Free NEET PG & INI-CET Radiology MCQs

Explanation

MRI uses a strong magnetic field and radiofrequency pulses, not ionising radiation, and is therefore preferred where radiation avoidance matters, such as in pregnancy, children, and repeated imaging. Ultrasound is also radiation-free. X-ray, CT, and fluoroscopy all use ionising radiation.

Explanation

Radiographic density increases from air (blackest) to fat, to soft tissue and water, to bone, to metal (whitest). Denser tissues absorb more X-rays, so less reaches the detector and the area appears white.

Explanation

Ultrasound uses high-frequency sound waves; reflected echoes from tissue interfaces build the image. It is safe, real-time, and radiation-free, making it first-line in obstetrics and for many abdominal and soft-tissue questions.

Explanation

CT attenuation is measured in Hounsfield units, with water set at 0, air about -1000, fat negative, and bone strongly positive. These values help characterise tissues such as fat, fluid, calcification, and acute blood.

Explanation

On T2-weighted images, water and fluid such as CSF and oedema appear bright. On T1-weighted images, fluid is dark and fat is bright. Recognising fluid-bright versus fluid-dark distinguishes the two basic sequences.

Explanation

ALARA, As Low As Reasonably Achievable, is the guiding principle of radiation protection — justify each exposure, optimise the dose, and use shielding and distance. It underlies preferring non-ionising modalities where appropriate.

Explanation

Doppler ultrasound detects motion, chiefly blood flow, assessing vascular patency, direction, and velocity — for example in diagnosing deep vein thrombosis, carotid stenosis, or testicular and ovarian torsion, where flow is absent.

Explanation

Iodinated contrast can cause contrast-induced nephropathy, so renal function must be checked and caution taken in renal impairment, with hydration and dose adjustment. Previous severe contrast reaction and uncontrolled thyrotoxicosis are other cautions.

Explanation

Gadolinium contrast in severe renal impairment is associated with nephrogenic systemic fibrosis, a rare but serious fibrosing condition. Renal function should be assessed, and the safest agents and lowest doses used when contrast is necessary.

Explanation

In renal impairment, iodinated contrast can reduce renal clearance of metformin, raising the risk of lactic acidosis. Guidelines advise assessing renal function and, in at-risk patients, withholding metformin around the time of contrast administration.

Explanation

If perforation is suspected, barium is avoided because leakage into the peritoneal cavity causes severe chemical peritonitis. A water-soluble iodinated contrast such as gastrografin is used instead, as it is resorbed safely.

Explanation

Ultrasound is first-line in pregnancy as it uses no ionising radiation; MRI, generally without gadolinium, is a further option. Ionising-radiation studies such as CT, fluoroscopy, and nuclear medicine are used only when the benefit clearly outweighs the risk.

Explanation

Tension pneumothorax shows a hyperlucent hemithorax with a collapsed lung and mediastinal shift away from the affected side, plus a depressed hemidiaphragm. It is a clinical emergency; treatment should not await imaging when the diagnosis is clinically obvious.

Explanation

A pleural effusion causes blunting of the costophrenic angle and a fluid meniscus that rises laterally on an erect film. Large effusions can shift the mediastinum away from the affected side. Ultrasound helps confirm the effusion and guide drainage.

Explanation

Chest X-ray signs of heart failure include cardiomegaly, upper-lobe venous diversion, Kerley B lines from interstitial oedema, perihilar 'bat-wing' opacity, and pleural effusions. These reflect raised pulmonary venous pressure.

Explanation

Lobar pneumonia shows homogeneous consolidation confined to a lobe, frequently with air bronchograms, where air-filled bronchi are outlined by surrounding consolidation. The volume of the lobe is usually preserved, unlike in collapse.

Explanation

Post-primary (reactivation) tuberculosis favours the apical and posterior segments of the upper lobes, often with cavitation. Primary TB more commonly affects the mid and lower zones with hilar lymphadenopathy, the Ghon complex.

Explanation

CT pulmonary angiography is the first-line imaging test for pulmonary embolism, directly demonstrating filling defects in the pulmonary arteries. A ventilation-perfusion scan is an alternative when CTPA is contraindicated, such as with contrast allergy.

Explanation

Lobar collapse causes volume loss, so the mediastinum, hilum, and hemidiaphragm are pulled toward the affected side, with crowding of the ribs. This contrasts with a tension pneumothorax or large effusion, which push the mediastinum away.

Explanation

Small bowel obstruction shows dilated, centrally located loops with valvulae conniventes, which cross the full width of the bowel, and multiple air-fluid levels on an erect film. Large bowel obstruction shows peripheral loops with haustra that do not fully cross.

Explanation

Free air under the diaphragm, or pneumoperitoneum, on an erect film indicates perforation of a hollow viscus such as a perforated peptic ulcer, and is a surgical emergency. An erect chest X-ray is a sensitive way to detect it.

Explanation

Sigmoid volvulus classically produces a massively dilated inverted-U loop arising from the pelvis, the 'coffee bean' or 'omega' sign. It is more common in elderly and constipated patients; decompression is often achieved endoscopically.

Explanation

Ultrasound is the first-line investigation for gallstones, showing echogenic foci with posterior acoustic shadowing, and it also assesses gallbladder wall thickening and duct dilatation. Most gallstones are radiolucent and missed on plain X-ray.

Explanation

Ultrasound is preferred first-line in children and pregnant women with suspected appendicitis to avoid ionising radiation, showing a non-compressible, dilated appendix. CT is more sensitive but is reserved for when ultrasound is inconclusive and radiation is acceptable.

Explanation

MRCP is a non-invasive MRI technique that clearly delineates the biliary tree and pancreatic duct, used to detect stones, strictures, and obstruction. ERCP is reserved for when intervention such as stone removal or stenting is needed.

Explanation

Intussusception shows a 'target' or doughnut sign on ultrasound. An air or contrast enema can both confirm the diagnosis and reduce the intussusception non-operatively, provided there is no perforation or peritonitis.

Explanation

A 'sunburst' or 'sunray' periosteal reaction with Codman's triangle, the elevated periosteum, are classic radiographic features of osteosarcoma, most commonly around the knee in adolescents. Ewing sarcoma instead shows a lamellated 'onion-skin' reaction.

Explanation

An 'onion-skin' lamellated periosteal reaction, typically in the diaphysis, is characteristic of Ewing sarcoma. This contrasts with the sunburst pattern of osteosarcoma, which usually arises at the metaphysis.

Explanation

Osteoarthritis shows joint space narrowing, osteophytes, subchondral sclerosis, and subchondral cysts — the mnemonic LOSS: Loss of joint space, Osteophytes, Subchondral cysts, Subchondral sclerosis. Rheumatoid arthritis instead shows periarticular osteopenia and erosions.

Explanation

Scaphoid fractures are often not visible on the initial X-ray. With clinical suspicion, such as anatomical snuffbox tenderness, the wrist is immobilised and imaging repeated in 10 to 14 days, or MRI is used, because a missed fracture risks avascular necrosis and non-union.

Explanation

Prostate cancer classically causes osteoblastic, sclerotic, dense white bone metastases. Renal and thyroid cancers typically cause osteolytic lesions. Breast and lung cancers can produce mixed patterns.

Explanation

Early stress fractures are often invisible on the initial plain X-ray. MRI, or a bone scan, is far more sensitive, detecting bone marrow oedema before cortical changes appear. MRI is generally preferred as it avoids radiation and gives anatomical detail.

Explanation

A non-contrast CT head is first-line in acute stroke to rapidly exclude haemorrhage before considering thrombolysis. Acute ischaemia may look normal early on CT; MRI, especially diffusion-weighted imaging, is more sensitive for early infarction.

Explanation

An extradural haematoma is a biconvex, lentiform, hyperdense collection that does not cross cranial sutures, typically from a middle meningeal artery tear after temporal trauma, often with a 'lucid interval'. A subdural haematoma is crescent-shaped and can cross sutures.

Explanation

A subdural haematoma is a crescent-shaped, concave collection following the brain surface that can cross suture lines, though not the midline dural reflections. It arises from torn bridging veins and is common in the elderly and in alcoholics after minor trauma.

Explanation

Subarachnoid haemorrhage shows hyperdense blood filling the basal cisterns and sulci on CT, typically after a sudden severe 'thunderclap' headache, often from a ruptured berry aneurysm. If CT is negative but suspicion remains, lumbar puncture for xanthochromia is done.

Explanation

MRI is the investigation of choice for multiple sclerosis, revealing demyelinating plaques, often periventricular as 'Dawson's fingers', disseminated in space and time. CT is insensitive for these lesions.

Explanation

Hydrocephalus is dilatation of the ventricular system from excess CSF, due to obstruction, impaired absorption, or overproduction. Imaging shows enlarged ventricles; treatment may involve a shunt or endoscopic third ventriculostomy.

Explanation

Crown-rump length is the most accurate measurement for dating in the first trimester. Later in pregnancy, biparietal diameter, head and abdominal circumference, and femur length are used to assess growth.

Explanation

A positive pregnancy test with an empty uterus, above the discriminatory beta-hCG level, and free pelvic fluid strongly raises concern for ectopic pregnancy, especially with an adnexal mass. It is a potential emergency requiring prompt evaluation.

Explanation

Non-contrast CT KUB is the investigation of choice for urinary tract stones, with high sensitivity and specificity, and it detects radiolucent stones missed on plain films. Ultrasound is preferred where radiation must be avoided, such as in pregnancy.

Explanation

Doppler ultrasound in testicular torsion shows absent or reduced blood flow to the affected testis. Torsion is nonetheless a clinical diagnosis and a surgical emergency — exploration should not be delayed for imaging when suspicion is high, given the narrow window to save the testis.

Explanation

A spiculated, irregular, radiating mass with clustered pleomorphic microcalcifications is highly suspicious for breast malignancy. Smooth, well-defined round lesions are more often benign, such as a fibroadenoma or cyst. Findings are graded using the BI-RADS system.

Explanation

In younger women, typically under 35, the breast tissue is dense, reducing mammographic sensitivity, so ultrasound is preferred first-line for a palpable lump. Mammography is more useful in older women with more fatty breast tissue.

Explanation

A technetium-99m bone scan surveys the whole skeleton in one study and is sensitive for metastases, occult fractures, and osteomyelitis, showing areas of increased bone turnover as 'hot spots'. It is sensitive but not specific.

Explanation

FDG-PET uses a radiolabelled glucose analogue that accumulates in metabolically active cells, including malignant ones, highlighting tumours and metastases. Combined PET-CT adds anatomical localisation and is widely used in oncological staging.

Explanation

A V/Q scan assesses pulmonary embolism by comparing ventilation and perfusion; a mismatch, with normal ventilation but reduced perfusion, suggests PE. It is an alternative to CTPA, useful when contrast is contraindicated or to limit radiation in some patients.

Explanation

Radioactive iodine (I-131) is taken up by thyroid tissue, allowing both imaging and treatment of hyperthyroidism and differentiated thyroid cancer, ablating residual or metastatic thyroid tissue. Uptake depends on functioning thyroid cells.

Explanation

Catheter angiography allows both diagnosis and treatment — embolisation can stop active bleeding from gastrointestinal haemorrhage, trauma, or postpartum haemorrhage by selectively occluding the bleeding vessel, often avoiding open surgery.

Explanation

Ultrasound or CT guidance lets the radiologist accurately target a lesion for biopsy or place a drain while avoiding vessels and other vital structures, improving both safety and diagnostic yield compared with a blind procedure.