Glossary

Radiology and image

189 entries in this specialty.

Microwave ablation Image-guided oncological interventional technique in which a needle antenna is introduced inside a solid tumor mass to apply electromagnetic energy in the microwave range. This energy induces a rotation of the water dipoles, generating heat that destroys pathological cells through coagulative necrosis.

Also: percutaneous microwave · microwave thermoablation · MWA

Radiofrequency ablation Minimally invasive image-guided therapeutic procedure in which a needle-shaped electrode is introduced directly into a solid tumor to apply high-frequency electromagnetic energy. This alternating current generates heat by ionic friction in the target tissues, reaching temperatures that destroy tumor cells by thermal coagulative necrosis while preserving healthy parenchyma.

Also: radiofrequency thermoablation · thermal ablation · RFA

Helical acquisition Continuous method of obtaining images in computed tomography that consists of the constant horizontal translational movement of the patient's stretcher through the gantry while the X-ray tube rotates and emits radiation uninterruptedly. It allows you to quickly collect a continuous volume of data free of intermediate anatomical gaps.

Also: spiral acquisition · TC helical · volumetric spiral scan

Digital subtraction angiography An interventional fluoroscopic imaging modality that uses computer processing to remove background bony structures and soft tissues from a series of continuously obtained radiographic images. By subtracting the baseline control image from the images obtained after the injection of iodinated contrast, it provides a clear visualization of the lumen of the vessels.

Also: digital subtraction arteriography · angiographic digital subtraction · ASD

Tilt angle Angle by which the net magnetization of hydrogen protons is deviated from its original parallel alignment direction along the main magnetic field upon application of a radiofrequency pulse. It is selected according to the type of sequence, using ninety degrees in spin-echo sequences and lower values in gradient-echo sequences to accelerate the acquisition speed.

Also: flip angle · rotation angle · magnetization deflection · excitation angle

Insonation angle Acute angle formed between the direction of the ultrasound beam emitted by the transducer and the direction of blood flow within the explored vessel. It is imperative to properly adjust this parameter on the equipment and keep it below sixty degrees, since the Doppler calculation of velocity depends directly on the cosine of said angle.

Also: Doppler angle · angle of acoustic incidence · flow beam angle

Positron annihilation Physical reaction that occurs when a positron emitted by an unstable nucleus of a radiopharmaceutical collides with a nearby free electron from the tissue. Both undergo a mutual decay of mass that transforms into the emission of two gamma photons of identical energy, five hundred and eleven kiloelectron-volts, traveling in opposite directions.

Also: positron decay · positron-electron collision · mutual annihilation radiation

Anisotropy in ultrasound Physical property presented by certain structures with organized fibrillar architecture, such as tendons or muscles, by which their ultrasound appearance changes depending on the angle of incidence with which the ultrasound beam interacts. If the transducer is not placed exactly perpendicular to the fibers, they may appear artificially dark, simulating tendinitis.

Also: tendon anisotropy · anisotropy artifact · variation of echogenicity by angle

Rotating anode Tungsten alloy component in the shape of a heavy disc that rotates at high revolutions inside the X-ray tube, designed to receive the impact of the jet of accelerated electrons coming from the cathode. By rotating at high speed, it effectively distributes the thermal energy generated over a larger area, preventing metal from being damaged locally.

Also: rotating anode · tungsten rotating disc · fast rotating anode

Radio frequency antenna Device designed to emit pulses of electromagnetic waves towards the patient's body in order to excite hydrogen protons, or to act as a receiver by capturing the weak electromagnetic signal that they release during the relaxation process. Its selection and positioning over the region of interest determines the quality and signal-to-noise ratio of the resonance study.

Also: radio frequency coil · resonance antenna · MR receiver coil

Mammary harpoon Flexible metal wire provided with a small anti-return hook or spring at its distal end that is introduced under ultrasound or mammographic control directly into a non-palpable breast lesion. It serves as a physical guide for the surgeon to locate the lesion during the surgical intervention and perform a precise removal while preserving healthy tissue.

Also: mammary needle marker · harpoon location guide · breast marking wire

Beamwidth Artifact Distortion of the ultrasound image that occurs when the ultrasound beam, diverging in deep planes, is wider than the small structure it is exploring, causing echoes from adjacent tissues to be averaged laterally. This visually translates into a loss of edge sharpness or the appearance of echoes in liquid structures.

Also: artifact by beam thickness · ultrasound beam dispersion · side beam blur

Magic Angle Artifact Increased signal intensity with a hyperintense appearance that appears in magnetic resonance sequences with short echo times, affecting tendons or ligaments that have organized collagen fibers and are oriented at an angle of fifty-five degrees with respect to the axis of the main field. It can falsely simulate tendonitis.

Also: magic angle · 55 degree collagen artifact · hypersignal due to fibrillar orientation

Ring Artifact Calibration error in computed tomography that manifests itself visually as a series of bright or dark concentric circles fixedly superimposed on the reconstructed image, centered on the axis of rotation of the equipment. It occurs when one or more individual detectors in the array have an abnormal response or faulty calibration, requiring recalibration of the system.

Also: circular CT artifact · concentric circles in CT · defective detector artifact

Zipper Artifact Linear band of noisy interference that crosses the magnetic resonance image from side to side, typically affecting the phase coding plane. It is caused by the penetration of electromagnetic waves or stray radio frequency signals into the interior of the resonator room, commonly through a poorly closed door or defective shielding.

Also: zipper artifact · radiofrequency interference in MRI · zipper line

Crossover Artifact Distortion that occurs in MRI studies that acquire multiple adjacent anatomical sections simultaneously, characterized by a loss of signal intensity and contrast. It is caused by the superposition of radiofrequency pulses between very close neighboring slices, requiring leaving safety spaces between slices.

Also: interference between MR slices · crosstalk · slice overlap artifact

Chemical Displacement Artifact Distortion in magnetic resonance imaging characterized by a bright band at one fat tissue-water interface and a dark band at the opposite interface, projected along the direction of frequency encoding. It is produced by the small difference in the precession frequency of the protons of water and fat, which alters the correct coding of their spatial position.

Also: chemical shift · chemical shift · chemical change artifact

Side Lobe Artifact Distortion that appears in ultrasound images characterized by the projection of false echoes coming from structures located on the sides of the main beam, due to the presence of secondary ultrasound beams that emerge at an angle from the edges of the transducer. This causes spurious echoes to be drawn inside cavities with anechoic content.

Also: ultrasound lateral lobe · side lobe echoes · secondary beam artifact

Motion Artifact Distortion or blurring that manifests itself in medical computed tomography or magnetic resonance images due to patient displacement or physiological movement of organs during data acquisition. It visually translates into double contours, ghost lines or low quality bands that compromise the diagnostic interpretation of the explored structures.

Also: movement artifact · motion blur · displacement artifact · image motion sickness

Refraction artifact Ultrasound distortion in which a real structure is visualized duplicated, displaced from its spatial location or with distorted edges, due to the deviation of the ultrasound beam when obliquely crossing an interface between two tissues with disparate propagation speeds. It is common when exploring through the rectus abdominis muscle, simulating duplications of pelvic structures.

Also: sound beam refraction · refraction duplication artifact · acoustic refractive deviation

Reverb artifact Alteration of the ultrasound image produced when the ultrasound beam repeatedly bounces back and forth between two highly reflective interfaces that are located in parallel. This generates a series of bright and equidistant horizontal lines that extend in depth, which do not correspond to real anatomical structures but to the late arrival of repeated echoes to the transducer.

Also: reverb echo · ultrasound reverberation · reverb lines

Magnetic susceptibility artifact Geometric distortion accompanied by loss of signal or abnormal brightness that occurs at the interface of tissues with very different magnetic properties, such as bone and air or in the presence of metallic implants. It is caused by the sudden alteration of the local magnetic field, which prevents adequate spatial coding of the magnetic resonance signal, affecting the interpretation of the paranasal sinuses or base of the skull.

Also: susceptibility distortion · magnetic interface artifact · signal loss due to susceptibility

Truncation artifact Distortion that occurs in magnetic resonance images at interfaces with very abrupt signal changes, manifesting as a series of thin light and dark lines parallel to the high transition interface. It is due to a mathematical limitation when trying to reconstruct a complex signal with a finite number of samples in K space, sometimes simulating spinal pathologies.

Also: Gibbs artifact · Gibbs oscillation · truncated edge artifact

Partial Volume Artifact Distortion that originates when a single volume voxel contains within it two or more structures with different densities or signal intensities, so that the computer linearly averages their values on the screen. This phenomenon can erroneously simulate lesions that do not exist or mask small pathological findings that are smaller than the section thickness.

Also: partial volume effect · partial volume average · artifact by slice thickness

Comet Tail Artifact Specific variant of the echographic reverberation artifact in which the repeated echoes occur in a structure so small or thin that the horizontal lines merge completely. The visual result is a single, bright, conical band with sharp edges projecting posteriorly, typical of the presence of cholesterol crystals in gallbladder adenomyomatosis or small gas bubbles.

Also: comet tail · microbubble artifact · comet tail reverb

Metal artifact Geometric distortion and signal loss in the form of bright and dark radiated bands that appear in tomography or resonance studies in the presence of high-density or ferromagnetic materials. It is caused by the massive absorption of photons in the case of X-rays, or by the local alteration of the main magnetic field in MRI, obscuring the tissues adjacent to prostheses or orthodontics.

Also: metal artifact · metallic susceptibility artifact · metal distortion · metal bands

Beam hardening artifact Distortion in computed tomography images that manifests as dark bands or areas of lower density located between high-density structures such as cortical bone or prosthesis. It occurs because the X-ray spectrum is polychromatic, so that lower energy photons are preferentially absorbed when passing through a dense object, increasing the average energy of the remaining beam and falsifying the attenuation values.

Also: beam hardening · beam filtration artifact · dark interosseous bands

Diagnostic arteriography Invasive fluoroscopic procedure that consists of puncture of a peripheral artery to introduce a catheter selectively to the vicinity of an organ, allowing an iodinated contrast medium to be injected directly to visualize the lumen of the vessels. It is used to accurately identify arterial stenoses, aneurysms or active bleeding.

Also: diagnostic arterial angiography · arterial angiographic study · radiological arterial catheterization

Arthro-MRI Advanced high-resolution joint imaging technique that combines the prior intra-articular injection of a dilute gadolinium paramagnetic agent with a subsequent detailed study using multiplanar magnetic resonance imaging. It is the test of choice to diagnose complex glenoid labrum injuries in the shoulder, ligament tears or hip cartilage tears.

Also: magnetic resonance arthrography · intra-articular magnetic resonance · arthro-resonance

Artro-CT Joint diagnostic technique that associates the sterile intra-articular injection of an iodinated contrast medium with the subsequent acquisition of high spatial resolution images using computed tomography. It is an alternative for patients with suspected cartilage lesions who have formal contraindications to undergoing magnetic resonance studies.

Also: computed tomography arthrography · arthrotomography · Joint CT with contrast

Arthrography Radiological procedure that consists of sterile puncture of a joint cavity to inject air, iodinated contrast medium or a gadolinium solution, in order to distend the joint and delimit its structures. It is performed prior to a CT or MRI study to evaluate labral tears or internal ligament injuries.

Also: joint contrast study · X-ray arthrography · joint opacification

Attenuation Reduction of the intensity of a beam of ionizing radiation or the energy of an ultrasound wave as it passes through a tissue structure, secondary to physical processes of absorption and dispersion. In computed tomography, this parameter directly determines the gray tones of the image, where dense tissues produce high attenuation and light tissues allow a greater passage of the beam.

Also: radiation attenuation · beam energy loss · ray beam absorption

Acoustic attenuation Progressive loss of ultrasound wave energy as it propagates through body tissues, due to processes of absorption, dispersion and reflection of the wave. Tissues with high collagen or calcium content produce rapid attenuation, limiting the viewing depth of high-frequency transducers.

Also: loss of ultrasound signal · in vivo sound attenuation · sonic damping

Vacuum-assisted biopsy Minimally invasive breast interventional procedure that uses a device equipped with a hollow needle connected to a continuous vacuum suction system. It allows multiple large cylinders of tissue to be extracted consecutively through a single percutaneous puncture, reducing artifacts due to fragmentation and optimizing diagnostic yield.

Also: vacuum breast biopsy · vacuum-assisted biopsy system · BAV mamaria

Radiation shielding A set of dense physical barriers, commonly made of lead sheets or very thick concrete walls, designed to attenuate or absorb X-rays and prevent scattered radiation from penetrating areas adjacent to the examination room. It is a pillar in the hospital infrastructure to guarantee the job security of health personnel.

Also: lead shield · radiological shielding protection · radiation protective barrier

Field of view Maximum linear dimension measured in centimeters of the anatomical zone or area of interest that is covered, coded and finally displayed in a digital medical image reconstructed on the screen. By reducing the field of view while keeping the matrix size constant, fine detail resolution is achieved, although susceptibility to peripheral aliasing artifact is increased.

Also: FOV · acquisition visual field · image browsing window

Main magnetic field High intensity and highly homogeneous static magnetic force produced continuously by the resonator magnet, responsible for parallel aligning the spins of the hydrogen atoms in the patient's body. Its power is measured in the Tesla unit, with clinical equipment with powers of one point five or three Teslas being common in normal practice.

Also: field B0 · static field intensity · main magnet

Ring pickup Contrast distribution pattern on CT or MRI characterized by bright peripheral enhancement surrounding a non-enhancing necrotic, cystic, or avascular center. It is typical of expansive processes such as brain abscesses, tumor metastases with central necrosis or foci of caseous necrosis.

Also: ring enhancement · peripheral ring capture · marginal enhancement pattern

PICC catheter Central venous line of peripheral insertion that is introduced through a superficial vein of the arm, usually the basilic vein, so that its distal end is located in the lower third of the superior vena cava. It is excellent venous access

Cyclotron Particle accelerator of circular design that uses oscillating magnetic and electric fields to accelerate ions to high energies, subsequently bombarding a stable target to produce positron-emitting radionuclides. It is equipment to supply short half-life radiopharmaceuticals to PET diagnostic units.

Also: positron accelerator · circular particle accelerator · cyclotron radionuclide generator

Percutaneous kyphoplasty Variant of vertebroplasty in which, before introducing the acrylic cement, a high-pressure balloon is inserted and inflated inside the collapsed vertebra to try to recover its anatomical height and reduce secondary angular kyphosis. It is a treatment for vertebral compression fractures that optimizes the restoration of the spine.

Also: balloon kyphoplasty · kyphoplasty · percutaneous restoration of the vertebral body

CAD-RADS Classification International coding system designed to standardize reporting of cardiac computed tomography of the coronary arteries in patients with chest pain or suspected heart disease. It classifies the findings into categories according to the degree of luminous stenosis observed in the arteries, providing therapeutic and follow-up recommendations.

Also: CAD-RADS · classification of coronary stenosis by CT · coronary structured report

EU-TIRADS Classification Adaptation of the TI-RADS classification promoted by the European Thyroid Association to harmonize and simplify the ultrasound evaluation of thyroid nodules within the European clinical context. It uses a visual scheme based on five categories of suspected diagnosis to guide decisions about aspiration biopsy or lesion control.

Also: EU-TIRADS · European classification of thyroid nodules · European thyroid scale

LI-RADS Classification Standardized reporting and classification system for tomography and resonance imaging designed for patients with chronic liver disease and high risk of developing hepatocellular carcinoma. It categorizes the observed liver nodules according to the probability of malignancy, based on dynamic patterns such as arterial hyperenhancement and delayed contrast washout.

Also: LI-RADS · liver injury data system · hepatocellular classification

PI-RADS Classification Standardization scheme used for the interpretation and reporting of magnetic resonance imaging studies of the prostate in suspected neoplasia. It assigns a score on a scale of one to five to indicate the likelihood of the presence of a clinically significant tumor, helping to determine the need for a targeted biopsy.

Also: PI-RADS · classification of prostate image · MRI prostate scale

TI-RADS Classification Standardized categorization and reporting system designed for the ultrasound assessment of thyroid nodules, assigning scores according to morphological criteria such as composition, echogenicity, shape, margins and echogenic foci. This classification stratifies the risk of malignancy of the lesion and determines the recommendations for performing an aspiration puncture.

Also: TI-RADS · classification of thyroid nodules · thyroid ultrasound stratification

Magnetic resonance cholangiopancreatography Non-invasive magnetic resonance imaging technique that uses highly T2-weighted sequences with long echo times to make static fluids of the bile and pancreatic ducts shine brightly while canceling out background tissue. It allows detailed anatomical reconstructions of the biliary tree to be obtained virtually, without the need for catheterization.

Also: cholangioresonance · MRCP · MRI of bile ducts

Percutaneous cholecystostomy Emergency interventional procedure that consists of the percutaneous insertion of a drainage catheter directly into the distended gallbladder under ultrasound and fluoroscopic guidance. It is indicated in patients with acute lithiasic cholecystitis who present a prohibitive surgical risk to undergo a cholecystectomy.

Also: cholecystostomy · percutaneous gallbladder drainage · transhepatic bladder biliary drainage

Parallel hole collimator Type of lead collimator used in gamma cameras that has parallel channels that allow the selective passage of those gamma photons that travel in a direction perpendicular to the face of the detector. Those photons emitted at an oblique angle are absorbed by the internal lead partitions, guaranteeing a faithful and distortion-free representation.

Also: parallel multichannel collimator · parallel lead collimator · parallel channel collimator

Pinhole collimator Lead shielding device provided with a single tiny hole of conical geometry at its end, which functions to project inverted and magnified images of small organs. It is the collimator of choice in thyroid or pediatric scintigraphy, as it provides spatial resolution of small anatomical details at the expense of sensitivity.

Also: pinhole collimator · single hole collimator · needle collimator

Barium contrast Aqueous suspension of barium sulfate, an insoluble mineral compound of high atomic weight that greatly attenuates X-rays, formulated for opacification and detailed study of the lumen of the digestive tract. Its administration orally or by enema allows optimal delineation of the contour of the esophageal, gastric, duodenal and colon mucosa, detecting strictures or masses.

Also: radiological barium sulfate · barium porridge · barium contrast

Gadolinium contrast Paramagnetic contrast agent for intravascular or intra-articular use that locally alters the relaxation times of water protons, selectively increasing the brightness on T1-weighted MRI sequences. It is used to delineate tissue vascularization, the integrity of the blood-brain barrier, and the presence of neoplastic or inflammatory lesions.

Also: paramagnetic contrast medium · gadolinium agent · magnetic gadolinium

Water-soluble iodinated contrast Chemical compound that contains iodine atoms with high electron density that attenuate X-rays, used intravenously, intraarterially or intracavitary to increase the contrast of vascular structures and organs in computed tomography and fluoroscopy. Its formulation is usually non-ionic and low osmolarity to minimize the risk of allergic reactions or kidney toxicity.

Also: iodinated contrast medium · iodinated agent · radiological iodine contrast

Scintillation Crystal Component of nuclear medicine equipment, commonly made of sodium iodide doped with thallium, capable of interacting with incident gamma photons to absorb their energy. This interaction generates flashes of visible or ultraviolet light proportional to the energy of the absorbed photon, which are transmitted to signal amplifier devices.

Also: scintillation detector · gamma radiation detector crystal · inorganic scintillation crystal

Piezoelectric crystal Fundamental active component located at the tip of the ultrasound transducer, made of synthetic ceramic materials that undergo high-frequency mechanical vibrations when stimulated by an alternating electrical current. These microvibrations translate into the emission of the ultrasound beam that penetrates the patient's body tissues.

Also: piezoelectric element · ceramic crystal transducer · active ultrasound crystal

Dacryocystography Radiological examination of the tear duct that uses cannulation of the punctum to inject a small amount of radiopaque contrast medium under fluoroscopic control. It allows to precisely delineate the presence and level of pathological obstructions in the lacrimal sac or nasolacrimal duct, useful in patients with persistent lacrimation.

Also: contrast study of tear ducts · dacryocystogram · tear x-ray

Breast density Qualitative and quantitative attribute that describes the proportion of fibroglandular and supporting tissue in relation to fatty tissue within the breast, assessed visually in mammographic studies. High breast density not only reduces the sensitivity of mammography to detect small lesions due to masking, but also represents a risk factor for the development of neoplasms.

Also: breast density pattern · density of the breast parenchyma · ACR density classification

Transjugular intrahepatic portosystemic shunt Complex interventional procedure that consists of the creation of an intrahepatic communication tract that connects the portal vein with a suprahepatic vein through the placement of a metallic stent. It is designed to reduce pressure in the portal territory in patients with advanced liver cirrhosis who suffer from bleeding from esophageal varices or ascites.

Also: TIPS derivation · percutaneous portosystemic shunt · TIPS

Flat panel detector Advanced direct digital radiology technology that uses an array of flat sensors to capture and convert X-rays directly into electrical signals without the need for intermediate reading processes. It provides diagnostic images almost instantaneously, with high resolution and dynamic range using lower radiation doses.

Also: direct digital detector · FPD · digital radiography flat panel

Radiation detector Electronic device designed to intercept attenuated X-ray photons emerging from the patient's body, transforming them into proportional electrical signals for computer processing. Its efficiency in capturing and converting photons largely determines the radiation dose required to form a high-quality diagnostic image.

Also: CT detector · radiation sensor · solid state detector

DICOM International medical data communication standard designed to unify the transmission, exchange, storage and printing of digital diagnostic images and associated clinical information between systems from different manufacturers. This file format tightly integrates patient demographic and clinical data directly into the metadata structure of each study.

Also: digital imaging and communications in medicine · DICOM medical image format · DICOM standard

Distortion of breast architecture Alteration of the normal structure of breast tissue in mammography or tomosynthesis studies, characterized by lines radiating from a central point or by a focal retraction of the parenchymal edges, without visible dense mass. It is an indirect sign of suspicion that may indicate the presence of underlying breast cancer, a radial scar or surgical sequelae.

Also: mammary parenchymal distortion · structural alteration of the breast · architectural distortion

Color Doppler Ultrasound technique that allows real-time visualization of the speed and direction of blood flow within the vessels or cardiac cavities by superimposing a color map on the gray scale image. By convention, red represents flow approaching the transducer face and blue indicates flow away from it, facilitating the detection of stenoses or shunts.

Also: color Doppler ultrasound · color flow map · Chromatic Doppler

Dosimeter High-precision portable device that must be carried by professional personnel exposed to ionizing radiation to record and quantify the accumulated radiation dose during a given period of time. Its periodic reading makes it possible to verify that the professional's exposure remains below the legal limits established to avoid biological damage.

Also: personal dosimeter · accumulated radiation meter · occupational dose sensor

Absorbed dose Physical quantity that quantifies the net amount of energy deposited by ionizing radiation per unit mass of any material or tissue exposed to the radiation beam, regardless of the type of radiation or its biological effect. It is expressed in the Gray unit and serves as the basis for the calculation of all dosimetric risk parameters.

Also: physical radiation dose · energy deposited by radiation · Radiological Gray

Radiation dose Net amount of ionizing energy deposited per unit of mass in the body tissues of the patient exposed to medical examinations with X-rays or other types of radiation, the estimation of which is crucial to monitor radiation safety. Its quantification allows clinical protocols to be optimized to keep exposure as low as reasonably possible.

Also: dose absorbed by tissues · radiation exposure · radiation dose received

Effective dose Dosimetric magnitude in radiological protection that evaluates the overall probability of the appearance of stochastic effects on the body of the exposed patient, calculated by adding the equivalent doses received by each organ according to its susceptibility. It is expressed in Sieverts and allows the risk associated with different imaging techniques to be compared.

Also: global effective dose · weighted stochastic risk dose

Equivalent dose Dosimetric magnitude calculated to evaluate the risk of biological damage from radiation, which is defined as the absorbed dose in a tissue or organ multiplied by a specific weighting factor that takes into account the effectiveness of the type of radiation. It is measured in the Sievert unit and is useful for safety monitoring in radiodiagnostic environments.

Also: radiation-weighted dose · absorbed dose equivalent

Percutaneous transhepatic biliary drainage Biliary interventional procedure that consists of puncture of the intrahepatic bile ducts through the skin to place a drainage catheter that allows bile flow, either externally or internally crossing into the duodenum. It is indicated in patients with obstructive jaundice secondary to non-resectable bile duct neoplasms.

Also: DBTP · percutaneous biliary drainage · transhepatic biliary catheterization

Compton Effect Physical interaction in intermediate diagnostic energy ranges in which an incident X-ray photon collides with an electron from the outer shell of an atom, transferring only a part of its energy and deflecting in a different direction. It is the main cause of the scattered radiation that blurs the sharpness of the image and the occupational dose received by the personnel in the room.

Also: Compton inversion · Compton scattering · electron scattering

Photoelectric effect Physical phenomenon of interaction in which a low-energy This process is mainly responsible for the natural contrast between tissues in conventional radiographs, as it occurs more likely in structures with a high atomic number such as calcium.

Also: photoelectric absorption · photoelectric interaction · absorbing photon collision

Piezoelectric effect Reversible physical property possessed by certain crystalline materials with a polarized structure by which they generate an electrical charge or voltage on their external faces when subjected to mechanical pressure, and vice versa. It is the fundamental physical principle by which ultrasound transducers work, allowing them to emit and receive high-frequency sound waves.

Also: piezoelectricity · piezoelectric principle · piezoelectric phenomenon

Deterministic effects Adverse biological reactions due to damage and cell death induced by ionizing radiation, which manifest clinically only when the cumulative dose exceeds a specific minimum threshold, increasing in severity proportionally to the dose. They include early or late-onset pathologies such as skin erythema, sterility or cataracts.

Also: tissue effects of radiation · deterministic damage · non-stochastic effects

Stochastic effects Secondary biological effects from exposure to ionizing radiation whose probability of appearance increases proportionally with the dose received, but the severity of the symptoms is independent of the dose. As there is no minimum dose threshold, theoretically any exposure can cause mutations that induce the development of tumors or hereditary anomalies.

Also: probabilistic effects of radiation · stochastic late effects · radiation-induced carcinogenesis

Shear wave elastography Advanced non-invasive ultrasound modality that measures tissue stiffness by generating transverse shear waves from acoustic pulses, calculating their propagation speed to quantitatively estimate tissue elasticity. It is used for the assessment and staging of the degree of fibrosis in patients with chronic liver disease without resorting to invasive biopsies.

Also: shear elastography · shear wave elastography · SWE · ultrasound of liver stiffness

Embolization of uterine fibroids Minimally invasive endovascular procedure guided by fluoroscopy that consists of selective catheterization of the uterine arteries to inject microspheres that obstruct tumor irrigation. This selective vascular deprivation induces ischemia that reduces the size of the fibroid and reduces symptoms of pain and menstrual bleeding.

Also: uterine embolization · occlusion of uterine arteries · endovascular fibroid therapy

Barium enema Dynamic radiological examination that consists of the retrograde introduction of a barium sulfate suspension combined with air insufflation through a rectal probe to distend and opacify the colon under fluoroscopic guidance. It allows the colonic lumen and intestinal mucosa to be evaluated to detect pathologies such as intraluminal polyps, diverticulosis, neoplastic strictures or inflammatory colitis.

Also: double contrast colon enema · colon by enema · rectal barium study

Space K Abstract data matrix at whose points the digitized radio frequency signals are stored in an encoded manner, ordered according to their spatial frequency before being processed by the resonance equipment software. By applying the mathematical algorithm of the fast Fourier transform, these spatial data are transformed into two-dimensional anatomical images.

Also: raw data matrix · spatial frequency domain · k-space

Magnetic resonance spectroscopy Non-invasive diagnostic technique that analyzes the chemical composition of a tissue in vivo by measuring the relative concentration of cellular metabolites in a selected anatomical region. Instead of generating a conventional anatomical image, it produces a frequency spectrum that shows peaks of substances such as choline, creatine or N-acetylaspartate, providing metabolic information in brain tumors.

Also: in vivo spectroscopy · MR spectroscopy · MRI metabolite analysis

Cutting thickness Selectable technical parameter that defines the width or thickness in millimeters of the anatomical section that is analyzed and illustrated in a single portion of the tomographic or resonance image. A smaller slice thickness substantially decreases the partial volume effect and improves in-plane resolution, at the expense of increasing background noise or total scan time.

Also: cutting thickness · slice width · anatomical slice thickness

Mammary stereotaxy Image-guided interventional technique that uses digital radiographs taken from two known oblique angles to calculate the exact position of a non-palpable breast lesion using mathematical coordinates. It is used to precisely guide the vacuum biopsy needle toward microcalcifications or architectural distortions.

Also: stereotaxic guide · stereotaxic breast biopsy · mammary stereotaxic localization

Early arterial phase Vascular acquisition that is carried out quickly between fifteen and twenty seconds after the start of the contrast injection, coinciding with the peak concentration of the agent in the main arterial system. It allows angiographic studies to be performed with minimal concurrent venous contamination, being useful for mapping malformations, aortic dissections or arteriovenous fistulas.

Also: pure arterial phase · early arterial angiography · fast arterial flow phase

Corticomedullary phase Uptake phase in computed tomography and magnetic resonance imaging that is acquired approximately between thirty and forty seconds after the start of the contrast injection, characterized by an enhancement of the renal cortex while the medulla still remains hypodense. It is ideal for the evaluation of renal artery anomalies, the vascularization of solid masses, and the detection of arteriovenous fistulas.

Also: renal arterial phase · corticomedullary enhancement · early renal phase

Balance phase Late acquisition phase that is typically performed between three and five minutes after the contrast bolus, when the agent has been distributed evenly between the vascular compartment and the interstitial space. It is useful to evaluate contrast clearance in tumors or progressive accumulation of contrast in fibrotic tissues, as occurs in cholangiocarcinomas.

Also: interstitial phase · late venous phase · late wash phase

Excretory phase Late acquisition phase typically acquired between five and ten minutes after contrast injection, at which time the contrast medium has been filtered by the glomeruli and fills the excretory urinary tract. It allows detailed visualization of the contour and internal anatomy of the renal calyces, renal pelvis, ureters and bladder, being useful to rule out urothelial tumor pathology.

Also: urinary elimination phase · late phase of urography · late urological phase

Nephrogenic phase Tomographic or resonance acquisition performed between eighty and one hundred seconds after contrast administration, an interval in which the entire renal parenchyma, including cortex and medulla, enhances homogeneously. It is considered the phase with the highest diagnostic sensitivity for the detection and precise characterization of renal cell carcinomas or cystic masses.

Also: renal parenchymal phase · nephrographic phase · homogeneous renal enhancement

Hepatic portal phase Tomographic acquisition obtained between sixty and seventy seconds after injecting the contrast, characterized by the enhancement of the healthy liver parenchyma through the venous supply of the portal vein. It is the reference phase in the screening of liver metastases of colorectal origin, which stand out for their lesser enhancement against the bright liver background.

Also: portal venous phase · portal phase · hepatic venous enhancement

In phase and out of phase Diagnostic magnetic resonance technique that acquires images at two different echo times in which the magnetic moments of water and fat are perfectly aligned or in opposite directions. It is important to diagnose the presence of intracellular lipids in adrenal adenomas or hepatic steatosis, with a signal drop observed in out-of-phase images.

Also: sequences in phase and opposition · first order chemical shift · in-phase and out-of-phase

Bowtie filter Design metal filter with thick edges and thin center, which is placed at the exit of the X-ray tube in tomography to homogenize the intensity and dose of radiation that reaches the detectors. By selectively attenuating the peripheral edges of the beam that interact with the thinnest parts of the patient, you reduce unnecessary radiation to the periphery.

Also: bow-tie filter · peripheral beam attenuator · CT beam filter

Plebography Minimally invasive radiological examination that consists of the injection of an iodinated contrast medium into the venous system of an extremity to evaluate patency and flow in real time, using x-ray images or fluoroscopy. It allows us to detect the presence of deep vein thrombosis, chronic valvular insufficiency or vascular malformations.

Also: venography · venous angiography · venous contrast study

Fluoroscopy Medical imaging technique that uses a continuous beam of X-rays projected onto a detector to generate real-time moving images of the internal structures of the human body. It is used to guide interventional procedures, evaluate the transit of digestive organs and monitor the precise placement of internal medical devices such as catheters or prostheses.

Also: radioscopy · x-rays in real time · dynamic x-ray imaging

Pulse repetition frequency Parameter that defines the total number of individual ultrasound pulses emitted by the ultrasound transducer in a single second, regulating the speed scale that the equipment is capable of measuring precisely through the Doppler effect. Correctly adjusting this value is critical to avoid the aliasing artifact in high-speed streams.

Also: PRF · pulse repetition rate · ultrasound sampling frequency

Gammacamera Detection equipment used in nuclear medicine to capture and record in a two-dimensional manner the gamma radiation photons emitted from inside the patient after the administration of a radiopharmaceutical. It is composed of lead collimators, a scintillation crystal, an array of photomultiplier tubes and computer systems responsible for processing the signal.

Also: scintillation camera · gamma camera · gamma emission radiation detector

Ventilation-perfusion scan Combined nuclear medicine examination that comparatively evaluates bronchial airflow and pulmonary vascular perfusion through the use of radiolabeled gases and albumin microaggregates. It is a diagnostic tool when pulmonary thromboembolism is suspected, in patients with contraindications to undergo tomography with iodinated contrast.

Also: V/Q scintigraphy · pulmonary functional study of nuclear medicine · ventilation and perfusion scintigraphy

Bone scan Functional nuclear medicine study that uses the intravenous administration of a bisphosphonate labeled with technetium-99m to evaluate bone turnover and metabolic activity of the entire skeleton. It is a sensitive tool for the early detection of bone metastases, stress fractures imperceptible in conventional radiology and prosthetic loosening because it shows early metabolic changes.

Also: bone scintigraphy · bone scan · bone metabolic study

Gantry Physical structure in the shape of a ring that constitutes the main body of a computerized tomography equipment, inside which the X-ray tube, the detector array and the collimation systems are housed. This component rotates at high revolutions continuously around the stretcher that supports the patient.

Also: TC gantry · tomographic gantry · CT acquisition ring

Percutaneous gastrostomy Insertion of a feeding tube through the anterior abdominal wall into the gastric lumen under the guidance of diagnostic imaging, such as fluoroscopy or ultrasound, dispensing with classic endoscopic access. It is indicated in patients with severe dysphagia secondary to oropharyngeal tumors or advanced neurological disorders that prevent oral feeding.

Also: radiological gastrostomy · radiological placement of gastrostomy tube · image-guided gastrostomy

Ultrasound gel Aqueous compound formulated to have an acoustic impedance similar to that of skin tissues, which is applied uniformly to the transducer and the patient's body surface. Its function is to eliminate the layer of air that is placed between the transducer and the skin, preventing the ultrasound from being reflected before entering the body.

Also: ultrasonic conductive gel · acoustic coupling medium · ultrasound gel

Hydrophilic guide Metal alloy wire coated with a special polymer that acquires a slippery consistency when it comes into contact with water or saline solution. Facilitates the interventional radiologist's smooth navigation through arterial stenoses, complex atheromatous plaques, or markedly tortuous vessels during endovascular procedures.

Also: slippery guide · guide with polymer coating · hydrophilic guide wire

Hyperintensity Area or region that shows a higher signal intensity than surrounding or reference tissues on an MRI sequence, resulting in a bright, white or light gray visual appearance. This phenomenon usually indicates the presence of free water or inflammatory processes on T2-weighted sequences, or the accumulation of fat, protein, melanin, or subacute hemorrhage on T1-weighted sequences.

Also: hypersignal · bright signal in MRI · signal increase at resonance · hyperintense focus

Hypointensity Anatomical region that presents a lower signal intensity compared to the surrounding or reference tissues in magnetic resonance studies, being displayed in dark or black tones. It is characteristic of structures with low proton density such as cortical bone, calcifications, air, rapid vascular flows or localized hemosiderin deposits.

Also: hyposignal · low signal in MR · dark signal · hypointense focus

HIS Hospital information system that manages the clinical, administrative and billing aspects of a hospital, including the unique electronic medical record of admitted or outpatient patients. Its integration with specific systems in the radiology area allows a continuous flow of data without transcription errors between clinicians and specialists.

Also: hospital information system · hospital information system · hospital management software

Diffusion-weighted image Advanced functional MRI sequence that generates a contrast map based on microscopic differences in the random Brownian motion of water molecules within biological tissues. It is used for the early diagnosis of acute ischemic stroke, as well as for the detection and characterization of malignant neoplasms with high cellular density.

Also: broadcast sequence · diffusion MRI · DWI

Acoustic impedance Physical property of body tissues that determines the resistance that a medium offers to the passage of ultrasound waves through it. It is defined as the product of the density of the tissue and the speed of sound propagation inside it, and is responsible for generating echoes at the interfaces where two structures with different physical properties interact.

Also: sonic impedance · acoustic resistance of tissues · impedance

CT dose rate Standardized parameter that mathematically quantifies the average radiation dose rate distributed in a single section or plane during a computed tomography study, measured using calibration phantoms in a controlled manner. It is a reference value to monitor equipment performance and compliance with optimization guidelines.

Also: CTDI · tomographic dose index · dose per CT rotation

Mechanical index Dimensionless parameter that indirectly estimates the potential of ultrasound pulses to produce non-thermal biological effects in the patient's tissues, particularly gas cavitation or microbubble collapse. It is monitored during clinical ultrasound studies, and must be maintained at safe values in accordance with the principles of medical prudence.

Also: IM · cavitation index · mechanical ultrasonic indicator

Thermal index Dimensionless parameter that theoretically calculates the estimated maximum temperature rise in the patient's tissues that could occur due to the absorption of the energy dissipated by the ultrasound beam after prolonged exposure. It is relevant in obstetric ultrasound studies, where it is imperative to regulate power to protect embryo-fetal development.

Also: IT · tissue heating indicator · ultrasonic temperature

Vascular introducer Intravascular access device composed of a short plastic cannula provided with an internal hemostatic valve that is inserted into an artery or vein using the Seldinger technique. It allows the passage of guides, catheters or angioplasty balloons of various calibers without retrograde bleeding or tears in the wall of the access vessel.

Also: hemostatic introducer · vascular introducer sheath · endovascular access port

Isointensity Characteristic of a structure or lesion that shows the same signal intensity as the reference tissue or adjacent parenchyma in a specific MRI sequence. This similarity frequently makes direct visual detection of the anomaly difficult, requiring the use of different acquisition planes or the administration of contrast media for its correct delimitation.

Also: isosignal · equivalent signal · homogeneous signal intensity · isointense region

Faraday cage Shielded enclosure made up of copper sheets or other conductive materials that surrounds the examination room where the high-field magnetic resonator is located. Its main function is to intercept and cancel external electromagnetic and radio frequency interference from neighboring antennas or electrical equipment, preventing them from affecting the studio signal.

Also: MR radiofrequency shielding · Faraday shielding · room RF shielding

Kilovoltage Electrical parameter that defines the maximum potential difference applied between the cathode and the anode in the X-ray tube, controlling the acceleration speed of the electrons and the penetration power of the beam. Increasing the kilovoltage increases the number of X-rays capable of passing through dense structures of the body.

Also: kVp · X-ray tube voltage · peak kilovoltage

Contrast wash Dynamic phenomenon that consists of the progressive decrease in the attenuation or signal intensity of a tumor lesion in the late phases compared to its maximum enhancement reached during the arterial phase. This rapid kinetics of uptake and subsequent loss of contrast is a fundamental criterion of suspicion for the characterization of malignant tumors such as hepatocellular carcinoma.

Also: contrast lightening · tumor washout · contrast tissue wash

Nyquist limit Maximum frequency or velocity of blood flow that a pulsed Doppler ultrasound system is capable of measuring without signal distortion, and is defined as half the value of the configured pulse repetition rate. If the frequency offset exceeds this limit, the signal is falsely represented in the opposite direction.

Also: Nyquist frequency · Doppler aliasing limit · spectral sampling limit

Lymphography Specialized radiological study that consists of the injection of an oily contrast medium into the lymphatic vessels of the back of the foot or hand to visualize, through serial x-rays, the path of the lymphatic ducts and the internal structure of the nodes. It was used to diagnose lymphedema, lymph node metastases or the spread of lymphomas.

Also: study of lymphatic pathways · lymphatic contrast

Lutetium 177 Short-range beta radiation-emitting radionuclide used in theragnosis and targeted molecular oncology for the treatment of neuroendocrine tumors and advanced prostate cancer. By emitting localized beta particles, it destroys tumor cells that express specific receptors with minimal collateral damage to surrounding healthy tissues.

Also: 177Lu · radiotherapeutic lutetium · lutetium beta emitter

Focal spot Specific physical area of the surface of the anode of the X-ray tube on which the accelerated electrons from the cathode directly impact, being the point of origin from which the radiation photons are emitted. A smaller focal spot improves spatial resolution and decreases the geometric penumbra of the image, at the expense of a lower tolerance to heating.

Also: X-ray focus · radiation focal point · geometric tube focus

ADC Map Parametric image calculated from the MRI diffusion sequences that numerically quantifies the magnitude of water molecular motion in each voxel, independent of the T2 brightness effect. It allows us to objectively distinguish the true restriction of diffusion, typical of processes with high cellularity such as malignant tumors or acute ischemia, from those false positive phenomena secondary to a prolonged T2 relaxation time.

Also: apparent diffusion coefficient map · ADC map · apparent diffusion coefficient

Image matrix Arrangement in the form of a two-dimensional grid organized in columns and rows whose intersections define the individual pixels that make up a digital medical image reconstructed from the detector data. A larger matrix provides greater spatial resolution of internal details, but requires greater computing power for digital processing.

Also: image grid · array size · digital matrix dimensions

Hepatospecific contrast medium Specialized MRI contrast agent that, after initial uptake in the vascular compartment, is selectively internalized by hepatocytes and secreted through the bile ducts. It allows late acquisitions to be performed to differentiate benign regenerative nodules from malignant lesions devoid of functioning hepatocytes, such as metastases or hepatocellular carcinomas.

Also: MR biliary contrast · hepatobiliary contrast · hepatospecific gadolinium

Breast microcalcifications Small calcium deposits in the tissue of the mammary gland, imperceptible to palpation, which are visualized on mammography as tiny bright spots of variable morphology and distribution. Those with a pleomorphic, linear or branching appearance and with a grouped or segmental distribution require a biopsy, since they frequently constitute the only representation of a ductal carcinoma in situ.

Also: tiny breast calcifications · mammary calcium deposits · grouped microcalcifications

Microcatheter Small-caliber, highly flexible catheter, designed with hydrophilic materials that reduce friction to advance through small diameter tortuous blood vessels safely. It is a tool in interventional radiology to perform selective embolizations in the brain or abdominal organs in a controlled manner.

Also: selective infusion catheter · vascular microcatheter · small bore coaxial catheter

Myelography Diagnostic radiological examination that uses lumbar puncture to introduce a water-soluble iodinated contrast medium directly into the subarachnoid space surrounding the spinal cord under X-ray guidance. It makes it possible to reveal the presence of extruded disc herniations, spinal canal tumors or severe spinal stenosis that compress the thecal sac.

Also: conventional myelography · contrast study of the thecal sac · myelogram

Milliampere Electrical parameter that regulates the intensity of the current that flows through the cathode filament in the X-ray tube, determining the amount of radiation photons emitted in the useful beam. It is multiplied directly by the exposure time to define the total dose administered in the radiographic examination.

Also: mA · X-ray tube current · filament current intensity

Acoustic mottling Fine, grainy texture pattern of grays and whites that dominates ultrasound images of the parenchyma of solid organs such as the liver or spleen. It does not represent details of the actual microanatomy of the organ but is the result of the constructive and destructive interference of countless scattered reflected echoes.

Also: dapple noise · ultrasound speckle · ultrasound grain pattern

Protodiastolic notch Drop in blood flow velocity that is recorded immediately after systole and at the beginning of diastole in the Doppler spectral analysis of certain arteries such as the uterine arteries during pregnancy. Its pathological persistence beyond the twenty-fourth week of gestation is associated with a risk of developing preeclampsia or growth restriction.

Also: protodiastolic notch · diastolic notch · uterine spectral notch

Contrast-induced nephropathy Acute and generally reversible deterioration of renal function that is manifested by a transient increase in serum creatinine after the administration of iodinated contrast media, ruling out other alternative causes. Its pathophysiology is related to renal medullary vasoconstriction and direct oxidative stress induced by the high osmolarity or chemotoxicity of the contrast agent used.

Also: renal failure due to contrast · contrast-induced kidney damage

Percutaneous nephrostomy Percutaneous placement of a drainage catheter directly inside the collecting system of the renal pelvis under ultrasound and fluoroscopic guidance to divert obstructed urinary flow outward temporarily. It is a fundamental emergency procedure to preserve kidney function in the face of mechanical obstructive processes such as impacted stones or masses.

Also: nephrostomy · percutaneous urinary diversion · nephrostomy catheter placement

PACS Computer network system designed for the acquisition, long-term secure digital storage, rapid transmission, and display of diagnostic medical images on specialized workstations. It facilitates the elimination of printed analog boards, optimizing workflow and allowing simultaneous access to studies from any area of the hospital.

Also: image archiving and communication system · picture archiving and communication system · PACS network

Propeller pitch Dimensionless technical parameter in helical computed tomography that describes the relationship between the longitudinal displacement of the patient's table during a complete rotation of the tube and the total collimation of the X-ray beam. A larger value of the unit accelerates the acquisition time of the study at the expense of a slight loss of image resolution in the Z axis.

Also: pitch · propeller pitch ratio · step factor

MRI perfusion Functional technique designed to quantitatively or semi-quantitatively evaluate microvascular blood flow, cerebral blood volume and mean transit time at the tissue level. It is typically performed by monitoring the passage of a bolus of gadolinium contrast medium through the capillary bed using high-speed temporal sequences, and is useful in vascular accidents.

Also: MRI perfusion · brain perfusion image · Tissue perfusion MRI

PET-CT Hybrid imaging modality that fuses the metabolic and functional information obtained by positron emission tomography with the anatomical resolution provided by a conventional computed tomography in a single session. This combination allows localization of the exact anatomical location of areas with pathological metabolism, crucially optimizing oncological staging.

Also: positron emission tomography fused with CT · PET/CT · hybrid PET-CT tomography

Pixel Smallest two-dimensional element that individually constitutes a digital image on the screen, to which a numerical value is assigned that represents the level of dimming, brightness or color of that position in flat space. Its dimensions depend on the selected combination between the size of the reconstruction matrix and the total size of the field of view.

Also: image element · digital image point · two-dimensional pixel

Dose-length product Radiological magnitude that estimates the total energy imparted to a patient during a CT scan, calculated by multiplying the CT dose rate of the scan by the total length of the anatomical region scanned. It is typically expressed in milliray per centimeter and serves as the key parameter for protocol comparison.

Also: DLP · dose-length product · estimated total TC dose

Maximum intensity projection Three-dimensional reconstruction algorithm that selects and projects only the voxels with the highest attenuation or signal intensity values along a given viewing path. It is used in vascular studies such as angiotomography or angioresonance, since it allows contrast-filled vascular structures to be continuously highlighted, separating them from the adjacent soft tissues.

Also: MIP projection · MIP · maximum density reconstruction

Minimum intensity projection Image processing algorithm that projects onto a single plane only those voxels that have the lowest attenuation or signal values along the selected projection line. It is useful in the study of the lung parenchyma and the airway, since it selectively enhances air-filled structures such as the bronchi, facilitating the detection of mild bronchiectasis.

Also: MinIP projection · MinIP · minimum density reconstruction

Subcutaneous venous port Long-lasting central venous access device composed of a titanium reservoir with a silicone membrane that is implanted in the subcutaneous tissue of the chest and connected to a central catheter. It allows repeated access in a sterile manner using special needles to administer long-term chemotherapy treatments.

Also: subcutaneous venous reservoir · port-a-cath catheter · chemotherapy implantable port

Transarterial chemoembolization Fluoroscopy-guided oncological interventional procedure that consists of selective catheterization of the arteries that nourish a tumor, typically hepatic, to administer a concentrated dose of chemotherapeutic agents followed by embolizing material. A double therapeutic effect is achieved by inducing high local toxicity on the neoplastic cells while obstructing the arterial blood flow that allows their growth.

Also: hepatic chemoembolization · TACE · embolization with chemotherapy

Braking radiation Electromagnetic ionizing radiation that is produced inside the This physical braking process generates a continuous spectrum of photons, which constitutes the vast majority of useful radiation in radiology.

Also: bremsstrahlung · deceleration radiation · continuous emission of X-rays

Scattered radiation X-ray photons that undergo a change in their original direction of propagation after interacting with the atoms of the patient's body tissues through physical scattering phenomena. This radiation does not provide useful diagnostic information to the image and contributes to degrading the contrast of the study, in addition to representing the main source of dose for the room staff.

Also: secondary radiation · scattered x-rays · radiation scattering

Radioembolization Advanced modality of arterial brachytherapy in which microspheres loaded with the radioactive isotope Yttrium-90 are injected directly into the hepatic artery that supplies a tumor. By selectively impacting the tumor capillaries, it provides a dose of beta radiation on the tumor cells while preserving the rest of the healthy parenchyma.

Also: selective intra-arterial radiation therapy · SIRT · embolization with Yttrium-90

Radiopharmaceutical Chemical compound formed by the union of a radiation-emitting radionuclide and a carrier molecule with selective affinity for a specific metabolic process, organ or cellular receptor. After administration, it allows the biological function and molecular distribution to be evaluated in real time using nuclear medicine equipment, serving for the detection of pathologies or for targeted therapeutic purposes.

Also: radioactive tracer · radiotracer · radiolabeled compound · functional radioactive agent

Computerized radiography Transition technology in digital radiology that replaces conventional film with a chassis provided with a photostimulable phosphor plate that stores a latent image after being exposed to X-rays. Subsequently, this chassis is processed in a semi-automated manner in a digitizing laser reader that scans the plate to extract the data.

Also: photostimulable phosphorus radiography · CR · phosphor plate system

Periosteal reaction Biological response of the periosteum to mechanical, infectious, inflammatory or aggressive neoplastic stimuli, characterized by the deposition of new bone on the external cortical surface. Its morphology on radiological studies, which varies from a benign continuous line to aggressive onion layer patterns, offers clues to determine the growth rate of the underlying lesion.

Also: periosteal bone neoformation · periosteal ossification · periosteum response

Multiplanar reconstruction Digital processing technique that allows two-dimensional anatomical planes to be reconstructed in any spatial orientation from a single volume of three-dimensional data previously acquired in the axial plane. Facilitates detailed anatomic evaluation of complex or tortuous structures by providing views in the sagittal, coronal, or oblique planes without the need to re-irradiate the patient.

Also: MPR reconstruction · multiplanar formatting · multiplanar reformatting · MPR

Three-dimensional reconstruction Computer process that integrates and processes large sets of two-dimensional volumetric data obtained by tomography or resonance to generate realistic and manipulable three-dimensional models of anatomical structures. It facilitates pre-surgical planning of complex surgeries, the evaluation of complex bone fractures or the spatial representation of vascular malformations.

Also: 3D reconstruction · volumetric rendering · three-dimensional data visualization

Rear acoustic reinforcement Ultrasound phenomenon that consists of an increase in the intensity of reflected echoes and visual brilliance behind a structure that attenuates sound very little. It typically occurs when the ultrasound beam passes through a structure with purely liquid content, such as a simple cyst or the urinary bladder, so that the remaining energy leaving the fluid is greater than that passing through adjacent solid tissues.

Also: posterior reinforcement · increased sonic transmission · acoustic afterglow · acoustic reinforcement

Anti-diffusion grid Flat device composed of a series of extremely thin lead sheets, which is placed between the patient and the chassis or detector to selectively absorb low-energy dispersed radiation. By allowing the passage of only those photons that travel in a straight line from the X-ray tube, it improves the contrast and definition of the images.

Also: Potter-Bucky grid · anti-diffusion grid · contrast protective grille

Signal-to-noise ratio Parameter that evaluates the technical quality of a medical image by comparing the intensity of the useful signal component that represents the true anatomical structures against the unwanted background variability or noise caused by the system itself. A higher signal-to-noise ratio provides sharper-looking images, significantly reducing graininess.

Also: SNR · signal-to-noise ratio · image signal quality

RIS Computerized management system designed to optimize the daily workflow of radiology departments, taking care of scheduling appointments, recording scans, billing, and distributing radiological reports. It integrates with PACS systems to automatically link the images corresponding to each scan.

Also: radiology information system · radiology information system · RIS software

Fat saturation Sequence programming technique in magnetic resonance that selectively suppresses the signal from hydrogen atoms bonded to lipids, based on the difference in the precession frequency of the protons of fat with respect to water. By obscuring normal adipose tissue, it facilitates visualization of focal areas of inflammation or contrast medium deposition in adjacent structures.

Also: fat suppression · fat saturation · fat-sat · chemical fat suppression

Magnetic susceptibility sequence Optimized high-resolution three-dimensional magnetic resonance sequence that is sensitive to small local inhomogeneities in the magnetic field generated by the presence of iron, calcium or blood degradation products. It facilitates the detection of cerebral microbleeds, vascular calcifications, cortical hemosiderin deposits or the presence of intravascular thrombi.

Also: susceptibility sequence · SWI · susceptibility-weighted image

Spin-echo sequence Magnetic resonance sequence that uses an initial excitation pulse of ninety degrees followed, after a predetermined time, by a refocusing pulse of one hundred and eighty degrees to correct field inhomogeneities. This configuration allows obtaining a signal with tissue contrast weighted in T1, T2 or proton density, reducing local susceptibility artifacts.

Also: spin echo sequence · spin-echo

FLAIR sequence T2-weighted MRI sequence specifically designed to suppress high-intensity signal from free cerebrospinal fluid. By canceling the brightness of free water in the ventricles and subarachnoid space, it allows adjacent hyperintense pathological lesions, such as demyelination plaques or early infarcts, to stand out with visual clarity.

Also: inversion recovery with fluid attenuation · liquid attenuation sequence · FLAIR

Gradient-echo sequence Rapid acquisition MRI sequence that uses tilt angles less than ninety degrees and dispenses with the one hundred and eighty degree refocusing pulse, instead using the inversion of a magnetic gradient. By allowing short repetition and echo times, it is ideal for dynamic contrast-enhanced studies, three-dimensional angiography, and the detection of hemorrhage.

Also: gradient echo sequence · gradient-echo · GRE

STIR sequence Inversion recovery MRI sequence designed to selectively and effectively suppress the high intensity signal generated by body fat tissue. It is useful for the detection of bone edema, muscle inflammatory processes and hidden fractures, as it eliminates the shine of fat from the bone marrow and fascial planes, making pathological fluids shine brightly.

Also: payback with short echo time · fat suppression by inversion · STIR

Sialography Diagnostic radiological study designed to evaluate the excretory ducts of the major salivary glands, through cannulation of the mouth opening and injection of a contrast agent. It is useful to diagnose the presence of mucus plugs, obstructive stones, chronic strictures or destruction of the parenchyma in Sjögren's syndrome.

Also: sialogram · radiography of salivary glands · study of salivary ducts

Sign of the scimitar Radiological finding visible on chest radiographs characterized by an anomalous pulmonary vein that descends in a curved and vertical manner along the right heart border towards the diaphragm, resembling a scimitar. It is indicative of scimitar syndrome, a congenital anomaly where there is a right partial anomalous pulmonary venous return draining into the inferior vena cava.

Also: sign of the curved sword · scimitar vein · radiological scimitar syndrome

Sign of the double bubble Radiographic and ultrasonographic finding showing two prominent air- or fluid-filled cavities in the upper abdomen of a newborn, corresponding to the dilated stomach and proximal duodenum. It represents the presence of a complete duodenal atresia, where the lumen of the duodenum is obstructed, preventing the passage of gas or fluids towards the distal tract.

Also: double radiological bubble · sign of duodenal atresia · double bubble image

Sign of the candle Anteroposterior radiographic image of the chest of infants and young children showing a prominent triangular density with sharp edges projecting laterally from the superior mediastinum, resembling the sail of a ship. It corresponds to the visualization of a normal thymus that should not be confused with a pathological mediastinal mass or a consolidation of the upper lobes.

Also: thymic candle sign · thymic ship sail · normal thymic silhouette

Sign of the severed colon Radiographic finding characterized by abrupt gas distension of the transverse colon that ends at the level of the splenic flexure, with absence of gas in the descending colon. It frequently occurs in the context of severe acute pancreatitis, where the inflammatory process spreads along the phrenicocolic ligament causing a localized spasm in the left colon.

Also: colon cut · colon interruption sign · sign of pancreatitis in the colon

Coffee bean sign Radiological finding visible on simple abdominal radiographs that consists of a large intestinal loop distended by gas that adopts an ovoid shape with a dense central band that resembles the indentation of a coffee bean. It is pathognomonic of sigmoid volvulus, a surgical emergency characterized by torsion of the sigmoid colon on its own mesentery.

Also: sigma volvulus sign · radiological coffee bean · coffee bean appearance

Halo sign Tomographic appearance consisting of a focal area of ground-glass attenuation that completely surrounds a dense, solid lung nodule or mass. In a clinical context of immunosuppression, it is an early and characteristic clinical sign of invasive bronchopulmonary aspergillosis, representing the presence of perilesional alveolar hemorrhage.

Also: tomographic halo · hemorrhagic halo · dimming halo sign

Inverted halo sign High-resolution computed tomography finding characterized by a central area of ground-glass attenuation that is surrounded by a peripheral ring of dense consolidation. It is classically associated with cryptogenetic organizing pneumonia, although it can also manifest itself in processes such as tuberculosis, pulmonary infarction or sarcoidosis.

Also: reverse halo · reverse halo sign · tomographic atoll

Swirl sign Tomographic image showing a concentric spiral arrangement of blood vessels, bands of fatty tissue, and mesentery that rotate around a central point or axis of torsion. It is an indicator of torsion or volvulus of an intestinal loop, an ovarian cyst or the mesentery itself, reflecting the imminent mechanical vascular compromise of the affected structure.

Also: mesenteric whirl · mesenteric torsion sign · torsion spiral image

Acute radiation syndrome Set of clinical manifestations that occur in an individual after exposure of the whole body to high doses of ionizing radiation in a short period of time. It is characterized by successive phases of involvement of the hematopoietic, gastrointestinal and cerebrovascular systems depending on the net dose received, with potential cellular lethality.

Also: radiation sickness · SRA · acute radiation poisoning

BI-RADS System Standardized classification scheme designed by the American College of Radiology to unify terminology, reporting of findings, and management recommendations in breast imaging studies such as mammography, ultrasound, and magnetic resonance imaging. It organizes the results into categories from zero to six according to the probability of malignancy observed, facilitating clear communication between specialists.

Also: BI-RADS classification · breast reporting system · BI-RADS

Rear acoustic shadow Ultrasound artifact characterized by a dark or black band that projects behind a structure with a high sound attenuation coefficient or highly reflective. It occurs because the ultrasound beam is completely reflected or absorbed by dense elements such as gallstones or bone calcifications, preventing the sound from continuing its path to deeper planes.

Also: acoustic shadow · post sonic attenuation · rear shadow cone · stone shadow

SPECT-CT Hybrid molecular imaging technique that integrates single photon emission computed tomography to evaluate perfusion or receptors with diagnostic computed tomography to specify anatomical location. It offers an improvement in diagnostic specificity compared to conventional scintigraphic studies, especially in the study of bone pathology, myocardial viability and neuroendocrine tumors.

Also: single photon tomography with CT · SPECT/CT · hybrid SPECT scintigraphy

Vascular stent Self-expandable or balloon-expandable tubular device, made of metal mesh, which is deployed percutaneously by catheter inside a stenosed blood vessel. Its function is to restore and keep open the vascular lumen, ensuring adequate blood flow and preventing restenosis of the vessel after a previous angioplasty.

Also: vascular endoprosthesis · endovascular endoprosthesis · intravascular metal mesh

SUV Quantitative parameter used in positron emission tomography that expresses the relationship between the concentration of radioactive activity in a region of interest and the total dose of radiopharmaceutical injected, normalized by the patient's body weight. It allows the degree of cellular metabolism of a lesion to be assessed, serving as a guide to differentiate malignant from benign processes or to monitor the tumor response to chemotherapy.

Also: standardized pickup value · standard uptake value · SUV capture rate

Dual Energy TC Computed tomography technique that simultaneously acquires two sets of images using two different x-ray spectra, either through two independent tubes or a single energy-switched tube. It allows the chemical composition of the materials to be characterized, making it easier to differentiate uric acid deposits in droplets from calcifications.

Also: DECT · dual energy tomography · Dual source spectral CT

Cone beam CT Computed tomography modality that uses an X-ray beam with conical geometry and a planar detector to acquire a complete three-dimensional volume in a single rotation around the patient. It is a technique adopted in dentistry, maxillofacial surgery and image-guided radiotherapy due to its high spatial resolution for bone structures.

Also: CBCT · cone beam tomography · digital volumetric tomography

Diffusion tensor Advanced diffusion-derived magnetic resonance technique that allows three-dimensional mapping of the direction and anisotropy of the movement of water molecules in the brain parenchyma. By modeling the preferential diffusion of protons along myelin bundles, it enables virtual reconstruction of the major white matter tracts of the central nervous system.

Also: MR tractography · diffusion tensor image

Theragnosis Therapeutic concept in nuclear medicine that integrates diagnosis using molecular images with a subsequent targeted radiotherapy treatment using the same molecular chemical vector coupled to different radionuclides. This makes it possible to first accurately identify the target cell receptors in the patient using tomography and initiate selective treatment.

Also: integrated therapy and diagnosis · targeted nuclear medicine · theranostic

Echo time Time interval elapsed in a magnetic resonance sequence between the emission of the initial radiofrequency pulse that excites the spins and the reading or recording of the resulting echo signal. It is a parameter selected by the operator to control the weighting of the image, where short values reduce the influence of T2 decay and long values maximize it.

Also: echo reading time · echo interval

Relaxation time T1 Intrinsic physical parameter of each tissue in magnetic resonance that describes the time required for sixty-three percent of the longitudinal magnetization of hydrogen nuclei to recover after the interruption of a radiofrequency pulse. It varies depending on the molecular mobility of the environment, so that lipids have an extremely short T1 time while pure liquids show a long T1.

Also: longitudinal relaxation time · time constant T1 · longitudinal recovery

Relaxation time T2 Physical constant in magnetic resonance that measures the time required for the transverse spin magnetization to decrease by sixty-three percent due to natural interactions between neighboring magnetic spins. It reflects the loss of phase coherence between hydrogen nuclei, being especially long in free liquids and short in solid tissues.

Also: transverse relaxation time · time constant T2 · transverse decay

Repeat time Time interval that consecutively separates the application of an initial radiofrequency excitation pulse from the next identical pulse in an MRI acquisition sequence. By modifying this parameter, the operator controls the degree of longitudinal magnetization recovery before the next pulse, determining the T1 or T2 weighting of the study.

Also: TR · pulse cycle time · repeat interval

Multi-slice computed tomography Evolution of conventional computed tomography that incorporates multiple parallel rows of detectors, allowing multiple simultaneous anatomical sections to be acquired during a single rotation of the X-ray tube. This technology allows for rapid, whole-body volumetric scans in a few seconds, with excellent isotropic spatial resolution.

Also: Multi-cut helical CT · multidetector computed tomography · TCMD · TCMC

Fluorodeoxyglucose positron emission tomography Nuclear medicine molecular imaging technique that uses a glucose analog labeled with fluorine-18 as a tracer to detect and in vivo the rate of glucose consumption of body cells. It is used in oncology because the vast majority of malignant tumor cells have a high rate of glycolysis.

Also: FDG-PET · FDG positron emission tomography · PET-FDG

Mammary tomosynthesis Three-dimensional imaging technology that takes multiple low-dose X-ray exposures to the breast from various angles while the tube travels in a predetermined arc. By processing this data using digital algorithms, it reduces the problem of tissue overlap that occurs in conventional mammography, improving the detection of small tumors in dense breasts.

Also: 3D mammography · breast tomosynthesis · three-dimensional digital mammography

Esophagogastroduodenal transit Dynamic radiological examination under fluoroscopic control that uses oral administration of a barium suspension, often combined with air to achieve a double contrast effect, to evaluate the motility and anatomy of the initial segments of the digestive tract. It allows evaluating swallowing disorders, hiatal hernias, acid reflux, ulcers or infiltrating masses.

Also: TEGD · esophagogastroduodenal series · dynamic swallowing study

Codman triangle Specific pattern of aggressive periosteal reaction that is observed when a rapidly growing tumor or infectious lesion violently elevates the periosteum, detaching it from the cortical bone. Visually, a small wedge of new ossified bone can be seen at the limit where the periosteum still remains attached to the normal cortex, being highly suggestive of osteosarcoma or Ewing's sarcoma.

Also: Codman sign · Codman's spur · Codman's periosteal triangle

X-ray tube Vacuum device provided with a cathode and an anode, designed to generate and emit beams of ionizing radiation in a controlled manner by bombarding high-speed electrons against a metallic target. It has cooling systems to dissipate the amount of thermal energy that is generated in parallel with the production of photons.

Also: radiation tube · x-ray generator · X-ray vial

Photomultiplier tube Electronic component coupled to the scintillation crystal of gamma cameras, whose function is to capture the flashes of light generated and multiply them electronically in a controlled manner. It produces a final electrical signal pulse of sufficient intensity so that computer processors can quantify the exact energy and origin of each photon.

Also: photomultiplier · twinkle light amplifier · PMT

Hounsfield Units Dimensionless quantitative scale used in computed tomography to numerically express the attenuation of different body tissues exposed to ionizing radiation. It is calibrated by standardly assigning a value of zero for distilled water and minus one thousand for air, which makes it easier to differentiate tissues with similar densities such as fat, fluid, muscle or calcium.

Also: Hounsfield scale · TC attenuation scale · TC numbers · CT units · HU

Computed tomography urography Multi-slice computed tomography protocol designed for detailed evaluation of the entire urinary tract, from the renal parenchyma to the urethra, through multiphase acquisitions that include an excretory or late phase. It is the tool of choice for the study of persistent hematuria and suspected urothelial neoplasms, as it provides a three-dimensional reconstruction of the ureters.

Also: urotomography · Uro-CT · computed tomography of the urinary tract

Percutaneous vertebroplasty Image-guided percutaneous procedure that consists of direct puncture of the affected vertebral body using a thick needle to inject rapid-setting acrylic bone cement. Its primary objective is to mechanically consolidate the fractured vertebra due to osteoporosis or neoplastic infiltration, quickly relieving the patient's pain.

Also: vertebroplasty · vertebral fracture cementation · percutaneous vertebral consolidation

Voxel Smaller three-dimensional volume element that represents a discrete portion of body tissue in the three-dimensional space of a reconstructed image, whose depth corresponds exactly to the selected slice thickness. By integrating real volume, the intensity of each pixel on the screen ultimately corresponds to the weighted average of the physical properties existing within its corresponding voxel.

Also: volume element · three-dimensional pixel · image volume unit

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