Veterinary Imaging Glossary

Making physical models from CT data for surgical planning, custom guides and client education.

See also3-D volume rendering

A reconstruction that displays a CT volume as a shaded 3-D model.

In practiceValuable for complex fractures, angular limb deformities and client communication.

See also3-D printing

Horizontal reverberation lines below the pleural line, seen in normally aerated lung or with pneumothorax.

See alsoB-lines

Away from the axis of a limb or digit. In a digit pair (cattle, the equine fetlock), the abaxial surface faces outward from the central axis running between or through the digits.

In practiceUse for the proximal sesamoid bones and claws of ruminants, where medial and lateral become ambiguous.

See alsoAxial

Needle collection of peritoneal fluid.

See alsoAFAST

Directed away from the mouth along the digestive tract.

In practiceDescribes the direction of normal peristalsis, or a lesion's position downstream of a reference point in the bowel.

See alsoOralOrad

A unique identifier for an imaging order, linking the order, images and report.

See alsoStudy

Increased brightness deep to fluid-filled structures that weaken sound less than surrounding tissue. Also called through-transmission.

In practiceSupports a cystic structure; solid lymphoma can also show some enhancement.

See alsoAnechoic

A tissue's resistance to sound passage. Large impedance differences at interfaces (soft tissue to gas or bone) reflect most of the sound.

In practiceExplains why ultrasound cannot see through gas or bone.

See alsoAcoustic shadowing

A dark band deep to a strongly reflecting or absorbing structure such as mineral or bone.

In practiceA clean shadow points to mineral; a dirty shadow points to gas.

See alsoClean shadowingDirty shadowing

A signed change or addition to a finalized report.

The maximum dorsoventral thickness of the adrenal gland on ultrasound.

In practiceUpper limits commonly used are about 6–7.5 mm in dogs, varying with body weight. Cats are about 4.3–4.5 mm.

See alsoAdrenomegaly

Adrenal gland enlargement.

In practiceBilateral symmetric enlargement suggests pituitary-dependent hyperadrenocorticism. A unilateral mass suggests adrenal tumor. Common spelling error: adenomegaly.

Abdominal focused assessment with sonography for trauma or triage. Checks four standard sites for free fluid.

In practiceIncludes an abdominal fluid score.

See alsoPoint-of-care ultrasoundTFAST

A bone lesion with features of rapid change: permeative or moth-eaten lysis, a long zone of transition, cortical destruction and active periosteal reaction.

In practiceThe differentials are mainly neoplasia (osteosarcoma) and fungal or bacterial osteomyelitis. Sampling is required.

See alsoOsteosarcomaOsteomyelitis

A dark, branching airway outlined by opaque, fluid-filled alveoli.

In practiceThe key sign of an alveolar pattern.

See alsoAlveolar pattern

As Low As Reasonably Achievable: the governing principle of radiation safety. Keep dose minimal through time, distance and shielding.

In practicePrefer sedation and positioning aids to manual restraint.

See alsoTime distance shielding

Wraparound of Doppler signals when flow velocity exceeds the measurable limit (the Nyquist limit).

In practiceRaise the scale or use CW Doppler.

See alsoColor Doppler

Lung opacity from fluid or cells filling the air spaces, with air bronchograms, border effacement and lobar signs.

In practiceLocation helps: cranioventral suggests aspiration pneumonia; caudodorsal in dogs suggests cardiogenic edema.

See alsoAir bronchogramLobar sign

Producing no echoes, appearing black. Typical of simple fluid.

See alsoHypoechoicEchogenicity

Acute noncompressive nucleus pulposus extrusion: a high-velocity extrusion of healthy disc material that bruises the cord without lasting compression.

In practiceUsually managed without surgery.

See alsoHNPEIVDE

Removal of identifying information from DICOM headers and image pixels.

In practiceRequired before sharing images for teaching, research or AI datasets.

See alsoDICOM tag

The forearm, between elbow and carpus.

See alsoCrus

In front of. In veterinary anatomy reserved mainly for the eye (anterior chamber, anterior uvea).

In practiceUse cranial or rostral elsewhere.

See alsoPosterior

Toward the apex, the narrow end of a cone-shaped structure such as the heart or a tooth root.

See alsoBasilarOcclusal

Failure of a structure to develop at all.

See alsoHypoplasia

A calculated map of diffusion. Low ADC confirms true restricted diffusion and rules out T2 shine-through.

See alsoDiffusion-weighted imaging

The bones of the limbs and the limb girdles.

See alsoAxial skeleton

Needle collection of joint fluid for analysis.

Contrast injected into a joint to outline cartilage, ligaments and joint pouches.

Lung infection from inhaling food, fluid or vomitus.

In practiceCranioventral alveolar pattern, often in the right middle lobe.

See alsoAlveolar pattern

Abnormal movement between C1 and C2, often from an absent or malformed dens.

In practiceCommon in toy breeds. Avoid flexed positioning; it can worsen cord compression.

Shrinkage of a previously normal structure.

In practiceMuscle atrophy on MRI or CT suggests neurologic or orthopedic chronicity.

The reduction of the X-ray beam as it passes through tissue; on CT, the brightness of a voxel.

In practiceDescribed as hyperattenuating, hypoattenuating or isoattenuating relative to a reference tissue.

See alsoHyperattenuatingHypoattenuating

The distal segment of a limb: carpus or tarsus to the digits. Manus in the forelimb, pes in the hindlimb.

See alsoManusPes

Toward the central axis of a limb or digit. In ruminants the axis runs between digits III and IV.

In practiceThe axial wall of a bovine claw faces the interdigital space.

See alsoAbaxial

The skull, vertebral column, ribs and sternum.

See alsoAppendicular skeleton

Vertical laser-like artifacts from the pleural line to the far field, moving with breathing.

In practiceMore than a few per site suggest edema, pneumonia or fibrosis.

See alsoA-linesVetBLUE

An insoluble, radiopaque GI contrast medium.

In practiceAvoid when perforation is suspected; use a water-soluble iodinated agent instead.

See alsoUpper GI study

Toward the base, the broad end of a roughly pyramidal structure.

In practiceThe heart base is where the great vessels attach; heart-base masses arise here.

See alsoApical

Streaks or dark bands between dense structures caused by the X-ray beam losing low-energy photons.

In practiceCommon between the petrous temporal bones on brain CT.

See alsoStreak artifact

SI unit of radioactivity: one decay per second. The older unit is the curie (1 mCi = 37 MBq).

In practiceI-131 doses for cats are often around 4 mCi (148 MBq) as a fixed dose, or set by individual calculation.

See alsoIodine-131

Affecting both sides of the body.

In practiceBilateral symmetric changes can suggest systemic or developmental disease.

See alsoUnilateral

Dental technique in which the beam is aimed perpendicular to the line that bisects the angle between the tooth's long axis and the sensor. Reduces foreshortening and elongation.

In practiceStandard for maxillary teeth and mandibular canines.

See alsoParallel technique

Exaggerated size of a dark signal void on GRE or SWI images, caused by susceptibility.

In practiceCharacteristic of hemorrhage and mineral.

See alsoSusceptibility-weighted imaging

Starting a CT scan automatically once contrast reaches a set HU threshold in a monitored vessel.

See alsoCT angiography

Display settings for bone detail, with a wide width and a high level.

See alsoWindow width

Loss of a structure's normal margin because it is in contact with something of the same opacity. The practical form of the silhouette sign.

See alsoSilhouette sign

Upper airway obstruction in short-nosed breeds from stenotic nares, long soft palate, everted saccules and tracheal hypoplasia.

Thickened or more visible bronchial walls, seen as doughnuts end-on and tram lines from the side.

In practiceCommon in feline asthma and chronic bronchitis.

See alsoDoughnut signTram lines

The tooth surface facing the cheek.

See alsoLingualPalatalVestibular

The tympanic bulla: the bony middle ear cavity. In the lung, a thin-walled air-filled space.

See alsoOtitis media

DICOM operations that query a PACS for studies (C-FIND) and retrieve them (C-MOVE).

See alsoC-STORE

The DICOM operation that sends images from one system to another.

See alsoDICOMC-FIND and C-MOVE

The heart lifted off the sternum on a lateral thoracic radiograph.

In practiceClassic sign of pneumothorax. Can also be positional.

See alsoPneumothorax

Moving in a caudal direction.

In practiceNot to be confused with cauda (as in cauda equina). Dictation software often confuses the two.

See alsoCraniad

Toward the tail. On the head, toward the back of the skull. On the proximal limb, the back surface of the limb.

In practiceDistal to the carpus and tarsus, the back of the limb is palmar or plantar, not caudal.

See alsoCranial

A proximal limb projection entering the caudal surface and exiting the cranial surface.

In practiceOften preferred for the stifle because the joint lies closer to the detector.

See alsoCraniocaudal

Containing a gas-filled or fluid-filled cavity within a mass or nodule.

In practiceCavitated lung lesions include abscess, neoplasia, bulla and granuloma.

Aligning the beam's central ray to the region of interest.

In practiceThorax: center on the caudal border of the scapula. Abdomen: center on the last rib.

Toward the center of the body, an organ, or a system.

See alsoPeripheral

Spinal cord compression in the caudal cervical spine from disc, ligament or bone changes. Also called wobbler syndrome.

In practiceDisc-associated form in Dobermans; osseous form in giant breeds.

Bright and dark bands at fat-water interfaces caused by the slightly different frequencies of fat and water protons.

Mismatch between caudal skull volume and the brain, crowding the cerebellum toward or through the foramen magnum.

See alsoSyringomyelia

Stones in the gallbladder or bile ducts.

In practiceOften incidental. Obstruction causes duct dilation.

A sharp, uniformly black shadow deep to mineral such as uroliths or bone.

See alsoAcoustic shadowingDirty shadowing

Advice to interpret an imaging finding alongside history, exam and lab results.

In practiceMost helpful when the report says which test or finding to correlate with.

A triangular cuff of periosteal new bone where a tumor lifts the periosteum.

In practiceSuggests aggressive disease, classically osteosarcoma, but not specific.

See alsoPeriosteal reaction

Narrowing the X-ray beam to the area of interest with the light-beam collimator.

In practiceReduces scatter and staff dose. ALARA practice requires visible collimation edges on every image.

See alsoALARAScatter radiation

Flow direction and velocity overlaid on the grayscale image. By convention red is toward the probe and blue away.

In practiceRed and blue mean direction, not arterial versus venous.

See alsoDopplerAliasing

Two or three directions joined to name an oblique location or direction, such as craniodorsal, caudolateral or dorsomedial. The first element usually carries more weight.

In practiceHip luxation is described as craniodorsal or caudoventral.

See alsoOblique projection

A tapering line of reverberation deep to a small strong reflector such as gas bubbles or metal.

See alsoReverberation artifactB-lines

Ultrasound diameter of the common bile duct.

In practiceCats: up to about 4 mm. More than 5 mm suggests obstruction.

See alsoCholelithiasis

Radiography with a photostimulable phosphor plate in a cassette, read afterward by a laser scanner.

See alsoDigital radiography

Cross-sectional X-ray imaging in which a rotating tube and detector array collect data reconstructed into thin slices.

In practiceRemoves superimposition. Excellent for bone, lung, nasal cavity and surgical planning.

See alsoHounsfield unitMultidetector CT

Fluid accumulation from heart failure: pulmonary edema in left-sided failure, effusions in right-sided failure.

In practiceLook for left atrial enlargement and pulmonary venous distension.

See alsoPulmonary edemaVertebral left atrial size

On the opposite side of the body from a reference structure.

In practiceContralateral comparison views are commonly obtained for limb lesions.

See alsoIpsilateral

Increase in signal or attenuation after IV contrast. Described by pattern: homogeneous, heterogeneous, ring, meningeal or dural tail.

In practiceCompare matching pre- and post-contrast slices before calling enhancement.

See alsoRing enhancementDural tail sign

A substance that changes how an imaging modality sees tissue, used to outline structures or show perfusion.

See alsoIodinated contrastGadoliniumBarium sulfate

The timing of a CT acquisition after IV contrast: noncontrast, arterial, portal venous and delayed.

In practiceMultiphase scans characterize liver masses and portosystemic shunts.

See alsoCT angiography

An adverse response to contrast medium, from mild (vomiting, hives) to severe (anaphylactoid shock).

In practiceHave an emergency plan; the risk is low with nonionic agents.

See alsoIodinated contrast

The ability to tell apart structures with small differences in opacity or signal.

In practiceLow on radiographs; much higher on CT and MRI.

See alsoSpatial resolution

Ultrasound with intravenous microbubble contrast to assess tissue perfusion.

In practiceUsed to characterize liver and spleen nodules.

Removal of a tissue core with a cutting needle (for example Tru-Cut) for histopathology.

In practiceGives tissue architecture; carries higher bleeding risk than FNA.

See alsoFine-needle aspiration

A wavy, undulating small intestinal wall seen on ultrasound.

In practiceNonspecific: pancreatitis, enteritis, peritonitis, neoplasia or ischemia.

Left atrial bulge on the caudodorsal heart border in a lateral view.

See alsoVertebral left atrial size

Moving in a cranial direction. A directional adverb, not a position.

In practiceExample: the lesion extends craniad from T13.

See alsoCaudad

Toward the head, used for the neck, trunk, tail and the limbs above the carpus and tarsus.

In practiceDo not use for structures on the head itself; use rostral there.

See alsoCaudalRostral

Tear of the main stabilizing stifle ligament, the most common cause of hindlimb lameness in dogs.

In practiceRadiographs show effusion and cranial tibial displacement. The ligament itself is not seen.

See alsoTibial plateau angleFat pad sign

A proximal limb projection entering the cranial surface and exiting the caudal surface.

In practiceStandard for the elbow, stifle and shoulder.

See alsoCaudocranial

The leg segment between stifle and tarsus.

See alsoAntebrachium

Collection of cerebrospinal fluid from the cerebellomedullary cistern or lumbar subarachnoid space.

In practiceUsually performed under the same anesthesia as MRI, after imaging rules out high intracranial pressure.

CT timed to the arterial or venous peak of an IV contrast bolus to show vessels.

In practiceThe reference test for portosystemic shunt mapping.

See alsoContrast phaseBolus tracking

CT after IV contrast with delayed phases to show the collecting systems and ureters.

In practiceThe test of choice for ectopic ureters.

See alsoExcretory urography

Sampling a lesion with needle position confirmed by CT, used for lung, bone and deep lesions.

See alsoCore biopsy

A probe with a convex face and a fan-shaped field, used for deep abdominal imaging.

See alsoTransducerMicroconvex transducer

Needle collection of urine directly from the bladder, often with ultrasound guidance.

Contrast study of the urinary bladder, given through a urinary catheter. Positive, negative (gas) or double contrast.

In practicePositive contrast to check bladder rupture; double contrast for mucosal detail.

See alsoUrethrography

Farther from the body surface.

See alsoSuperficial

Narrowing of the lumbosacral vertebral canal compressing the cauda equina.

In practiceMRI or CT shows disc protrusion, ligament thickening and foraminal narrowing.

The lowest part of an organ or cavity relative to gravity during imaging.

In practiceFluid, cells and sediment collect in dependent regions; gas rises to nondependent regions.

See alsoNondependentRecumbency

Right. Refers to the animal's right, not the viewer's.

In practiceAppears in OD (oculus dexter) and AD (auris dextra).

See alsoSinister

Digital Imaging and Communications in Medicine: the international standard for storing, transmitting and displaying medical images and their metadata.

In practiceEvery modality, PACS and viewer must speak DICOM for images to move cleanly.

See alsoPACSDICOM tag

A labeled data element in a DICOM file header, such as Patient Name (0010,0010) or Modality (0008,0060).

In practiceVeterinary systems often misuse human fields; species and breed go in Patient Species Description and Patient Breed Description.

See alsoDICOM

Web-based (RESTful) DICOM services for query (QIDO-RS), retrieval (WADO-RS) and storage (STOW-RS).

In practiceUsed by browser viewers such as OHIF.

See alsoDICOM

A ranked list of possible causes for a finding.

See alsoImpression

Spread evenly throughout an organ or region.

See alsoFocalMultifocal

A sequence sensitive to water molecule motion. Restricted diffusion appears bright on DWI and dark on the ADC map.

In practiceKey for acute infarcts and for separating abscess from tumor.

See alsoApparent diffusion coefficient

Radiography with flat-panel detectors that convert X-rays to a digital image directly or via a scintillator, without a cassette to process.

See alsoComputed radiography

Widening of a hollow structure or vessel. Also spelled dilatation.

See alsoDistension

A gray, reverberation-filled shadow deep to gas.

See alsoAcoustic shadowingReverberation artifact

Infection of an intervertebral disc and adjacent vertebral endplates.

In practiceRadiographs lag 2–3 weeks behind signs. MRI and CT find it earlier.

Moving in a distal direction.

See alsoProximad

Farther from the trunk or point of attachment, toward the free end of a limb or structure.

In practiceIn dentistry distal has a separate meaning: toward the back of the dental arch.

See alsoProximalMesial

Stretching of a hollow organ by its contents, such as gas or fluid.

See alsoDilation

The PennHIP measure of passive hip laxity, from 0 (tight) to 1 (fully luxated).

In practiceA lower DI means lower osteoarthritis risk.

See alsoPennHIP

A PennHIP projection in which the femoral heads are pushed laterally with a distractor device to measure joint laxity.

See alsoPennHIPDistraction index

A chemical-shift technique that produces water-only, fat-only, in-phase and out-of-phase images from one acquisition.

In practiceReliable fat suppression on high-field systems.

See alsoFat suppression

Ultrasound measurement of motion, mainly blood flow, from the frequency shift of returning echoes.

See alsoColor DopplerSpectral DopplerPower Doppler

Toward the back, or the upper surface of the body in a standing animal. Distal to the carpus and tarsus, the front (cranial-facing) surface of the limb.

In practiceDorsal on the distal limb is a frequent source of confusion for clients; it means the front of the foot.

See alsoVentralPalmarPlantar

Any plane parallel to the dorsal surface of the body, at right angles to the median and transverse planes. Equivalent to the human coronal plane.

In practiceVeterinary reports use dorsal where human reports say coronal.

See alsoSagittal planeTransverse plane

Lying on the back.

In practiceUsed for VD projections and most abdominal ultrasound.

See alsoRecumbency

A distal forelimb projection entering the front of the limb and exiting the palmar surface.

A distal hindlimb projection entering the front of the limb and exiting the plantar surface.

A projection entering the dorsal surface and exiting the ventral surface, with the patient in sternal recumbency.

In practiceBetter for cardiac silhouette and caudal lobar vessels. Safer for patients in respiratory distress.

See alsoVentrodorsal

Gradual use of higher exposures than needed, masked by digital post-processing.

See alsoExposure indexALARA

A badge worn to measure an individual's occupational radiation dose.

In practiceWorn at the collar outside the lead apron. Ring badges are used when hands are near the beam.

Gas-distended stomach compartments separated by a soft-tissue band, the "reverse C" or "Popeye arm" appearance.

In practiceClassic for gastric dilatation-volvulus (GDV) on a right lateral radiograph.

See alsoGastric dilatation-volvulus

A thickened bronchus seen end-on as a ring.

See alsoBronchial pattern

Thickened, enhancing dura extending from the edge of a brain mass.

In practiceSupports meningioma but is not specific to it.

See alsoMeningiomaContrast enhancement

Mineral deposition in damaged or necrotic tissue, with normal blood calcium.

In practiceSeen in old hematomas, tumors and calcinosis circumscripta.

See alsoMineralization

The time from excitation to signal collection.

See alsoRepetition time

Ultrasound of the heart, using 2-D, M-mode and Doppler.

See alsoM-modePhased array

The brightness of a tissue on ultrasound, reflecting how strongly it returns echoes.

In practiceAlways compare against a reference organ, such as liver versus falciform fat or spleen.

See alsoHyperechoicHypoechoicAnechoicIsoechoic

The pattern of echoes within an organ, such as fine, coarse, homogeneous or heterogeneous.

See alsoEchogenicityHeterogeneous

A ureter that opens outside the bladder trigone, causing incontinence in young animals.

In practiceCT urography or cystoscopy confirms.

See alsoCT urography

Digital processing that sharpens borders.

In practiceOverprocessing creates a dark halo (Überschwinger or rebound artifact) that can mimic implant loosening or pneumothorax.

See alsoÜberschwinger artifact

Thin shadows at the curved edges of round structures caused by refraction.

In practiceSeen beside the kidney poles and gallbladder; not a lesion.

See alsoAcoustic shadowing

Abnormal fluid accumulation in a body cavity or joint.

See alsoPleural effusionPeritoneal effusionPericardial effusion

Ultrasound technique that estimates tissue stiffness.

A set of developmental elbow problems: fragmented medial coronoid process, ununited anconeal process, OCD and incongruity.

In practiceCT is more sensitive than radiographs for medial coronoid disease.

See alsoFragmented medial coronoid process

New bone at the attachment of a tendon, ligament or joint capsule.

See alsoOsteophyte

Radiographs or fluoroscopy after oral contrast to evaluate the esophagus.

In practiceUsed for megaesophagus, strictures and vascular ring anomalies.

See alsoVideofluoroscopic swallow study

Radiographs taken after IV iodinated contrast to show the kidneys, ureters and bladder. Also called IV pyelogram (IVP).

In practiceLargely replaced by CT urography for ectopic ureter.

See alsoCT urography

A thoracic radiograph exposed during expiration.

In practiceLungs look more opaque. The heart contacts more sternum and can look falsely enlarged.

See alsoPeak inspiration

A number from a digital system that reports the radiation reaching the detector.

In practiceWatch for exposure creep: rising doses hidden by automatic image processing.

See alsoDose creep

The standard hip-dysplasia projection: dorsal recumbency, femurs extended and parallel, patellae centered.

In practiceRequired for OFA submission.

See alsoFrog-leg projectionOFAPennHIP

On or toward the outer surface of an organ wall or body cavity.

See alsoInternal

Outside the brain parenchyma but within the skull, for example arising from meninges or bone.

In practiceMeningioma is the classic extra-axial tumor.

See alsoIntra-axial

Outside the dura, within the vertebral canal. Most intervertebral disc extrusions are extradural.

See alsoIntramedullaryIntradural-extramedullary

Outside the wall of a hollow organ.

See alsoMural

On a lateral stifle, compression or loss of the infrapatellar fat pad triangle by joint effusion.

In practiceSupports stifle effusion, often cruciate disease.

See alsoCranial cruciate ligament rupture

Techniques that null the bright signal of fat, such as STIR, chemical fat saturation and Dixon.

In practiceUsed post-contrast to make enhancing tissue near fat stand out.

See alsoSTIRDixon

18F-fluorodeoxyglucose: a glucose analog PET tracer taken up by metabolically active cells.

See alsoPositron emission tomography

Lower airway inflammation in cats with bronchoconstriction.

In practiceBronchial pattern, hyperinflation and right middle lobe collapse are typical.

See alsoBronchial pattern

Strongly attracted by a magnet, as iron, nickel and many steels are.

In practiceOxygen cylinders, scissors and clippers must stay out of the magnet room.

See alsoMRI safety zones

Spinal cord infarction from fibrocartilage emboli, causing sudden, usually painless, often asymmetric deficits.

In practiceMRI may be normal early or show a focal intramedullary T2 hyperintensity.

See alsoANNPE

The area covered by an image.

See alsoMatrix

The descriptive section of a radiology report, recording observations without final interpretation.

See alsoImpression

Sampling cells with a fine needle for cytology, often guided by ultrasound.

In practiceLow risk. Coagulation testing is advised for vascular organs.

See alsoCore biopsy

Contrast injected into a draining tract to trace its course and find a foreign body.

The five basic radiographic opacities: gas, fat, soft tissue (including fluid), mineral (bone) and metal.

In practiceFluid and soft tissue share one opacity, so radiographs cannot tell them apart.

See alsoOpacity

Fluid-attenuated inversion recovery: a T2-weighted sequence that suppresses free fluid such as CSF.

In practiceLesions near ventricles and edema stand out. Bright CSF on FLAIR can suggest high protein or cells.

See alsoT2-weightedInversion recovery

A lateral projection with the joint flexed to separate overlapping structures.

In practiceFlexed elbow views help evaluate the anconeal process.

A straight horizontal border between gas and fluid on a horizontal-beam radiograph.

See alsoHorizontal beam

Real-time X-ray imaging, used to watch motion and to guide procedures.

In practiceUsed for swallowing studies, tracheal collapse evaluation and stent placement.

See alsoVideofluoroscopic swallow study

Confined to one small, discrete area.

See alsoMultifocalDiffuse

The area on the tube's anode where X-rays are produced. A small focal spot gives sharper images; a large one handles higher outputs.

Ingested or inserted foreign material. On radiographs it can be radiopaque or seen only by the obstruction it causes.

In practiceUltrasound detects many radiolucent foreign bodies with acoustic shadowing.

See alsoMechanical obstruction

The percentage reduction in left ventricular diameter from diastole to systole on M-mode.

In practiceAn index of systolic function.

See alsoM-mode

A break in bone. Described by location, configuration (transverse, oblique, spiral, comminuted), displacement and whether it's open or closed.

See alsoSalter-Harris fracture

A fragment or fissure of the medial coronoid process of the ulna. The most common form of elbow dysplasia.

See alsoElbow dysplasia

Gas in the peritoneal or retroperitoneal space outside the bowel.

In practiceWithout recent surgery or abdominocentesis, suggests GI perforation, an emergency. Horizontal-beam views help.

See alsoPneumoperitoneum

The number of sound wave cycles per second, in megahertz.

In practiceHigher frequency gives better resolution but less penetration. Lower frequency reaches deeper with less detail.

VD pelvis with the hips flexed and abducted.

In practiceUseful for fractures and femoral head assessment when extension is painful.

See alsoExtended VD hip

A paramagnetic contrast agent given intravenously. It shortens T1, so enhancing tissue turns bright on T1W images.

In practiceEnhancement shows a broken blood-brain barrier, inflammation or increased vascularity.

See alsoContrast enhancementT1-weighted

Distension of the gallbladder with thick, immobile mucus. It can rupture.

In practiceKiwi-fruit pattern on ultrasound. Linked to endocrine disease and certain breeds.

See alsoKiwi-fruit pattern

Gravity-dependent echogenic bile in the gallbladder.

In practiceUsually incidental in dogs. Mobility separates it from a mucocele or mass.

See alsoSedimentGallbladder mucocele

The detector used for scintigraphy. It records gamma photons and maps where tracer accumulates.

See alsoScintigraphy

Rotation and gas distension of the stomach, a surgical emergency in large deep-chested dogs.

In practiceOne right lateral radiograph is usually enough to confirm.

See alsoDouble-bubble sign

Ultrasound wall thickness measured from mucosal surface to serosa.

In practiceTypical upper limits: dog stomach about 5 mm, duodenum about 5–6 mm; cat duodenum about 2.4–2.8 mm. Values vary by body size.

See alsoWall layering

Drug-induced unconsciousness with loss of protective reflexes, usually with intubation.

In practiceRequired for most MRI and many CT studies. Breath-holds improve thoracic CT.

See alsoSedation

Affecting the whole organ or body system.

See alsoDiffuse

A single, large area of bone loss with a clear border.

In practiceThe least aggressive lysis pattern.

See alsoLysis

Back-and-forth shimmering of the pleural line with breathing, showing visceral and parietal pleura are in contact.

In practiceIts absence suggests pneumothorax.

See alsoLung pointTFAST

A primary brain tumor of glial cells (astrocytoma, oligodendroglioma).

In practiceTypically intra-axial. Brachycephalic breeds are predisposed.

See alsoIntra-axial

Widening of the subarachnoid contrast column around an intradural-extramedullary mass on myelography.

See alsoIntradural-extramedullary

A fast sequence family that is sensitive to magnetic field differences. T2*-weighted GRE shows hemorrhage and mineral as dark signal voids.

In practiceUse to detect microbleeds.

See alsoT2*Susceptibility artifactSusceptibility-weighted imaging

A collection of small mineral or mixed-opacity particles in the GI tract proximal to a partial obstruction.

In practiceSuggests a chronic partial obstruction.

See alsoMechanical obstruction

SI unit of absorbed dose: one joule of energy per kilogram of tissue.

In practiceRadiation therapy doses are prescribed in Gy.

See alsoSievert

A device of thin lead strips placed between patient and detector to absorb scatter radiation.

In practiceGenerally used when part thickness exceeds about 10 cm. Grid lines can appear as artifacts if the grid is misaligned.

See alsoScatter radiation

The time for radioactivity to fall by half. Physical half-life is set by the isotope; biologic half-life is set by elimination from the body.

See alsoIodine-131

A hypoechoic rim around a nodule on ultrasound.

In practiceTarget lesions in liver or spleen are often malignant.

See alsoTarget sign

Rules for how images display on a workstation.

In practiceConvention: lateral images face left with cranial to the viewer's left; VD and DV images show the patient's right on the viewer's left.

Saved display rules arranging series and priors on the reading screen.

See alsoHanging protocol

Acute extrusion of degenerated nucleus pulposus through a ruptured annulus into the vertebral canal.

In practiceTypical of chondrodystrophic breeds. Often needs surgery when deficits are severe.

See alsoIntervertebral disc diseaseIVDE

Gradual protrusion of the annulus fibrosus into the vertebral canal without rupture.

In practiceCommon in older large-breed dogs. Slower onset.

See alsoIntervertebral disc disease

CT with continuous table movement during tube rotation. Also called spiral CT.

See alsoPitch

A malignant tumor of blood vessel cells, commonly splenic, right atrial or hepatic.

In practiceCavitated splenic mass with hemoabdomen in a large-breed dog. Echocardiogram and thoracic films stage it.

See alsoHemoabdomen

Blood in the peritoneal cavity.

In practiceEchogenic fluid on AFAST. Often from a ruptured splenic or liver mass.

See alsoAFASTHemangiosarcoma

Per-rectal or splenic portal scintigraphy to detect portosystemic shunting.

In practiceLargely replaced by CT angiography, which also maps shunt anatomy.

See alsoPortosystemic shunt

Enlarged liver.

In practiceRadiograph clue: rounded liver margins extending well past the costal arch.

See alsoMicrohepatia

Mixed or uneven in opacity, echogenicity, attenuation or signal.

In practiceThe most common misspelling in SVI reports is heterogenous.

See alsoHomogeneous

MRI at 1.0 T and above, commonly 1.5 T or 3 T.

In practiceBetter resolution and more sequence options, such as DWI, SWI and spectroscopy.

See alsoLow-field MRI

Abnormal hip development causing laxity and early osteoarthritis.

In practiceGraded by OFA or measured by PennHIP.

See alsoOFAPennHIPNorberg angle

Health Level Seven: a messaging standard for exchanging clinical and administrative data such as orders and results.

See alsoRIS

Hydrated nucleus pulposus extrusion: extrusion of hydrated disc material, usually in the cervical spine, often compressive.

In practiceMRI shows a T2-bright extradural mass dorsal to the disc.

See alsoANNPE

The tarsus or tarsal joint.

Uniform in opacity, echogenicity, attenuation or signal throughout.

In practiceCommon misspelling in reports: homogenous.

See alsoHeterogeneous

A projection taken with the X-ray tube turned to fire parallel to the table, with the patient standing or recumbent.

In practiceShows fluid lines and free gas. Standard in equine limb work.

See alsoStanding lateral

The CT scale of attenuation, with water set at 0 HU and air at −1000 HU. Fat is about −100 HU and cortical bone above +700 HU.

In practiceMeasure HU with a region of interest before and after contrast to judge enhancement.

See alsoAttenuationRegion of interest

Enlargement of the ventricular system of the brain.

In practiceCongenital in toy breeds; acquired from obstruction. Mild asymmetric ventricles can be normal.

Dilation of the renal pelvis and collecting system, usually from obstruction.

In practiceReport pelvic width; mild pyelectasia can occur with fluid therapy.

See alsoPyelectasia

Brighter than the reference tissue on CT.

See alsoHypoattenuatingAttenuation

Brighter than the reference tissue.

See alsoHypoechoicEchogenicity

Brighter than the reference tissue on MRI.

See alsoHypointenseSignal intensity

Excess thyroid hormone production, common in older cats, usually from benign adenomatous hyperplasia.

In practiceThyroid scintigraphy shows the extent. I-131 is curative for most cats.

See alsoRadioiodine therapy

Thickening of the left ventricular wall, the most common heart disease in cats.

In practiceEcho is required; radiographs may be normal.

See alsoValentine-shaped heart

Bilateral periosteal new bone on the distal limbs, secondary to a thoracic or abdominal mass.

In practiceFinding HO should prompt thoracic imaging.

See alsoPeriosteal reaction

Darker than the reference tissue on CT.

See alsoHyperattenuatingAttenuation

Darker than the reference tissue.

See alsoHyperechoicEchogenicity

Darker than the reference tissue on MRI.

See alsoHyperintenseSignal intensity

Underdevelopment of an organ or structure.

In practiceTracheal hypoplasia in brachycephalic breeds.

See alsoAplasia

Reduced or absent intestinal motility. Functional ileus has no physical blockage; mechanical ileus does.

In practiceDiffuse mild dilation favors functional ileus.

See alsoMechanical obstruction

Having indistinct margins that blend into surrounding tissue.

In practiceSuggests infiltrative or aggressive processes, or edema.

See alsoWell-defined

Loosening, migration or breakage of orthopedic hardware.

In practiceA lucent zone around screws can mean loosening or infection; compare with prior studies.

See alsoÜberschwinger artifact

The conclusion section of a radiology report, giving the most likely diagnosis or differentials and their priority.

In practiceThe section the referring vet reads first.

See alsoFindingsStructured report

An abnormality unrelated to the clinical question.

In practiceIncidentalomas such as adrenal or splenic nodules may need follow-up imaging.

Below. In veterinary anatomy limited to a few head structures.

See alsoSuperior

Between two structures that are medial and lateral to each other.

In practiceExample: the intermediate ridge of the tibial cochlea in the horse, a common OCD site.

See alsoMiddle

On or toward the inner surface of an organ wall or body cavity.

See alsoExternal

A lung pattern of hazy increased opacity that blurs vessel margins without air bronchograms. Unstructured or structured (nodular).

In practiceThe most commonly overcalled pattern. Expiration, underexposure and obesity mimic it.

See alsoBronchial patternAlveolar pattern

Degeneration of intervertebral discs leading to extrusion (Hansen type I) or protrusion (Hansen type II) and spinal cord compression.

In practiceMRI is the test of choice. Chondrodystrophic breeds such as Dachshunds are predisposed to type I.

See alsoHansen type IHansen type IIIVDE

Within the brain or spinal cord parenchyma.

In practiceIntra-axial versus extra-axial location is the first step in sorting a brain mass.

See alsoExtra-axial

Inside the dura but outside the spinal cord.

In practiceCan produce a golf-tee sign on myelography.

See alsoIntramedullaryExtraduralGolf-tee sign

Within the lumen of a hollow organ or vessel.

See alsoMuralExtramural

Within the spinal cord itself. Also, within the medullary cavity of a bone.

In practiceIntramedullary spinal lesions widen the cord and thin the surrounding contrast or CSF.

See alsoIntradural-extramedullaryExtradural

A dental or nasal projection with the detector placed in the mouth.

In practiceAlso called an occlusal projection when the sensor sits flat on the occlusal plane.

See alsoBisecting angle technique

Telescoping of one segment of intestine into the next.

In practiceUltrasound shows a multilayered target in cross-section.

See alsoTarget sign

Radiation intensity falls with the square of distance from the source. Doubling distance cuts exposure to one quarter.

See alsoTime distance shielding

A sequence that uses an initial inversion pulse to null a chosen tissue, such as fat (STIR) or fluid (FLAIR).

See alsoSTIRFLAIR

Water-soluble, iodine-based X-ray contrast for intravascular, urinary, myelographic and some GI uses.

In practiceNonionic, low-osmolar agents (iohexol, iopamidol) are standard for IV and intrathecal use.

See alsoIohexolContrast medium

A radionuclide with an 8-day half-life that emits beta and gamma radiation. It is taken up by thyroid tissue.

See alsoRadioiodine therapy

A nonionic, low-osmolar iodinated contrast agent used for CT, urography and myelography.

See alsoIodinated contrast

On the same side of the body as a reference structure.

See alsoContralateral

The same brightness as the reference tissue.

In practiceIsoechoic nodules are easy to miss; look for contour change or mass effect.

See alsoEchogenicity

The same brightness as the reference tissue on MRI.

See alsoSignal intensity

A voxel with equal dimensions in all three directions, so reformatted planes keep full detail.

See alsoVoxel

Intervertebral disc extrusion: nucleus pulposus displaced through the annulus into the vertebral canal.

See alsoHansen type I

A stellate or finely striated, nonmobile gallbladder content pattern with radiating lines, the hallmark of a gallbladder mucocele.

In practiceUnlike sludge, the contents do not shift when the patient is repositioned.

See alsoGallbladder mucocele

Kilovoltage peak: the maximum energy of X-ray photons produced. It controls beam penetration and image contrast.

In practiceHigher kVp gives a longer grayscale (lower contrast), suited to the thorax.

See alsomAs

Left atrium to aorta ratio on a short-axis echocardiogram.

In practiceA ratio of 1.6 or more is commonly used to define left atrial enlargement in dogs with MMVD.

See alsoMyxomatous mitral valve disease

The tooth surface facing the lips.

See alsoLingualPalatalVestibular

The precession frequency of hydrogen protons in a magnetic field. It is proportional to field strength (about 64 MHz at 1.5 T).

See alsoTesla

Away from the median plane, toward the side of the body or the outer side of a limb.

In practiceAlso a projection name: a lateral radiograph is a side-to-side view.

See alsoMedial

A lateral limb projection entering laterally and exiting medially. The standard lateral in equine distal limb studies.

See alsoMediolateral

Protective garment, typically 0.5 mm lead equivalent, worn during radiography and fluoroscopy.

In practiceCheck aprons, gloves and thyroid shields for cracks at least yearly.

Echo view from the left apex showing all four chambers, used for mitral and tricuspid Doppler.

A lateral projection with the patient's left side against the detector (right-left, RtLe).

In practiceGas moves into the pylorus in left lateral recumbency, helping to show pyloric foreign bodies.

See alsoRight lateral

A radiopaque L or R label placed in the field at exposure.

In practiceDigital annotation added afterward is not a substitute for a physical marker.

Any abnormal area of tissue, without implying a cause.

String, thread or fabric that anchors in place while the intestine bunches along it.

In practiceCheck under the tongue in cats.

See alsoPlicationString-of-pearls sign

A flat-faced probe with a rectangular field of view, usually high frequency.

In practiceIdeal for GI wall layering, thyroid, tendons and lymph nodes.

See alsoTransducer

The surface of a mandibular tooth facing the tongue.

See alsoBuccalPalatal

A sharp line where an opaque lung lobe meets an aerated one.

In practiceConfirms an alveolar pattern or lobar consolidation.

See alsoAlveolar pattern

Having a bumpy, rounded-lobe contour.

See alsoMargination

A line along the greatest length of an organ or limb.

In practiceUltrasound images in long axis are parallel to this line.

See alsoShort axis

MRI below about 1.0 T, often an open magnet.

In practiceCheaper to run. Longer scans and thicker slices.

See alsoHigh-field MRI

The place where normal glide sign meets an absent glide sign.

In practiceDiagnostic of pneumothorax and marks its edge.

See alsoGlide sign

Display settings for the lung parenchyma, with a wide width and a low level.

See alsoWindow width

Complete dislocation of a joint.

See alsoSubluxation

Left ventricular internal diameter in diastole, normalized to body weight.

In practiceA value of 1.7 or more supports left ventricular enlargement in canine MMVD staging.

See alsoMyxomatous mitral valve disease

Enlargement of one or more lymph nodes.

See alsoLymphadenopathy

Lymph node enlargement or abnormality.

In practiceReport size, shape (round versus oval), echogenicity and whether the hilus is preserved.

See alsoLymphadenomegaly

Bone destruction, seen as loss of opacity.

In practicePatterns, from least to most aggressive: geographic, moth-eaten, permeative.

See alsoGeographic lysisMoth-eaten lysisPermeative lysis

Motion mode: a one-line ultrasound display over time, used for cardiac dimensions and wall motion.

In practiceUsed to measure fractional shortening.

See alsoFractional shortening

A perceived bright or dark line at the edge of two opacities, produced by the visual system and not present in the image.

In practiceCan mimic a pneumothorax line or fracture.

Artificially high signal in tendons and ligaments oriented about 55° to the main magnetic field on short-TE sequences.

In practiceCan mimic tendinopathy. Confirm on long-TE sequences.

Cross-sectional imaging using a strong magnetic field and radiofrequency pulses to map the signal of hydrogen protons in tissue.

In practiceThe modality of choice for brain, spinal cord and soft-tissue joint structures.

See alsoT1-weightedT2-weightedTesla

Enlargement of a structure on the image when it lies farther from the detector.

In practiceKeep the area of interest close to the detector, and use calibration markers for measuring.

See alsoObject-image distance

The forefoot: carpus, metacarpus and digits.

See alsoPes

The character of a lesion's edge: smooth, irregular, lobulated, spiculated, well- or ill-defined.

In practiceOne of the Röntgen signs.

See alsoRöntgen signs

Milliampere-seconds: tube current multiplied by exposure time. It controls the number of X-ray photons and so image noise and brightness.

In practiceShort exposure times reduce motion blur in the thorax.

See alsokVp

A space-occupying lesion, usually larger than 3 cm in the lung, of any cause.

In practiceMass describes a shape, not a diagnosis. Cytology or histopathology decides benign versus malignant.

See alsoNodule

Displacement or compression of nearby structures by a lesion.

In practiceIn the brain: midline shift, ventricle compression, herniation.

The number of pixels in rows and columns of an image.

In practiceLarger matrix gives finer detail but lower signal per pixel.

See alsoField of view

A reconstruction that shows the brightest voxel along each ray through a volume.

In practiceHighlights contrast-filled vessels and small lung nodules.

See alsoMultiplanar reconstruction

Methylene diphosphonate: a Tc-99m bone agent that concentrates in sites of active bone turnover.

In practiceBone scans in horses for occult lameness.

A physical blockage of the intestinal lumen.

In practiceRadiographic hint: two populations of bowel, with dilated loops beside normal ones.

See alsoIleusTwo-population sign

Toward the median plane of the body or, in a limb, toward the side facing the body.

See alsoLateral

The patella slipping out of the trochlear groove medially. Graded I–IV.

See alsoLuxation

The single plane dividing the body into left and right halves.

See alsoSagittal plane

A lateral limb projection entering medially and exiting laterally.

In practiceThe usual lateral projection of a limb.

See alsoLateromedial

Same as rim sign: a hyperechoic band in the renal medulla parallel to the corticomedullary junction.

In practiceCan accompany nephrocalcinosis, ethylene glycol toxicity, leptospirosis, hypercalcemia, or nothing at all.

Diffuse dilation of the esophagus with poor motility.

In practiceIncreases aspiration pneumonia risk; check for it on every thoracic radiograph.

See alsoEsophagram

Suffix meaning enlargement, as in hepatomegaly, splenomegaly, cardiomegaly and renomegaly.

See alsoHepatomegalySplenomegaly

A tumor arising from the meninges. The most common primary brain tumor in dogs and cats.

In practiceTypically extra-axial, broad-based and strongly enhancing, often with a dural tail.

See alsoDural tail signExtra-axial

A group of non-infectious inflammatory brain diseases presumed to be immune-mediated.

In practiceMRI is suggestive but not definitive. CSF and infectious testing support the diagnosis.

In the dental arch, toward the midline at the front of the mouth.

See alsoDistal

A small convex probe that fits between ribs and suits small patients.

In practiceThe workhorse probe for feline and small canine abdomens.

See alsoTransducer

Small liver.

In practiceSeen with portosystemic shunts, cirrhosis or deep-chested conformation.

See alsoHepatomegaly

Between two structures related as proximal and distal, cranial and caudal, dorsal and ventral, or superficial and deep.

In practiceExample: the middle phalanx.

See alsoIntermediate

Deposition of calcium salts in soft tissue.

In practiceDystrophic mineralization occurs in damaged tissue; metastatic mineralization occurs with high calcium-phosphorus product.

See alsoDystrophic mineralization

A duplicate image of a structure that appears across a strong curved reflector such as the diaphragm.

In practiceMimics a diaphragmatic hernia or thoracic mass when liver appears above the diaphragm.

A DICOM service that sends scheduled patient and order data to the scanner, avoiding manual entry.

In practicePrevents mismatched or misspelled patient records.

See alsoDICOM

Multiple small to medium holes in bone that may join together.

In practiceIntermediate to aggressive.

See alsoLysis

Blurring or double edges caused by patient breathing or movement during acquisition.

In practiceBreath-hold under anesthesia or faster scanning reduces it.

Imaging of vessels with MRI, with or without contrast (for example, time-of-flight).

See alsoCT angiography

A heavily T2-weighted sequence that makes CSF very bright to outline the subarachnoid space, similar to a conventional myelogram.

In practiceFast screen for spinal cord compression.

See alsoMyelography

The ACR four-zone model controlling access to the scanner. Zone IV is the magnet room.

In practiceScreen every person and object before Zone IV. Ferromagnetic items become projectiles.

See alsoFerromagnetic

CT with several detector rows that acquire many slices per rotation, allowing fast, thin-slice volume scans.

In practiceAllows whole-body scans in seconds, often under sedation alone.

See alsoComputed tomography

Present in several separate areas.

In practiceMultifocal lesions raise metastasis, infection or a multicentric process higher on the differential list.

See alsoFocalDiffuse

Reformatting a CT or MRI volume into other planes, such as dorsal or sagittal.

In practiceNeeds thin-slice, near-isotropic data.

See alsoIsotropic voxel

Within the wall of a hollow organ.

See alsoIntraluminalExtramural

Injection of iodinated contrast into the subarachnoid space, followed by radiographs or CT, to outline the spinal cord.

In practiceLargely replaced by MRI. CT myelography still helps when MRI is unavailable.

See alsoMR myelography

Degeneration of the mitral valve causing regurgitation and left heart enlargement.

In practiceThe most common heart disease in dogs. Staged by ACVIM guidelines.

See alsoVertebral heart score

Tumor in the nasal cavity, most often carcinoma in dogs and lymphoma in cats.

In practiceCT shows turbinate destruction, mass, and possible cribriform plate erosion. Biopsy confirms.

See alsoRhinitis

A small, round, well-circumscribed lesion. In the lung, usually under 3 cm.

See alsoMassPulmonary nodule

The highest part of an organ or cavity relative to gravity during imaging.

In practiceFree gas collects in nondependent regions.

See alsoDependent

The angle on a VD hip radiograph between a line joining the femoral head centers and a line to the craniolateral acetabular rim.

In practiceAn angle of 105° or more is generally considered normal.

See alsoHip dysplasia

The distance from the structure being imaged to the detector.

See alsoMagnificationSource-image distance

Any plane that is not parallel to a standard anatomic plane.

In practiceOblique MRI planes are often aligned to a specific joint or the optic nerves.

A projection angled between two standard directions, named with the angle, as in D45L-PaMO (dorso 45° lateral-palmaromedial oblique).

In practiceOblique projections clear overlap from margins such as the carpal bones or the medial coronoid process.

See alsoProjection

The chewing surface of a tooth, or the surface that meets the opposing tooth.

In practiceAn occlusal radiograph places the film or sensor in the mouth.

See alsoApical

Orthopedic Foundation for Animals: the registry that grades hip and elbow radiographs.

In practiceFinal hip certification at 24 months of age.

See alsoHip dysplasiaExtended VD hip

The degree to which a structure blocks X-rays, shown as whiteness on the image. The veterinary term for what human radiology often calls density.

In practiceThe five radiographic opacities, least to most opaque: gas, fat, soft tissue/fluid, mineral/bone, metal.

See alsoRadiolucentRadiopaqueFive opacities

A skull projection with the mouth held open to show the tympanic bullae, nasal cavity or dens without overlap.

In practiceRostrocaudal open-mouth view for bullae; VD open-mouth for the nasal cavity.

See alsoBulla

Moving in the direction of the mouth. The -ad suffix denotes motion or direction toward.

See alsoAboralCraniad

Toward or relating to the mouth. In the GI tract, upstream toward the mouth.

See alsoAboral

Two projections taken at right angles to each other.

In practiceAt least two orthogonal projections are the minimum for every radiographic study.

Degenerative joint disease with cartilage loss, osteophytes, subchondral sclerosis and joint effusion. Also called DJD.

See alsoOsteophyte

A defect where abnormal cartilage forms a flap in a joint, from disrupted endochondral ossification.

In practiceCommon sites: caudal humeral head, medial humeral condyle, femoral condyles and talar ridges.

Infection of bone, bacterial or fungal.

In practiceCan look as aggressive as tumor. Fungal infection should be on the list in endemic areas such as Texas (coccidioidomycosis).

See alsoAggressive bone lesion

A bony outgrowth at the margins of a joint, a hallmark of degenerative joint disease.

See alsoEnthesophyteOsteoarthritis

The most common primary bone tumor in dogs, usually in the metaphysis of long bones in large breeds.

In practice"Away from the elbow, toward the knee": distal radius, proximal humerus, distal femur and proximal tibia. Aggressive lysis and periosteal reaction.

See alsoAggressive bone lesionCodman's triangle

Inflammation of the middle ear, often with fluid or soft tissue in the tympanic bulla.

In practiceCT is more sensitive than radiographs.

See alsoBulla

Picture Archiving and Communication System: software and storage that receives, stores, distributes and displays medical images.

See alsoDICOMVNARIS

The surface of a maxillary tooth facing the palate.

See alsoBuccalLingual

The back surface of the forelimb from the carpus distally, including the pads.

In practiceUsed in projection names such as DPa (dorsopalmar).

See alsoDorsalPlantar

Ultrasound diameter of the pancreatic duct.

In practiceIncreases with age in cats; up to about 2.5 mm can be normal.

See alsoPancreatitis

Ultrasound thickness of the pancreas.

In practiceFeline left limb: up to about 9 mm. Thickness alone does not diagnose pancreatitis.

See alsoPancreatitis

Inflammation of the pancreas.

In practiceUltrasound: hypoechoic, enlarged pancreas with hyperechoic surrounding fat. Normal ultrasound does not rule it out.

See alsoSteatitis

A self-limiting inflammatory bone disease of young large-breed dogs, with patchy medullary opacity in long bones.

In practiceShifting-leg lameness. Radiographic signs can lag behind pain.

Dental technique in which the sensor is placed parallel to the tooth and the beam perpendicular to both.

In practiceUsable mainly for caudal mandibular teeth.

See alsoBisecting angle technique

Relating to the wall of a body cavity, such as the parietal pleura or peritoneum.

See alsoVisceral

Averaging of different tissues within one voxel, blurring small structures or edges.

In practiceThin slices reduce it.

See alsoVoxel

A fracture through bone weakened by disease, often tumor.

In practiceLook for lysis around the fracture line.

See alsoAggressive bone lesion

Timing a thoracic exposure at the height of inspiration for maximum lung aeration.

In practiceExpiratory films mimic interstitial lung disease and cardiomegaly.

See alsoExpiratory film

A hip-screening method from the University of Pennsylvania that measures laxity with compression, distraction and extended views.

In practiceCan be done from 16 weeks of age. Requires certified staff.

See alsoDistraction index

Fluid within the pericardial sac.

In practiceLook for a heart-base mass or right atrial mass on echo. Tamponade causes right atrial collapse.

See alsoPericardiocentesis

Needle drainage of fluid from the pericardial sac, usually ultrasound-guided.

In practiceLifesaving in cardiac tamponade.

See alsoPericardial effusion

New bone formed by the periosteum in response to injury, infection or tumor.

In practiceSmooth and solid suggests benign. Lamellar, spiculated, sunburst or interrupted suggests aggressive.

See alsoCodman's triangle

Toward the edge of an organ or the surface of the body, away from the center.

In practicePeripheral pulmonary nodules lie near the pleural surface.

See alsoCentral

Free fluid in the abdomen.

In practiceSmall volumes are easier to find on ultrasound than on radiographs.

See alsoEffusionAFAST

Numerous tiny, poorly defined holes with a wide zone of transition.

In practiceThe most aggressive lysis pattern, typical of malignancy or severe osteomyelitis.

See alsoLysis

Tc-99m in its anion form. It is taken up by thyroid, salivary glands and gastric mucosa.

In practiceUsed for feline hyperthyroidism, often reported as a thyroid-to-salivary ratio.

See alsoThyroid scintigraphy

The hindfoot: tarsus, metatarsus and digits.

See alsoManus

A small-footprint probe that steers the beam electronically, giving a sector image from a small window.

In practiceStandard for echocardiography.

See alsoEchocardiography

A catecholamine-secreting adrenal medulla tumor that can invade the caudal vena cava.

In practiceCT defines vascular invasion before surgery.

See alsoAdrenomegaly

In helical CT, table travel per rotation divided by the beam collimation width.

In practiceHigher pitch means faster scans with less dose but lower resolution.

See alsoHelical CT

The back surface of the hindlimb from the tarsus distally, including the pads.

In practiceUsed in projection names such as DPl (dorsoplantar).

See alsoDorsalPalmar

Fluid in the pleural space.

In practiceCauses include heart failure, pyothorax, chylothorax, neoplasia and hemothorax. Thoracocentesis is diagnostic.

See alsoPleural fissure lines

Thin opaque lines between lung lobes caused by fluid or pleural thickening.

In practiceAn early sign of pleural effusion.

See alsoPleural effusion

Pleating or bunching of intestine, typical of a linear foreign body.

See alsoLinear foreign body

Air in the mediastinum, outlining vessels and the esophagus.

In practiceCan follow tracheal tears, venipuncture trauma or alveolar rupture.

Free gas in the peritoneal cavity.

See alsoFree gas

Air in the pleural space, causing lungs to retract from the chest wall.

In practiceLook for cardiac elevation, retracted lobes and absent lung markings peripherally.

See alsoCardiac elevationGlide sign

Focused, goal-directed ultrasound at the bedside to answer specific questions, such as free fluid.

In practiceAFAST, TFAST and VetBLUE are standard protocols.

See alsoAFASTTFASTVetBLUE

An abnormal vessel carrying portal blood around the liver into the systemic circulation. Intrahepatic or extrahepatic.

In practiceCT angiography maps the vessel for surgical or interventional planning. Small liver and renomegaly are common radiographic clues.

See alsoCT angiography

Imaging of positron-emitting tracers such as FDG, showing metabolic activity. Usually combined with CT (PET-CT).

In practiceUsed for cancer staging at some referral centers.

See alsoFDG

Behind. In veterinary anatomy reserved mainly for the eye (posterior segment).

See alsoAnterior

A Doppler mode showing the presence of flow, without direction, with greater sensitivity to slow flow.

See alsoColor Doppler

Earlier studies of the same patient, used for comparison.

In practiceComparison often changes the impression. Include priors whenever possible.

The direction the X-ray beam travels through the patient, named entry point first and exit point second (Smallwood et al., 1985).

In practiceA VD projection enters ventrally and exits dorsally. Views are named by projection, not by which side touches the cassette.

See alsoViewSmallwood nomenclature

A sequence where contrast reflects the number of hydrogen protons, with minimal T1 or T2 weighting.

In practiceUseful for joint cartilage and menisci.

Moving in a proximal direction.

See alsoDistad

Closer to the trunk or point of attachment. For vessels and nerves, closer to the heart or CNS.

See alsoDistal

Fluid in the lung interstitium and alveoli. Cardiogenic edema in dogs is often perihilar and caudodorsal; in cats, it is patchy and variable.

See alsoAlveolar patternCongestive heart failure

Spread of tumor to the lungs, usually as multiple nodules.

In practiceCT finds nodules down to 1–2 mm; radiographs miss nodules under about 5 mm.

See alsoThree-view thoraxPulmonary nodule

A small, round opacity in the lung.

In practiceRule out summation and end-on vessels before calling one.

See alsoNoduleSummation

Mild dilation of the renal pelvis.

In practiceCommon spelling error: pyelectasea.

See alsoHydronephrosis

Graininess in an image from too few X-ray photons reaching the detector.

In practiceIncrease mAs.

See alsomAs

An image made by passing X-rays through a patient onto a detector.

In practicePreferred term over X-ray, which properly names the radiation.

See alsoRadiography

The making of diagnostic images with X-rays.

See alsoDigital radiographyComputed radiography

Treatment of hyperthyroidism or thyroid carcinoma with iodine-131, which emits beta particles that destroy hyperfunctioning thyroid tissue.

In practiceThe curative standard for feline hyperthyroidism. Cats are hospitalized until emission levels allow release.

See alsoIodine-131Thyroid scintigraphy

Letting X-rays pass easily and appearing dark, like gas or fat.

See alsoRadiopaque

Blocking X-rays strongly and appearing white, like bone, metal or contrast medium.

See alsoRadiolucent

A ruler, ball or object of known size placed in the image for calibration.

In practiceNeeded for accurate TPLO and TTA planning.

See alsoMagnification

A radioactive tracer bound to a carrier that targets a tissue or function.

See alsoTechnetium-99m

A repeat study at a set interval to track a finding.

In practiceState the interval and the modality, for example a recheck ultrasound in 4–6 weeks.

Response Evaluation Criteria in Solid Tumors: a standard way to measure tumor response by changes in lesion diameter. Veterinary versions (VCOG) are used in trials.

In practiceMeasure the same lesions in the same plane on each scan.

The mathematical filter used to build CT images, from smooth (soft tissue) to sharp (bone, lung).

In practiceSharp kernels show fine detail but add noise. Many protocols reconstruct both.

The position of a lying animal, named for the body surface that touches the table: right lateral, left lateral, sternal (ventral) or dorsal recumbency.

In practiceRecumbency changes lung aeration and gas distribution, so it must be recorded with the study.

See alsoDependent

A user-drawn area on an image used to measure values such as HU, signal or size.

See alsoHounsfield unit

Affecting a defined portion of an organ or body area.

See alsoFocal

Regulatory limits on measured dose rate or retained activity that must be met before a treated patient goes home.

In practiceSet by state radiation control programs; they also set home precautions.

See alsoRadioiodine therapy

Bone reshaping in response to stress, injury or disease.

In practiceSmooth, well-marginated remodeling suggests chronicity.

See alsoPeriosteal reaction

Kidney length on a VD radiograph compared with the length of the L2 vertebral body.

In practiceDogs: about 2.5–3.5. Cats: about 2.0–3.0.

The time between successive excitation pulses.

In practiceShort TR plus short TE weights toward T1; long TR plus long TE weights toward T2.

See alsoEcho time

Lung borders pulled away from the chest wall by pleural fluid or air.

In practiceScalloped margins suggest fluid; dark space without lung markings suggests air.

See alsoPneumothoraxPleural effusion

Behind the peritoneum, in the dorsal abdomen. Contains the kidneys, adrenal glands, ureters, aorta and caudal vena cava.

In practiceRetroperitoneal fluid often follows trauma or ureteral rupture.

Repeating, evenly spaced bright lines caused by sound bouncing between two strong reflectors.

In practiceA-lines in lung; comet-tail and ring-down artifacts are variants.

See alsoComet-tail artifactA-lines

Right heart enlargement on a VD or DV view, the heart shaped like a backward D.

Inflammation of the nasal cavity, from infectious, allergic or foreign-body causes.

In practiceFungal rhinitis (aspergillosis) shows turbinate destruction without a mass.

See alsoNasal neoplasia

A lateral projection with the patient's right side against the detector. In Smallwood terms this is a left-right lateral (LeRt).

In practiceOne of the standard three thoracic views for metastasis screening.

See alsoLeft lateralThree-view thorax

Standard echo view from the right side showing the heart in long axis, including left atrium and ventricle.

See alsoRight parasternal short-axis view

Standard echo view from the right side slicing across the heart, used to measure the LA:Ao ratio and LV dimensions.

See alsoLA:Ao ratio

Concentric rings on CT images caused by a miscalibrated or failed detector element.

In practiceAn equipment fault that needs service.

Contrast enhancement around the rim of a lesion with a nonenhancing center.

In practiceAbscess, necrotic tumor, granuloma or resolving hemorrhage.

See alsoContrast enhancement

Radiology Information System: manages orders, scheduling, workflow and reporting.

See alsoPACS

On the head, toward the tip of the nose.

In practiceThe correct counterpart to caudal on skull, nasal, dental and brain images.

See alsoCaudalCranial

Unintended tilt of the patient during positioning.

In practiceOn a VD, check that the sternum overlies the spine. Rotation distorts the cardiac silhouette and mimics lesions.

The six features used to describe any radiographic finding: size, shape, number, location, margination and opacity. Some lists add architecture and function.

In practiceWorking through Röntgen signs keeps descriptions systematic and keeps diagnosis out of the findings section.

See alsoOpacity

Any plane parallel to the median plane. A parasagittal plane is a sagittal plane off the midline.

In practiceA standard CT and MRI reconstruction.

See alsoMedian planeDorsal planeTransverse plane

A fracture involving the growth plate (physis) in a young animal, classified I to V.

In practiceType V (crush) may be invisible at first and show up later as premature closure.

See alsoFracture

X-rays deflected within the patient. They degrade contrast and are the main source of dose to staff.

In practiceCollimate tightly, use a grid for thick parts, and stand back.

See alsoGridCollimation

Nuclear medicine imaging that maps the distribution of a radiopharmaceutical with a gamma camera.

In practiceUsed for thyroid, bone, portal shunt and renal function studies.

See alsoRadiopharmaceuticalGamma camera

Increased bone opacity from thickened trabeculae or new bone.

In practiceSeen at the subchondral bone in osteoarthritis and around chronic lesions.

Drug-induced reduction in awareness and movement while the patient keeps protective reflexes.

In practiceImproves positioning and reduces repeats and staff exposure.

See alsoGeneral anesthesia

Dependent echogenic particles in the gallbladder or urinary bladder.

In practiceMobile sediment shifts when the patient is repositioned. Gallbladder sludge is often incidental in older dogs.

See alsoGallbladder sludgeGallbladder mucocele

A set of related images within a study, such as one MRI sequence or one CT reconstruction.

See alsoStudy

How crisply the abdominal serosal surfaces stand out against intra-abdominal fat.

In practiceReduced serosal detail suggests fluid, carcinomatosis, steatitis or simply a thin or young patient.

See alsoPeritoneal effusion

A line perpendicular to the long axis of an organ.

In practiceShort-axis echo views slice across the ventricles.

See alsoLong axis

False echoes placed in an anechoic structure by off-axis sound energy.

In practiceCan mimic sediment in the gallbladder or bladder.

See alsoSlice-thickness artifact

SI unit of effective dose, reflecting biologic risk. Occupational doses are reported in millisieverts (mSv).

See alsoGray

Brightness on an MRI image. Described as hyperintense, hypointense or isointense relative to a reference tissue.

In practiceFor brain lesions, compare to normal gray matter.

See alsoHyperintenseHypointense

The ratio of true image signal to random noise.

In practiceOn MRI, raised by larger voxels, more averages or higher field strength.

Loss of the visible border between two structures of the same opacity that touch each other.

In practicePleural fluid effaces the cardiac silhouette; a cranioventral lung pattern effaces the heart border.

See alsoBorder effacement

Left. Refers to the animal's left.

In practiceAppears in OS (oculus sinister) and AS (auris sinistra).

See alsoDexter

A tangential projection that profiles a curved surface, such as the dorsal radial carpal bones, the trochlear groove or the navicular bone.

See alsoTangential projection

Echoes partially averaged into a fluid structure from adjacent tissue because the beam has thickness. Also called partial-volume artifact.

See alsoSide-lobe artifact

Maximum small intestinal diameter divided by the height of the L5 vertebral endplate on radiographs.

In practiceA ratio above about 1.6 in dogs suggests obstruction.

See alsoMechanical obstruction

The standard veterinary system for naming radiographic projections. It was published in 1985 and adopted by the ACVR. Names give the beam's entry and exit points using NAV directional terms and abbreviations.

In practiceThe standard reference for consistent labeling and reports.

See alsoProjection

Display settings tuned to separate soft tissues, with a narrow width centered near 40 HU.

See alsoWindow width

The ground-bearing surface of the hoof in ungulates.

In practiceSolar margin of the distal phalanx is a key landmark in equine foot radiographs.

See alsoPalmarPlantar

The distance from the X-ray tube's focal spot to the detector. Commonly 100 cm (40 in).

See alsoObject-image distance

A measure of detail in the image, expressed in line pairs per millimeter.

See alsoSpatial resolution

The ability to show small structures as separate; the fineness of detail.

In practiceMeasured in line pairs per mm on radiographs, voxel size on CT and MRI.

See alsoContrast resolution

The rate radiofrequency energy is absorbed by tissue during MRI, in watts per kilogram.

In practiceHigh-SAR sequences can raise body temperature; monitor small patients.

A Doppler display of velocity over time. Pulsed-wave (PW) samples one location; continuous-wave (CW) measures high velocities along a line.

In practiceCW Doppler measures stenotic and regurgitant jets.

See alsoDoppler

Having fine, radiating projections from the margin.

In practiceIn bone, spiculated periosteal reaction suggests an aggressive lesion.

See alsoPeriosteal reaction

The classic MRI sequence family, using a refocusing pulse. Fast or turbo spin echo (FSE/TSE) is the clinical standard.

See alsoGradient echo

Enlarged spleen.

In practiceDiffuse causes include sedation, congestion, infiltration and extramedullary hematopoiesis.

Bony spurs along the ventral and lateral margins of vertebral endplates, sometimes bridging the disc space.

In practiceVery common and usually an incidental finding.

A horizontal-beam lateral projection of a standing patient.

In practiceUsed for pleural fluid or pneumothorax in unstable small animals, and routinely in horses.

See alsoHorizontal beam

Diffusely hypoechoic liver parenchyma with brighter portal walls.

In practiceCan indicate lymphoma, hepatitis, congestion or normal in some patients.

An urgent interpretation, prioritized ahead of routine studies.

In practiceTeleradiology services typically quote turnaround times for STAT and routine reads.

See alsoTurnaround time

Inflamed fat, seen on ultrasound as hyperechoic, often hyperattenuating, fat around an inflamed organ.

In practiceBright mesentery around the pancreas supports pancreatitis.

See alsoPancreatitis

Abnormal narrowing of a passage or vessel.

Lying on the sternum, belly down. Also called ventral recumbency.

In practiceUsed for DV thoracic projections and many CT scans.

See alsoRecumbency

The joint between femur, tibia and patella. Equivalent to the human knee.

Short tau inversion recovery: a fat-suppressed sequence that makes fluid and edema bright.

In practiceSensitive for bone marrow edema, muscle and soft-tissue inflammation.

See alsoFat suppression

Bright and dark lines radiating from metal or dense objects.

In practiceMetal artifact reduction software helps.

See alsoBeam hardening

A projection taken while force is applied to a joint to show instability or ligament rupture.

In practiceMedial or lateral stress views of the carpus and tarsus.

Rows of small gas bubbles in bunched intestine.

In practiceSeen with linear foreign bodies.

See alsoLinear foreign bodyPlication

A report built from standard sections or fields: history, technique, findings, impressions and recommendations.

In practiceKeeps findings separate from conclusions and makes data searchable.

See alsoImpression

All the images acquired for one patient during one exam, identified by a Study Instance UID.

See alsoSeriesAccession number

The proximal segment of a limb: humerus or femur.

See alsoZeugopodiumAutopodium

Partial loss of contact between joint surfaces.

In practiceCommon misspelling: subluxations used as singular.

See alsoLuxation

Overlap of structures in a 2-D projection that creates an apparent opacity or lesion.

In practiceSummation of vessels and ribs can mimic a pulmonary nodule. Check it on the orthogonal view.

See alsoSilhouette sign

Closer to the body surface.

See alsoDeep

Above. In veterinary anatomy limited to a few head structures such as the eyelids.

See alsoInferior

Signal loss and distortion near metal or air-tissue boundaries.

In practiceMicrochips cause large voids in the neck. Note implants on the request.

See alsoGradient echo

A high-field GRE technique that maximizes sensitivity to blood products, iron and calcium.

In practiceMore sensitive than T2* for microhemorrhage.

See alsoGradient echoBlooming

Multiple hypoechoic nodules throughout the spleen.

In practiceDifferentials include lymphoma, mast cell tumor, extramedullary hematopoiesis and nodular hyperplasia. FNA helps sort them.

See alsoSplenomegaly

Fluid-filled cavities within the spinal cord.

In practiceOften linked to Chiari-like malformation in Cavalier King Charles Spaniels.

See alsoChiari-like malformation

A sequence where contrast depends mainly on T1 relaxation. Fat is bright, fluid is dark.

In practiceThe anatomy sequence, and the one repeated after gadolinium.

See alsoT2-weightedGadolinium

T2-star: signal decay that includes field inhomogeneity. T2*-weighted GRE images make blood products and mineral look dark.

See alsoGradient echoSusceptibility-weighted imaging

A sequence where contrast depends mainly on T2 relaxation. Fluid and most lesions are bright.

In practiceThe pathology sequence: edema, inflammation and most tumors are T2 hyperintense.

See alsoT1-weightedFLAIR

A beam directed along the surface of a curved structure to show its edge in profile.

See alsoSkyline projection

Concentric rings on ultrasound in cross-section. In intestine, the multilayered appearance of intussusception.

See alsoIntussusception

The most widely used diagnostic radionuclide. It emits 140 keV gamma rays with a 6-hour half-life.

In practicePertechnetate for thyroid scans; MDP for bone scans.

See alsoPertechnetateMDP

A table setting kVp and mAs by body region and measured thickness.

In practiceMeasure the patient with calipers at the thickest point of the area being imaged.

See alsokVpmAs

Remote interpretation of images sent electronically to a radiologist at another location.

In practiceRequires good image quality, full history and correctly labeled studies.

See alsoPACS

The unit of magnetic field strength. Clinical veterinary magnets range from about 0.2 T (low field) to 3 T (high field).

In practiceHigher field gives more signal and faster, thinner imaging.

See alsoLow-field MRIHigh-field MRI

Thoracic focused assessment with sonography for trauma or triage. Checks for pneumothorax, pleural and pericardial effusion.

See alsoPoint-of-care ultrasoundAFASTGlide sign

Needle or catheter drainage of fluid or air from the pleural space.

In practiceTherapeutic and diagnostic. Image afterward to check remaining fluid or air.

Right lateral, left lateral and a VD or DV projection of the thorax.

In practiceStandard for metastasis checks. A nodule is better aerated and easier to see in the nondependent lung.

See alsoRight lateralLeft lateral

A malignant thyroid tumor, more common in dogs than cats, often large and invasive.

In practiceCT and scintigraphy assess invasion and metastasis.

Imaging the thyroid with pertechnetate to assess function, locate hyperfunctioning tissue and find ectopic thyroid.

In practiceGuides I-131 dose decisions and can reveal thyroid carcinoma.

See alsoPertechnetateRadioiodine therapy

A scintigraphic comparison of thyroid and salivary gland uptake.

In practiceA ratio above roughly 1.0–1.5 supports hyperthyroidism in cats; reference ranges vary by facility.

See alsoThyroid scintigraphy

The angle between the tibial plateau and a line perpendicular to the tibial axis on a lateral stifle radiograph.

In practiceUsed to plan TPLO surgery.

See alsoCranial cruciate ligament rupture

The three practical controls for radiation exposure: minimize time near the source, maximize distance (dose falls with the square of distance) and use shielding.

See alsoALARAInverse square law

Flattening of the tracheal rings, usually in toy breeds, worsening with breathing phase.

In practiceFluoroscopy shows the dynamic collapse best.

See alsoFluoroscopy

Tracheal diameter at the thoracic inlet divided by the thoracic inlet diameter on a lateral radiograph.

In practiceUsed to screen for tracheal hypoplasia. Reference values differ for brachycephalic breeds, especially bulldogs.

See alsoBrachycephalic obstructive airway syndrome

Thickened bronchial walls seen side-on as parallel lines.

See alsoBronchial pattern

The ultrasound probe. It sends and receives sound pulses. Main types are linear, curvilinear (convex), microconvex and phased array.

In practiceUse high-frequency linear transducers for superficial structures and microconvex for small-animal abdomen.

See alsoLinear transducerPhased array

A malignant tumor of the urothelium, often at the bladder trigone or urethra. Also called urothelial carcinoma.

In practiceBRAF mutation testing on urine supports the diagnosis.

Any plane perpendicular to the long axis of the body or a limb; a cross section. Equivalent to the human axial plane.

In practiceUsually the acquisition plane for CT.

See alsoDorsal planeSagittal plane

The time from study submission to finalized report.

See alsoSTAT read

Two distinct groups of small intestinal loops, some dilated and some normal.

In practiceSuggests mechanical obstruction.

See alsoMechanical obstruction

Unique Identifier: a globally unique string identifying a DICOM study, series or image.

See alsoStudy

Imaging with high-frequency sound waves echoed back from tissue interfaces.

In practiceBest for soft-tissue organ architecture. Limited by gas and bone.

See alsoEchocardiography

Sampling a lesion with the needle tracked in real time on ultrasound.

See alsoFine-needle aspirationCore biopsy

Affecting one side only.

See alsoBilateral

Serial radiographs after oral barium to evaluate the esophagus, stomach and small intestine.

In practiceUltrasound has largely replaced it; still useful for some obstructions and motility questions.

See alsoBarium sulfate

Blockage of a ureter, often by a calcium oxalate stone in cats.

In practiceUltrasound shows ureteral and pelvic dilation proximal to the obstruction.

See alsoHydronephrosis

Retrograde contrast study of the urethra.

In practiceStandard for urethral rupture or stricture, especially in male dogs.

See alsoCystography

Stones in the urinary tract.

In practiceStruvite and calcium oxalate are radiopaque; urate and cystine may be faint. Ultrasound finds most of them.

See alsoClean shadowing

Heart shape on a VD or DV view with the atria enlarged at the base.

In practiceSeen in feline cardiomyopathy.

See alsoHypertrophic cardiomyopathy

Abnormal pulmonary vessel size: enlarged (overcirculation, congestion, heartworm) or small (hypovolemia, shock, right-to-left shunts).

In practiceCompare the lobar artery and vein, which run side by side.

Toward the belly or underside of the body.

See alsoDorsal

A projection entering the ventral surface and exiting the dorsal surface, with the patient in dorsal recumbency.

In practiceThe preferred projection for lung and pleural detail, except in dyspneic patients.

See alsoDorsoventral

A measure of heart size on a lateral thoracic radiograph: the long and short cardiac axes laid along the vertebrae from T4, summed in vertebral lengths (Buchanan and Bücheler, 1995).

In practiceA common reference upper limit is 10.5 in dogs, but it varies by breed. Compare with priors.

See alsoVertebral left atrial size

A radiographic measure of left atrial size in dogs, from the carina to the caudal left atrial border, expressed in vertebral lengths from T4.

In practiceA VLAS of 2.3 or more supports left atrial enlargement in MMVD.

See alsoVertebral heart scoreLA:Ao ratio

The outward-facing tooth surface, toward the vestibule of the mouth. Covers both buccal and labial surfaces.

See alsoLingualPalatal

Veterinary bedside lung ultrasound exam: a regional lung protocol counting B-lines.

See alsoB-linesPoint-of-care ultrasound

Fluoroscopic recording of swallowing with contrast-laced food or liquid.

In practiceDefines oropharyngeal and esophageal dysphagia.

See alsoFluoroscopyEsophagram

Informal synonym for a radiographic projection. Strictly, a view describes the image from the detector's side, so projection is the preferred term.

See alsoProjection

Software for displaying DICOM images, with tools for measurement, window and level, MPR and annotation.

See alsoPACS

Relating to the organs within a body cavity, or the serosal layer covering them.

See alsoParietal

Vendor-neutral archive: long-term image storage in standard formats, independent of any one PACS vendor.

See alsoPACS

A volume element: the 3-D unit of a CT or MRI dataset. A pixel is its 2-D display.

See alsoIsotropic voxel

Normal ultrasound appearance of the GI wall as five alternating layers: mucosal surface, mucosa, submucosa, muscularis and serosa.

In practiceLoss of layering suggests neoplasia (especially lymphoma or carcinoma) more than inflammation.

See alsoGastrointestinal wall thickness

Having sharp, easily traced margins.

In practiceWell-defined margins favor slow-growing or benign processes, though not reliably.

See alsoIll-definedMargination

Display controls setting the range of grayscale values shown (width) and their center (level).

In practiceAdjusting window and level on radiographs and CT reveals soft tissue or bone detail from the same data.

See alsoWindow widthWindow level

The HU value at the center of the displayed grayscale.

In practiceTypical settings: lung WW 1500 / WL −500; bone WW 2000 / WL 500; soft tissue WW 400 / WL 40.

See alsoWindow width

The range of HU values displayed across the grayscale.

In practiceNarrow for brain soft tissue, wide for lung and bone.

See alsoWindow levelWindow and level

Anatomy outside the field of view folding onto the opposite side of the image. Also called aliasing.

The middle segment of a limb: radius and ulna, or tibia and fibula.

See alsoStylopodiumAutopodium

The width of the boundary between a bone lesion and normal bone.

In practiceA short zone suggests a benign process; a long zone suggests an aggressive one.

See alsoLysis

A dark halo beside high-contrast edges such as metal implants, caused by edge-enhancement processing. Also called a rebound or halo artifact.

In practiceDo not mistake it for bone lysis around implants.

See alsoEdge enhancement