Nuclear Medicine — MCQs
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Which of the following statements about the half-life of radioisotopes is false?
Hot spot in heart is seen in which scan
Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?
Isotope used in ventriculography is
FDG-PET negative tumor is:
Which common tracer in PET is usually administered in the form of a glucose sugar?
99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of
Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?
The Renal function is best assessed by:
Isotope used in RAIU (Radioactive Iodine Uptake test) is:
Nuclear Medicine Indian Medical PG Practice Questions and MCQs
Question 171: Which of the following statements about the half-life of radioisotopes is false?
- A. Co-60: 5.26 years
- B. I-131: 60 years (Correct Answer)
- C. Ra-226: 1626 years
- D. Ir-192 : 74 days
Explanation: ***I-131: 60 years*** - The half-life of **Iodine-131 (I-131)** is approximately **8 days**, not 60 years. This makes the statement false. - I-131 is commonly used in nuclear medicine for thyroid imaging and treatment, and its relatively short half-life is advantageous for patient safety. *Co-60: 5.26 years* - The half-life of **Cobalt-60 (Co-60)** is indeed approximately **5.26 years**. - Co-60 is a significant radioisotope used in **radiotherapy** and for sterilization of medical equipment. *Ra-226: 1626 years* - The half-life of **Radium-226 (Ra-226)** is approximately **1626 years**, making this statement correct. - Ra-226 is a naturally occurring radioisotope with a very long half-life, historically used in medicine and still present in some environmental contexts. *Ir-192 : 74 days* - The half-life of **Iridium-192 (Ir-192)** is approximately **73.8 days (often rounded to 74 days)**, making this statement correct. - Ir-192 is commonly used in **brachytherapy** for cancer treatment and **industrial radiography**.
Question 172: 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 173: Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?
- A. Thallium 201
- B. Tc-99m Sestamibi
- C. Tc-99m Pyrophosphate (Correct Answer)
- D. 18-FDG PET
Explanation: ***Tc-99m Pyrophosphate*** - This radioisotope binds to **calcium deposits** in infarcted myocardial tissue, which accumulate 12-24 hours after injury. - It is particularly useful for detecting **acute myocardial infarction** (hot spot imaging) when cardiac biomarkers may be unreliable or in cases of delayed presentation. - Shows positive uptake in necrotic tissue, making it a "positive" or "hot spot" agent for acute MI. *Thallium 201* - **Thallium 201** is a potassium analog that is actively transported into viable myocardial cells. - It is primarily used for assessing **myocardial perfusion** and viability, showing areas of reduced blood flow or scar tissue. - Acts as a "cold spot" agent - infarcted areas show reduced uptake. *Tc-99m Sestamibi* - **Tc-99m Sestamibi** is a commonly used tracer for **myocardial perfusion imaging (SPECT)**, indicating blood flow to the heart muscle. - It accumulates in viable myocardial cells in proportion to blood flow and is not specific for acute myocardial necrosis. - Used primarily for stress testing and perfusion assessment, not acute infarct detection. *18-FDG PET* - **18-FDG PET** (Fluorodeoxyglucose Positron Emission Tomography) primarily measures **glucose metabolism** in the myocardium. - It is predominantly used to assess **myocardial viability** in areas of hibernating myocardium rather than acute infarction. - Helps distinguish viable but ischemic tissue from scar tissue.
Question 174: Isotope used in ventriculography is
- A. Diatrizoate
- B. Technetium (Tc) (Correct Answer)
- C. Gallium
- D. Lipoidate
Explanation: ***Technetium (Tc)*** - **Technetium-99m** is the most commonly used radioisotope in nuclear medicine for various imaging studies, including **ventriculography**. - It is preferred due to its short half-life (6 hours), favorable energy emission (140 keV), and availability, making it ideal for tracking blood flow within the **cardiac ventricles**. *Diatrizoate* - **Diatrizoate** is an **iodinated contrast medium** primarily used in conventional X-ray angiography and computed tomography (CT) scans. - It is not a radioisotope and therefore cannot be used for nuclear medicine procedures like **radionuclide ventriculography**. *Gallium* - **Gallium (Ga-67)** is a radioisotope used in nuclear medicine, but its primary application is in **tumor and infection imaging**, particularly for inflammatory conditions and lymphomas. - It is not suitable for **ventriculography** as it localizes in different tissues and organs, not specifically in cardiac chambers for blood pool imaging. *Lipoidate* - **Lipoidate (Ethiodized oil)** is an **iodinated oil-based contrast agent** historically used for lymphangiography and myelography. - It is not a radioisotope and is not used for **cardiac ventriculography**.
Question 175: FDG-PET negative tumor is:
- A. Typical carcinoid (Correct Answer)
- B. Atypical carcinoid
- C. Small cell carcinoma
- D. Large cell neuroendocrine carcinoma
Explanation: ***Typical carcinoid*** - **Typical carcinoid tumors** generally have a low metabolic rate and thus do not avidly take up **FDG (fluorodeoxyglucose)**, appearing **FDG-PET negative**. - These tumors are characterized by low mitotic activity and lack of necrosis, contributing to their low glucose metabolism. *Atypical carcinoid* - **Atypical carcinoid tumors** have a higher proliferative index and increased metabolic activity compared to typical carcinoids. - They tend to be **FDG-PET positive** due to their higher glucose utilization. *Small cell carcinoma* - **Small cell carcinoma** is a highly aggressive tumor type with rapid proliferation and high metabolic activity. - It is typically **FDG-PET positive**, reflecting its significant glucose uptake. *Large cell neuroendocrine carcinoma* - **Large cell neuroendocrine carcinoma (LCNEC)** is also an aggressive tumor with a high mitotic rate and often exhibits necrosis. - Similar to small cell carcinoma, LCNEC is generally **FDG-PET positive** due to its high metabolic demand.
Question 176: Which common tracer in PET is usually administered in the form of a glucose sugar?
- A. Aluminum - 12
- B. Fluorine 18 (Correct Answer)
- C. Carbon 11
- D. Oxygen 15
Explanation: ***Fluorine 18*** - **18F-FDG** (Fluorodeoxyglucose) is the most common PET tracer, utilizing **Fluorine-18** as its radioactive component. - FDG is a glucose analog, meaning it mimics glucose and is taken up by metabolically active cells, allowing for imaging of **glucose metabolism**. *Aluminum - 12* - **Aluminum-12** is not a common radionuclide used in PET imaging. - The most common tracers in PET are **positron emitters** like Fluorine-18, Carbon-11, Nitrogen-13, and Oxygen-15. *Carbon 11* - **Carbon-11** can be used in PET tracers (e.g., 11C-methionine), but it is **less common** than 18F-FDG due to its shorter half-life. - Its short half-life (20 minutes) requires an **on-site cyclotron** for production, limiting its widespread use. *Oxygen 15* - **Oxygen-15** is employed in PET tracers (e.g., 15O-water for cerebral blood flow), but it has an **even shorter half-life** (2 minutes) than Carbon-11. - Its extremely short half-life makes it **impractical** for routine clinical use in the form of a glucose sugar.
Question 177: 99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of
- A. Hepatoma
- B. Left ventricular function wall motion
- C. Hepatic hemangioma
- D. GI Bleeding (Correct Answer)
Explanation: ***GI Bleeding*** - Technetium-99m labeled RBC scintigraphy (**<sup>99m</sup>Tc-RBC scan**) is highly sensitive for detecting **active gastrointestinal bleeding**, especially slow or intermittent bleeding. - The labeled red blood cells extravasate at the site of bleeding, accumulating and outlining the bleeding focus over time. *Hepatoma* - **Hepatoma** (hepatocellular carcinoma) is primarily diagnosed using imaging modalities like **CT, MRI**, and **ultrasound**, often with contrast enhancement. - While nuclear medicine scans like **FDG-PET** can be used in some cases for staging or assessing viability, <sup>99m</sup>Tc-RBC scans are not a primary diagnostic tool for hepatoma. *Left ventricular function wall motion* - **Left ventricular function** and **wall motion abnormalities** are typically assessed using **echocardiography**, cardiac **MRI**, or **nuclear cardiology studies** like **SPECT** or **PET** using tracers that localize in the myocardium (e.g., <sup>99m</sup>Tc-Sestamibi or Thallium-201). - <sup>99m</sup>Tc-RBC scans are sometimes used for **gated blood pool scans** to assess global ejection fraction, but not directly for wall motion analysis in the same way as other dedicated cardiac modalities. *Hepatic hemangioma* - **Hepatic hemangiomas** can be characterized by **<sup>99m</sup>Tc-RBC scintigraphy**, which shows **early photopenia** followed by **delayed fill-in and retention** of the tracer due to the characteristic slow blood flow within these benign vascular tumors. - While it can be used for confirmation, it's not the most commonly used primary diagnostic tool (which is often **ultrasound** or **MRI** with specific contrast patterns), and GI bleeding is a more direct application where the scan detects extravasation rather than vascular pooling.
Question 178: Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?
- A. Meckel's diverticulum (Correct Answer)
- B. Duodenal diverticulum
- C. Pharyngeal diverticulum
- D. Colonic diverticulum
Explanation: ***Meckel's diverticulum*** - **Meckel's diverticulum** is a **congenital outpouching** of the small intestine that often contains **ectopic gastric mucosa**. - The **Tc-99m pertechnetate scan** identifies the **parietal cells of ectopic gastric mucosa**, which absorb and secrete pertechnetate, making it the diagnostic modality of choice. *Duodenal diverticulum* - A **duodenal diverticulum** is an **outpouching of the duodenum** and typically does not contain ectopic gastric mucosa. - It is usually **asymptomatic** and incidentally found during imaging for other conditions. *Pharyngeal diverticulum* - A **pharyngeal diverticulum**, also known as **Zenker's diverticulum**, is an outpouching of the **posterior hypopharynx**. - It does not contain gastric mucosa and is typically diagnosed with a **barium swallow study**. *Colonic diverticulum* - **Colonic diverticula** are **sac-like protrusions** of the colonic wall, often found in the sigmoid colon. - They are diagnosed with **colonoscopy** or **CT colonography** and do not contain gastric mucosa.
Question 179: The Renal function is best assessed by:
- A. Tc 99m DMSA
- B. Tc 99m DTPA
- C. Tc 99m pertechnetate
- D. Tc 99m MAG3 (Correct Answer)
Explanation: ***Tc 99m MAG3*** - **Technetium-99m mercaptoacetyltriglycine (MAG3)** is the **preferred agent for dynamic renal scintigraphy** and assessment of **overall renal function**. - It is a **renal tubular agent** with a high extraction fraction (40-50%) that assesses **effective renal plasma flow (ERPF)** and **tubular secretion**. - **Superior to DTPA** for functional assessment due to better image quality, faster clearance, and excellent performance even in **impaired renal function**. - Provides comprehensive evaluation of **renal perfusion, function, and excretion** in a single study. *Tc 99m DMSA* - **Technetium-99m dimercaptosuccinic acid (DMSA)** is a **cortical imaging agent** used primarily for **static renal imaging**. - Excellent for assessing **renal anatomy**, detecting **cortical scarring**, **pyelonephritis**, and **differential renal function**. - It binds to the cells of the **proximal tubules** and is retained (40-50% at 6 hours), making it unsuitable for dynamic functional studies or excretion assessment. *Tc 99m DTPA* - **Technetium-99m diethylenetriaminepentaacetic acid (DTPA)** is a **glomerular filtration agent** used to measure **GFR**. - Excreted solely by **glomerular filtration** (no tubular secretion), making it the gold standard for **GFR measurement**. - However, it has a **lower extraction fraction (20%)** compared to MAG3, resulting in poorer image quality and less reliable assessment in patients with **impaired renal function**. - MAG3 has largely replaced DTPA as the preferred agent for routine dynamic renal studies. *Tc 99m pertechnetate* - **Technetium-99m pertechnetate** is primarily used for **thyroid imaging** and detecting **Meckel's diverticulum** (taken up by mucous-secreting cells). - **Not used for renal function assessment** as it does not provide reliable information about glomerular or tubular function.
Question 180: Isotope used in RAIU (Radioactive Iodine Uptake test) is:
- A. I131
- B. I123 (Correct Answer)
- C. I125
- D. I127
Explanation: ***I123*** - **Iodine-123 (I-123)** is the preferred isotope for **Radioactive Iodine Uptake (RAIU)** tests due to its ideal physical characteristics. - It emits **gamma rays** suitable for imaging, has a relatively short half-life of 13 hours, and minimal beta emissions, reducing patient radiation exposure. *I131* - **Iodine-131 (I-131)** is primarily used for **thyroid ablation** and treatment of thyroid cancers due to its high-energy beta emissions, which are destructive to tissue. - While it can be used for imaging, its longer half-life and higher radiation dose make it less ideal for diagnostic uptake studies compared to I-123. *I125* - **Iodine-125 (I-125)** has a very long half-life (59 days) and emits low-energy gamma photons and X-rays. - It is often used in **radioimmunoassays (RIAs)** and for brachytherapy, not typically for diagnostic RAIU scans. *I127* - **Iodine-127 (I-127)** is the **stable, non-radioactive** isotope of iodine that is naturally abundant in the body and in nutritional sources. - It is not used in radioactive uptake studies because it does not emit radiation.
Practice by Chapter
Physics of Nuclear Medicine
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Neurological Nuclear Medicine
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