Contrast and Radiological Procedures — MCQs

Contrast and Radiological Procedures Indian Medical PG Practice Questions and MCQs

Question 241: Rim sign in IVP is seen in

A. Hydronephrosis (Correct Answer)
B. Chronic Pyelonephritis
C. Renal Cell Carcinoma
D. Polycystic Kidney Disease

Explanation: ***Hydronephrosis*** - The **rim sign** in IVP (Intravenous Pyelography) refers to the opacification of the renal parenchyma surrounding a dilated pelvicalyceal system, forming a "rim" of contrast. - This sign is characteristic of acute obstruction leading to **hydronephrosis**, where the contrast accumulates in the compressed renal tissue and then slowly excretes into the dilated collecting system, outlining it. *Chronic Pyelonephritis* - Characterized by **focal cortical thinning**, scarring, and clubbing of the calyces, not a rim sign. - The kidney may appear small and irregularly outlined on IVP due to **parenchymal loss**. *Renal Cell Carcinoma* - Often presents as a **mass lesion** that distorts the collecting system, but typically does not cause a rim sign. - May show vascularity on imaging and can cause direct invasion or displacement of renal structures. *Polycystic Kidney Disease* - Involves multiple **cysts** of varying sizes throughout both kidneys, leading to significant renal enlargement and distortion of the collecting system. - The appearance is typically described as a "Swiss cheese" or "moth-eaten" pattern due to the numerous cysts, not a rim sign.

Question 242: Best method of detection of a retained glass intraocular foreign body is

A. USG
B. Radiography
C. Tonometry
D. CT scan (Correct Answer)

Explanation: ***CT scan*** - **CT scans** are highly sensitive and specific for detecting **retained glass intraocular foreign bodies** due to their excellent spatial resolution and ability to visualize foreign materials with different densities. - Unlike MRI, CT is safe with metallic foreign bodies and provides precise localization, aiding surgical planning. *Radiography* - While helpful for detecting radio-opaque foreign bodies like metal, **plain X-rays display limited soft tissue contrast** and may struggle to visualize small or less dense objects like glass effectively within the complex orbital structures. - **Glass foreign bodies can be difficult to discern** from surrounding bony structures or soft tissues on conventional radiographs, leading to false negatives. *USG* - **Ultrasound (USG)** is effective for imaging soft tissues and can detect some foreign bodies, but its utility is limited when the object is small, non-reflective, or located deep within the globe, especially behind structures like the lens or iris. - **Acoustic shadowing** and artifact creation can also obscure the foreign body or mimic its presence, reducing diagnostic accuracy for glass. *Tonometry* - **Tonometry measures intraocular pressure** and is primarily used to screen for or monitor glaucoma. - It provides no information about the presence or location of **intraocular foreign bodies**.

Question 243: The most sensitive imaging modality to detect early renal tuberculosis is:

A. Intravenous urography
B. Magnetic resonance imaging (Correct Answer)
C. Ultrasound
D. Computed tomography

Explanation: ***Magnetic resonance imaging*** - **MRI** is the most sensitive imaging modality for detecting **early renal tuberculosis** due to its superior soft tissue contrast resolution. - It can identify subtle **parenchymal inflammatory changes**, early granulomas, and edema before calcification or cavitation occurs. - MRI is particularly useful for detecting **early renal cortical involvement** and small lesions that may be missed by other modalities. - Provides excellent anatomical detail without ionizing radiation. *Computed tomography* - **CT** is excellent for detecting **established renal tuberculosis** with calcifications, cavitations, and collecting system abnormalities. - However, calcifications and cavitations represent **intermediate to late findings**, not early disease. - CT is less sensitive than MRI for detecting subtle parenchymal inflammatory changes in early stages. - More useful once the disease has progressed to structural changes. *Ultrasound* - **Ultrasound** is useful for screening and follow-up but has significant limitations for early disease detection. - May miss small lesions, subtle parenchymal changes, and early calcifications. - Operator-dependent and limited by **acoustic windows** and patient body habitus. *Intravenous urography* - **IVU** primarily detects changes in the **collecting system** such as strictures, calyceal clubbing, and ureteral abnormalities. - These represent **late manifestations** of renal tuberculosis, not early disease. - Has largely been replaced by cross-sectional imaging (CT/MRI) for evaluating renal pathology. - Less sensitive for parenchymal involvement compared to CT or MRI.

Question 244: What percentage of gallstones are radiopaque?

A. 10% (Correct Answer)
B. 20%
C. 30%
D. 40%

Explanation: ***10%*** - Approximately **10% of gallstones** contain enough calcium to be visible on a plain X-ray and are considered **radiopaque** (some sources cite up to 15%). - The majority of gallstones are primarily composed of cholesterol, which is **radiolucent** and not visible on plain radiographs. - **Pigment stones** (calcium bilirubinate) are more likely to be radiopaque than cholesterol stones. *20%* - This percentage is too high; the actual proportion of radiopaque gallstones is significantly lower. - Most gallstones are **cholesterol-based** (about 80%) and therefore not visible on standard X-rays. *30%* - This percentage greatly overestimates the number of radiopaque gallstones. - The lack of significant calcium content in most gallstones makes them **undetectable by plain X-ray imaging**. *40%* - This percentage is incorrect and far exceeds the actual proportion of radiopaque gallstones. - **Ultrasound or CT scan** are the preferred imaging modalities for detecting gallstones, not plain X-ray.

Question 245: The X-ray appearance of a CBD stone on cholangiography is:

A. Meniscus sign (Correct Answer)
B. Non-central occlusion
C. Abrupt cut-off
D. Benign tapering

Explanation: ***Meniscus sign*** - A **meniscus sign** on cholangiography is characteristic of a **filling defect** caused by a gallstone within the **common bile duct (CBD)**. - The contrast agent outlines the stone, creating a crescent-shaped or **meniscus-like appearance** around it. *Non-central occlusion* - This term usually refers to an incomplete or **partial blockage** that doesn't necessarily have the distinct outline of a stone. - While a stone can cause occlusion, "meniscus sign" specifically describes the **radiographic appearance** of the stone itself. *Abrupt cut-off* - An **abrupt cut-off** suggests a sudden and complete obstruction, often seen with **malignant strictures** or **impacted stones** without clear outlining. - It does not specifically describe the characteristic rimming of contrast around a stone that defines a meniscus sign. *Benign tapering* - **Benign tapering** typically indicates a gradual, smooth narrowing of the duct, often associated with **inflammatory strictures** or **fibrotic changes**. - This appearance is different from the distinct filling defect caused by a stone.

Question 246: Which of the following devices typically requires the most stringent safety protocols before MRI scanning?

A. Prosthetic cardiac valves
B. Insulin pump
C. Cochlear implants
D. Automatic Cardioverter-defibrillators (Correct Answer)

Explanation: ***Automatic Cardioverter-defibrillators*** - **Implantable cardioverter-defibrillators (ICDs)**, while increasingly MRI-conditional, require stringent protocols due to potential for **heating, lead damage, and inappropriate pacing/shocks**. - Detailed device interrogation, programming to asynchronous modes or MRI mode, and continuous monitoring are often required to mitigate risks and ensure patient safety. *Prosthetic cardiac valves* - Most modern **prosthetic cardiac valves** (both mechanical and bioprosthetic) are **MRI-conditional** or **MRI-safe** and generally do not pose significant risks. - They are typically made of non-ferromagnetic materials, reducing concerns about displacement or heating. *Insulin pump* - External insulin pumps are generally considered **MR-unsafe** and must be **removed from the patient** before entering the MRI scan room. - While removal is a safety protocol, they don't involve complex internal electronic interactions in the same way an implanted ICD does, making their protocol simpler (remove and resume). *Cochlear implants* - Many **cochlear implants** are now **MRI-conditional**, but they often require specific protocols such as removing the external processor and sometimes applying a head bandage to secure the implant. - Older models or certain configurations may still be considered MR-unsafe due to potential for magnet displacement or device damage.

Question 247: The posterior urethra is best visualized by:

A. Static cystogram
B. Retrograde urethrogram
C. Voiding cystogram (Correct Answer)
D. CT cystogram

Explanation: ***Voiding cystogram*** - A **voiding cystogram (VCUG)** involves filling the bladder with contrast and then imaging during urination, which allows visualization of the **posterior urethra** as urine passes through it. - This dynamic imaging technique is essential for evaluating urethral anatomy and function, particularly for detecting reflux or strictures in the posterior urethra. *Static cystogram* - A **static cystogram** primarily visualizes the **bladder** when it is filled with contrast, without the act of urination. - It does not provide dynamic visualization of the urethra during emptying, which is crucial for assessing the posterior urethra. *Retrograde urethrogram* - A **retrograde urethrogram (RUG)** involves injecting contrast directly into the urethra from the external meatus, primarily visualizing the **anterior urethra**. - While it can provide some information on the posterior urethra, its main utility is for the anterior segment, and it's less effective for the dynamic assessment of the posterior urethra during voiding. *CT cystogram* - A **CT cystogram** uses computed tomography after bladder filling with contrast, providing excellent anatomical detail of the **bladder wall** and surrounding structures. - It is not the primary modality for visualizing the *lumen* of the urethra, especially for dynamic function during voiding, and is often used for trauma or fistula evaluation.

Question 248: Four-vessel carotid angiography is done by injecting dye into:

A. Radial artery
B. Brachial artery
C. Cubital vein
D. Femoral artery (Correct Answer)

Explanation: ***Femoral artery*** - The **femoral artery** is the most common and safest access point for **catheter-based angiography**, including four-vessel carotid angiography, due to its large diameter and superficial location. - A catheter is inserted into the femoral artery and guided through the aorta to the origins of the **carotid and vertebral arteries** for dye injection and imaging. *Radial artery* - While the **radial artery** can be used for angiography, it is less commonly preferred for four-vessel carotid angiography due to the smaller vessel size and potentially more challenging navigation. - It is more frequently used for **coronary angiography** or less extensive peripheral studies. *Brachial artery* - The **brachial artery** is another potential arterial access site, but it is generally avoided for routine angiography due to an increased risk of **nerve damage** (median nerve) and vascular complications compared to the femoral approach. - It is sometimes used as an alternative when femoral access is not feasible. *Cubital vein* - The **cubital vein** is a venous access point and is not suitable for **arterial angiography**. - Contrast dye injected into a vein would not reach the carotid arteries directly in sufficient concentration to visualize them, as it would first pass through the heart and pulmonary circulation.

Question 249: Dysphagia lusoria is diagnosed by what?

A. USG
B. Fluoroscopy
C. Plain radiograph
D. CT Angiography (Correct Answer)

Explanation: ***CT Angiography*** - **CT angiography** is the gold standard for diagnosing dysphagia lusoria. - It clearly visualizes the **aberrant right subclavian artery** compressing the esophagus, which is the underlying cause of the condition. *USG* - **Ultrasound** is not suitable for diagnosing dysphagia lusoria. - It has limited ability to visualize the **deep thoracic structures** and arterial anomalies causing esophageal compression. *Fluoroscopy* - While it can show **esophageal compression** during a barium swallow, it doesn't clearly delineate the vascular anomaly. - It is often used as a **screening tool** but not for definitive diagnosis of the aberrant vessel. *Plain radiograph* - A **plain radiograph** offers very limited information for diagnosing dysphagia lusoria. - It cannot visualize the **aberrant vasculature** or the specific compression of the esophagus.

Question 250: Which of the following is least required for visualization of the gallbladder in oral cholecystography?

A. Patency of cystic duct (Correct Answer)
B. Motor mechanisms of gall bladder
C. Ability to absorb water
D. Functioning liver

Explanation: ***Patency of cystic duct*** - While a **patent cystic duct** is essential for bile to flow in and out of the gallbladder, the question asks what is *least* required for *visualization* of the gallbladder in oral cholecystography. - The contrast medium is absorbed, metabolized by the liver, and then concentrated in the gallbladder. The ability to concentrate is more critical for visualization than a patent cystic duct for this specific question. *Functioning liver* - A **functioning liver** is required to absorb the oral contrast agent from the intestine and then secrete it into the bile. - Without a functioning liver, the contrast agent cannot be processed and delivered to the gallbladder, making visualization impossible. *Motor mechanisms of gall bladder* - The **motor mechanisms** of the gallbladder are crucial for concentrating the bile and the contrast material. - The gallbladder absorbs water from the bile, increasing the concentration of the contrast agent, which enhances its visibility on X-ray. *Ability to absorb water* - The gallbladder's **ability to absorb water** from the bile is fundamental for concentrating the contrast medium. - This concentration process makes the gallbladder sufficiently radio-opaque to be visualized during oral cholecystography.

Practice by Chapter

Iodinated Contrast Media

Practice Questions

MRI Contrast Agents

Practice Questions

Ultrasound Contrast Agents

Practice Questions

Adverse Reactions to Contrast Media

Practice Questions

Management of Contrast Reactions

Practice Questions

Contrast-Induced Nephropathy

Practice Questions

Barium Studies

Practice Questions

Intravenous Urography

Practice Questions

Angiography Techniques

Practice Questions

Lymphangiography

Practice Questions

Contrast Administration Protocols

Practice Questions

Pretesting and Premedication

Practice Questions

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