Glossary

The boundary around an MRI magnet where the fringe field drops below 5 Gauss (0.5 mT). Below 5 Gauss, the field is generally considered…

FDA's premarket pathway for devices substantially equivalent to existing legally marketed predicates. Cleared devices receive a "K-number"…

Amorphous selenium flat-panel detector. Direct-conversion X-ray detector — selenium converts incident X-ray photons directly to electrical…

American College of Radiology accreditation for imaging facilities. Required (or near-required by payer policy) for CMS reimbursement of…

Siemens Advanced Modeled Iterative Reconstruction — the model-based iterative successor to SAFIRE on Siemens CT platforms. Standard on…

Application Entity title — DICOM identifier for a network-connected device. Used in every DICOM association handshake (C-ECHO, C-STORE,…

Hologic's stereotactic biopsy attachment. Converts a Selenia Dimensions / 3Dimensions mammography unit into an upright stereotactic-biopsy…

Elekta's current-generation 160-leaf multileaf collimator. Tungsten leaves with a projected width of 5 mm at isocenter across the full…

Canon Medical's Advanced intelligent Clear-IQ Engine — deep-learning CT reconstruction. Successor to the iterative-reconstruction-era AIDR…

Canon Medical (legacy Toshiba) Adaptive Iterative Dose Reduction 3D — the first-generation iterative reconstruction available across the…

GE HealthCare's blanket-like conforming receive coils for MRI. The AIR coil platform replaces rigid body / spine / head coils with…

GE HealthCare's deep-learning MRI reconstruction — the defining software feature on the current Signa MRI family (Artist 1.5T, Explorer,…

Total thermal energy an X-ray tube's anode can absorb before reaching damage threshold. Measured in HU (heat units) or MHU (mega-heat…

GE's first-generation iterative reconstruction algorithm. Reduces image noise, enabling lower-dose scans at equivalent image quality.…

GE's second-generation model-based iterative reconstruction. Successor to ASiR; standard on Revolution CT-era platforms and…

Standard 2D grayscale ultrasound image. 'B' for brightness — pixel intensity represents the amplitude of the returning echo at each depth…

Bismuth germanate (Bi₄Ge₃O₁₂) scintillator. Used in pre-ToF PET (Discovery VCT, Discovery STE). High light yield but slow decay (~300 ns)…

Siemens Healthineers' BioMatrix Technology — a platform-level MRI feature set introduced with the MAGNETOM Vida (first 3T BioMatrix, ECR…

Hologic's synthesized 2D image, reconstructed from the 3D tomosynthesis projection set rather than a separate 2D exposure. FDA-approved…

Dental cone-beam CT — volumetric imaging for dental implants, endodontics (root-canal anatomy), orthognathic / orthodontic planning, TMJ…

Cone-Beam CT — volumetric kV imaging acquired on the linac's on-board imaging system before each treatment fraction. Standard for…

Lateral skull radiograph used in orthodontic planning. Standardized geometry — patient positioned in a cephalostat with fixed…

Philips's late-generation Allura Xper generator (paired with R8.2 software). Upgradeable to Azurion HE — the software / workstation /…

Philips's image-processing and acquisition pipeline for interventional X-ray that reduces fluoroscopic dose 43–83% versus baseline Xper…

Two-stage cryocooler that maintains the MRI magnet's cold shields at ~40 K, limiting helium boil-off from the inner cryogen reservoir at…

Restricting the X-ray beam to the region of interest. In CT, collimation determines beam width along the z-axis (e.g., 64 × 0.625 mm = ~40…

Doppler imaging mode that displays blood-flow velocity as a colored overlay on the B-mode image. Convention: red toward the probe, blue…

Philips' combination of compressed sensing + SENSE parallel imaging — MRI acceleration that can shorten acquisition times by up to ~50% on…

Clear plastic mammography compression paddle that flattens breast tissue against the detector for imaging. Compression evens tissue…

Canon Medical (legacy Toshiba) coneXact reconstruction algorithm — the software that enables the Aquilion CX / CXL to generate 128 unique…

Computed Radiography — legacy phosphor-plate-and-reader system that bridged film-screen and direct DR. Photostimulable phosphor plate…

Computed Tomography Dose Index — standardized measurement of CT dose per scan rotation, measured in a CTDI phantom. Reported in mGy. The…

Curved-footprint (convex) ultrasound probe for abdominal, OB / GYN, and general radiology imaging. Wider field of view than linear, at…

Continuous-wave Doppler — measures peak velocities beyond PW Doppler aliasing limits. The trade-off: no range-gate, so the velocity…

Dose-Area Product (also kerma-area product, KAP) — fluoroscopic dose multiplied by beam area at the patient surface, integrated over the…

Data Acquisition System. The electronics chain that digitizes the analog signal from the CT detector array — converting per-channel…

FDA pathway for novel low / moderate-risk devices without a predicate. Briefer than PMA but more rigorous than 510(k) — establishes a new…

Siemens Healthineers' deep-learning MRI reconstruction — accelerates acquisition and/or raises effective image quality on…

Digital Imaging and Communications in Medicine — the universal standard for medical-imaging file formats and network communication. Every…

DICOM Modality Worklist — pulls scheduled exams from RIS / EHR to the scanner console, eliminating manual demographic entry at the…

DICOM C-STORE transaction — scanner pushes images to PACS over a DICOM association. The basic "send images to archive" operation, the…

GE's deep-learning CT image reconstruction — branded TrueFidelity, commonly referred to by the generic DLIR (deep-learning image…

Dose-Length Product — total CT dose × scan length, expressed in mGy·cm. Summary dose metric for a CT exam, derived from CTDI and reported…

Detective Quantum Efficiency — measure of how efficiently an X-ray detector converts incoming photons into useful signal. Expressed as a…

Direct (digital) radiography flat-panel detector — wired or wireless, with CsI on a-Si (indirect-conversion scintillator) or a-Se…

Philips digital MR receive coils for the dStream broadband architecture. RF digitization is performed at the coil connector; optical /…

Philips' digital receive architecture for MRI. Analog-to-digital conversion moves from the scanner console out to the coil itself — the…

Diffusion-Weighted Imaging — MR sequence sensitive to the random Brownian motion of water molecules. Areas of restricted diffusion (acute…

Small-diameter curved or microconvex ultrasound probe designed for internal-cavity imaging — transvaginal (TV), transrectal (TR), and…

Echo-Planar Imaging — ultra-fast MR sequence that acquires the whole 2D image in one excitation by rapid gradient-reversal switching.…

Fluorine-18 fluorodeoxyglucose — the dominant PET oncology tracer. Glucose analog labeled with the F-18 positron emitter. Half-life ~110…

FDA classifies device recalls into three classes by severity:

Fluorine-18-labeled fluorodeoxyglucose — the dominant PET tracer globally. Glucose analogue that is taken up by metabolically active cells…

Full-Field Digital Mammography — digital 2D mammography. Replaced screen-film mammography as the reimbursed standard in the 2000s.…

Linac beam mode where the flattening filter is removed from the treatment head. Profile is forward-peaked instead of flat, but dose rate…

Fast Healthcare Interoperability Resources — modern RESTful healthcare interoperability standard. JSON-based, web-native. The HL7…

Classical CT reconstruction algorithm — analytic single-pass method that filters projection data and back-projects to form the image. The…

Fluid-Attenuated Inversion Recovery — MR inversion-recovery sequence that nulls cerebrospinal-fluid signal. Periventricular lesions…

Real-time X-ray imaging during procedures. Continuous-wave or pulsed acquisition with the operator visualizing anatomy and instruments…

The effective area of the anode where X-rays are produced. Smaller focal spots produce sharper images but dissipate heat less efficiently…

Diameter of the opening in the CT gantry through which the patient table passes. 70 cm is the standard clinical bore; 78–82 cm wide-bore…

Germanium-68 rod source used for PET daily QC and normalization calibration. Half-life ~271 days. Decays to Ga-68 (positron-emitting…

GE HealthCare's garnet-based CT scintillator — the first new commercial CT scintillator material in roughly 20 years at launch. The…

Magnetic field gradient amplitude, measured in mT/m. Defines how sharply the field varies across space — combined with slew rate (T/m/s),…

GE HealthCare's fast-kVp-switching dual-energy CT approach. The X-ray tube rapidly alternates between low-energy (typically 40 kVp) and…

CT acquisition mode where the patient table moves continuously through the gantry while the gantry rotates and the X-ray tube fires.…

Health Level Seven — legacy healthcare messaging standard (v2.x) for clinical and administrative data interchange. The dominant interface…

Hounsfield Unit — the CT image pixel value, normalized to water (0 HU) and air (−1000 HU). Named for Godfrey Hounsfield, who built the…

Heat-rejection requirement placed on the room's air-conditioning by imaging equipment. Measured in kW or BTU/hr. Comprises cabinet heat…

International electrical-safety standard for medical electrical equipment. Modality-specific particular standards include 60601-2-33…

Integrating the Healthcare Enterprise — non-standards-body that defines implementation profiles for healthcare interoperability. IHE…

Intensity-Modulated Radiation Therapy — uses MLC to vary beam intensity across each treatment field, producing highly conformal dose…

Siemens's integrated Parallel Acquisition Technique — parallel-imaging acceleration that uses multi-coil spatial information to skip…

Family of CT reconstruction methods that iteratively refine the image to reduce noise at the cost of more computation per slice. Modeled…

High-power microwave vacuum-tube amplifier. Generates the RF energy that accelerates electrons through the linac waveguide. Used on…

Peak kilovoltage across the X-ray tube. Sets the energy spectrum of the X-ray photons; together with mA·s (tube current × exposure time),…

Flat-footprint ultrasound probe with parallel elements. High-frequency (5–18 MHz typical) — short-range, fine-detail imaging at the cost…

Cerium-doped lutetium-yttrium orthosilicate scintillator (Lu(2-x)YxSiO5:Ce). Fast decay time (~40 ns) and high light yield make it the…

Ultrasound acquisition along a single sample line, plotted over time. The result is a 1D position × time strip — high temporal resolution…

Tube current in milliamperes. Controls the number of X-ray photons produced per unit time. Together with kVp (peak voltage) and exposure…

Product of tube current (mA) and exposure time (seconds). The primary exposure parameter in radiography and the core dose driver. CT…

Simpler RF source than the klystron — a self-oscillating microwave generator that produces the RF energy for the linac waveguide. Used on…

Ultrasound transducer with a 2D grid of elements — enables electronic volumetric (3D / 4D) beam steering without mechanical scanheads.…

Manufacturer and User Facility Device Experience — the FDA adverse-event reporting database. Manufacturers must submit MDRs (Medical…

Mega Heat Units — the thermal capacity of an X-ray tube's anode. 1 HU = 1 watt-second × 1.35 (for three-phase generators); 1 MHU = 1…

Varian's standard-tier multi-leaf collimator. 120 leaves total, 5 mm leaf width at isocenter across the central 20 cm field, 10 mm at the…

Multi-Leaf Collimator — array of motorized tungsten leaves that dynamically shape the treatment beam aperture, enabling IMRT, VMAT, SRS /…

Modality Performed Procedure Step — DICOM message from the modality to RIS announcing procedure start / complete / discontinue. Closes the…

Mammography Quality Standards Act — federal law requiring FDA certification, ACR (or approved state body) accreditation, annual…

Philips's family of high-output rotating-anode X-ray tubes used in cath-lab and interventional systems. The dominant tube class on the…

Monitor Unit — the unit of linac dose-delivery measurement, defined by the dose registered on the in-head ionization chamber under a…

Monitor Units delivered per minute — linac dose rate. Standard tiers:

Nuclear Regulatory Commission — federal U.S. regulator of byproduct radioactive material in medicine. Agreement States (37 states)…

Philips' parallel-pixel ultrasound beamformer architecture on the EPIQ premium platform. Replaces the legacy line-by-line scan-converter…

On-Board Imager — Varian's on-linac kV imaging system. A kV X-ray tube and flat-panel detector are mounted on retractable arms orthogonal…

Picture Archiving and Communication System — the hospital's image archive and viewing infrastructure. Every modality's images flow into…

Single curved 2D dental image showing all teeth and jaw anatomy in one acquisition. The X-ray tube and detector rotate around the patient…

GE's high-output CT X-ray tube family. Performix Pro VCT 100 (~8.0 MHU) is the LightSpeed VCT-class tube. Predecessor and value-tier…

Positron Emission Tomography — detects coincident 511 keV photons from positron annihilation following injection of a positron-emitting…

Physical test object with known properties used to verify imaging scanner calibration. Modality-specific:

Small-footprint ultrasound probe with closely-spaced elements driven with phase-controlled timing to electronically steer the beam.…

A category of CT detector technology that counts and energy-resolves individual X-ray photons rather than integrating their summed signal…

Canon Medical (legacy Toshiba) Pianissimo Noise Reduction — the MRI gradient acoustic-noise-reduction technology that shipped on the…

In helical CT, the ratio of table travel per rotation to total detector z-axis coverage. Pitch 1 spreads the helix thinner with gaps;…

FDA Premarket Approval — full safety and effectiveness review for high-risk or novel devices. The most rigorous FDA pathway, distinct from…

Photomultiplier Tube — vacuum-tube photodetector that converts scintillation light from gamma-camera or PET crystals into an electrical…

Low-dose localizer image acquired before the diagnostic CT scan. The X-ray tube parks in a fixed position (AP / lateral) while the table…

Physical receptacle on an ultrasound cart where a transducer connects. Premium carts have 3–4 active probe ports for rapid swapping…

A programmed timing pattern of RF pulses and gradient switching that acquires MRI images. T1, T2, FLAIR, DWI, EPI, gradient-echo, MR…

Pulsed-wave Doppler — Doppler sampling from a defined range gate along the beam, measuring velocity at a specific anatomical point. The…

Philips's single-crystal ultrasound transducer technology. Replaces the conventional polycrystalline-ceramic piezoelectric stack with a…

GE HealthCare's Bayesian penalized-likelihood PET reconstruction algorithm. Combines maximum-likelihood iterative reconstruction with a…

Qualified Medical Physicist — board-certified clinical medical physicist (American Board of Radiology, American Board of Medical Physics,…

Siemens' photon-counting CT detector — the direct-conversion cadmium-telluride (CdTe) detector at the heart of the NAEOTOM Alpha family.…

Catastrophic loss of superconductivity in the magnet. The superconducting wire transitions to normal resistance, energy stored in the…

Varian's volumetric-modulated arc therapy (VMAT) implementation. During beam delivery, the gantry rotates continuously while the multileaf…

Mathematical filter applied during CT image reconstruction. Sharp kernels (bone, lung) emphasize edges and high-frequency content at the…

Radiofrequency Power Amplifier (RPA) — broadband, high-power amplifier that drives the MRI transmit coil. Duty-cycle-limited; produces the…

Radiology Information System — scheduling, ordering, and reporting system for radiology. Typically integrated with PACS (image storage /…

Time for one full gantry rotation on a CT scanner. Typical range: 0.25–0.35 s (fast, cardiac-tier) to 2.0+ s (slow, low-dose pediatric /…

Radiation Safety Officer — the named, qualified individual responsible for the radiation-safety program at a facility that handles…

Rb-82 — cardiac PET perfusion tracer. Generator-produced from strontium-82 parent (~25-day half-life in generator); very short half-life…

Specific Absorption Rate — RF power deposited in tissue per unit mass, measured in W/kg. Regulatory limit protects against tissue heating…

Stereotactic Body Radiotherapy — SRS applied outside the cranium. Lung, liver, prostate, spine, pancreas, adrenal, oligometastatic…

Philips' parallel imaging technique for MRI. Uses the spatial sensitivity profiles of a multi-element receive coil to reconstruct the full…

Process of making the MRI magnetic field homogeneous across the scan volume. Two layers:

Siemens' spatial-compounding ultrasound imaging technology. Acquires multiple steered-angle scan lines per frame (up to 13 lines of sight…

Solid-state semiconductor light-sensor technology that replaces conventional photomultiplier tubes (PMTs) in modern PET detectors. A SiPM…

Rate at which the MR gradient field changes, measured in T/m/s. Defines how fast the gradient can switch between values within a pulse…

Number of simultaneous slices a CT scanner acquires per gantry rotation. Drives whole-body coverage speed, cardiac temporal resolution,…

Rotating electrical interface in a CT gantry. Transfers power, control signals, and detector data between the stationary frame and…

GE's prospective ECG-gated cardiac CT acquisition mode. Synchronizes scan timing to a single cardiac phase per heartbeat, eliminating the…

Single-Photon Emission Computed Tomography — gamma camera rotates around the patient acquiring projection data, reconstructed into 3D…

Stereotactic Radiosurgery — single-fraction (or few-fraction, "fractionated SRS") high-precision ablative radiation. Brain metastases,…

Siemens' rotating-anode X-ray tube family with a liquid-metal bearing instead of the conventional ball-bearing anode axle. A thin film of…

Bone density expressed in standard deviations relative to young-adult peak bone mass. The headline DXA clinical number used in WHO…

Unit of magnetic field strength. 1 T = 10,000 Gauss. Named for Nikola Tesla. Clinical MRI field strengths span:

AAPM Task Group 142 — the consensus standard for linear-accelerator quality assurance. Defines daily, monthly, and annual test schedules.…

High-voltage switching vacuum tube in the linac's pulse-forming network (PFN). Drives the modulated high-voltage pulse that feeds the…

Siemens's Total imaging Matrix coil platform — multi-element matrix coils that can combine up to dozens of elements across body coverage…

Siemens' fourth-generation Total imaging matrix coil and receive platform. Introduced on MAGNETOM Aera / Skyra (2010) and carried across…

Time-of-Flight PET — measures the timing difference between the two coincident 511 keV photons from a single annihilation event,…

Digital Breast Tomosynthesis (DBT) — the X-ray tube sweeps a limited arc (typically ±7.5° to ±25° depending on vendor) acquiring ~9–25…

Ultrasound probe — converts electrical signal to acoustic waves and back. Piezoelectric crystal stacks (conventional) or silicon CMUT…

GE HealthCare's deep-learning image reconstruction stack for CT — the FDA-cleared (2019) trained-neural-network reconstruction algorithm…

Siemens' extended-axial-FOV PET detector option on Biograph TruePoint-era platforms (Biograph 16 / 40 / 64). TrueV adds 48 detector blocks…

Expected useful life of an X-ray tube, typically measured in scans, mA·s, or hours depending on modality. The single most-watched…

Siemens' Ultra Fast Ceramic scintillator — the CT detector material that shipped on the SOMATOM Sensation family and continued into…

Philips's earlier high-frequency interventional-X-ray generator platform — revisions R7.x and R8.1 shipped on Allura Xper. Predecessor to…

Volumetric Modulated Arc Therapy — the gantry rotates continuously while MLC, dose rate, and gantry speed modulate simultaneously.…

GE's table-shuttle acquisition mode that covers volumes larger than the detector z-coverage in a single breath-hold by oscillating the…

Copper cavity structure that accelerates electrons through cavity-by-cavity RF coupling driven by the klystron or magnetron.…

Display parameters that map CT Hounsfield Unit values to screen brightness. "Level" centers the display range; "window" sets the range…

Philips matrix-array transducer technology. The flagship X6-1 probe uses ~9,000 active elements — roughly 35× a conventional phased-array…

Bone density expressed in standard deviations relative to age-matched peers (versus T-score, which compares to young-adult peak). Z ≤ −2.0…

Siemens' flying focal spot technology. Inside the STRATON tube, an electron-beam deflection mechanism rapidly switches the focal spot…