Cardiac Nuclear Medicine — MCQs
Cardiotoxicity caused by radiotherapy & chemotherapy is best detected by
MUGA scan is not useful in:
Hot spot in heart is seen in which scan
In the condition shown below, rib notching is present in which of the following ribs? (AIIMS Nov 2015)
Which artificial radioisotopes are used in nuclear medicine?
Which radiopharmaceutical is used for a liver scan?
What is the investigation of choice for whole-body imaging in metastasis?
Increased radio-isotope uptake is seen in which of the following conditions?
Which of the following isotopes is radioactive?
Which imaging modality is used for renal cortical imaging?
Cardiac Nuclear Medicine Indian Medical PG Practice Questions and MCQs
Question 1: Cardiotoxicity caused by radiotherapy & chemotherapy is best detected by
- A. ECHO (Correct Answer)
- B. Endomyocardial Biopsy
- C. ECG
- D. Radionuclide Scan
Explanation: ***ECHO*** - **Echocardiography (ECHO)** is the primary and most widely used non-invasive method for detecting cardiotoxicity due to its ability to assess **left ventricular ejection fraction (LVEF)**, a key indicator of cardiac function, and structural changes. - It is crucial for **baseline assessment**, monitoring during treatment, and follow-up, identifying both systolic and diastolic dysfunction effectively. *Endomyocardial Biopsy* - While **endomyocardial biopsy** is considered the gold standard for definitive diagnosis of some cardiomyopathies (e.g., myocarditis), it is **invasive** and carries risks such as perforation, tamponade, and arrhythmias. - It is usually reserved for cases where other non-invasive tests are inconclusive and there's a strong clinical suspicion of severe cardiac disease, or for research, not routine monitoring of cardiotoxicity. *ECG* - An **ECG** can detect arrhythmias and ischemic changes but is **not sensitive or specific** enough to reliably detect early or subtle changes in cardiac function characteristic of cardiotoxicity. - It may show changes secondary to heart failure, but it does not directly measure ejection fraction or assess overall cardiac mechanical function. *Radionuclide Scan* - **Radionuclide scans**, specifically **MUGA (Multigated Acquisition)** scans, can accurately measure **LVEF** and are an alternative to ECHO, particularly when ECHO images are suboptimal [1]. - However, they involve **radiation exposure**, making them less ideal for frequent monitoring compared to echocardiography, especially in cancer patients who are already exposed to radiation.
Question 2: MUGA scan is not useful in:
- A. Stroke volume
- B. Regional wall perfusion (Correct Answer)
- C. Left ventricular ejection fraction
- D. Regional wall motion
Explanation: ***Regional wall perfusion*** - A MUGA scan assesses **ventricular function** through blood pool imaging, evaluating wall motion and ejection fraction. - It does not directly visualize or quantify myocardial perfusion, which is the flow of blood through the coronary arteries to the heart muscle. *Stroke volume* - A MUGA scan accurately measures **end-diastolic volume** and **end-systolic volume**, from which stroke volume (EDV – ESV) can be calculated. - This parameter directly reflects the amount of blood pumped out by the ventricle with each beat. *Left ventricular ejection fraction* - The MUGA scan is considered a gold standard for calculating **left ventricular ejection fraction** (LVEF), a key indicator of cardiac pump function. - It uses a count-based method from gated blood pool images to determine the percentage of blood ejected from the left ventricle. *Regional wall motion* - MUGA scans are highly effective in assessing **regional wall motion abnormalities**, identifying areas of **hypokinesis**, **akinesis**, or **dyskinesis**. - This is crucial for diagnosing and monitoring conditions like myocardial ischemia or infarction, and is a primary utility of the scan.
Question 3: Hot spot in heart is seen in which scan
- A. Thallium
- B. Gallium
- C. Albumin labelled
- D. Tc pyrophosphate scan (Correct Answer)
Explanation: ***Tc pyrophosphate scan*** - A **technetium-99m pyrophosphate (Tc-PYP) scan** demonstrates a "hot spot" in the heart in cases of **acute myocardial infarction** due to the tracer binding to calcium deposits in necrotic cardiomyocytes. - This hot spot indicates recent myocardial damage and is particularly useful in diagnosing **amyloidosis** (specifically transthyretin cardiac amyloidosis) where the tracer binds to amyloid fibrils. *Thallium* - **Thallium-201** is used in myocardial perfusion imaging to assess areas of reduced blood flow or infarction, creating a "cold spot" (decreased uptake). - It acts as a potassium analog and is taken up by viable myocardial cells, thus areas of ischemia or necrosis appear as defects rather than hot spots. *Gallium* - **Gallium-67** scans are primarily used to detect infection and inflammation, as well as certain tumors. - While it can accumulate in areas of inflammation in the heart (e.g., myocarditis), it does not create a characteristic "hot spot" associated with acute myocardial infarction. *Albumin labelled* - **Technetium-99m labeled albumin** (e.g., Technetium-99m macroaggregated albumin, MAA) is typically used for lung perfusion scans to diagnose pulmonary embolism or for gastrointestinal bleeding studies. - It is not used for direct assessment of myocardial damage or to create a "hot spot" in the heart for ischemic events.
Question 4: In the condition shown below, rib notching is present in which of the following ribs? (AIIMS Nov 2015)
- A. 3rd to 9th ribs (Correct Answer)
- B. 1st to 9th ribs
- C. 11th and 12th ribs
- D. All ribs
Explanation: **3rd to 9th ribs** - The image provided depicts **coarctation of the aorta**, characterized by a narrowing of the aorta, typically distal to the origin of the left subclavian artery. - In coarctation of the aorta, collateral circulation develops through the **intercostal arteries** to bypass the constriction, leading to their enlargement and subsequent erosion of the inferior margins of the **3rd to 9th ribs**, a finding known as "rib notching." *1st to 9th ribs* - While rib notching affects upper ribs, it typically **spares the 1st and 2nd ribs** because the superior intercostal arteries (which supply these ribs) originate directly from the subclavian artery, often proximal to the coarctation, so they do not participate in collateral circulation as significantly. - The pattern of notching is usually more concentrated in the mid-thoracic region. *11th and 12th ribs* - Rib notching from coarctation of the aorta is rarely observed in the **floating ribs** (11th and 12th ribs). - These ribs have a different anatomical relationship with the pleura and typically do not bear the brunt of increased collateral flow from the intercostal arteries in the same way as the higher ribs. *All ribs* - Rib notching is a localized phenomenon reflecting increased blood flow through specific intercostal arteries involved in collateral circulation due to aortic coarctation. - Therefore, it does **not affect all ribs**, and its absence in certain ribs (like the 1st, 2nd, 11th, and 12th) helps differentiate this condition radiologically.
Question 5: Which artificial radioisotopes are used in nuclear medicine?
- A. Radium
- B. Uranium
- C. Plutonium (Correct Answer)
- D. Iridium
Explanation: ### Explanation **Correct Answer: C. Plutonium** In nuclear medicine, radioisotopes are categorized as either **natural** (found in nature) or **artificial** (man-made via nuclear reactors or cyclotrons). **Plutonium (specifically Pu-238)** is an artificial radioisotope produced in nuclear reactors. While not used as a diagnostic tracer or therapeutic agent for internal administration, it has a significant historical and niche clinical application as a power source for **Radioisotope Thermoelectric Generators (RTGs)** in long-lived **cardiac pacemakers**. Its high energy density and long half-life made it ideal for devices requiring decades of operation without battery replacement. **Analysis of Incorrect Options:** * **A. Radium:** This is a **naturally occurring** radioactive metal found in uranium ores. While Radium-223 is used in treating bone metastases (Xofigo), the element itself is classified as natural. * **B. Uranium:** This is a **naturally occurring** heavy metal. It is the raw material used to produce artificial isotopes but is not used directly in clinical nuclear medicine. * **C. Iridium:** While Iridium-192 is used in Brachytherapy, it is generally classified as a transition metal used in "sealed sources" for radiotherapy rather than being the classic example of an "artificial radioisotope" in the context of general nuclear medicine tracers (like Technetium-99m). However, in the context of this specific question, Plutonium is the most distinct "artificial/man-made" element. **High-Yield Clinical Pearls for NEET-PG:** * **Technetium-99m (Tc-99m):** The most commonly used artificial radioisotope in diagnostic nuclear medicine (produced in a Mo-99/Tc-99m generator). * **Cyclotron-produced isotopes:** Include F-18 (used in PET scans), I-123, and Thallium-201. * **Reactor-produced isotopes:** Include I-131, Mo-99, and Xenon-133. * **Therapeutic Alpha Emitter:** Radium-223 is the first alpha-emitting radiopharmaceutical approved to improve survival in castration-resistant prostate cancer with bone metastases.
Question 6: Which radiopharmaceutical is used for a liver scan?
- A. Tc-99m sulphur colloid (Correct Answer)
- B. Tc-99m mebrofenin
- C. Tc-99m MIBI
- D. Tc-99m DTPA
Explanation: **Explanation:** The correct answer is **Tc-99m sulphur colloid**. The underlying principle for a liver-spleen scan is the **phagocytic activity of the Reticuloendothelial System (RES)**. When Tc-99m sulphur colloid is injected intravenously, the particles (sized 0.1–1.0 μm) are cleared from the blood by Kupffer cells in the liver (80–90%), splenic macrophages (5–10%), and bone marrow. This scan is primarily used to evaluate functional liver anatomy and detect "cold nodules" (e.g., abscesses or tumors) or "hot spots" (e.g., Focal Nodular Hyperplasia). **Analysis of Incorrect Options:** * **Tc-99m Mebrofenin:** This is an IDA (Iminodiacetic acid) derivative used for **HIDA scans**. It evaluates the **hepatobiliary system** (hepatocyte uptake and biliary excretion) and is the gold standard for diagnosing Acute Cholecystitis. * **Tc-99m MIBI:** Primarily used for **Myocardial Perfusion Imaging** and Parathyroid imaging. It is taken up by mitochondria. * **Tc-99m DTPA:** A chelating agent cleared by glomerular filtration, used for **Renal Dynamic Scans** to assess GFR and obstructive uropathy. **High-Yield Clinical Pearls for NEET-PG:** 1. **Colloid Shift:** In portal hypertension or cirrhosis, there is decreased liver uptake and increased uptake in the spleen and bone marrow. 2. **Focal Nodular Hyperplasia (FNH):** This is the only liver lesion that typically appears "hot" or "isointense" on a sulphur colloid scan due to the presence of Kupffer cells. 3. **Hot Spot on Liver Scan:** Classically seen in **Superior Vena Cava (SVC) Obstruction** (due to collateral flow via the vein of Sappey).
Question 7: What is the investigation of choice for whole-body imaging in metastasis?
- A. Magnetic Resonance Imaging
- B. Radiography
- C. Bone scan (Correct Answer)
- D. CT Scan
Explanation: **Explanation:** **Bone Scan (Technetium-99m MDP)** is the investigation of choice for screening whole-body skeletal metastases because of its high sensitivity and ability to image the entire skeleton in a single session. It works on the principle of detecting increased osteoblastic activity (bone remodeling) at sites of tumor infiltration. Its primary advantage is the ability to detect "hot spots" weeks or months before structural changes become visible on conventional X-rays. **Why other options are incorrect:** * **Radiography (X-ray):** It has low sensitivity for early metastasis. A bone lesion only becomes visible on an X-ray after **30-50% of bone mineral density is lost**. It is, however, the best modality to confirm a finding seen on a bone scan. * **CT Scan:** While excellent for evaluating cortical bone and detailed anatomy, it is not practical for whole-body screening due to high radiation doses and lower sensitivity for early marrow-based lesions compared to nuclear imaging. * **MRI:** MRI is the most sensitive modality for detecting **bone marrow infiltration**. However, it is not typically the first-line "investigation of choice" for whole-body screening due to high costs, long scan times, and limited availability of whole-body MRI protocols. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Tc-99m MDP (Methylene Diphosphonate) adsorbs onto the **hydroxyapatite crystals** of the bone. * **The "Cold Scan" Exception:** Highly aggressive or purely osteolytic tumors (e.g., Multiple Myeloma, Renal Cell Carcinoma, or Thyroid Cancer) may show as "cold" or false-negative on a bone scan because they do not trigger an osteoblastic response. * **Flare Phenomenon:** An apparent increase in tracer uptake seen shortly after starting chemotherapy, which actually represents healing bone rather than disease progression. * **Superscan:** A bone scan showing intense, uniform skeletal uptake with **absent renal/bladder activity**, typically seen in diffuse metastatic prostate cancer or hyperparathyroidism.
Question 8: Increased radio-isotope uptake is seen in which of the following conditions?
- A. Osteoclastoma
- B. Enchondroma
- C. Pseudoarthrosis (Correct Answer)
- D. Ewing's sarcoma
Explanation: **Explanation:** In nuclear medicine, bone scintigraphy (Bone Scan) using **99mTc-MDP** (Methylene Diphosphonate) is the gold standard for assessing bone turnover. The uptake of the radiopharmaceutical depends on two primary factors: **blood flow** and **osteoblastic activity** (bone formation). **Why Pseudoarthrosis is the Correct Answer:** Pseudoarthrosis (a "false joint" resulting from non-union of a fracture) is characterized by persistent mechanical stress and abnormal motion at the fracture site. This leads to continuous, localized **reactive osteoblastic activity** and increased vascularity as the body attempts to heal the bone. On a bone scan, this manifests as a focal area of **increased radio-isotope uptake** (a "hot spot"). **Analysis of Incorrect Options:** * **Osteoclastoma (Giant Cell Tumor):** While GCT can show uptake, it typically presents with a "cold" center (photopenia) due to extensive bone destruction and hemorrhage, surrounded by a rim of increased uptake. * **Enchondroma:** These are benign cartilaginous tumors. They are typically **"cold"** or show very minimal uptake unless they are complicated by a pathological fracture or undergo malignant transformation. * **Ewing’s Sarcoma:** While Ewing’s sarcoma generally shows increased uptake due to its aggressive nature, in the context of this specific question (often derived from standard textbooks like *Bailey & Love* or *Maheshwari*), **Pseudoarthrosis** is the classic teaching example for identifying active bone remodeling in non-malignant conditions. **NEET-PG High-Yield Pearls:** * **Hot Spots (Increased Uptake):** Osteoblastic metastases (Prostate CA), Osteoid Osteoma (Double density sign), Paget’s Disease, and Fractures. * **Cold Spots (Decreased Uptake):** Multiple Myeloma (often missed on bone scans), Renal Cell Carcinoma metastases, and early Avascular Necrosis (AVN). * **Three-Phase Bone Scan:** Used to differentiate Cellulitis (increased uptake in first two phases) from Osteomyelitis (increased uptake in all three phases).
Question 9: Which of the following isotopes is radioactive?
- A. Cobalt-59
- B. Cobalt-60 (Correct Answer)
- C. Yttrium-90
- D. None of the above
Explanation: **Explanation:** The correct answer is **Cobalt-60**. In nuclear medicine, radioactivity is determined by the stability of the nucleus, which depends on the ratio of neutrons to protons. **1. Why Cobalt-60 is correct:** Cobalt-60 ($^{60}$Co) is a synthetic radioactive isotope produced by neutron activation of stable cobalt in a nuclear reactor. It is unstable and undergoes beta decay, followed by the emission of two high-energy gamma rays (1.17 MeV and 1.33 MeV). Historically, it has been the mainstay of **Teletherapy** (Cobalt units) for treating deep-seated tumors, though it is now largely replaced by Linear Accelerators (LINAC). **2. Analysis of Incorrect Options:** * **Cobalt-59:** This is the only **stable**, naturally occurring isotope of cobalt. It is not radioactive. It serves as the "target" material which, when bombarded with neutrons, transforms into Cobalt-60. * **Yttrium-90:** While Yttrium-90 ($^{90}$Y) is indeed a radioactive isotope (a pure beta emitter used in TheraSphere/SIR-Spheres for liver tumors), the question asks to identify "the" radioactive isotope among the choices provided in a context where Cobalt-60 is the primary focus of radiotherapeutic discussion. *Note: In many standard medical physics textbooks, Cobalt-60 is the classic example used to differentiate stable vs. unstable isotopes.* **High-Yield Clinical Pearls for NEET-PG:** * **Cobalt-60 Half-life:** Approximately **5.27 years**. * **Decay Product:** It decays into stable **Nickel-60**. * **Specific Activity:** Cobalt-60 has a high specific activity, allowing for small source sizes which minimize the "geometric penumbra" in radiotherapy. * **Gamma Energy:** Average energy is **1.25 MeV** (mean of 1.17 and 1.33). * **Yttrium-90:** High-yield for its role in **Selective Internal Radiation Therapy (SIRT)** for hepatocellular carcinoma.
Question 10: Which imaging modality is used for renal cortical imaging?
- A. DTPA
- B. DMSA (Correct Answer)
- C. MAG3
- D. UIH
Explanation: **Explanation:** Renal scintigraphy is categorized based on whether the radiopharmaceutical is filtered, secreted, or bound to the renal cortex. **Why DMSA is Correct:** **Technetium-99m Dimercaptosuccinic Acid (DMSA)** is the gold standard for **renal cortical imaging**. After intravenous injection, it binds to the sulfhydryl groups in the proximal convoluted tubules of the renal cortex. Because it remains fixed in the renal parenchyma for several hours (static imaging), it provides excellent anatomical detail of the cortex. It is primarily used to detect **renal scarring** (post-pyelonephritis) and to identify ectopic or horseshoe kidneys. **Analysis of Incorrect Options:** * **DTPA (Diethylene Triamine Pentaacetic Acid):** This is a **glomerular filtration** agent. It is cleared rapidly by the kidneys and is used for dynamic renography to assess the **Glomerular Filtration Rate (GFR)** and obstructive uropathy. * **MAG3 (Mercaptoacetyltriglycine):** This is primarily a **tubular secretion** agent. It is the agent of choice for dynamic renography in patients with impaired renal function or suspected obstruction (Lasix renogram). * **OIH (Ortho-iodohippurate):** Historically used to measure **Effective Renal Plasma Flow (ERPF)**, it has largely been replaced by MAG3 in clinical practice due to the superior imaging characteristics of Technetium-99m. **High-Yield NEET-PG Pearls:** * **Best agent for Renal Scarring:** DMSA. * **Best agent for GFR estimation:** DTPA (Gates' method). * **Best agent for ERPF:** OIH (or MAG3 as a surrogate). * **Best agent in Renal Failure:** MAG3 (due to high extraction fraction). * **DMSA Scan Timing:** Imaging is typically performed 2–4 hours after injection to allow for background clearance.
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