FMGE 2018 — Radiology

Q: Mark the false statement regarding testing of COVID-19.

First line screening assay: N gene assay.. ***First line screening assay: N gene assay.*** * While the **nucleocapsid (N) gene** is a common target for COVID-19 PCR assays, the statement that it is the *first-line screening assay* is often a simplification or outdated, as many assays target multiple genes (e.g., N, E, RdRp) for increased sensitivity and specificity from the outset. * Different health organizations and diagnostic kits have varied recommendations for initial screening targets, but there isn't a universal consensus that the N gene alone is the specific 'first-line screening assay' in all contexts when considering the breadth of available PCR tests. *Confirmatory assay: RdRp gene assay.* * The **RdRp (RNA-dependent RNA polymerase) gene** is a highly specific and conserved target for SARS-CoV-2 detection and is often used in **confirmatory PCR assays**. * Detection of the RdRp gene, sometimes alongside other targets like the E (envelope) gene, helps in confirming the presence of the virus. *Peripheral ground glass opacities on CT is the hallmark feature.* * **Peripheral ground glass opacities (GGOs)** are indeed a **hallmark radiological finding** in COVID-19 pneumonia, seen on CT scans. * These opacities reflect alveolar inflammation and fluid accumulation, especially in the early and moderate stages of the disease. *Most predominant method of diagnosis of COVID-19 is PCR.* * **Reverse transcription-polymerase chain reaction (RT-PCR)** remains the **gold standard and most predominant method** for diagnosing active COVID-19 infection. * PCR tests directly detect viral genetic material, offering high sensitivity and specificity in symptomatic and asymptomatic individuals. [Practice more Radiology PYQs on OnCourse]

Q: Which of the following investigations work on the same principle?

CT and X-ray. ***CT and X-ray*** - Both **Computed Tomography (CT)** and **X-ray** imaging utilize **ionizing radiation** to generate images of the body's internal structures. - They work by passing X-ray beams through the patient, with different tissues absorbing the radiation to varying degrees, which is then detected to create an image. *MRI and PET Scan* - **Magnetic Resonance Imaging (MRI)** uses **strong magnetic fields and radio waves** to create detailed images of soft tissues, based on water content. - **Positron Emission Tomography (PET) scans** use **radioactive tracers** to visualize metabolic activity and blood flow, detecting gamma rays emitted from the patient. *CT and MRI* - **CT scans** use **ionizing radiation** (X-rays) to produce cross-sectional images. - **MRI scans** use **magnetic fields and radio waves** and do not involve ionizing radiation. *USG and HIDA Scan* - **Ultrasound (USG)** uses **high-frequency sound waves** to create real-time images of organs and structures. - **Hepatobiliary Iminodiacetic Acid (HIDA) scans** are a type of nuclear medicine study that uses a **radioactive tracer** to evaluate liver and gallbladder function. [Practice more Radiology PYQs on OnCourse]

Q: Best way to localize extra-adrenal pheochromocytoma:

Nuclear medicine scan (MIBG scan). ***Nuclear medicine scan (MIBG scan)*** - **Iodine-131-metaiodobenzylguanidine (MIBG) scan** is the imaging modality of choice for localizing extra-adrenal pheochromocytomas due to its high specificity for **neuroendocrine tumors** like pheochromocytomas and paragangliomas. - MIBG is structurally similar to **norepinephrine** and is actively taken up by adrenergic neurons, allowing visualization of hypersecreting chromaffin cells wherever they are located in the body. *X-ray* - **X-rays** provide limited soft tissue detail and are generally not useful for localizing pheochromocytomas, especially extra-adrenal ones. - They may show calcifications in some tumors but lack the sensitivity and specificity needed for definitive localization. *Clinical examination* - A **clinical examination** can identify signs and symptoms suggestive of pheochromocytoma (e.g., hypertension, palpitations, sweating) but cannot localize the tumor itself. - Localization requires **imaging studies** due to the variable and often deep-seated location of these tumors. *VMA excretion* - **Vanillylmandelic acid (VMA) excretion** is a biochemical test used to diagnose pheochromocytoma by measuring catecholamine metabolites in urine. - While it confirms the presence of a catecholamine-secreting tumor, it provides **no information about the tumor's location**. [Practice more Radiology PYQs on OnCourse]

Q: Which is NOT a feature of pleural effusion?

Muffled heart sound. ***Muffled heart sound*** - This is **NOT a feature of pleural effusion** and is the correct answer to this negation question. - Muffled heart sounds are characteristic of **pericardial effusion** or **cardiac tamponade**, where fluid accumulates in the pericardial sac around the heart itself. - Pleural effusion involves fluid in the pleural space surrounding the lungs, not the heart. - While massive pleural effusions can displace mediastinal structures, they do not typically cause muffled heart sounds. *Horizontal fluid level* - This **IS a feature** when air is also present in the pleural space (**hydropneumothorax**). - In **simple pleural effusion** (fluid only), the fluid typically forms a **meniscus-shaped curve** with blunting of the costophrenic angles on upright chest X-ray, not a horizontal level. - However, when both air and fluid are present, a distinct horizontal air-fluid level is visible on upright imaging. - Since the question asks about pleural effusion broadly, and effusions can be associated with air (empyema with gas-forming organisms, post-thoracentesis), this can be considered a radiological feature in certain contexts. *Low lung volume* - This **IS a feature** of pleural effusion. - The accumulating pleural fluid causes **compression atelectasis** of the adjacent lung parenchyma. - This results in **reduced functional lung volume** on the affected side, visible on chest imaging. *Decreased chest movements* - This **IS a feature** of pleural effusion. - Fluid in the pleural space restricts normal lung expansion and chest wall movement. - On physical examination, there are **diminished respiratory excursions** on the affected side. - This is one of the classic clinical signs of pleural effusion. [Practice more Radiology PYQs on OnCourse]

4 Previous Year Questions with Answers & Explanations

Questions

Mark the false statement regarding testing of COVID-19.

Which of the following investigations work on the same principle?

Best way to localize extra-adrenal pheochromocytoma:

Which is NOT a feature of pleural effusion?

FMGE 2018 - Radiology FMGE Practice Questions and MCQs

Question 1: Mark the false statement regarding testing of COVID-19.

A. First line screening assay: N gene assay. (Correct Answer)
B. Confirmatory assay: RdRp gene assay.
C. Peripheral ground glass opacities on CT is the hallmark feature.
D. Most predominant method of diagnosis of COVID-19 is PCR.

Explanation: ***First line screening assay: N gene assay.*** * While the **nucleocapsid (N) gene** is a common target for COVID-19 PCR assays, the statement that it is the *first-line screening assay* is often a simplification or outdated, as many assays target multiple genes (e.g., N, E, RdRp) for increased sensitivity and specificity from the outset. * Different health organizations and diagnostic kits have varied recommendations for initial screening targets, but there isn't a universal consensus that the N gene alone is the specific 'first-line screening assay' in all contexts when considering the breadth of available PCR tests. *Confirmatory assay: RdRp gene assay.* * The **RdRp (RNA-dependent RNA polymerase) gene** is a highly specific and conserved target for SARS-CoV-2 detection and is often used in **confirmatory PCR assays**. * Detection of the RdRp gene, sometimes alongside other targets like the E (envelope) gene, helps in confirming the presence of the virus. *Peripheral ground glass opacities on CT is the hallmark feature.* * **Peripheral ground glass opacities (GGOs)** are indeed a **hallmark radiological finding** in COVID-19 pneumonia, seen on CT scans. * These opacities reflect alveolar inflammation and fluid accumulation, especially in the early and moderate stages of the disease. *Most predominant method of diagnosis of COVID-19 is PCR.* * **Reverse transcription-polymerase chain reaction (RT-PCR)** remains the **gold standard and most predominant method** for diagnosing active COVID-19 infection. * PCR tests directly detect viral genetic material, offering high sensitivity and specificity in symptomatic and asymptomatic individuals.

Question 2: Which of the following investigations work on the same principle?

A. MRI and PET Scan
B. CT and MRI
C. CT and X-ray (Correct Answer)
D. USG and HIDA Scan

Explanation: ***CT and X-ray*** - Both **Computed Tomography (CT)** and **X-ray** imaging utilize **ionizing radiation** to generate images of the body's internal structures. - They work by passing X-ray beams through the patient, with different tissues absorbing the radiation to varying degrees, which is then detected to create an image. *MRI and PET Scan* - **Magnetic Resonance Imaging (MRI)** uses **strong magnetic fields and radio waves** to create detailed images of soft tissues, based on water content. - **Positron Emission Tomography (PET) scans** use **radioactive tracers** to visualize metabolic activity and blood flow, detecting gamma rays emitted from the patient. *CT and MRI* - **CT scans** use **ionizing radiation** (X-rays) to produce cross-sectional images. - **MRI scans** use **magnetic fields and radio waves** and do not involve ionizing radiation. *USG and HIDA Scan* - **Ultrasound (USG)** uses **high-frequency sound waves** to create real-time images of organs and structures. - **Hepatobiliary Iminodiacetic Acid (HIDA) scans** are a type of nuclear medicine study that uses a **radioactive tracer** to evaluate liver and gallbladder function.

Question 3: Best way to localize extra-adrenal pheochromocytoma:

A. X-ray
B. Clinical examination
C. VMA excretion
D. Nuclear medicine scan (MIBG scan) (Correct Answer)

Explanation: ***Nuclear medicine scan (MIBG scan)*** - **Iodine-131-metaiodobenzylguanidine (MIBG) scan** is the imaging modality of choice for localizing extra-adrenal pheochromocytomas due to its high specificity for **neuroendocrine tumors** like pheochromocytomas and paragangliomas. - MIBG is structurally similar to **norepinephrine** and is actively taken up by adrenergic neurons, allowing visualization of hypersecreting chromaffin cells wherever they are located in the body. *X-ray* - **X-rays** provide limited soft tissue detail and are generally not useful for localizing pheochromocytomas, especially extra-adrenal ones. - They may show calcifications in some tumors but lack the sensitivity and specificity needed for definitive localization. *Clinical examination* - A **clinical examination** can identify signs and symptoms suggestive of pheochromocytoma (e.g., hypertension, palpitations, sweating) but cannot localize the tumor itself. - Localization requires **imaging studies** due to the variable and often deep-seated location of these tumors. *VMA excretion* - **Vanillylmandelic acid (VMA) excretion** is a biochemical test used to diagnose pheochromocytoma by measuring catecholamine metabolites in urine. - While it confirms the presence of a catecholamine-secreting tumor, it provides **no information about the tumor's location**.

Question 4: Which is NOT a feature of pleural effusion?

A. Horizontal fluid level
B. Low lung volume
C. Muffled heart sound (Correct Answer)
D. Decreased chest movements

Explanation: ***Muffled heart sound*** - This is **NOT a feature of pleural effusion** and is the correct answer to this negation question. - Muffled heart sounds are characteristic of **pericardial effusion** or **cardiac tamponade**, where fluid accumulates in the pericardial sac around the heart itself. - Pleural effusion involves fluid in the pleural space surrounding the lungs, not the heart. - While massive pleural effusions can displace mediastinal structures, they do not typically cause muffled heart sounds. *Horizontal fluid level* - This **IS a feature** when air is also present in the pleural space (**hydropneumothorax**). - In **simple pleural effusion** (fluid only), the fluid typically forms a **meniscus-shaped curve** with blunting of the costophrenic angles on upright chest X-ray, not a horizontal level. - However, when both air and fluid are present, a distinct horizontal air-fluid level is visible on upright imaging. - Since the question asks about pleural effusion broadly, and effusions can be associated with air (empyema with gas-forming organisms, post-thoracentesis), this can be considered a radiological feature in certain contexts. *Low lung volume* - This **IS a feature** of pleural effusion. - The accumulating pleural fluid causes **compression atelectasis** of the adjacent lung parenchyma. - This results in **reduced functional lung volume** on the affected side, visible on chest imaging. *Decreased chest movements* - This **IS a feature** of pleural effusion. - Fluid in the pleural space restricts normal lung expansion and chest wall movement. - On physical examination, there are **diminished respiratory excursions** on the affected side. - This is one of the classic clinical signs of pleural effusion.