Nuclear Medicine Practice Questions

Q: Which of the following statements about the half-life of radioisotopes is false?

I-131: 60 years. ***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**.

Q: Hot spot in heart is seen in which scan

Tc pyrophosphate scan. ***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.

Q: Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?

Tc-99m Pyrophosphate. ***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.

Q: Isotope used in ventriculography is

Technetium (Tc). ***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**.

Q: FDG-PET negative tumor is:

Typical carcinoid. ***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.

Q: Which common tracer in PET is usually administered in the form of a glucose sugar?

Fluorine 18. ***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.

Q: 99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of

GI Bleeding. ***GI Bleeding*** - Technetium-99m labeled RBC scintigraphy (** 99m 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, 99m 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., 99m Tc-Sestamibi or Thallium-201). - 99m 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 ** 99m 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.

Q: Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?

Meckel's diverticulum. ***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.

Q: The Renal function is best assessed by:

Tc 99m MAG3. ***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.

Q: Isotope used in RAIU (Radioactive Iodine Uptake test) is:

I123. ***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.

Question 1

Which of the following statements about the half-life of radioisotopes is false?

Accepted Answer

I-131: 60 years

Answer

Co-60: 5.26 years

Answer

Ra-226: 1626 years

Answer

Ir-192 : 74 days

Question 2

Hot spot in heart is seen in which scan

Accepted Answer

Tc pyrophosphate scan

Answer

Thallium

Answer

Gallium

Answer

Albumin labelled

Question 3

Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?

Accepted Answer

Tc-99m Pyrophosphate

Answer

Thallium 201

Answer

Tc-99m Sestamibi

Answer

18-FDG PET

Question 4

Isotope used in ventriculography is

Accepted Answer

Technetium (Tc)

Answer

Diatrizoate

Answer

Gallium

Answer

Lipoidate

Question 5

FDG-PET negative tumor is:

Accepted Answer

Typical carcinoid

Answer

Atypical carcinoid

Answer

Small cell carcinoma

Answer

Large cell neuroendocrine carcinoma

Question 6

Which common tracer in PET is usually administered in the form of a glucose sugar?

Accepted Answer

Fluorine 18

Answer

Aluminum - 12

Answer

Carbon 11

Answer

Oxygen 15

Question 7

99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of

Accepted Answer

GI Bleeding

Answer

Hepatoma

Answer

Left ventricular function wall motion

Answer

Hepatic hemangioma

Question 8

Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?

Accepted Answer

Meckel's diverticulum

Answer

Duodenal diverticulum

Answer

Pharyngeal diverticulum

Answer

Colonic diverticulum

Question 9

The Renal function is best assessed by:

Accepted Answer

Tc 99m MAG3

Answer

Tc 99m DMSA

Answer

Tc 99m DTPA

Answer

Tc 99m pertechnetate

Question 10

Isotope used in RAIU (Radioactive Iodine Uptake test) is:

Accepted Answer

I123

Answer

I131

Answer

I125

Answer

I127

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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