RD5.1-4 | Core Image Interpretation Skills — Glossary

A plain-film calibre guide for bowel dilatation suggesting obstruction: small bowel greater than ~3 cm, large bowel greater than ~6 cm, and caecum greater than ~9 cm.

A recent fracture showing a sharp, lucent, NON-corticated fracture line with adjacent soft-tissue swelling and clinical tenderness from recent trauma.

An air-filled bronchus made visible because the surrounding alveoli are filled with fluid/soft-tissue density (e.g. consolidation); its ABSENCE in a mediastinal density is one feature favouring a normal thymus over consolidation.

A horizontal interface between gas and fluid visible only on a horizontal-beam (erect or decubitus) film; multiple central stepladder levels suggest small-bowel obstruction, and a level in the pleura or an abscess indicates a hydropneumothorax/collection.

As Low As Reasonably Achievable — the radiation-protection principle that justifies preferring a single low-dose hand–wrist film for most paediatric bone-age requests.

Antero-posterior radiograph (beam front-to-back, often portable/supine); the heart is farther from the detector and is magnified, so cardiomegaly cannot be diagnosed and the mediastinum appears wider.

An estimate of skeletal maturity expressed in years, derived from the appearance and fusion of ossification centres; it correlates with but is not identical to chronological age.

The maximum transverse cardiac diameter divided by the maximum internal thoracic diameter on a PA erect film; normal is less than 0.5 in adults (normally larger in infants).

The bifurcation of the trachea into the main bronchi, typically projecting around the T4–T5 level on a frontal film; the reference landmark for endotracheal tube tip depth (target ~3–5 cm above it).

The junction of the superior vena cava with the right atrium; the target position for a central venous catheter or PICC tip.

A catheter placed via a central vein (internal jugular or subclavian) whose tip should lie at the cavoatrial junction/lower SVC; a tip in the right atrium risks arrhythmia or perforation.

A tube placed in the pleural cavity to drain air (directed apically) or fluid (directed basally); the last side-hole must lie within the pleural cavity for the drain to function.

Interposition of the colon between the liver and the right hemidiaphragm, mimicking free air; distinguished from true pneumoperitoneum by haustral folds visible within the gas.

A healed or healing fracture showing sclerotic, rounded, CORTICATED margins (smoothed by remodelling) without soft-tissue swelling, often an incidental, non-tender finding.

The actual time elapsed since birth; the quantity that radiographic age estimation tries to infer, always with a margin of error.

A common cause of a bone age that LAGS chronological age, in which skeletal maturation and growth are delayed but ultimately normal; a key context where the bone age–chronological age gap is informative.

A smooth, sclerotic (white) rim around a lucency or bony edge indicating chronicity/healing; its presence around a fracture line marks the fracture as old rather than acute.

An abnormally deep, lucent lateral costophrenic angle on a SUPINE film indicating a pneumothorax when the classic upright lung edge is not visible.

The shaft (central portion) of a long bone.

Malposition of an endotracheal tube tip into a main bronchus (usually the right), ventilating only one lung and causing collapse of the opposite (usually left) lung; corrected by withdrawing the tube.

An airway tube placed through the larynx into the trachea; correctly positioned with its tip approximately 3–5 cm above the carina in a neutral neck to ventilate both lungs without endobronchial intubation.

The process by which an epiphysis unites with its metaphysis as the growth plate ossifies; occurs in an orderly, region-specific sequence from puberty into the early-to-mid twenties.

The secondary ossification centre at the end of a growing long bone, separated from the metaphysis by the physis; appears, ossifies and fuses at predictable ages.

A radiograph taken with the patient upright and the X-ray beam horizontal; required to demonstrate free air rising under the diaphragm and air–fluid levels forming a horizontal interface.

Displacement of the elbow fat pads (especially a visible posterior fat pad) by a joint effusion, an indirect sign of an occult intra-articular fracture even when no fracture line is seen.

A bone-age method in which a single hand–wrist film is matched as a whole against sex-specific reference plates; fast but observer-dependent and biased toward its 20th-century North American source population.

Large-bowel mucosal sacculations that do NOT cross the full width of the lumen; dilated peripheral loops with haustra localise an obstruction to the large bowel.

The apophysis along the iliac crest whose progressive ossification and fusion (~20–21 years per Indian reference values) is used both in scoliosis maturity assessment and as a late age-estimation marker.

Ossification-appearance and epiphyseal-fusion ages derived from Indian populations (per Reddy's), preferred over Western atlas values in Indian medico-legal age estimation.

The stated uncertainty around an age estimate; a defensible radiographic age opinion always reports an age range with a margin rather than a single exact year.

The medial clavicular growth centre, which fuses LAST of the major epiphyses (~18–25 years), making it the key radiographic marker distinguishing a late adolescent from an adult.

Displacement of the mediastinum to one side; shift AWAY from a hemithorax suggests a space-occupying process such as tension pneumothorax or large effusion, while shift TOWARD suggests volume loss (collapse).

The flared portion of a long bone adjacent to the physis, between the epiphysis and the diaphysis (shaft); a site of active bone remodelling in children.

A tube passed through the nose into the stomach for feeding or drainage; correctly positioned when it runs in the midline, bisects the carina and has its tip below the left hemidiaphragm — confirmed radiographically before feeding.

The principle that an endotracheal tube tip moves toward the carina with neck flexion and away with extension ('the tube goes where the chin goes'); tube depth must be judged with the neck position noted.

An oblique channel through the cortex transmitting the nutrient vessel; a normal finding with a corticated margin that must not be mistaken for a cortical fracture.

A focus of bone formation that appears within cartilage at a predictable age; primary centres form the shaft and secondary centres (epiphyses) form the bone ends — the basis for radiographic age estimation.

Postero-anterior chest radiograph — beam passes from behind the patient to a detector against the chest; the heart is close to the detector and minimally magnified, so the cardiothoracic ratio (<0.5 normal) is valid on this view.

The radiolucent cartilaginous plate between the metaphysis and the epiphysis at which a child's long bone grows in length; appears as a normal lucent line and must not be mistaken for a fracture.

A peripherally inserted central catheter advanced from an arm vein to a central position; its tip target is the same cavoatrial junction as a CVC.

Free gas within the peritoneal cavity, usually from a perforated viscus; seen as free air under the diaphragm on an erect chest film and as the Rigler (double-wall) sign on a supine abdominal film.

Air in the pleural cavity seen as a lung edge with absent peripheral lung markings; the mandatory complication to exclude after any central-line or other thoracic insertion (supine films may show only a deep sulcus sign).

A chest radiograph taken at the bedside with an anteroposterior, usually supine, technique; it magnifies the heart and mediastinum so true heart size cannot be judged, and is read mainly for tubes/lines and acute lung change.

The first centre of bone formation in a developing bone (the shaft of a long bone), generally present at birth for the major long bones.

A balloon-tipped catheter floated through the right heart into the pulmonary artery; its tip should lie in a main/proximal pulmonary artery, not wedged peripherally (infarction risk).

The five basic levels of X-ray attenuation that determine brightness on a film: air (darkest), fat, soft tissue/water, bone/calcification, and metal/contrast (brightest); structures are distinguished only where densities differ.

The population-, sex- and method-specific dataset against which an individual's skeletal maturity is compared to estimate age; selecting an appropriate one is the central skill in age estimation.

The cardiac chamber receiving the SVC and IVC; a central catheter tip lying within it (rather than at the cavoatrial junction) risks arrhythmia and perforation and should be withdrawn.

On a supine abdominal film, gas outlining BOTH the inner and the outer wall of a bowel loop because there is gas inside the bowel and free gas outside it — an indicator of pneumoperitoneum.

A grading (0–5) of iliac crest apophyseal ossification and fusion used to assess skeletal maturity, especially for scoliosis management and as a corroborative late age marker.

The error of stopping the search after the first finding and missing a second, important abnormality; countered by always completing the full systematic read after the targeted emergency pass.

A fixed, memorised sequence for reading every region of a radiograph so that no zone is skipped, reducing 'satisfaction of search' errors where a reader stops after the first finding.

A later centre of bone formation, principally the epiphysis at the end of a long bone, appearing postnatally at predictable ages and used in age estimation.

The tendency for skeletal maturation (and growth) to occur earlier in successive, better-nourished generations, a source of bias when an older reference standard is applied to a modern cohort.

The loss of a normal border between two structures of the SAME radiographic density when they come into contact; e.g. right-middle-lobe consolidation effaces the right heart border, localising the pathology.

Free intraperitoneal gas seen as a black crescent between the diaphragm and the liver (right) on an erect chest film — the classic radiographic sign of a perforated viscus.

The large central vein returning blood from the head, neck and upper limbs to the right atrium; its lower part is the desired location for a central catheter tip.

A bone-age method that assigns a maturity stage to each of a defined set of hand–wrist bones, sums them into a maturity score and converts the score to bone age; more reproducible and granular than atlas matching.

A pneumothorax under positive pressure causing mediastinal shift AWAY from the affected side and cardiorespiratory compromise; a CLINICAL diagnosis requiring immediate needle decompression — do not wait for imaging.

The triangular density produced by the normal large thymus at the mediastinal border on a neonatal/infant chest film; a NORMAL appearance distinguished from pathology by its wavy border, absence of air bronchograms and lack of structure displacement.

A gently undulating ('wavy') lateral margin of the normal infant thymus produced by the overlying ribs — a feature confirming the density is the normal thymus rather than a mass.

The systematic ICU-film approach of identifying and checking every device against its landmark and searching for insertion complications before the routine lung review.

The mucosal folds of the small bowel that cross the FULL width of the lumen on an abdominal film, distinguishing dilated small bowel from large bowel (whose haustra do not cross the full lumen).

The standard radiographic projection for the paranasal sinuses; correctly angled it projects the petrous ridges below the maxillary antra so the normally lucent maxillary and frontal sinuses can be assessed.