NEET-PG 2013 - Radiology Practice Questions

Q: What is the maximum radiation dose (in Gray) that bone tissue can tolerate?

50 Gray. ***Correct Option: 50 Gray*** - The **maximum radiation tolerance dose** for bone tissue is approximately **50-60 Gray (Gy)** based on radiobiology literature and clinical practice. - Among the given options, **50 Gy** represents the most appropriate threshold for bone tolerance. - According to **Emami et al. tolerance doses** and **QUANTEC guidelines**, bone can typically tolerate up to 60 Gy without significant risk of complications. - Doses approaching or exceeding **60 Gy** carry increased risk of **osteoradionecrosis**, particularly in the **mandible and weight-bearing bones**. - **Clinical significance**: In radiation therapy planning, doses of 50-60 Gy to bone are commonly used therapeutically for tumors involving or adjacent to bone. *Incorrect Option: 40 Gray* - 40 Gy is **below the accepted tolerance threshold** for bone tissue. - This dose is generally **well-tolerated** by bone without significant risk of necrosis or fracture. - Commonly used in palliative and definitive radiation protocols without major bone complications. *Incorrect Option: 30 Gray* - 30 Gy is **considerably below** the tolerance limit for bone. - This dose level is **safe for bone tissue** and carries minimal risk of radiation-induced bone damage. - Often used in palliative treatments with excellent bone tolerance. *Incorrect Option: 20 Gray* - 20 Gy is a **low radiation dose** from the perspective of bone tolerance. - This dose is **highly unlikely** to cause any significant bone damage or complications. - Represents a conservative therapeutic dose well within safety margins.

Q: Which imaging modality is most effective in differentiating between epidermoid cyst and arachnoid cyst?

Magnetic Resonance Imaging (MRI). ***Magnetic Resonance Imaging (MRI)*** - **MRI** is superior for differentiating epidermoid and arachnoid cysts due to its excellent **soft tissue contrast** and ability to detect fluid signal characteristics. - **Diffusion-weighted imaging (DWI)**, a specific MRI sequence, is crucial; **epidermoid cysts** show high signal on DWI (diffusion restriction) due to their keratin content, while **arachnoid cysts** follow CSF signal on all sequences and do not restrict diffusion. *Ultrasound (USG)* - **Ultrasound** has limited utility for intracranial lesions in adults due to the bony skull, which prevents sound wave penetration. - It may be used in infants through the fontanelles but lacks the resolution and specific sequences needed to characterize these cysts. *Computed Tomography (CT) scan* - While a **CT scan** can identify these cysts as hypodense lesions, it lacks the detailed **tissue characterization** and signal patterns provided by MRI. - Both cysts would appear as **hypodense lesions**, making differentiation difficult based on density alone, especially after contrast administration. *Positron Emission Tomography (PET) scan* - A **PET scan** primarily assesses metabolic activity and would not effectively differentiate between benign **non-metabolic cysts** like epidermoid and arachnoid cysts. - It is more commonly used for detecting **malignancies** or assessing brain activity patterns, not for structural differentiation of fluid-filled lesions.

Q: Which of the following conditions is the MOST COMMON cause of rib notching?

Coarctation of aorta. ***Coarctation of aorta*** - **Coarctation of the aorta** is the classic and **most common cause** of rib notching. - The notching is caused by the enlargement and tortuosity of the **intercostal arteries** as they provide collateral circulation to bypass the narrowed aorta. *Chronic superior venacava obstruction* - Chronic superior vena cava (SVC) obstruction may lead to the development of collateral circulation through the azygos and hemiazygos veins, but it does **not typically cause rib notching**. - Rib notching is specifically related to collateral flow bypassing an aortic obstruction, not a venous obstruction. *Atrial septal defect* - An **atrial septal defect (ASD)** is a communication between the atria that can lead to right heart volume overload and pulmonary hypertension. - While it's a congenital heart defect, an ASD does **not cause rib notching** as it does not involve an obstruction of systemic arterial flow requiring collateral circulation via the intercostal arteries. *Congenital interruption of aorta* - While **congenital interruption of the aorta** also involves an aortic obstruction, it is a **much rarer condition** than coarctation of the aorta. - Due to its rarity, it is not considered the most common cause of rib notching, even though it would theoretically lead to similar collateral vessel formation.

Q: For pericardial calcifications, which is the best investigation?

CT scan. ***Correct: CT scan*** - **CT scans** are highly sensitive and specific for detecting **pericardial calcifications** due to their excellent spatial resolution and ability to measure calcium density (Hounsfield units). - They provide detailed anatomical information about the **pericardium** and can accurately map the extent, location, and thickness of calcified areas. - **CT is the gold standard** for detecting and quantifying pericardial calcification, particularly in constrictive pericarditis. *Incorrect: Ultrasound* - While ultrasound (echocardiography) can visualize the pericardium and may detect calcifications, its ability to definitively identify and characterize **calcifications** is limited compared to CT. - **Acoustic shadowing** from calcifications can obscure underlying structures, making a precise assessment challenging. - Useful for detecting pericardial effusion and thickening, but not optimal for calcification assessment. *Incorrect: MRI* - **MRI excels** in visualizing soft tissues, pericardial inflammation, and fluid collections, but it is **poor at detecting calcium**. - Calcifications typically appear as signal voids (black) on MRI, making it difficult to differentiate them from other structures, air, or motion artifacts. - MRI is valuable for assessing pericardial inflammation and constriction but not the preferred method for calcification. *Incorrect: Transesophageal echocardiography* - TEE offers high-resolution images of cardiac structures and is primarily used for assessing valve function, intracardiac masses, endocarditis, and aortic pathology. - Its utility in detecting and characterizing **pericardial calcifications** is limited compared to CT, especially for diffuse or subtle calcifications. - The pericardium is not optimally visualized with TEE compared to transthoracic echocardiography.

Q: Barium swallow is used for -

Esophagus. ***Esophagus*** - A **barium swallow** specifically visualizes the **esophagus**, pharynx, and sometimes the early stomach. - It's used to identify abnormalities like **dysphagia**, strictures, **achalasia**, or tumors by coating the mucosal lining. *Colon* - The colon is typically examined using a **barium enema**, where barium sulfate is administered rectally. - This procedure is effective for visualizing the large intestine for conditions like **polyps**, diverticula, or inflammatory bowel disease. *Duodenum* - While a barium swallow may transiently show the **duodenum**, its primary target is the esophagus and stomach. - More detailed imaging of the duodenum often requires an **upper GI series (UGI)**, which is a broader study of the upper digestive tract. *Jejunum* - The jejunum is part of the small intestine and is best visualized through a **small bowel follow-through (SBFT)** procedure. - This involves ingesting barium and taking serial X-rays as it progresses through the small bowel, to detect conditions like **Crohn's disease** or obstructions.

Q: "String of beads" appearance on horizontal abdominal view X-ray is suggestive of:

Small bowel obstruction. ***Small bowel obstruction*** - A "string of beads" appearance on a horizontal abdominal view X-ray refers to small gas bubbles trapped between the valvulae conniventes in a dilated small bowel loop. - This finding is highly suggestive of **complete small bowel obstruction**, particularly when accompanied by multiple air-fluid levels and dilated bowel loops. *Intussusception* - While it causes obstruction, intussusception usually appears as a **target sign** (doughnut sign) on ultrasound or a **meniscus sign** on barium enema, not a string of beads on plain X-ray. - Plain X-rays may show signs of **bowel obstruction**, but the string of beads is not characteristic. *Sigmoid volvulus* - Sigmoid volvulus is characterized by a **dilated loop of colon** forming an inverted U-shape, often described as a **coffee bean sign** or **omega sign**, on plain X-ray. - This involves the large bowel, and the "string of beads" specifically relates to gas in the small bowel. *Large bowel obstruction* - Large bowel obstruction typically presents with a **dilated colon** proximal to the obstruction and a collapsed distal colon, often with absent or minimal gas in the rectum and sigmoid. - While air-fluid levels can be present, the "string of beads" is a specific sign of gas within dilated small bowel loops, distinguishing it from most large bowel obstructions.

Q: What condition is indicated by the double bubble sign on an abdominal X-ray?

Duodenal atresia. ***Duodenal atresia*** - The **double bubble sign** on an abdominal X-ray is pathognomonic for **duodenal atresia**, characterized by two air-filled bubbles: one in the stomach and one in the proximal duodenum, separated by the pylorus. - This congenital anomaly results from a complete obstruction of the duodenum, preventing the passage of air and fluid past this point. *Duodenal stenosis* - While also an obstruction of the duodenum, **duodenal stenosis** is an incomplete obstruction, meaning some gas will pass beyond the duodenum. - This would result in gas being present in the distal bowel, which is not seen with a classic "double bubble" where the bowel distal to the duodenum is gasless. *Volvulus* - **Volvulus** involves the twisting of a loop of intestine, leading to obstruction and potentially ischemia. - While it can cause obstruction, it typically presents with a "corkscrew" appearance on an upper GI series or signs of diffuse bowel distension, not the isolated double bubble. *All of the options* - The double bubble sign is highly specific to **duodenal atresia** due to the complete obstruction it signifies. - Other conditions like duodenal stenosis and volvulus cause different radiological patterns, making this option incorrect.

Q: Investigation with least radiation dose in the diagnosis of Meckel's diverticulum is -

Technetium -99m scanning. ***Technetium-99m scanning*** - **Technetium-99m pertechnetate scan** (Meckel's scan) is the **gold standard investigation** for diagnosing Meckel's diverticulum with ectopic gastric mucosa - Among the investigations that can actually **diagnose Meckel's diverticulum**, it has the **lowest radiation dose** (approximately 1-2 mSv) - The radioisotope is specifically taken up by ectopic gastric mucosa, providing both diagnostic utility and relatively low radiation exposure - **Sensitivity: 85-95%** for detecting ectopic gastric mucosa in Meckel's diverticulum - The radiation dose is comparable to a few months of natural background radiation and significantly lower than CT or contrast studies *MRI* - While **MRI uses no ionizing radiation**, it is **not a standard or practical investigation** for diagnosing Meckel's diverticulum - MRI cannot identify ectopic gastric mucosa specifically - It is rarely used in clinical practice for this indication - The question asks about investigation "in the diagnosis" of Meckel's diverticulum, implying a test that is actually used diagnostically *CT* - **Computed Tomography (CT)** delivers a **high radiation dose** (typically 5-10 mSv or more) - While it can identify structural abnormalities, it is not specific for Meckel's diverticulum - Not the first-line investigation for this condition *Contrast radiography* - **Contrast studies** (barium studies) use **moderate ionizing radiation** (3-5 mSv) - Limited utility in diagnosing Meckel's diverticulum as it primarily assesses luminal patency - Cannot identify ectopic gastric mucosa - Lower sensitivity compared to Tc-99m scanning

Q: What is the echogenic lesion size criterion for chronic pancreatitis?

> 3 mm. ***> 3 mm*** - An echogenic lesion **greater than 3 mm** in size is a diagnostic criterion for **chronic pancreatitis** when observed on ultrasound imaging. - This represents one of the **major features** in ultrasound diagnosis of chronic pancreatitis, particularly when echogenic foci demonstrate acoustic shadowing (suggesting calcifications). - This criterion is part of established diagnostic frameworks and helps differentiate pathological calcifications from minor, non-specific findings. *> 4 mm* - While a **4 mm threshold** would indicate significant findings, the established diagnostic criterion for chronic pancreatitis uses **> 3 mm** as the cutoff. - Using a higher threshold would reduce sensitivity for detecting chronic pancreatitis. *> 2 mm* - A lesion larger than **2 mm** is generally considered below the established diagnostic threshold for **chronic pancreatitis**. - This size may represent early changes or incidental findings that are not yet definitive for diagnosis. *> 1 mm* - A lesion **greater than 1 mm** is too small to be a definitive criterion for **chronic pancreatitis** and could represent minor, non-pathological findings. - Such small echogenic foci lack sufficient specificity for diagnosing chronic pancreatic disease.

Q: What is the CT scan finding in a carotid cavernous sinus fistula?

Enlarged superior ophthalmic vein. ***Enlarged superior ophthalmic vein*** * A carotid cavernous sinus fistula (CCSF) causes **high-pressure arterial blood** to shunt into the **venous system** of the cavernous sinus. * This increased pressure leads to retrograde flow and congestion in the draining veins, most notably the **superior ophthalmic vein**, causing its dilation. *Enlarged inferior ophthalmic vein* * While the inferior ophthalmic vein can also be involved in some cases of CCSF, the **superior ophthalmic vein** is typically more prominent and consistently affected due to its primary drainage pathway. * The inferior ophthalmic vein is less frequently the primary or most notable imaging finding compared to the superior ophthalmic vein. *Enlarged superior ophthalmic artery* * A CCSF involves an abnormal connection between the **carotid artery** (an artery) and the **cavernous sinus** (a venous structure), leading to venous, not arterial, dilation. * Arteries in the orbital region, like the superior ophthalmic artery, would not typically enlarge as a direct result of increased venous pressure in the cavernous sinus. *Enlarged inferior ophthalmic artery* * Similar to the superior ophthalmic artery, the inferior ophthalmic artery is an **arterial structure** and would not enlarge due to a high-flow arteriovenous shunt within the cavernous sinus. * The pathological changes in CCSF are primarily observed in the **venous drainage pathways**.

Question 1

What is the maximum radiation dose (in Gray) that bone tissue can tolerate?

Accepted Answer

50 Gray

Answer

30 Gray

Answer

20 Gray

Answer

40 Gray

Question 2

Which imaging modality is most effective in differentiating between epidermoid cyst and arachnoid cyst?

Accepted Answer

Magnetic Resonance Imaging (MRI)

Answer

Ultrasound (USG)

Answer

Computed Tomography (CT) scan

Answer

Positron Emission Tomography (PET) scan

Question 3

Which of the following conditions is the MOST COMMON cause of rib notching?

Accepted Answer

Coarctation of aorta

Answer

Atrial septal defect

Answer

Chronic superior venacava obstruction

Answer

Congenital interruption of aorta

Question 4

For pericardial calcifications, which is the best investigation?

Accepted Answer

CT scan

Answer

Ultrasound

Answer

MRI

Answer

Transesophageal echocardiography

Question 5

Barium swallow is used for -

Accepted Answer

Esophagus

Answer

Colon

Answer

Duodenum

Answer

Jejunum

Question 6

"String of beads" appearance on horizontal abdominal view X-ray is suggestive of:

Accepted Answer

Small bowel obstruction

Answer

Intussusception

Answer

Sigmoid volvulus

Answer

Large bowel obstruction

Question 7

What condition is indicated by the double bubble sign on an abdominal X-ray?

Accepted Answer

Duodenal atresia

Answer

Duodenal stenosis

Answer

Volvulus

Answer

All of the options

Question 8

Investigation with least radiation dose in the diagnosis of Meckel's diverticulum is -

Accepted Answer

Technetium -99m scanning

Answer

MRI

Answer

CT

Answer

Contrast radiography

Question 9

What is the echogenic lesion size criterion for chronic pancreatitis?

Accepted Answer

> 3 mm

Answer

> 2 mm

Answer

> 1 mm

Answer

> 4 mm

Question 10

What is the CT scan finding in a carotid cavernous sinus fistula?

Accepted Answer

Enlarged superior ophthalmic vein

Answer

Enlarged inferior ophthalmic vein

Answer

Enlarged superior ophthalmic artery

Answer

Enlarged inferior ophthalmic artery

NEET-PG 2013 — Radiology