NEET-PG 2015 — Radiology

Q: What is the cardiothoracic ratio in children?

50-55%. ***50-55%*** - The normal **cardiothoracic ratio** in children is generally considered to be **50-55%** on a **posterior-anterior (PA) chest X-ray**. - In **infants and young children (under 2 years)**, the ratio can be **up to 55-60%** due to relatively larger cardiac size and more horizontal positioning of the heart. - In **older children (over 2 years)**, the normal ratio approaches adult values of **less than 50%**. - A ratio consistently greater than 55% could indicate **cardiomegaly**, which warrants further investigation. *30-35%* - This range is typically too low and would suggest an **unusually small heart** for the chest cavity, which is not a normal finding in children. - A very low ratio like this is not characteristic of the pediatric population and may indicate technical issues with the radiograph. *40-45%* - While this range approaches normal values for **older children and adults**, it is generally on the lower side for the average **pediatric cardiothoracic ratio**. - This percentage alone is not the best answer when considering the entire pediatric age spectrum, including infants and younger children. *60-65%* - A cardiothoracic ratio in this range would typically be considered **abnormal** and indicative of **cardiomegaly** in children beyond infancy. - Such an elevated ratio would suggest an enlarged heart, prompting further cardiac evaluation including **echocardiography** to assess for structural heart disease. [Practice more Radiology PYQs on OnCourse]

Q: Radiological sign in case of Perthes disease?

Flattening of femoral head. ***Flattening of femoral head*** - **Flattening** and **fragmentation** of the femoral head are characteristic radiological findings in **early-stage** Perthes disease. - This flattening is a direct consequence of the **avascular necrosis** and subsequent **remodeling** of the femoral epiphysis. *Fragmentation of femoral head epiphysis* - While **fragmentation** is a key feature of Perthes disease, it's typically observed **after** the initial flattening and sclerosis in the avascular stage. - It represents the process of **resorption** and **revascularization** as the bone attempts to heal. *Lateral femoral head displacement* - **Lateral displacement** of the femoral head is a more common finding in conditions like **slipped capital femoral epiphysis (SCFE)**, where the epiphysis slips from the metaphysis. - In Perthes disease, the primary issue is the **necrosis and collapse** of the femoral head itself, rather than displacement from the neck. *Limited hip abduction* - **Limited hip abduction** is a clinical sign, not a radiological sign, and it is a common symptom in Perthes disease due to pain, inflammation, and deformity of the femoral head. - Radiological signs are visual abnormalities observed on imaging studies like X-rays. [Practice more Radiology PYQs on OnCourse]

Q: Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?

Ultrasound. ***Ultrasound*** - **First-line imaging modality** for suspected acute appendicitis in young adults, especially in children, pregnant women, and young females - **Advantages:** No ionizing radiation, readily available, cost-effective, can be performed at bedside - **High specificity** (>90%) when positive findings are present - **Graded compression technique** helps visualize the appendix and assess for periappendiceal inflammation - **Limitations:** Operator-dependent, may be difficult in obese patients or with overlying bowel gas *CT scan (Contrast-enhanced)* - **Most sensitive imaging modality** (sensitivity >95%) for acute appendicitis - Considered when ultrasound is inconclusive or technically difficult - **Gold standard** in adults, especially in obese patients - Provides excellent visualization of the appendix and complications (perforation, abscess) - However, involves **ionizing radiation**, making it less ideal as first-line in young patients *MRI* - **Preferred in pregnant women** when ultrasound is inconclusive - No ionizing radiation exposure - High accuracy but **limited availability**, longer scan time, and higher cost - Not typically used as first-line imaging in non-pregnant young adults *Plain radiography (X-ray)* - **Limited role** in diagnosing acute appendicitis - Non-specific findings; may show fecalith, loss of psoas shadow, or signs of perforation - Cannot reliably visualize the appendix - **Not recommended** as initial imaging for suspected appendicitis [Practice more Radiology PYQs on OnCourse]

Q: What is the best investigation for diagnosis and staging of renal cell carcinoma with thrombus extending into the IVC?

CT scan. ***CT scan*** - **CT scan** with contrast is the gold standard for diagnosing renal cell carcinoma and evaluating the extent of tumor thrombus into the **IVC**. - It provides detailed anatomical information on the tumor, staging, and involvement of adjacent structures. *Angiography* - **Angiography** is an invasive procedure primarily used for mapping the vascular supply of the tumor preoperatively or for embolization, not as a primary diagnostic tool. - It carries risks associated with contrast agents and catheterization and provides less comprehensive detail on tumor extension compared to CT. *Colour doppler imaging* - While useful for detecting blood flow and confirming the presence of a thrombus, **color Doppler imaging** (ultrasound) has limitations in accurately assessing the cranial extent of an IVC thrombus. - Its diagnostic accuracy is highly operator-dependent and less reliable for deep structures like the IVC compared to CT. *IVP* - **Intravenous Pyelogram (IVP)** assesses the urinary tract's structure and function but has limited utility in detecting soft tissue masses like renal cell carcinoma or IVC thrombus. - It involves radiation exposure and contrast material, and has largely been replaced by more advanced imaging techniques like CT and MRI for renal masses. [Practice more Radiology PYQs on OnCourse]

Q: Rigler's sign is suggestive of?

Pneumoperitoneum. ***Correct: Pneumoperitoneum*** - **Rigler's sign** (double wall sign) is the visualization of both the **inner (mucosal) and outer (serosal) surfaces** of the bowel wall on an abdominal X-ray. - This occurs when **free intraperitoneal air** outlines both sides of the bowel wall, making it a **pathognomonic sign of pneumoperitoneum**. - Commonly seen in **bowel perforation** from causes like peptic ulcer, trauma, or iatrogenic injury. *Incorrect: Pneumothorax* - Refers to air in the **pleural space** (thoracic cavity), not the peritoneal cavity. - Diagnosed on chest X-ray by the **visceral pleural line** with absent lung markings peripherally. - Completely different anatomical compartment from where Rigler's sign is observed. *Incorrect: Peritonitis* - Represents **inflammation of the peritoneum**, which is a clinical and pathological diagnosis. - While pneumoperitoneum from perforation can **lead to peritonitis**, Rigler's sign specifically indicates the **presence of free air**, not inflammation itself. - Peritonitis has no specific pathognomonic radiological sign like Rigler's. *Incorrect: Hemothorax* - Refers to **blood in the pleural cavity** (thoracic, not abdominal). - Appears as a **pleural effusion** with meniscus sign on chest X-ray. - Unrelated to abdominal radiological findings or free air. [Practice more Radiology PYQs on OnCourse]

23 Previous Year Questions with Answers & Explanations

Questions

What is the cardiothoracic ratio in children?

Radiological sign in case of Perthes disease?

Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?

What is the best investigation for diagnosis and staging of renal cell carcinoma with thrombus extending into the IVC?

Rigler's sign is suggestive of?

All are done to minimize radiation exposure to the patient under fluoroscopy, except which of the following?

Substance used for PET scan is

Precisely directed high dose radiation is used in which of the following therapies?

Which of the following is not considered a contraindication for undergoing an MRI?

Q10

Which condition is characterized by a specific appearance on CT scans that resembles small centrilobular nodules with branching linear structures?

NEET-PG 2015 - Radiology NEET-PG Practice Questions and MCQs

Question 1: What is the cardiothoracic ratio in children?

A. 30-35%
B. 40-45%
C. 50-55% (Correct Answer)
D. 60-65%

Explanation: ***50-55%*** - The normal **cardiothoracic ratio** in children is generally considered to be **50-55%** on a **posterior-anterior (PA) chest X-ray**. - In **infants and young children (under 2 years)**, the ratio can be **up to 55-60%** due to relatively larger cardiac size and more horizontal positioning of the heart. - In **older children (over 2 years)**, the normal ratio approaches adult values of **less than 50%**. - A ratio consistently greater than 55% could indicate **cardiomegaly**, which warrants further investigation. *30-35%* - This range is typically too low and would suggest an **unusually small heart** for the chest cavity, which is not a normal finding in children. - A very low ratio like this is not characteristic of the pediatric population and may indicate technical issues with the radiograph. *40-45%* - While this range approaches normal values for **older children and adults**, it is generally on the lower side for the average **pediatric cardiothoracic ratio**. - This percentage alone is not the best answer when considering the entire pediatric age spectrum, including infants and younger children. *60-65%* - A cardiothoracic ratio in this range would typically be considered **abnormal** and indicative of **cardiomegaly** in children beyond infancy. - Such an elevated ratio would suggest an enlarged heart, prompting further cardiac evaluation including **echocardiography** to assess for structural heart disease.

Question 2: Radiological sign in case of Perthes disease?

A. Flattening of femoral head (Correct Answer)
B. Fragmentation of femoral head epiphysis
C. Lateral femoral head displacement
D. Limited hip abduction

Explanation: ***Flattening of femoral head*** - **Flattening** and **fragmentation** of the femoral head are characteristic radiological findings in **early-stage** Perthes disease. - This flattening is a direct consequence of the **avascular necrosis** and subsequent **remodeling** of the femoral epiphysis. *Fragmentation of femoral head epiphysis* - While **fragmentation** is a key feature of Perthes disease, it's typically observed **after** the initial flattening and sclerosis in the avascular stage. - It represents the process of **resorption** and **revascularization** as the bone attempts to heal. *Lateral femoral head displacement* - **Lateral displacement** of the femoral head is a more common finding in conditions like **slipped capital femoral epiphysis (SCFE)**, where the epiphysis slips from the metaphysis. - In Perthes disease, the primary issue is the **necrosis and collapse** of the femoral head itself, rather than displacement from the neck. *Limited hip abduction* - **Limited hip abduction** is a clinical sign, not a radiological sign, and it is a common symptom in Perthes disease due to pain, inflammation, and deformity of the femoral head. - Radiological signs are visual abnormalities observed on imaging studies like X-rays.

Question 3: Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?

A. Ultrasound (Correct Answer)
B. CT scan (Contrast-enhanced)
C. Plain radiography (X-ray)
D. MRI

Explanation: ***Ultrasound*** - **First-line imaging modality** for suspected acute appendicitis in young adults, especially in children, pregnant women, and young females - **Advantages:** No ionizing radiation, readily available, cost-effective, can be performed at bedside - **High specificity** (>90%) when positive findings are present - **Graded compression technique** helps visualize the appendix and assess for periappendiceal inflammation - **Limitations:** Operator-dependent, may be difficult in obese patients or with overlying bowel gas *CT scan (Contrast-enhanced)* - **Most sensitive imaging modality** (sensitivity >95%) for acute appendicitis - Considered when ultrasound is inconclusive or technically difficult - **Gold standard** in adults, especially in obese patients - Provides excellent visualization of the appendix and complications (perforation, abscess) - However, involves **ionizing radiation**, making it less ideal as first-line in young patients *MRI* - **Preferred in pregnant women** when ultrasound is inconclusive - No ionizing radiation exposure - High accuracy but **limited availability**, longer scan time, and higher cost - Not typically used as first-line imaging in non-pregnant young adults *Plain radiography (X-ray)* - **Limited role** in diagnosing acute appendicitis - Non-specific findings; may show fecalith, loss of psoas shadow, or signs of perforation - Cannot reliably visualize the appendix - **Not recommended** as initial imaging for suspected appendicitis

Question 4: What is the best investigation for diagnosis and staging of renal cell carcinoma with thrombus extending into the IVC?

A. CT scan (Correct Answer)
B. Angiography
C. Colour doppler imaging
D. IVP

Explanation: ***CT scan*** - **CT scan** with contrast is the gold standard for diagnosing renal cell carcinoma and evaluating the extent of tumor thrombus into the **IVC**. - It provides detailed anatomical information on the tumor, staging, and involvement of adjacent structures. *Angiography* - **Angiography** is an invasive procedure primarily used for mapping the vascular supply of the tumor preoperatively or for embolization, not as a primary diagnostic tool. - It carries risks associated with contrast agents and catheterization and provides less comprehensive detail on tumor extension compared to CT. *Colour doppler imaging* - While useful for detecting blood flow and confirming the presence of a thrombus, **color Doppler imaging** (ultrasound) has limitations in accurately assessing the cranial extent of an IVC thrombus. - Its diagnostic accuracy is highly operator-dependent and less reliable for deep structures like the IVC compared to CT. *IVP* - **Intravenous Pyelogram (IVP)** assesses the urinary tract's structure and function but has limited utility in detecting soft tissue masses like renal cell carcinoma or IVC thrombus. - It involves radiation exposure and contrast material, and has largely been replaced by more advanced imaging techniques like CT and MRI for renal masses.

Question 5: Rigler's sign is suggestive of?

A. Pneumothorax
B. Pneumoperitoneum (Correct Answer)
C. Peritonitis
D. Hemothorax

Explanation: ***Correct: Pneumoperitoneum*** - **Rigler's sign** (double wall sign) is the visualization of both the **inner (mucosal) and outer (serosal) surfaces** of the bowel wall on an abdominal X-ray. - This occurs when **free intraperitoneal air** outlines both sides of the bowel wall, making it a **pathognomonic sign of pneumoperitoneum**. - Commonly seen in **bowel perforation** from causes like peptic ulcer, trauma, or iatrogenic injury. *Incorrect: Pneumothorax* - Refers to air in the **pleural space** (thoracic cavity), not the peritoneal cavity. - Diagnosed on chest X-ray by the **visceral pleural line** with absent lung markings peripherally. - Completely different anatomical compartment from where Rigler's sign is observed. *Incorrect: Peritonitis* - Represents **inflammation of the peritoneum**, which is a clinical and pathological diagnosis. - While pneumoperitoneum from perforation can **lead to peritonitis**, Rigler's sign specifically indicates the **presence of free air**, not inflammation itself. - Peritonitis has no specific pathognomonic radiological sign like Rigler's. *Incorrect: Hemothorax* - Refers to **blood in the pleural cavity** (thoracic, not abdominal). - Appears as a **pleural effusion** with meniscus sign on chest X-ray. - Unrelated to abdominal radiological findings or free air.

Question 6: All are done to minimize radiation exposure to the patient under fluoroscopy, except which of the following?

A. Decreasing fluoroscopic time
B. Increasing fluoroscopic time (Correct Answer)
C. Using low dose of radiation
D. Decrease in field of view

Explanation: ***Increasing fluoroscopic time*** - **Increasing fluoroscopic time** directly leads to a greater cumulative dose of radiation received by the patient. - This action goes against the principle of **ALARA (As Low As Reasonably Achievable)** for radiation safety. *Decreasing fluoroscopic time* - **Decreasing fluoroscopic time** reduces the total duration of X-ray exposure, thereby minimizing the radiation dose to the patient. - This is a fundamental practice in radiation protection. *Using low dose of radiation* - Employing **low-dose radiation protocols** means using the minimum amount of radiation necessary to obtain diagnostic images. - This directly reduces the patient's exposure while maintaining image quality for diagnosis. *Decrease in field of view* - A **decrease in the field of view** (collimation) restricts the X-ray beam to only the area of interest, limiting irradiation of surrounding healthy tissues. - This targeted approach significantly reduces the overall radiation dose to the patient.

Question 7: Substance used for PET scan is

A. Gadolinium
B. Gastrografin
C. Iodine
D. 18F-FDG (Correct Answer)

Explanation: ***18F-FDG*** - **18F-FDG (Fluorodeoxyglucose)** is a glucose analog labeled with a **positron-emitting radioisotope**, fluorine-18 (18F). - It is the most commonly used radiotracer in PET scans, as it accumulates in cells with high metabolic activity, particularly **cancer cells** and activated brain cells. *Gadolinium* - **Gadolinium** is a paramagnetic contrast agent primarily used in **MRI scans** to enhance the visualization of blood vessels and abnormal tissues. - It does not emit positrons and is therefore not suitable for PET imaging. *Gastrografin* - **Gastrografin** is an oral, water-soluble contrast agent containing **iodine**, typically used in **X-rays** and **CT scans** of the gastrointestinal tract. - It is not a radioactive tracer and has no application in PET imaging. *Iodine* - **Iodine** in various forms can be used as a contrast agent in **X-rays** and **CT scans**, or as a radioactive isotope (e.g., **I-131**) for **thyroid imaging** and treatment. - While some isotopes of iodine are radioactive, they are not typically used for PET imaging, which relies on positron emission.

Question 8: Precisely directed high dose radiation is used in which of the following therapies?

A. EBRT
B. IMRT
C. Brachytherapy
D. Stereotactic radiosurgery (Correct Answer)

Explanation: ***Stereotactic radiosurgery*** - **Stereotactic radiosurgery (SRS)** is a highly precise radiation therapy that uses focused, high-dose radiation beams to target small tumors or abnormalities with **sub-millimeter accuracy**. - It delivers **very high doses per fraction** (typically 15-24 Gy in a single session) using stereotactic guidance systems. - Commonly used for **brain metastases, AVMs, acoustic neuromas**, and other small intracranial targets. *IMRT* - **Intensity-modulated radiation therapy (IMRT)** is an advanced form of 3D-conformal radiation therapy that modulates beam intensity to conform to tumor shape. - While IMRT is precise, it uses **conventional fractionation** (1.8-2 Gy per fraction over many treatments), not the high-dose approach of SRS. *EBRT* - **External beam radiation therapy (EBRT)** is a general term for radiation delivered from outside the body. - It encompasses various techniques but *does not specifically indicate the **stereotactic precision and high-dose per fraction** characteristic of SRS*. *Brachytherapy* - **Brachytherapy** involves placing radioactive sources **directly inside or next to the tumor**. - While it delivers high doses locally, it is not "precisely directed high-dose radiation" from external beams like SRS.

Question 9: Which of the following is not considered a contraindication for undergoing an MRI?

A. Cardiac pacemaker
B. Cochlear implant
C. Ryle's tube (Correct Answer)
D. Metallic splinter in eye

Explanation: ***Ryle's tube*** - A **Ryle's tube** is a form of nasogastric tube made of radiopaque plastic, which is entirely **MRI-safe** and does not interact with magnetic fields. - It is made from inert materials that are **non-ferromagnetic**, posing no risk during an MRI scan. *Cardiac pacemaker* - **Cardiac pacemakers** contain metallic components that can malfunction, demagnetize, or migrate due to the strong magnetic fields and radiofrequency pulses of an MRI. - This can lead to **arrhythmias**, **pacemaker failure**, or **heating of leads**, posing a significant risk to the patient. *Cochlear implant* - **Cochlear implants** contain strong magnets and electronic components that can be damaged or displaced by the MRI's magnetic field. - This can cause **pain**, **implant damage**, or **hearing loss** for the patient. *Metallic splinter in eye* - A **metallic splinter in the eye** is a severe contraindication because the strong magnetic field can cause the metal fragment to move. - This movement can lead to **tissue damage**, **hemorrhage**, or **blindness** if it dislodges in the delicate structures of the eye.

Question 10: Which condition is characterized by a specific appearance on CT scans that resembles small centrilobular nodules with branching linear structures?

A. Pulmonary tuberculosis (Correct Answer)
B. Silicosis
C. Pulmonary hydatid cyst
D. Small cell carcinoma

Explanation: ***Pulmonary tuberculosis*** - This description ("small centrilobular nodules with **branching linear structures**") is characteristic of the **tree-in-bud pattern** seen on CT scans, which is a hallmark finding in active **endobronchial spread of tuberculosis**. - The tree-in-bud pattern results from the impaction of tuberculous **granulomas** and caseous material in the terminal and respiratory bronchioles. *Silicosis* - Characterized by multiple small, well-defined **nodules** (often in the upper lobes) that tend to calcify, but typically lacks the fine **branching linear structures**. - It’s associated with occupational exposure to **silica dust** and may progress to **massive progressive fibrosis**. *Pulmonary hydatid cyst* - Presents as a well-defined, usually **single, large cystic lesion** on CT, often with internal membranes if ruptured (water lily sign or crumpled membrane sign). - It does not typically manifest with small centrilobular nodules or branching linear structures. *Small cell carcinoma* - Usually appears as a **large central mass**, often with mediastinal lymphadenopathy, and sometimes associated with obstructive pneumonitis. - It does not typically present as diffuse small centrilobular nodules with branching patterns.