saturation, and separate shim volumes on each breast. Allows sagittal or axial acquisition. Cf VIEWS, BLISS | ||
| VIBRANT-XV | Volume Imaging for BReast AssessmeNT | ✔ | VIBRANT with GEM parallel imaging. See VIBRANT and see GEM. Cf VIEWS, BLISS | ||
| VIBRANT-Flex | Volume Imaging for BReast AssessmeNT | ✔ | VIBRANT with 2-echo Dixon water-fat separation, see VIBRANT and see Dixon). Uses ARC parallel imaging. Cf VIEWS, BLISS | ||
| VIEWS | Volume Imaging with Enhanced Water Signal | ✔ | Bilateral 3D spoiled turbo gradient echo measurement technique for the breast with fat saturation or water stimulation. Cf VIBRANT, BLISS | ||
| VISTA | Volumetric ISotropic T2w Acquisition | ✔ | See SPACE. Cf also Cube. A neuro VISTA implementation with tissue-specific flip angle sweep is called 3D BrainView | ||
| VOI | Volume of Interest | ✔ | ✔ | ✔ | |
| Voxel | VOlume Element | ✔ | ✔ | ✔ | |
| VPS | Views Per Segment | ✔ | ✔ | ||
| VRMS | Volume Root Mean Square | ✔ | ✔ | ✔ | Statistic used to denote level of main magnetic field homogeneity over a specified volume (units: ppm). Allows the user to estimate the volumes over which he or she may peform various scan sequences. VRMS = [(1/V)∫[Bz(r)-Bz(0)]²dV]½ where Bz(r) and Bz(0)are the z component of the total magnetic field at point r and the centre of the imaging volume V, respectively. The integration is over the imaging volume V |
| VRT | Volume Rendering Technique | ✔ | |||
| VSS | Very Selective Saturation | ✔ | |||
| WALTZ | Wideband Alternating-phase Low-power Technique for Zero-residual splitting | ✔ | ✔ | Phase-cycling method of proton decoupling used in spectroscopy. The acronym expansion may be erroneous; it has also been said that name derives from the pulse structure (+90°, -180°, +270°) which resembles the rhythm of a waltz (1,2,3; 1,2,3; etc) | |
| WATS | WATer Selective | ✔ | |||
| WAVE | WAter selective Volume Excitation | ✔ | Water excitation using composite RF pulses (ProSet), parallel imaging (SENSE), breath hold, isotropic voxels | ||
| WB | Whole Body | ✔ | ✔ | ✔ | |
| WET | Water suppression Enhanced through T1 effects | ✔ | Use of multiple RF pulses each followed by a dephasing gradient to perform a more effective overall saturation of magnetisation over a range of T1 species and B1 inhomogeneities | ||
| WFS | Water-fat shift | ✔ | |||
| WS | Water Suppression | ✔ | |||
| XL | eXceL | ✔ | |||
| XL | Extra Large (coil) | ✔ | |||
| XV | eXtended Volume | ✔ | Usually indicates addition of a parallel imaging method, which allows more coverage is the same imaging time. E.g. LAVA-XV and VIBRANT-XV (parallel imaging method: GEM), TRICKS-XV (parallel imaging method: ASSET) | ||
| XYZ | The magnet coordinate system | ✔ | |||
| ZIP | Zero filling Interpolation Processing | ✔ | ✔ | ||
If a manufacturer does not have an acronym for a technique it does not does not mean that particular technique is not available; sometimes a marketing name is introduced from one vendor whilst other vendors use a generic name for a method. Additionally, similar techniques may not produce the same results; whilst manufacturers' offerings may be based on the same general MR physics methods, their equivalence in terms of practical functionality and/or clinical utility should not be assumed.
Some information comparing techniques, including Hitachi and Toshiba pulse sequences, may be found online: 1 (pdf), 2 (pdf), 3, 4 (pdf), 5, 6