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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
CAIPIRINHA Controlled Aliasing in Parallel Imaging Results in Higher Acceleration RF excitation of more than one 2D slice at the same time. Also known as multiband, or simultaneous multiple slice excitation. The reconstructed image from multiple slices is overlapped; CAIPIRINHA describes the basic idea of applying a phase shift to ease the unfolding
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 A circularly polarized electromagnetic wave 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 (∝2M0) 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, [3D] VIEW
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
ENCASE ENhanced Coronal Acquisition with Sagittal Excitation Allows arms-down imaging for large FOV 3D FFE or 3D TFE in the coronal plane. Normally oversampling is used to remove aliasing from arms, but residual aliasing signal can occur (curved local dark/bright fringes, sometimes called "flame" artefact). ENCASE moves the RF excitation from the slice direction to the phase direction. The width of the excited volume is thus restricted to the encoded volume of interest, excluding the arms
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
FOCUS not an acronym ? 2D spatially-selective echo-panar (in excitation k-space) RF excitation pulse reduces the excitation volume in both the phase encoding and slice select directions
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
LIPO not an acronym but connotes removal of fat Gradient reversal fat suppression. Fat suppression method for spin echo (usually DWI) at higher field strengths. If the gradient applied with the refocusing RF pulse has a reversed polarity compared to the gradient applied with the excitation RF pulse, any through-plane chemical shift of fat signal will occur in the opposite direction. At higher field strengths (where the shift is far enough, 3T+), off-resonant fat does not receive both the excitation and refocusing pulses, and so does not contribute to the spin echo
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 magnetic (or electric) field vector to a given plane along the direction of propagation
LPC Local Phase Correction Removes phase errors in quantitative flow imaging with an optimized spatial low pass filter to subtract the background offset which is mainly caused by residual eddy currents
LPH Left-Posterior-Head Frame of reference for user-defined diffusion encoding directions. See also MPS and XYZ
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
MAGiC Creation of multiple image contrasts from a single MRI scan, using Bloch simulation. Contrast of images can be changed after the scan by synthetically changing acquisition parameters such as TR, TE and TI. See SyMRI.com
MAP Multi-Angle Projection
MARS Metal Artefact Reduction Sequences Pulse sequence optimisation to achieve metal-artefact minimisation (e.g. increase receiver bandwidth, etc; more info here). Not a specific method or product
MART Modulated Angle Refocusing Train
MAST Motion Artifact Suppression Technique
MAVRIC SL Multi-Acquisition with Variable Resonances Image Combination, SLab selective 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. A spectrally-correlated deblurring technique is applied to the final composite image
MC MultiChunk
MC MultiConnect
MDDW Multi Directional Diffusion Weighting
MDE Myocardial Delayed Enhancement Late Gadolinium Enhancement (LGE). Washout of injected contrast agent is slower in necrotic tissue. About 15 minutes after injection that tissue is enhanced compared to normal myocardium. A 2D segmented inversion recovery (IR) gradient echo sequence is usually used, or a PSIR acquisition
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
mDIXON XD modified DIXON See mDIXON. For mDIXON FFE (FFE = gradient echo) "XD" refers to extension to all body areas, by use of a 7-peak fat model and correction for B0 variation in large fields of view. Shorter minimum echo spacing is allowed, echo-times optimisation is improved. mDIXON XD allows subtractionless contrast-enhanced magnetic resonance angiography (CE-MRA)
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
MOLLI Modified Look-Locker Inversion Recovery Method of cardiac T1 mapping in a breath hold which provides high-precision, and with careful optimisation, good accuracy. A sequence of single-shot balanced SSFP images are acquired, one-per-heartbeat, after an inversion recovery preparation pulse. More images are acquired after subsequent inversion pulses. All images acquired are used in a single recovery-curve data set from which a T1 map is calculated. If images are acquired after administration of contrast agent as well, the extracellular volume (ECV) can be calculated
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
MRE Magnetic Resonance Elastography Evaluation of tissue stiffness. Motion encoding gradients are synchronized with a mechanical source of vibration applied to the patient. The amplitude of the shear wave in the tissue is encoded in the phase of the MRI image, and a tissue stiffness map may be calculated
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
MultiVane XD not an acronym XD denotes a significantly improved method for blade corrections (http://dx.doi.org/10.1002/mrm.24929) compared to original PROPELLER (see PROPELLER). No reference blade is used, and no iterations are required; linear equations for the relative shift between each pair of blades are formed and the entire system of equations is solved at once. Compatibility with SENSE parallel imaging is also added for higher acquisition speeds
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 See nema.org
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 The precession of the net magnetisation vector when it is out of alignment with the external magnetic field. The precessing net magnetisation generates an oscillating magnetic field which is measured in appropriately placed signal detection equipment. For a particular magnetic field strength the (resonant) frequency of precession can be calculated via the Larmor equation
NOE Nuclear Overhauser Effect Spectroscopy method in which an additional sequence is executed before the pulse sequence to saturate a difference nucleus; sensitivity of the measurement nucleus is enhanced due to polarization transfer via cross relaxation
NPW No Phase Wrap
NSA Number of Signals Averaged Number of repetitions of data acquisition, for signal averaging. Cf ACQ, NEX
og Gradient overplus
O-MAR Orthopedic Metal Artefact Reduction See VAT
O-MAR XD Orthopedic Metal Artefact Reduction As O-MAR but with added correction of through-plane distortion using SEMAC. See VAT, SEMAC
OP Out-of-Phase
OVS Outer Volume Suppression See REST
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 Modification of the readout gradient amplitudes in EPI, and additionally the relative phases of refocusing pulses in FSE (but not if single shot). Corrects undesired phase shifts such as those due to eddy currents or mechanical vibration. A prescan is required
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 Phase Contrast
pCASL Pseudo-Continuous Arterial Spin Labeling
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
PROMO PROspective MOtion correction technique In 3D PROMO patient motion is monitored throughout the scan using a three-plane spiral image navigators. Using image-based ROI tracking the scan can adjust to follow the motion and reacquire motion-corrupted k-space profiles
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
QISS Quiescent Interval Single Shot Non-[contrast] enhanced MRA for peripheral arteries. An in-plane saturation pulse suppresses background tissue signal, and a tracking saturation pulse to suppress venous signal prior to a quiescent inflow period. A 2D ECG-gated balanced SSFP readout follows
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 Saturation of signal using prepulses to suppress signal and/or define a volume (OVS)
RESOLVE Read-out Segmentation Of Long Variable Echo-trains Multi-shot diffusion-weighted EPI, using readout segmentation (collecting only sub-portions of k-space lines, with each shot) and a 2D navigator
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
RTFA Real-Time Field Adjustment
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
SEMAC Slice Encoding for Metal Artifact Correction SEMAC employs additional z-phase encoding steps to resolve distorted excitation profiles that cause through-plane distortions. By positioning all spins in a region-of-interest to their actual spatial locations, the through-plane distortions can be corrected by summing up the resolved spins in each voxel
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, [3D] VIEW
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
VAT View angle tilting Correction of in-plane distortion by View Angle Tilting (VAT). A gradient is added in the slice direction during readout, which matches the slice-selection gradient, in such a way that the view angle is tilted. Inhomogeneity induced geometrical shifts and hence the intensity changes are corrected, since the addition of the compensation which is independent from the field inhomogeneities, including both chemical shifts and susceptibility
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
VIEW Volume Imaging with Echo Weighting Commonly 3D VIEW. See SPACE. Cf also Cube, VISTA
VISTA Volumetric ISotropic T2w Acquisition See SPACE. Cf also Cube, [3D] VIEW. 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)
WARP not an acronym? Standard WARP: see MARS. WARP VAT: see VAT. Advanced WARP: see SEMAC
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 in 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
ZOOM not an acronym Orthogonal excitation and refocussing RF pulses used to reduce the volume from which signal is detected
ZOOM ZOnal Oblique Multisection EPI Oblique excitation and refocussing RF pulses used to reduce the volume from which signal is detected (small FOV imaging)
ZOOMit not an acronym 2D RF pulses used to excite a reduced FOV requiring parallel-transmit hardware

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