Radiology for NEET PG 2026: X-Ray Signs, CT Patterns, and Complete Imaging Guide

Radiology contributes approximately 2 to 3 percent of the NEET PG paper — around 3 to 6 questions out of 180. These questions are almost exclusively pattern recognition: a described finding, a named sign, or a clinical scenario where you must identify the correct imaging modality or characteristic appearance. Radiology PYQs are highly predictable — the same signs, the same TB patterns, the same CT findings appear cycle after cycle.

This guide covers every high-yield Radiology topic with the depth NEET PG demands. The signs tables alone capture more than 60 sign-disease pairs tested in PYQs. For where Radiology sits against the rest of the paper, see the subject wise weightage — Radiology; for how to slot it into your timetable, see the NEET PG 2026 preparation strategy.

Before starting revision, use the NEET PG 2026 score calculator to track how your subject-wise accuracy maps to your projected rank. Radiology is one of the most efficiently studied subjects — 5 to 7 focused days of PYQ-based preparation can reliably get you every Radiology question.

Radiology rewards the same habit as the other sign-heavy subjects: learn the eponym, learn the disease, move on. If you are batching them, Dermatology for NEET PG 2026 works identically, and Anaesthesia for NEET PG 2026 covers the third of the small, high-repetition subjects.

The 14 Most-Tested Radiology Topics in NEET PG PYQs

Rank	Topic	Frequency	Format
1	Named X-ray and CT signs — disease associations	Very High	Direct factual
2	Tuberculosis — primary, post-primary, miliary	Very High	Pattern recognition
3	Pneumothorax vs tension pneumothorax	Very High	Clinical scenario
4	Pleural effusion — X-ray findings and types	High	Direct factual
5	CT head — extradural vs subdural haematoma	High	Comparison MCQ
6	GI radiology — barium studies and named findings	High	Direct factual
7	Pulmonary embolism — Westermark sign, Hampton's hump	High	Direct factual
8	Cardiac radiology — cardiomegaly, boot-shaped heart	Moderate	Direct factual
9	Paediatric radiology — steeple, double bubble, thumb sign	Moderate	Clinical scenario
10	Silhouette sign — principle and applications	Moderate	Concept plus application
11	Ultrasound — high-yield findings	Moderate	Direct factual
12	MRI — named sequences and disease patterns	Moderate	Direct factual
13	Radiation physics — dose, units, safety	Low-Moderate	Direct factual
14	Interventional radiology — procedures and indications	Low-Moderate	Direct factual

Chest X-Ray: A Systematic Approach

NEET PG clinical scenario questions often describe a chest X-ray finding, so reading the description correctly matters as much as knowing the signs.

Step	What to Check
A — Airway	Trachea midline or deviated; carina angle
B — Breathing	Lung fields for opacification, lucency, consolidation, cavities, nodules, pleural lines
C — Cardiac	Heart size (cardiothoracic ratio), borders, shape
D — Diaphragm	Levels, costophrenic angles, free air beneath
E — Everything else	Bones, soft tissues, tubes, lines, foreign bodies

The cardiothoracic ratio is normally 0.5 or less on a PA film taken in full inspiration. Above 0.5 indicates cardiomegaly. An AP film magnifies the cardiac silhouette, so the ratio is unreliable there.

The Complete Radiology Signs Reference

Chest X-Ray Signs

Sign	Appearance	Condition
Silhouette sign	Loss of the interface between two adjacent structures of the same density	Consolidation touching a cardiac border — right middle lobe loses the right heart border, lingula the left
Air bronchogram	Dark branching airways visible through white opacified lung	Consolidation — air in airways surrounded by fluid-filled alveoli
Meniscus sign	Concave upper border of fluid, highest peripherally	Pleural effusion
Vertical fluid line	Straight horizontal fluid level	Hydropneumothorax
Westermark sign	Focal oligaemia distal to an embolus	Pulmonary embolism
Hampton's hump	Peripheral wedge-shaped opacity based on the pleura	Pulmonary infarction from PE
Fleischner lines	Linear opacities representing atelectasis	Pulmonary embolism; post-operative atelectasis
Kerley B lines	Short horizontal peripheral lines perpendicular to the pleura	Pulmonary oedema; lymphangitis carcinomatosa
Bat wing pattern	Bilateral perihilar opacification sparing the periphery	Cardiogenic pulmonary oedema
Sail sign (thymic)	Triangular right mediastinal opacity	Normal thymus in infants
Sail sign (atelectasis)	Triangular opacity of a collapsed lobe	Right middle or left lower lobe collapse
Golden S sign	S-shaped curve from a collapsed upper lobe plus a central mass	Right upper lobe collapse from a hilar mass, usually bronchogenic carcinoma
Pleural cap	Opacity above the lung apex	Apical pleural thickening; Pancoast tumour; haemothorax
Cervicothoracic sign	A lesion disappearing above the clavicle is posterior; one still visible is anterior	Localising mediastinal masses
Tram-track lines	Parallel opacities from thickened bronchial walls	Bronchiectasis
Signet ring sign	Dilated airway larger than its adjacent pulmonary artery	Bronchiectasis
Tree-in-bud pattern	Centrilobular nodules with branching opacities	Endobronchial spread of tuberculosis
Halo sign	Ground-glass opacity surrounding a nodule	Invasive aspergillosis; early haemorrhagic nodule
Reverse halo (atoll) sign	Central lucency ringed by ground-glass or consolidation	Cryptogenic organising pneumonia; fungal infection
Galaxy sign	Large central opacity with satellite nodules	Pulmonary sarcoidosis
Eggshell calcification	Calcification confined to the rim of hilar nodes	Silicosis; sarcoidosis; treated lymphoma
Popcorn calcification	Irregular calcification throughout a nodule	Pulmonary hamartoma
Air crescent sign	Crescent of air around a mass within a cavity	Aspergilloma
Monod sign	The fungal ball moves with position change	Aspergilloma
Water lily sign	Undulating membranes within a cyst	Pulmonary hydatid — collapsed endocyst
Cannon ball metastases	Multiple large rounded lung opacities	Choriocarcinoma; renal cell carcinoma; testicular germ cell tumour
Boot-shaped heart	Upturned apex with reduced pulmonary vascularity	Tetralogy of Fallot
Egg on its side	Narrow superior mediastinum with a large oval heart	D-transposition of the great arteries
Box-shaped heart	Markedly enlarged globular heart	Ebstein anomaly; massive pericardial effusion
Snowman heart	Large supracardiac shadow	Supracardiac total anomalous pulmonary venous connection
Rib notching	Inferior rib erosion from collateral arteries	Coarctation of the aorta
Figure 3 sign	Aortic knob with pre- and post-stenotic dilatation	Coarctation of the aorta

Pneumothorax and Tension Pneumothorax

A simple pneumothorax shows a visible pleural line with absent lung markings beyond it, partial collapse on the affected side, and a midline or minimally deviated trachea with no mediastinal shift.

Tension pneumothorax is different, and it is an emergency.

X-Ray Feature	Direction	Significance
Tracheal deviation	Away from the affected side	Trapped air pushing the mediastinum
Mediastinal shift	Away from the affected side	Compressive effect
Diaphragm	Depressed and flattened on the affected side	Air expanding downward
Lung	Completely collapsed to a white opacity at the hilum	Total collapse
Contralateral lung	Compressed by the shifted mediastinum	Reduced ventilation
Heart	Shifted away from the pneumothorax	May mimic dextrocardia

The clinical triad is absent breath sounds on the affected side, tracheal deviation away from it, and hypotension. Treatment is immediate needle decompression at the second intercostal space in the midclavicular line. Do not wait for X-ray confirmation.

Paediatric Signs

Sign	Appearance	Condition
Steeple sign	Subglottic tracheal narrowing on AP neck film	Viral croup
Thumb sign	Swollen epiglottis on lateral neck film	Acute epiglottitis
Double bubble sign	Two air bubbles, stomach and duodenum	Duodenal atresia; annular pancreas
Triple bubble sign	Three air bubbles	Jejunal atresia
Ground glass abdomen	Diffuse fine granular opacity in a neonate	Meconium ileus; early necrotising enterocolitis
Soap bubble appearance	Multiple small bubbles in the right lower quadrant	Meconium ileus
Football sign	Large rounded abdominal lucency	Massive pneumoperitoneum
Bird of prey sign	Beak-like narrowing of the sigmoid	Sigmoid volvulus
Coffee bean sign	Large omega-shaped bowel loop	Sigmoid volvulus

Gastrointestinal Signs

Sign	Imaging	Appearance	Condition
String sign of Kantor	Barium meal	String-like narrowing of terminal ileum	Crohn's disease
Lead pipe colon	Barium enema	Loss of haustra, rigid smooth colon	Long-standing ulcerative colitis
Cobblestone pattern	Barium	Deep ulcers alternating with oedematous mucosa	Crohn's disease
Rose-thorn ulcers	Barium	Spike-like projections from the bowel wall	Crohn's disease
Collar-stud ulcer	Barium	Flask-shaped ulcer penetrating the mucosa	Ulcerative colitis
Apple core lesion	Barium or CT	Circumferential annular constricting lesion	Colonic carcinoma
Bird's beak	Barium swallow	Smooth tapering of the distal oesophagus	Achalasia cardia
Corkscrew oesophagus	Barium swallow	Segmental spasms	Diffuse oesophageal spasm
Rigler sign	Plain film	Both sides of the bowel wall visible	Pneumoperitoneum
Psoas shadow loss	Plain film	Loss of the psoas outline	Retroperitoneal abscess, haematoma or tumour
Whirlpool sign	CT	Swirling mesenteric vessels	Midgut or caecal volvulus
Accordion sign	CT	Thickened colonic haustra	Pseudomembranous colitis
Target sign	CT or ultrasound	Concentric layers around bowel wall	Intussusception
Mercedes-Benz sign	Plain film or CT	Y-shaped lucency in the gallbladder	Gallstone fissures; pneumobilia
Double duct sign	CT or MRCP	Simultaneous dilatation of CBD and pancreatic duct	Carcinoma of the head of the pancreas

Tuberculosis Radiology

Primary Tuberculosis

Primary TB is the initial infection, commonest in children and the immunocompromised.

The Ghon focus is a small peripheral parenchymal opacity, usually in the upper or lower lobe. Together with hilar or paratracheal lymphadenopathy it forms the Ghon complex. Once healed and calcified — calcified focus plus calcified hilar node — it becomes the Ranke complex.

X-ray findings are parenchymal consolidation in any lobe but often lower zones in children, hilar lymphadenopathy that is often bilateral, and pleural effusion in a quarter to a third of cases, usually right-sided.

Post-Primary (Reactivation) Tuberculosis

Finding	Location	Significance
Consolidation and infiltrates	Upper lobe apical and posterior segments	Highest oxygen tension — M. tuberculosis prefers upper zones
Cavitation	Upper lobes	Active disease; air-fluid level if secondarily infected
Fibrosis and volume loss	Upper lobes	Old healed disease
Calcification	Upper lobes and hilar nodes	Healed disease
Satellite lesions	Around the main lesion	Bronchogenic spread
Tree-in-bud pattern	Lower lobes	Endobronchial spread, smear-positive
Pleural effusion	Unilateral	Active disease

Simon foci are old calcified apical scars from healed childhood primary TB that later reactivate.

Miliary Tuberculosis

Miliary TB follows haematogenous dissemination, seeding both lungs.

On chest X-ray it appears as innumerable tiny nodules of 1 to 3 mm distributed uniformly throughout both lung fields — the name comes from millet seeds. The nodules are all roughly the same size, evenly distributed with no zone predominance, and both lungs are affected symmetrically. That even, random distribution is exactly what distinguishes it: silicosis is upper-zone predominant, sarcoidosis upper and mid.

Suspect it in immunocompromised patients, in disseminated disease affecting lungs plus another organ, and alongside TB meningitis, which often accompanies it. High-resolution CT is more sensitive than plain film for early disease and shows random 1 to 4 mm nodules in all zones.

Named Signs by Organ System

Spine and Bone

Sign	Appearance	Condition
Winking owl sign	Destruction of a pedicle, invisible on one side	Metastatic bone disease
Rugger jersey spine	Dense bands at vertebral endplates with central lucency	Renal osteodystrophy; myelofibrosis
Ivory vertebra	Uniformly dense vertebral body	Paget's disease; metastases; lymphoma
Picture frame vertebra	Cortical rim with central lucency	Paget's disease
Codfish vertebra	Biconcave, fish-shaped vertebra	Osteoporosis; sickle cell anaemia
H-shaped vertebra	Central endplate depression only	Sickle cell anaemia
Bamboo spine	Ossification of spinal ligaments	Ankylosing spondylitis
Sunray spiculation	Radiating spicules from the bone surface	Osteosarcoma
Codman's triangle	Periosteal elevation forming a triangle	Osteosarcoma and other aggressive bone tumours
Onion peel periosteal reaction	Multiple layers of periosteal new bone	Ewing's sarcoma
Soap bubble appearance	Multi-loculated expansile lucency	Giant cell tumour; aneurysmal bone cyst
Shepherd's crook deformity	Varus deformity of the proximal femur	Polyostotic fibrous dysplasia
Pencil-in-cup deformity	Pencil-shaped bone end in a cup-shaped erosion	Psoriatic arthritis at the DIP joints
Rat bite erosion	Marginal erosions with overhanging edges	Gout

Neurological Imaging

Sign	Imaging	Appearance	Condition
Biconvex hyperdensity	CT head	Lens-shaped hyperdense collection	Extradural haematoma
Crescent hyperdensity	CT head	Crescent-shaped collection	Acute subdural haematoma
Banana sign	Antenatal ultrasound	Cerebellum compressed anteriorly	Open spina bifida (Chiari II)
Lemon sign	Antenatal ultrasound	Frontal bone scalloping	Open spina bifida (Chiari II)
Hot cross bun sign	MRI pons	Cross-shaped T2 hyperintensity	Multiple system atrophy, cerebellar type
Swallow tail sign	MRI midbrain	Bilateral comma-shaped dorsal hyperintensity	A normal finding — absent in Parkinson's disease
Panda sign	MRI midbrain	Panda face appearance	Wilson's disease; Wernicke's encephalopathy
Eye of the tiger sign	MRI	Central T2 hyperintensity within a hypointense globus pallidus	Pantothenate kinase-associated neurodegeneration
Double PCL sign	MRI knee	Bow-shaped fragment anterior to the PCL	Bucket handle meniscal tear
Honda sign	Bone scan or MRI pelvis	H-shaped uptake in the sacrum	Sacral insufficiency fracture

CT Head: Extradural vs Subdural Haematoma

Feature	Extradural	Subdural
Cause	Temporal bone fracture tearing the middle meningeal artery	Bridging vein tear from deceleration
Blood lies between	Skull and dura	Dura and arachnoid
CT shape	Biconvex, lens-shaped	Crescent-shaped
Crosses sutures	No — the dura is anchored at sutures	Yes — freely
Crosses midline	No	Yes, can cross the falx
Density when acute	Hyperdense	Hyperdense; isodense when subacute, hypodense when chronic
Typical location	Temporal or temporoparietal	Frontoparietal
Clinical course	Classic lucid interval then rapid deterioration	No lucid interval acutely; gradual decline when chronic
Associated skull fracture	In over 80 percent	Often absent; associated with cerebral atrophy in the elderly
Treatment	Emergency craniotomy	Craniotomy or burr holes depending on severity

The shape difference is the single most tested radiological distinction in this topic: extradural is biconvex and does not cross sutures; subdural is crescentic and does.

Ultrasound

Finding	Appearance	Condition
Hyperechoic focus with posterior acoustic shadow	Bright spot with a dark shadow behind	Calculus — gallstone, renal stone, calcified mass
Posterior acoustic enhancement	Increased brightness behind a fluid collection	Cystic lesion
Target sign	Echogenic centre with hypoechoic rim	Metastatic liver lesion; intussusception
Snowstorm appearance	Multiple echogenic foci with no fetal parts	Hydatidiform mole
FAST examination	Anechoic fluid in the hepatorenal, splenorenal and pelvic spaces	Free intraperitoneal fluid in trauma
Sonographic Murphy's sign	Maximum tenderness under the probe over the gallbladder	Acute cholecystitis
Whirlpool pattern	Swirling mesenteric vessels	Volvulus

Obstetric Finding	Gestational Age	Significance
Gestational sac	4–5 weeks	Earliest ultrasound finding of pregnancy
Yolk sac	5–6 weeks	Confirms intrauterine pregnancy
Fetal cardiac activity	6 weeks	Earliest cardiac activity
Crown-rump length	7–13 weeks	Most accurate dating
Nuchal translucency	11–13+6 weeks	Screening for Down's syndrome
Banana and lemon signs	Second trimester	Spina bifida
Snowstorm pattern	Any	Hydatidiform mole

MRI Sequences and Patterns

Sequence	Fluid	Best For
T1-weighted	Dark	Anatomy; fat; subacute blood; gadolinium enhancement
T2-weighted	Bright	Oedema; most pathology; CSF
FLAIR	Suppressed (dark)	Periventricular lesions; MS plaques
Diffusion-weighted	Bright when restricted	Acute stroke; abscess; epidermoid
GRE / SWI	—	Haemorrhage; calcification; cavernoma
MRCP	Bright	Biliary and pancreatic duct anatomy

Pattern	Condition
Periventricular T2 hyperintensities perpendicular to the ventricles (Dawson's fingers)	Multiple sclerosis
Diffusion restriction in cortex or basal ganglia	Acute stroke; Creutzfeldt-Jakob disease
Bilateral basal ganglia T2 hyperintensity	Wilson's disease; carbon monoxide poisoning; manganese toxicity
Hot cross bun sign in the pons	Multiple system atrophy, cerebellar type
Eye of the tiger in the globus pallidus	Pantothenate kinase-associated neurodegeneration
Absent swallow tail sign	Parkinson's disease
Mammillary body hyperintensity	Wernicke's encephalopathy
Cortical ribboning on diffusion imaging	Creutzfeldt-Jakob disease

Radiation Physics

Quantity	SI Unit	Old Unit	Meaning
Radioactivity	Becquerel	Curie	Disintegrations per second
Exposure	Coulomb per kg	Roentgen	Ionisation in air
Absorbed dose	Gray	Rad	Energy deposited per unit mass
Equivalent dose	Sievert	Rem	Absorbed dose times radiation weighting factor
Effective dose	Sievert	Rem	Equivalent dose times tissue weighting factor

One gray equals 100 rad; one sievert equals 100 rem.

The half-value layer is the thickness of material reducing X-ray intensity to 50 percent. Lead has the lowest half-value layer, making it the best shielding material.

By the Bergonié-Tribondeau law, tissues are more radiosensitive when rapidly dividing, undifferentiated and mitotically active. In order of sensitivity: gonads and germinal cells, bone marrow, intestinal mucosa, the basal layer of skin, the lens of the eye — uniquely sensitive despite slow turnover — then thyroid. Neural tissue, muscle, bone and cartilage are the most resistant.

High-Yield Radiology PYQ Checklist

Drill these daily with the TROCAR daily quiz rather than reading them once.

• Silhouette sign — adjacent structures of the same density lose their interface
• Right middle lobe consolidation loses the right heart border; lingula the left
• Air bronchogram — consolidation, not collapse
• Meniscus sign — pleural effusion
• Westermark sign — pulmonary embolism
• Hampton's hump — pulmonary infarction
• Kerley B lines — pulmonary oedema or lymphangitis
• Golden S sign — right upper lobe collapse with a central mass
• Steeple sign — croup; thumb sign — epiglottitis
• Air crescent sign — aspergilloma
• Water lily sign — pulmonary hydatid
• Cannon ball metastases — choriocarcinoma, renal cell carcinoma, testicular germ cell tumour
• Boot-shaped heart — Tetralogy of Fallot
• Egg on its side — D-transposition of the great arteries
• Snowman heart — supracardiac TAPVC
• Rib notching and figure 3 sign — coarctation of the aorta
• Tension pneumothorax — trachea and mediastinum deviate away, diaphragm pushed down
• Tension pneumothorax — needle decompression without waiting for X-ray
• Primary TB — Ghon complex; healed becomes the Ranke complex
• Post-primary TB — upper lobe apical and posterior segments, with cavitation
• Miliary TB — uniform 1 to 3 mm nodules, random distribution, no zone predominance
• Tree-in-bud — endobronchial spread of TB
• Extradural haematoma — biconvex, does not cross sutures
• Subdural haematoma — crescentic, crosses sutures
• Chronic subdural — hypodense; subacute — isodense and easily missed
• Double bubble sign — duodenal atresia
• Rigler sign — pneumoperitoneum
• String sign of Kantor — Crohn's disease
• Lead pipe colon — ulcerative colitis
• Apple core lesion — colonic carcinoma
• Bird's beak — achalasia
• Coffee bean sign — sigmoid volvulus
• Double duct sign — carcinoma of the head of the pancreas
• Accordion sign — pseudomembranous colitis
• Panda sign — Wilson's disease or Wernicke's
• Absent swallow tail sign — Parkinson's disease
• Hot cross bun sign — multiple system atrophy
• Eye of the tiger — PKAN
• Honda sign — sacral insufficiency fracture
• Sunray spiculation — osteosarcoma; onion peel — Ewing's sarcoma
• Codman's triangle — any aggressive bone tumour
• Bamboo spine — ankylosing spondylitis
• Most radiosensitive — gonads and bone marrow; lens of the eye despite slow turnover
• Most radioresistant — neural tissue and muscle
• Half-value layer — thickness reducing intensity to 50 percent; lead is lowest