NEET-PG 2012 - Radiology PYQs Practice Questions

Q: Half-life of iodine-131 is

8 days. ***8 days*** - The half-life of **iodine-131** is approximately 8.02 days, which makes it suitable for both diagnostic imaging and therapeutic applications in thyroid conditions. - This specific half-life allows sufficient time for the isotope to localize in the thyroid gland and deliver a therapeutic dose, while also ensuring it clears from the body relatively quickly to minimize long-term radiation exposure. *8 hours* - A half-life of 8 hours would be too short for many therapeutic applications of iodine-131, as it would decay too rapidly to deliver an effective dose to the thyroid. - Isotopes with such short half-lives are typically used for diagnostic imaging where rapid clearance and minimal patient exposure are paramount, such as **technetium-99m**. *8 weeks* - A half-life of 8 weeks would be excessively long for clinical use of iodine-131, leading to prolonged radiation exposure for the patient. - Such long half-lives increase the risk of adverse effects from cumulative radiation, making it unsuitable for routine diagnostic or therapeutic procedures. *8 months* - A half-life of 8 months is impractically long for any medical application requiring regular administration, as it would lead to very high and persistent radiation doses. - This duration would result in significant and unacceptable long-term radiation hazards, making its use unfeasible for imaging or therapy. [Practice more Radiology PYQs on OnCourse]

Q: Central stellate scar is typically associated with which of the following conditions?

Focal nodular hyperplasia (FNH). ***Focal nodular hyperplasia (FNH)*** - FNH is a benign liver lesion characterized by a central fibrous scar with radiating septa, giving it the characteristic appearance of a **central stellate scar** on imaging. - This scar contains **malformed blood vessels** and bile ductules, which are key diagnostic features. - On dynamic imaging, FNH typically shows **spoke-wheel arterial enhancement** pattern and the central scar shows **delayed enhancement** on MRI. *Hepatic adenoma* - Hepatic adenomas are typically composed of sheets of **hepatocytes** with absent portal triads and are usually **homogeneous** on imaging without a central scar. - They are associated with **oral contraceptive use** and have a risk of hemorrhage and malignant transformation. *Chronic liver disease* - Chronic liver disease, such as **cirrhosis**, is characterized by widespread **fibrosis** and **nodule formation** throughout the liver, but it does not typically present with a solitary lesion with a central stellate scar. - The scarring in cirrhosis is diffuse and leads to architectural distortion, rather than a focal central scar. *Hepatocellular carcinoma* - Hepatocellular carcinoma (HCC) typically presents as a **vascular mass** that may or may not be solitary, usually arising in the context of chronic liver disease or cirrhosis. - Although the **fibrolamellar variant of HCC** (seen in younger patients without cirrhosis) can show a central scar, this is less common and the scar typically shows **hypointensity on T2-weighted imaging**, unlike FNH where the scar is **hyperintense on T2**. - Typical HCC does not show a distinct central stellate scar as a characteristic feature. [Practice more Radiology PYQs on OnCourse]

Q: What is the primary mechanism of heat loss in a modern X-ray tube?

Radiation. ***Radiation*** - The **primary mechanism** of heat loss in a modern X-ray tube is **radiation** (infrared emission). - The anode surface reaches extremely high temperatures (>1000°C) during X-ray production, causing it to emit significant **infrared radiation**. - Modern X-ray tubes use **high-emissivity materials** (tungsten-rhenium alloys) on the anode to maximize radiative heat transfer. - Since the tube operates in a **vacuum**, radiation is the only effective mechanism for heat dissipation from the anode itself. *Evaporation* - **Evaporation** requires a liquid-to-gas phase change, which is not applicable in the solid-state environment of an X-ray tube anode. - The **vacuum environment** inside the tube prevents any evaporative cooling. - This mechanism is irrelevant for heat loss from the anode. *Conduction* - **Conduction** does transfer heat from the focal spot through the anode body to the rotor bearings. - However, this is heat transfer *within* the tube components, not the primary mechanism for heat loss *from the tube*. - Heat conducted through components must ultimately be dissipated by **radiation** (from anode) or **convection** (from housing via cooling oil). *Convection* - **Convection** requires fluid movement (liquid or gas), which cannot occur in the **vacuum** inside the X-ray tube envelope. - While cooling oil outside the tube uses convection to remove heat from the housing, this is secondary heat removal, not the primary mechanism of heat loss from the anode. - The anode loses heat primarily via **radiation** first, then that heat may be further managed by convection in the cooling system. [Practice more Radiology PYQs on OnCourse]

Q: What is the recommended thickness of lead apron to prevent radiation exposure?

0.5 mm. ***0.5 mm*** - A **0.5 mm lead equivalent apron** is the universally accepted standard for protecting against primary beam radiation in most medical imaging procedures, including fluoroscopy and interventional radiology. - This thickness provides adequate **radiation attenuation** to significantly reduce dose to the wearer while maintaining reasonable comfort and mobility. *1 mm* - While offering increased attenuation, a **1 mm lead equivalent apron** is considerably heavier and less practical for routine use, leading to greater physical strain without a proportional increase in necessary protection for most procedures. - The additional weight and bulk can hinder movement and reduce compliance, especially during long procedures. *3 mm* - A **3 mm lead equivalent apron** would be excessively heavy and restrictive for medical personnel, making it highly impractical for general use in radiology departments. - The degree of protection offered by such an apron far exceeds the requirements for standard diagnostic and interventional procedures, incurring unnecessary physical burden. *7 mm* - A **7 mm lead equivalent apron** is an extreme thickness that would be entirely unfeasible for an individual to wear due to its immense weight and stiffness. - This level of shielding is typically found in fixed architectural barriers for radiation protection, such as walls of an X-ray room, not in personal protective equipment. [Practice more Radiology PYQs on OnCourse]

Q: What is the most effective imaging method for the diagnosis of adenomyosis?

MRI. ***MRI*** - **MRI** offers superior soft tissue contrast, allowing for detailed visualization of the **junctional zone** and **myometrial thickening** characteristic of adenomyosis. - It can effectively differentiate adenomyosis from other uterine pathologies like **leiomyomas**, due to its ability to detect **heterogeneous myometrial signal** and small myometrial cysts. *CT scan* - **CT scans** have limited utility in diagnosing adenomyosis due to their **poor soft tissue contrast** in evaluating diffuse uterine conditions. - They expose the patient to **ionizing radiation** and are generally reserved for detecting calcifications or larger structural abnormalities in the pelvis. *Ultrasound* - **Transvaginal ultrasound** is often the first-line imaging modality due to its accessibility and non-invasiveness, but its diagnostic accuracy for adenomyosis is **operator-dependent** and can be limited in subtle cases. - While it can suggest adenomyosis through findings like **globular uterus** or **heterogeneous myometrium**, it often lacks the resolution to definitively characterize the extent and nature of the lesion compared to MRI. *Hysterosalpingography* - **Hysterosalpingography** is primarily used to evaluate the patency of the **fallopian tubes** and the contour of the uterine cavity, making it unsuitable for direct visualization of myometrial pathology. - While it might show an **irregular uterine cavity** if adenomyosis is severe and extends to the endometrium, it cannot definitively diagnose or characterize the condition within the myometrium. [Practice more Radiology PYQs on OnCourse]

Question 1

Half-life of iodine-131 is

Accepted Answer

8 days

Answer

8 hours

Answer

8 weeks

Answer

8 months

Question 2

Central stellate scar is typically associated with which of the following conditions?

Accepted Answer

Focal nodular hyperplasia (FNH)

Answer

Hepatic adenoma

Answer

Chronic liver disease

Answer

Hepatocellular carcinoma

Question 3

What is the primary mechanism of heat loss in a modern X-ray tube?

Accepted Answer

Radiation

Answer

Evaporation

Answer

Conduction

Answer

Convection

Question 4

What is the recommended thickness of lead apron to prevent radiation exposure?

Accepted Answer

0.5 mm

Answer

1 mm

Answer

3 mm

Answer

7 mm

Question 5

What is the most effective imaging method for the diagnosis of adenomyosis?

Accepted Answer

MRI

Answer

CT scan

Answer

Hysterosalpingography

Answer

Ultrasound

Question 6

Which of the following techniques uses piezoelectric crystals?

Accepted Answer

Ultrasonography

Answer

NMR imaging

Answer

X-ray diffraction

Answer

Xeroradiography

Question 7

Step ladder pattern of gas shadow is seen in

Accepted Answer

Intestinal obstruction

Answer

Gastric outlet obstruction

Answer

Duodenal obstruction

Answer

Sigmoid volvulus

Question 8

Which chamber enlargement shows a double right heart border with a wide subcarinal angle?

Accepted Answer

Left atrium

Answer

Left ventricle

Answer

Right atrium

Answer

Right ventricle

Question 9

Parrot beak appearance is seen in which of the following conditions?

Accepted Answer

Volvulus

Answer

Rectal atresia

Answer

CA colon

Answer

Intussusception

Question 10

Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?

Accepted Answer

Aortic aneurysm

Answer

Astrocytoma

Answer

Neurofibromatosis

Answer

Ependymoma

NEET-PG 2012 — Radiology