Pulmonary Nuclear Medicine — MCQs

10 questions

Which of the following is the current preferred first-line diagnostic test for pulmonary embolism?

Which technetium is most commonly used in bone pathology?

A 55-year-old man who has been on bed rest for the past 10 days complains of sudden onset breathlessness and chest pain. His chest X-ray is normal. Which of the following is the next investigation of choice for making the diagnosis?

The most appropriate first-line imaging modality to detect adrenal metastasis due to bronchogenic carcinoma is:

In a patient with high clinical suspicion of pulmonary thromboembolism, best investigation would be?

Which of the following is the best inotrope agent for use in right heart failure secondary to pulmonary hypertension?

Which one of the following hepatic lesions can be diagnosed with high accuracy by using nuclear imaging?

A dense nephrogram is obtained by

The T1/2 of Iodine-131 is:

Q10

Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?

Pulmonary Nuclear Medicine Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following is the current preferred first-line diagnostic test for pulmonary embolism?

A. Pulmonary angiography (PA).
B. CT pulmonary angiography (CTPA). (Correct Answer)
C. Ventilation-perfusion (V/Q) scan.
D. D-dimer assay.

Explanation: ***CT pulmonary angiography (CTPA)*** * **CT pulmonary angiography** is considered the **gold standard** for diagnosing pulmonary embolism due to its high resolution and ability to directly visualize emboli within the pulmonary arteries. * It provides direct visualization of the **pulmonary vasculature** and can detect both central and peripheral emboli, as well as alternative diagnoses. *Ventilation-perfusion (V/Q) scan* * A **V/Q scan** measures airflow and blood flow in the lungs and is used when CTPA is contraindicated (e.g., renal failure, contrast allergy), but it is generally less specific for PE. * It is considered **indeterminate** in a significant proportion of cases, especially in patients with pre-existing lung disease, limiting its definitive diagnostic capability. *Pulmonary angiography (PA)* * **Selective pulmonary angiography** was historically the gold standard but is now rarely performed due to its **invasive nature** and the availability of less invasive, yet highly accurate, alternatives like CTPA. * It involves direct catheterization of the pulmonary artery and injection of contrast, carrying risks like vessel injury and arrhythmia. *D-dimer assay* * A **D-dimer assay** is a blood test used to rule out pulmonary embolism in patients with a low pretest probability, but it is **not diagnostic** on its own. * Elevated D-dimer levels can indicate clot formation but are **non-specific** and can be raised in many other conditions (e.g., infection, inflammation, surgery, pregnancy).

Question 2: Which technetium is most commonly used in bone pathology?

A. 99mTc-MDP (Correct Answer)
B. 99mTc-Sestamibi
C. 99mTc-Pyrophosphate
D. 99mTc-Exametazime

Explanation: ***99mTc-MDP*** - **Technetium-99m Methylene Diphosphonate (99mTc-MDP)** is the agent of choice for routine **bone scintigraphy** due to its optimal pharmacokinetics and high affinity for bone. - It readily binds to the **hydroxyapatite crystals** of bone, especially in areas of increased osteoblastic activity, making it excellent for detecting bone metastases, fractures, and infections. *99mTc-Sestamibi* - **Technetium-99m Sestamibi (99mTc-Sestamibi)** is primarily used for **myocardial perfusion imaging** to assess cardiac function. - It also has applications in parathyroid imaging for detecting **parathyroid adenomas**, but not for general bone pathology. *99mTc-Pyrophosphate* - **Technetium-99m Pyrophosphate (99mTc-Pyrophosphate)** was an older bone-seeking agent but has largely been replaced by MDP due to MDP's superior imaging characteristics. - Its main current use is in diagnosing **cardiac amyloidosis**, not for routine bone scans. *99mTc-Exametazime* - **Technetium-99m Exametazime (99mTc-Exametazime)**, also known as HMPAO, is specifically used for **leukocyte imaging** to detect infection and inflammation. - It is also used for **brain perfusion imaging** to assess cerebral blood flow, not for direct visualization of bone pathology.

Question 3: A 55-year-old man who has been on bed rest for the past 10 days complains of sudden onset breathlessness and chest pain. His chest X-ray is normal. Which of the following is the next investigation of choice for making the diagnosis?

A. Echocardiography
B. Pulmonary arteriography
C. CT Pulmonary Angiogram (CTPA)
D. Lung ventilation-perfusion scan (Correct Answer)

Explanation: ***Lung ventilation-perfusion scan*** - In a patient with suspected **pulmonary embolism (PE)** and a normal chest X-ray [1], a **V/Q scan** is a reasonable next step, especially if the patient's renal function precludes contrast-enhanced CTPA [2]. - It assesses areas of the lung that are ventilated but not perfused, indicating a probable PE. *Echocardiography* - While echocardiography can show signs of **right ventricular strain** in massive PE [1], it is not the primary diagnostic tool for confirming PE itself. - It is more useful for assessing cardiac function and ruling out other causes of chest pain and breathlessness. *Pulmonary arteriography* - This is considered the **gold standard** for diagnosing PE but is an **invasive procedure** with higher risks. - It is usually reserved for cases where non-invasive tests are inconclusive or when there's a strong clinical suspicion despite negative non-invasive tests. *CT Pulmonary Angiogram (CTPA)* - **CTPA** is generally considered the **first-line imaging study** for diagnosing PE due to its high diagnostic accuracy and widespread availability [2]. - However, the question states "next investigation of choice," and if there are contraindications to CTPA (e.g., **renal insufficiency**, contrast allergy), a V/Q scan becomes the preferred alternative [2].

Question 4: The most appropriate first-line imaging modality to detect adrenal metastasis due to bronchogenic carcinoma is:

A. PET scan
B. MRI of the abdomen
C. Adrenal radionuclide scan
D. Contrast Enhanced CT abdomen (Correct Answer)

Explanation: **Contrast Enhanced CT abdomen** - **Contrast-enhanced CT abdomen** is generally considered the most sensitive and cost-effective imaging modality for detecting **adrenal metastases**. - It allows for detailed visualization of adrenal gland morphology, including size, shape, and enhancement patterns, which can help differentiate benign from malignant lesions. *PET scan* - While **PET (Positron Emission Tomography) scans** are highly sensitive for detecting metabolically active metastatic disease, they are often used as a secondary imaging modality to characterize indeterminate lesions found on CT or MRI. - **PET scans** can have false positives in benign adrenal tumors (e.g., adenomas rich in fat) and are less readily available or higher in cost for initial screening compared to CT. *MRI of the abdomen* - **MRI of the abdomen** can be very useful for further characterization of adrenal masses, especially for distinguishing between lipid-rich adenomas and metastases. - However, for initial detection, especially in the context of screening for distant metastases from bronchogenic carcinoma, **CT is generally preferred due to its wider availability, speed, and lower cost**. *Adrenal radionuclide scan* - **Adrenal radionuclide scans** (e.g., using MIBG or iodocholesterol) are primarily used for functional imaging of adrenal glands, typically to detect specific types of tumors like pheochromocytomas or aldosteronomas. - These scans are **not sensitive for detecting adrenal metastases** from bronchogenic carcinoma, as the metastatic lesions do not typically exhibit the specific uptake patterns targeted by these radiotracers.

Question 5: In a patient with high clinical suspicion of pulmonary thromboembolism, best investigation would be?

A. D-dimer
B. CT angiography (Correct Answer)
C. Catheter angiography
D. Color Doppler

Explanation: ***CT angiography*** - In a patient with **high clinical suspicion** of pulmonary embolism (PE), CT angiography of the pulmonary arteries is the preferred and often definitive diagnostic test. - It allows for direct visualization of thrombi within the pulmonary arterial tree with high sensitivity and specificity. *D-dimer* - While useful for **ruling out PE** in patients with low or intermediate pre-test probability, a positive D-dimer is non-specific and requires further investigation in high-suspicion cases. - It has a high **negative predictive value** but a low positive predictive value, meaning a normal D-dimer makes PE unlikely, but an elevated one does not confirm it. *Catheter angiography* - This is an **invasive procedure** that is typically reserved for cases where CT angiography is inconclusive or contraindicated, or when interventional treatment is contemplated. - It carries risks such as **bleeding** and **contrast-induced nephropathy**, making it less appropriate as a first-line diagnostic in most situations. *Color Doppler* - Color Doppler ultrasound is primarily used to diagnose **deep vein thrombosis (DVT)** in the lower extremities, which is a common source of PE. - It is **not used to directly diagnose PE** in the pulmonary arteries; however, finding a DVT can support the diagnosis of PE indirectly.

Question 6: Which of the following is the best inotrope agent for use in right heart failure secondary to pulmonary hypertension?

A. Milrinone (Correct Answer)
B. Dobutamine
C. Digoxin
D. Dopamine

Explanation: ***Milrinone*** - Milrinone is a **phosphodiesterase-3 inhibitor** that increases myocardial contractility and causes **pulmonary and systemic vasodilation**. - Its vasodilatory effect is particularly beneficial in **pulmonary hypertension** as it can help reduce **pulmonary vascular resistance (PVR)**, a critical factor in right heart failure. - The combination of **positive inotropy** and **selective pulmonary vasodilation** makes it the optimal choice for right ventricular failure secondary to pulmonary hypertension. *Dobutamine* - Dobutamine is a **beta-1 agonist** that primarily increases myocardial contractility with some beta-2 mediated vasodilation. - While it improves cardiac output, its lesser effect on **pulmonary vascular resistance** compared to milrinone makes it less ideal for right heart failure specifically complicated by pulmonary hypertension. *Digoxin* - Digoxin is a **cardiac glycoside** that increases contractility but has a slow onset of action and a narrow therapeutic window, making it less suitable for acute management. - It does not significantly reduce **pulmonary vascular resistance** and is primarily used for chronic heart failure or rate control in atrial fibrillation. *Dopamine* - Dopamine is a **catecholamine** with dose-dependent effects: at moderate doses (5-10 mcg/kg/min), it acts as a **beta-1 agonist** providing inotropic support. - However, at higher doses it causes **alpha-adrenergic vasoconstriction** which can **increase pulmonary vascular resistance**, potentially worsening right heart failure in pulmonary hypertension. - Unlike milrinone, it lacks specific pulmonary vasodilatory properties beneficial for reducing RV afterload.

Question 7: Which one of the following hepatic lesions can be diagnosed with high accuracy by using nuclear imaging?

A. Cholangiocarcinoma
B. Hepatocellular carcinoma
C. Hepatic adenoma
D. Focal nodular hyperplasia (Correct Answer)

Explanation: ***Focal nodular hyperplasia*** - **Focal nodular hyperplasia** (FNH) contains functioning Kupffer cells, which take up **Technetium-99m sulfur colloid** used in nuclear imaging. - FNH typically shows **normal or increased uptake** on sulfur colloid scans, which distinguishes it from other hepatic lesions with high accuracy. - The presence of functional **Kupffer cells and hepatocytes** allows FNH to be diagnosed with high specificity using nuclear imaging. *Cholangiocarcinoma* - **Cholangiocarcinoma** is a malignant tumor of the bile ducts and does not contain Kupffer cells. - It appears as a **photopenic defect** (decreased or absent uptake) on nuclear scans due to its lack of functional liver cells. *Hepatocellular carcinoma* - **Hepatocellular carcinoma** (HCC) is a primary liver malignancy that typically lacks functional Kupffer cells. - HCC usually shows **decreased or absent uptake** on **Technetium-99m sulfur colloid scans**, appearing as a cold lesion. *Hepatic adenoma* - A **hepatic adenoma** is a benign liver tumor that lacks Kupffer cells and thus does not take up the tracer in nuclear imaging. - Adenomas appear as **photopenic defects** on sulfur colloid scans and are better characterized by their enhancement patterns on MRI or CT.

Question 8: A dense nephrogram is obtained by

A. Dehydrating the patient
B. Rapid (Bolus) injection of dye (Correct Answer)
C. Using non ionic media
D. Increasing the dose of contrast media

Explanation: ***Rapid (Bolus) injection of dye*** - A **rapid bolus injection** of contrast material ensures a high concentration reaches the kidneys simultaneously, leading to optimal opacification and a **dense nephrogram**. - This method allows for the collection of a **large bolus of undiluted contrast** in the renal vessels and parenchyma, improving visualization of the renal parenchyma during the nephrographic phase. - The dense nephrogram phase occurs when contrast is within the renal tubules and interstitium, producing uniform opacification. *Dehydrating the patient* - **Dehydration** would concentrate the urine in the collecting system, but it does not directly contribute to the **dense nephrogram** appearance of the renal parenchyma. - While dehydration may improve visualization of the pelvicalyceal system on delayed images, it can increase the risk of **contrast-induced nephropathy**. *Using non ionic media* - **Non-ionic contrast media** are associated with fewer adverse reactions and greater patient safety compared to ionic media due to their lower osmolality. - However, the type of contrast media (ionic vs. non-ionic) does not primarily determine the **density of the nephrogram** itself, but rather patient tolerability and safety profile. *Increasing the dose of contrast media* - While increasing the dose might provide more contrast overall, it does not guarantee a **dense nephrogram**, which requires a high concentration of contrast to be present acutely in the renal parenchyma. - A dense nephrogram is better achieved by **rapid bolus injection technique** rather than simply increasing the total dose. - Excessive contrast increases the risk of **adverse reactions** and contrast-induced nephropathy without necessarily improving nephrographic density proportionally.

Question 9: The T1/2 of Iodine-131 is:

A. 8 days (Correct Answer)
B. 12 hours
C. 13 days
D. 2 days

Explanation: ***8 days*** - Iodine-131 (¹³¹I) has a relatively short half-life of **8.02 days**, making it suitable for diagnostic and therapeutic uses with a controlled radiation exposure window. - This **half-life** allows for effective patient monitoring and targeted treatment while minimizing long-term radiation risks. *12 hours* - This is an incorrect value; 12 hours is a significantly shorter half-life than that of **Iodine-131**. - Other isotopes, such as **Iodine-123**, have a half-life of 13.2 hours, which is closer to this value but still distinct from **Iodine-131**. *13 days* - This value is close but incorrect; the correct half-life for **Iodine-131** is approximately **8 days**. - A 13-day half-life would imply a longer period of radioactivity, altering its clinical applications. *2 days* - This is an incorrect half-life for **Iodine-131**, which has a significantly longer half-life of approximately 8 days. - A 2-day half-life would mean the isotope decays much faster than it actually does.

Question 10: Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?

A. Iodohippurate
B. Tc99m-DTPA (Correct Answer)
C. Tc99m-MAG3
D. Tc99m-DMSA

Explanation: ***Tc99m-DTPA*** - Technetium-99m-Diethylenetriaminepentaacetic acid (**Tc99m-DTPA**) is a radiopharmaceutical that is cleared almost exclusively by **glomerular filtration** (~98%), making it the ideal agent for measuring GFR. - Its **renal clearance rate** directly correlates with the GFR, providing an accurate, non-invasive assessment of kidney function. - Used for dynamic renal scintigraphy to calculate GFR quantitatively. *Iodohippurate* - **Iodohippurate (OIH)** is primarily cleared by **tubular secretion** (~80%), similar to Para-aminohippuric acid (PAH). - It is used to measure **renal plasma flow (RPF)** or **effective renal plasma flow (ERPF)**, not GFR. - Not suitable for GFR measurement due to its tubular handling mechanism. *Tc99m-MAG3* - Technetium-99m-Mercaptoacetyltriglycine (**Tc99m-MAG3**) is predominantly handled by **tubular secretion** (~90%). - Used to assess **effective renal plasma flow (ERPF)** and is preferred in patients with impaired renal function due to its high extraction efficiency. - Has largely replaced OIH in clinical practice but does not measure GFR. *Tc99m-DMSA* - Technetium-99m-Dimercaptosuccinic acid (**Tc99m-DMSA**) binds to the **proximal tubular cells** in the renal cortex (~40-50% accumulation). - Used for **static renal cortical scintigraphy** to evaluate renal morphology, differential renal function, and detect cortical scarring. - Not cleared by glomerular filtration and unsuitable for GFR measurement.

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