Master every high-yield radiology topic for NEET PG 2026: chest X-ray systematic approach, CT abdomen, USG obstetric and abdominal, MRI basics, contrast agents, radiation physics, mammography BIRADS, nuclear medicine, and interventional radiology.
Version 1.0 — Published March 2026
Radiology contributes 8-12 direct questions to NEET PG, but imaging-based stems across medicine, surgery, and pediatrics push the effective yield to 15-20 marks. Master these 9 high-yield areas:
Radiology is the imaging backbone of clinical medicine. Every clinical subject — medicine, surgery, pediatrics, OBG — tests imaging interpretation within its own question pool. A student who reads X-rays, CTs, and ultrasounds systematically does not just answer radiology questions; they answer clinical vignettes across the entire paper with more confidence and speed.
The challenge is that radiology has a wide knowledge base but a narrow high-yield zone. NBE returns to the same imaging signs, modality choices, and contrast complications year after year. This guide covers the nine areas that generate the highest question density, with the specific findings and clinical associations that NBE tests. Pair it with the Radiology subject hub and daily image-based MCQ practice for maximum retention.
Chest X-ray interpretation is the single most tested imaging skill in NEET PG. It appears as standalone radiology questions and embedded within clinical stems in medicine, surgery, and pediatrics. The systematic approach is not optional — it is what separates candidates who score from those who miss the second finding.
Every chest X-ray in NEET PG should be read using this structured sequence:
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
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Join on Telegram →| Step | Structure | What to look for |
|---|
| A | Airways | Tracheal deviation, carina angle (normal <90 degrees), bronchial cutoff |
| B | Bones | Rib fractures, lytic lesions, cervical rib, clavicle fractures |
| C | Cardiac | CTR (normal <0.5 on PA film), chamber enlargement signs, pericardial effusion |
| D | Diaphragm | Costophrenic angle blunting, free gas under diaphragm, elevated hemidiaphragm |
| E | Edges/soft tissues | Mediastinal widening, subcutaneous emphysema, breast shadow |
| F | Fields (lung) | Consolidation, collapse, mass, pneumothorax, fibrosis |
| G | Gastric bubble | Side confirmation (left), hiatus hernia |
| H | Hilum | Lymphadenopathy, vascular prominence, eggshell calcification |
| I | Instruments | ET tube, central lines, pacemaker, chest drain position |
| J | Junction areas | Apices (Pancoast tumor), behind heart (left lower lobe pathology) |
Silhouette sign is the loss of a normal radiographic silhouette when two structures of similar density are in contact. A right middle lobe consolidation obliterates the right heart border. A lingular consolidation obliterates the left heart border. A left lower lobe consolidation obliterates the left hemidiaphragm. This sign localizes the pathology — NBE uses it to ask "which lobe is involved?"
Air bronchogram is the visualization of air-filled bronchi within opacified (consolidated) lung parenchyma. It confirms alveolar consolidation and rules out pleural effusion or mass as the cause of opacification. Classic association: lobar pneumonia.
Meniscus sign (concave upward fluid level at the costophrenic angle) confirms pleural effusion. A minimum of 200 mL of fluid is needed to blunt the costophrenic angle on a standard PA film. Lateral decubitus films detect as little as 50 mL.
For detailed chest X-ray MCQ practice with step-by-step reading, see the chest X-ray cardiomegaly image walkthrough.
CT abdomen with contrast is the workhorse of abdominal imaging. NEET PG tests specific enhancement patterns that distinguish benign from malignant lesions and guide surgical decisions.
The triphasic CT (arterial, portal venous, delayed phases) is the key to liver lesion characterization:
| Lesion | Arterial phase | Portal venous phase | Delayed phase | Key feature |
|---|---|---|---|---|
| Hemangioma | Peripheral nodular enhancement | Progressive centripetal fill-in | Complete fill-in | "Light bulb" sign on T2 MRI |
| HCC | Intense arterial enhancement (WASH-IN) | Washout (becomes hypodense) | Washout with capsule enhancement | Arterial enhancement + washout = diagnostic |
| Metastasis | Ring enhancement (hypervascular) or hypodense | Hypodense to liver | Hypodense | "Target" or "bull's eye" sign |
| FNH | Homogeneous arterial enhancement | Isodense to liver | Central scar enhancement | Central scar with spoke-wheel vascularity |
| Hepatic adenoma | Heterogeneous arterial enhancement | Rapid washout | Variable | Risk of hemorrhage; OCP association |
HCC diagnosis on CT requires arterial phase enhancement (wash-in) followed by portal venous or delayed phase washout. In a cirrhotic liver, this pattern in a lesion >1 cm is diagnostic without biopsy (AASLD guidelines). This diagnostic criterion is directly tested in NEET PG.
Bosniak classification guides management of cystic renal lesions on CT:
| Category | Features | Malignancy risk | Management |
|---|---|---|---|
| I | Simple cyst, thin wall, no septa, no calcification, no enhancement | ~0% | No follow-up needed |
| II | Few thin septa, fine calcification, <3 cm hyperdense cyst, no enhancement | ~0% | No follow-up |
| IIF | Multiple thin septa, minimal thickening, thick calcification, >3 cm hyperdense, no enhancement | 5-10% | Follow-up imaging |
| III | Thickened irregular walls/septa, measurable enhancement | 40-60% | Surgical exploration |
| IV | Enhancing soft tissue component | >90% | Surgical excision |
The double duct sign (simultaneous dilatation of the common bile duct and the main pancreatic duct) on CT or MRCP suggests periampullary or pancreatic head malignancy. This is a high-yield association tested alongside the Whipple procedure indication.
Acute pancreatitis on CT: CT severity index (CTSI) combines the Balthazar grade (A-E based on pancreatic and peripancreatic changes) with the degree of necrosis. A CTSI score of 7-10 indicates severe pancreatitis with a high complication rate (Balthazar et al., Radiology, 1990).
Ultrasound is the first-line imaging modality in obstetrics, hepatobiliary disease, and many abdominal emergencies. It is radiation-free, portable, and real-time — making it the default initial investigation in multiple clinical scenarios tested in NEET PG.
Dating parameters by trimester:
| Parameter | Trimester | Accuracy | Notes |
|---|---|---|---|
| Crown-rump length (CRL) | First (6-13 weeks) | Plus or minus 5-7 days | Most accurate single dating parameter |
| Biparietal diameter (BPD) | Second (14-26 weeks) | Plus or minus 7-10 days | Measured outer edge to inner edge |
| Femur length (FL) | Second/Third | Plus or minus 14 days | Also screens for skeletal dysplasia |
| Abdominal circumference (AC) | Third | Least accurate for dating | Best for growth assessment (IUGR detection) |
Nuchal translucency (NT) measurement at 11-13+6 weeks is the key first-trimester screening parameter for Down syndrome. An NT >3.5 mm is considered significantly elevated. Combined with maternal age, free beta-hCG (elevated), and PAPP-A (decreased), this constitutes the combined first-trimester screening test (detection rate approximately 90%).
Ectopic pregnancy on USG shows an empty uterus with adnexal mass and free fluid in the pouch of Douglas. The "ring of fire" sign on Doppler shows increased vascularity around the ectopic mass. A discriminatory beta-hCG level of 1500-2000 IU/L (transvaginal USG) is the threshold at which an intrauterine pregnancy should be visible — absence at this level raises suspicion for ectopic pregnancy.
Gallstones appear as echogenic foci with posterior acoustic shadowing and gravitational dependence (move with position change). Wall thickening >3 mm with pericholecystic fluid suggests acute cholecystitis. The Murphy sign on ultrasound (sonographic Murphy) — tenderness when the probe is pressed directly over the gallbladder — has a positive predictive value above 90% for acute cholecystitis.
Hydronephrosis grading on USG: Grade I (renal pelvis dilatation only), Grade II (pelvis + calyces dilated, preserved parenchyma), Grade III (gross dilatation with cortical thinning), Grade IV (thinned cortex with loss of corticomedullary differentiation). Grading guides the urgency of intervention.
Appendicitis on USG shows a non-compressible, aperistaltic, blind-ended tubular structure with diameter >6 mm and a target appearance on cross-section. Sensitivity is 75-90% (operator-dependent). An appendicolith with posterior shadowing increases specificity.
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Start Free Practice →MRI uses radiofrequency pulses in a magnetic field to generate images based on hydrogen proton behavior in different tissues. NEET PG tests the fundamental signal characteristics, not the physics equations.
The core distinction every candidate must know:
| Tissue | T1 weighted | T2 weighted | Clinical significance |
|---|---|---|---|
| Fat | Bright (high signal) | Intermediate | T1 is the "anatomy" sequence |
| Water/CSF | Dark (low signal) | Bright (high signal) | T2 is the "pathology" sequence |
| Muscle | Intermediate | Low-intermediate | Reference tissue |
| Cortical bone | Dark | Dark | Signal void (no mobile protons) |
| Acute blood | Variable | Dark (deoxyhemoglobin) | Evolves with hemoglobin degradation |
| Subacute blood | Bright (methemoglobin) | Variable | Key for dating hemorrhage |
| Gadolinium enhancement | Bright | N/A (not used on T2) | Enhancing lesions = T1 post-contrast |
Mnemonic: T1 = anatomy (fat is bright, making anatomical landmarks visible). T2 = pathology (water is bright, making edema, inflammation, and tumors stand out).
DWI detects restricted water molecule movement. In acute ischemic stroke, cytotoxic edema restricts diffusion within minutes of onset — DWI shows bright signal in the infarct area when CT and conventional MRI are still normal. This makes DWI the most sensitive early imaging for acute stroke (within 30 minutes of onset).
Apparent diffusion coefficient (ADC) map confirms true restricted diffusion (low ADC = true restriction) versus T2 shine-through (high ADC = no true restriction). An infarct shows DWI bright + ADC dark. This DWI/ADC correlation is tested in NEET PG neurology and radiology questions.
FLAIR suppresses CSF signal while keeping pathological fluid (edema) bright. This makes it ideal for detecting periventricular lesions in multiple sclerosis (Dawson fingers — ovoid lesions perpendicular to the lateral ventricles on sagittal FLAIR). FLAIR is also superior to T2 for detecting subarachnoid hemorrhage when CT is negative (subacute SAH).
Contrast agents enhance tissue differentiation on imaging. Knowing which agent goes with which modality and which complications to expect is a perennial NEET PG topic.
Iodinated contrast is used for CT angiography, CT abdomen with contrast, and intravenous urography.
Complications:
Contraindications: Previous severe reaction (anaphylaxis), severe renal impairment without adequate hydration, uncontrolled thyrotoxicosis, and metformin use (withhold for 48 hours post-contrast due to lactic acidosis risk with concurrent renal impairment).
Nephrogenic systemic fibrosis (NSF) is the feared complication — progressive fibrosis of skin, joints, and internal organs in patients with severe renal impairment (eGFR <30). NSF is virtually eliminated by avoiding gadolinium in patients with GFR below 30 and using group II macrocyclic agents when MRI is essential (Grainger & Allison's Diagnostic Radiology, 7th Edition).
Barium is used for barium swallow, barium meal, and barium enema. Never use barium if perforation is suspected — free barium in the peritoneal cavity causes severe chemical peritonitis with high mortality. Use water-soluble contrast (Gastrografin) instead. Barium aspiration causes chemical pneumonitis.
Radiation physics generates 2-3 questions per NEET PG paper, shared between radiology and PSM (community medicine). The questions test dose units, protection principles, and biological effects.
| Quantity | SI Unit | Definition | Old Unit |
|---|---|---|---|
| Absorbed dose | Gray (Gy) | Energy absorbed per unit mass of tissue | Rad (1 Gy = 100 rad) |
| Equivalent dose | Sievert (Sv) | Absorbed dose x radiation weighting factor | Rem (1 Sv = 100 rem) |
| Exposure | Coulomb/kg | Charge produced in air by X-rays or gamma rays | Roentgen (R) |
| Activity | Becquerel (Bq) | Disintegrations per second | Curie (Ci) |
Radiation weighting factors (used to calculate equivalent dose from absorbed dose): alpha particles = 20, neutrons = 5-20 (energy dependent), beta/gamma/X-rays = 1. Alpha particles have the highest weighting factor despite the shortest range — a favorite NBE question.
The International Commission on Radiological Protection (ICRP Publication 103, 2007) sets the following limits:
| Feature | Deterministic effects | Stochastic effects |
|---|---|---|
| Threshold | Yes (dose threshold exists) | No (any dose carries some risk) |
| Severity | Increases with dose | Independent of dose (all-or-nothing) |
| Examples | Skin erythema, cataract, sterility, radiation sickness | Cancer, genetic effects |
| Probability | 100% above threshold | Increases with dose |
Cataracts are the most important deterministic effect tested in NEET PG. The threshold dose for cataract formation is approximately 0.5 Gy for single exposure (ICRP 118 revision). This is why lens dose monitoring is mandatory for interventional radiologists.
Mammography is the standard screening modality for breast cancer. NEET PG tests the BIRADS classification and the mammographic findings that distinguish benign from malignant lesions.
| BIRADS | Assessment | Malignancy risk | Management |
|---|---|---|---|
| 0 | Incomplete | N/A | Additional imaging needed |
| 1 | Negative | ~0% | Routine screening |
| 2 | Benign | ~0% | Routine screening |
| 3 | Probably benign | <2% | Short-interval follow-up (6 months) |
| 4 | Suspicious | 2-95% | Biopsy recommended |
| 5 | Highly suggestive of malignancy | >95% | Biopsy and treatment planning |
| 6 | Known biopsy-proven malignancy | 100% | Surgical management |
The critical distinction tested in NEET PG is BIRADS 3 versus BIRADS 4: BIRADS 3 gets follow-up imaging, BIRADS 4 gets biopsy. Students who confuse these two lose the management question.
Malignant indicators: Irregular spiculated mass with ill-defined margins, pleomorphic or linear microcalcifications (casting type), architectural distortion, skin thickening, and nipple retraction.
Benign indicators: Round or oval mass with well-defined margins, coarse "popcorn" calcifications (fibroadenoma), oil cyst (fat necrosis), and smooth-bordered macrocalcifications.
Microcalcifications are the most commonly tested mammographic finding. Clustered pleomorphic microcalcifications suggest DCIS (ductal carcinoma in situ) and require biopsy. Scattered, round, uniform microcalcifications are typically benign (Sutton's Textbook of Radiology, 8th Edition).
Nuclear medicine uses radioactive tracers to assess organ function, not just anatomy. NEET PG tests the specific tracer-organ combinations and the diagnostic implications of uptake patterns.
Tracers: Tc-99m pertechnetate (trapped but not organified — gives morphological information) or I-131 (trapped AND organified — gives functional information and is used for therapy).
Hot nodule (increased uptake) — functioning adenoma, low malignancy risk (<1%). Surrounding thyroid is suppressed.
Cold nodule (decreased uptake) — non-functioning, 15-20% risk of malignancy. Requires FNAC for further evaluation.
NBE tests the clinical decision: "A thyroid scan shows a cold nodule. What is the next step?" Answer: FNAC (fine-needle aspiration cytology), not surgery.
DMSA (dimercaptosuccinic acid) — static renal cortical imaging. Binds to proximal tubular cells. Used for detecting renal scars (especially in pediatric vesicoureteral reflux), assessing differential renal function, and identifying ectopic kidneys. The gold standard for renal scarring (Felson's Principles of Chest Roentgenology reference approach applied to renal imaging).
DTPA (diethylenetriaminepentaacetic acid) — dynamic study. Filtered at the glomerulus (like inulin). Used for GFR estimation, renal perfusion assessment, and diagnosing obstruction (with furosemide challenge — the MAG3/DTPA diuretic renogram). In obstruction, the tracer accumulates and does not wash out after furosemide.
Tc-99m methylene diphosphonate (MDP) is taken up by osteoblastic activity. It is the most sensitive modality for detecting skeletal metastases (more sensitive than X-ray for early disease).
Super scan — diffusely increased skeletal uptake with absent kidney activity. Seen in widespread skeletal metastases (especially prostate cancer) or metabolic bone disease. NBE tests this as "What is the most likely cause of absent renal activity on bone scan?"
Photopenic (cold) areas on bone scan indicate avascular lesions — pure lytic metastases (multiple myeloma is the classic example — predominantly lytic, often bone scan negative), avascular necrosis, or radiation-treated areas.
F-18 fluorodeoxyglucose PET-CT detects metabolically active tissue. Primary indications tested in NEET PG: lymphoma staging and response assessment, solitary pulmonary nodule characterization, search for unknown primary with known metastases. False positives: infection, inflammation, granulomatous disease (tuberculosis — important in the Indian context).
Interventional radiology (IR) uses image-guided minimally invasive procedures for diagnosis and treatment. NEET PG tests the indications for common IR procedures, not technical details.
| Procedure | Indication | Image guidance | Key fact |
|---|---|---|---|
| Percutaneous abscess drainage | Intra-abdominal, hepatic, or pelvic abscess | USG or CT | First-line for accessible collections >3 cm |
| TIPS (Transjugular intrahepatic portosystemic shunt) | Refractory variceal bleeding, refractory ascites | Fluoroscopy | Creates shunt between hepatic and portal veins; complication: hepatic encephalopathy |
| Uterine artery embolization | Symptomatic uterine fibroids, postpartum hemorrhage | Fluoroscopy | Alternative to hysterectomy; contraindicated if future fertility desired (relative) |
| Bronchial artery embolization | Massive hemoptysis | Fluoroscopy | Bronchial artery (not pulmonary) is the bleeding source in 90% of massive hemoptysis |
| Percutaneous nephrostomy | Obstructive uropathy with sepsis or renal failure | USG | Emergency drainage when retrograde stenting fails |
| Angioplasty/stenting | Peripheral arterial disease, renal artery stenosis | Fluoroscopy | Endovascular alternative to surgical bypass |
TIPS is the most commonly tested IR procedure. Know the indication (refractory variceal bleeding after failed endoscopic therapy), the mechanism (intrahepatic shunt reduces portal pressure), and the main complication (hepatic encephalopathy from portal blood bypassing the liver).
Embolization for postpartum hemorrhage is increasingly tested as an alternative to surgical intervention. Uterine artery embolization has a success rate >90% for PPH (Grainger & Allison's Diagnostic Radiology) and preserves the uterus, making it valuable when future fertility is desired.
Radiology in NEET PG rewards systematic image reading and pattern recognition over rote memorization. The study approach should reflect this.
Learn the ABCDE-FGHIJ framework for chest X-ray and a structured approach for CT and USG. Read 5 normal images of each modality before studying pathology — you must know normal to recognize abnormal. Use Felson's Principles of Chest Roentgenology for the chest X-ray foundation.
Study 3-5 pathological images per day, applying your systematic framework each time. Build a table of "sign-diagnosis" associations (silhouette sign + location = lobe; enhancement pattern = lesion type). Solve 15-20 radiology MCQs daily, including image-based questions from previous NEET PG papers.
Practice radiology in the context of clinical vignettes — not isolated imaging questions. When studying medicine or surgery topics, always review the imaging findings for that condition. This cross-subject integration is how NBE actually tests radiology.
For targeted imaging MCQ practice with detailed visual explanations, explore the NEETPGAI practice module and the medicine high-yield guide for imaging-medicine integration.
Radiology contributes 8-12 direct questions in NEET PG (2021-2024 analysis), but the effective yield is higher because medicine, surgery, pediatrics, and OBG questions frequently include imaging findings. A chest X-ray or CT scan in the stem is essentially a radiology question regardless of the subject tag. Mastering systematic image reading adds 15-20 marks across subjects.
Chest X-ray is the most commonly tested modality, appearing in 3-5 questions per paper. It is tested both as standalone radiology questions (CTR, silhouette sign, air bronchogram) and embedded in clinical vignettes across medicine, surgery, and pediatrics. CT abdomen is the second most tested, followed by USG in obstetrics. MRI questions are less frequent but carry high marks when they appear.
Use the ABCDE-FGHIJ approach: A (Airways), B (Bones), C (Cardiac silhouette), D (Diaphragm), E (Edges and soft tissues), F (Fields), G (Gastric bubble), H (Hilum), I (Instruments), J (Junction areas). This prevents the common error of jumping to the obvious finding and missing a second abnormality. Practice with 5 normal chest X-rays before studying pathology.
T1 weighted images show fat as bright and water as dark — good for anatomical detail. T2 weighted images show water as bright and fat as intermediate — good for detecting pathology (edema, inflammation, tumors). The mnemonic: T1 = anatomy (fat bright), T2 = pathology (water bright). Gadolinium contrast enhances on T1 images.
Iodinated contrast is used for CT — complications include anaphylactoid reactions, contrast-induced nephropathy (risk with eGFR below 30), and thyroid storm. Gadolinium for MRI carries the risk of nephrogenic systemic fibrosis in severe renal impairment. Barium sulfate for GI studies is contraindicated if perforation is suspected due to risk of barium peritonitis.
BIRADS standardizes mammography reporting from 0 (incomplete) to 6 (proven malignancy). The key exam distinction is BIRADS 3 (probably benign, follow-up at 6 months) versus BIRADS 4 (suspicious, biopsy needed). NBE tests the management decision at each BIRADS level.
Thyroid scans (hot vs cold nodule management), DMSA (renal cortical scarring), DTPA (renal perfusion and obstruction), bone scan (skeletal metastases), and PET-CT (lymphoma staging). Know the tracer-organ combinations and the clinical decisions they guide.
ICRP limits: 20 mSv/year averaged over 5 years for occupational exposure (max 50 mSv/year), 1 mSv/year for general public, 1 mSv to fetus for remainder of pregnancy. Alpha particles have the highest radiation weighting factor (20). Deterministic effects have a threshold dose; stochastic effects (cancer) do not.
Start your radiology preparation today. Open the Radiology subject page and solve your first 15 imaging MCQs — the systematic reading skills you build now will serve you across every clinical subject on exam day. Want unlimited AI-powered radiology MCQs with image-based explanations? Explore NEETPGAI Pro.
Written by: NEETPGAI Editorial Team Reviewed by: Pending SME Review Last reviewed: March 2026
This article is reviewed by qualified medical professionals for clinical accuracy and exam relevance. For corrections or updates, contact the editorial team.