Nuclear Medicine 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.

Q: Which radionuclide is best suited for measuring glomerular filtration rate (GFR)?

DTPA. ***DTPA*** - **DTPA (⁹⁹ᵐTc-DTPA)** is cleared almost exclusively by **glomerular filtration**, making it an excellent marker for GFR measurement. - Its rapid plasma clearance correlates well with **inulin clearance**, which is the gold standard for GFR. - **⁹⁹ᵐTc labeling** provides superior imaging properties, ready availability from generators, and optimal gamma energy for detection. *DMSA* - **DMSA (⁹⁹ᵐTc-dimercaptosuccinic acid)** primarily binds to the **renal cortex** and is used to assess renal parenchymal function and anatomy. - It does not accurately reflect GFR because it is mainly handled by **tubular uptake**, not glomerular filtration. *Ortho-Iodohippurate* - **Ortho-Iodohippurate (¹³¹I-OIH or ⁹⁹ᵐTc-MAG3)** is predominantly cleared by **tubular secretion**, making it a good measure of **effective renal plasma flow (ERPF)**. - While it provides information on renal function, it is not suitable for direct GFR assessment. *EDTA* - **EDTA (⁵¹Cr-EDTA)** is also cleared by glomerular filtration and can accurately measure GFR, particularly used in Europe. - However, **DTPA is preferred** due to the advantages of **⁹⁹ᵐTc labeling** (better availability, imaging properties, and lower radiation dose) compared to **⁵¹Cr labeling**. - Both are valid GFR markers, but DTPA is more commonly used in routine clinical practice.

Q: What is the primary function of a gamma camera?

To image radioactivity emitted from organs. ***To image radioactivity emitted from organs*** - A **gamma camera** (also known as a scintillation camera) is a device used in nuclear medicine to capture images of organs and tissues after a **radioactive tracer** has been introduced into the body. - It works by detecting the **gamma rays** emitted directly from the radiopharmaceutical concentrated within specific organs, allowing for functional and anatomical assessment. *Detecting background radiation levels* - While gamma cameras can detect low levels of radiation, their primary design and sensitivity are optimized for imaging deliberately introduced **radiopharmaceuticals** within a patient, not for general background radiation monitoring. - Devices like **Geiger counters** or radiation survey meters are specifically designed for measuring ambient background radiation levels. *Measuring contamination on surfaces* - Measuring surface contamination typically involves handheld radiation detectors or **wipe tests**, which are designed to quantify loose radioactive material on surfaces. - A gamma camera is a large, stationary imaging device primarily focused on visualizing internal distribution of **radioactive tracers** within the body. *Scanning the surface of a tumor* - While gamma cameras can help locate tumors within organs, they image the **radioactivity emitted from within the tumor** after a tracer has been taken up by its cells, not by scanning its surface directly. - Visualizing the surface of a tumor is typically done with techniques like direct observation, endoscopy, or advanced imaging modalities such as MRI or CT.

Q: Which of the following is used in the treatment of well-differentiated thyroid carcinoma?

I131. ***I131*** - **Radioactive iodine (I131)** is specifically absorbed by **well-differentiated thyroid cancer cells** because these cells retain the ability to uptake iodine, unlike other types of cancer cells. - Used for **ablating residual thyroid tissue** after surgery and for treating **metastatic well-differentiated thyroid carcinoma** [1]. *99m Tc* - **Technetium-99m (99m Tc)** is primarily used for **diagnostic imaging** (e.g., thyroid scans, bone scans), not for therapeutic treatment of thyroid cancer. - It has a short half-life and emits gamma rays, making it suitable for imaging but generally not for delivering sustained radiation for therapeutic effect. *32p* - **Phosphorus-32 (32p)** is a beta-emitting radionuclide used in the treatment of certain hematological malignancies, such as **polycythemia vera**, and for palliative treatment of bone metastases. - It is not selectively taken up by thyroid cancer cells and therefore is not used in the treatment of thyroid carcinoma. *MIBG* - **Metaiodobenzylguanidine (MIBG)**, often labeled with I123 (diagnostic) or I131 (therapeutic), is used in the diagnosis and treatment of **neuroendocrine tumors** like **pheochromocytoma** and **neuroblastoma**. - Its uptake mechanism targets cells of neuroectodermal origin, which is distinct from the iodine uptake mechanism of thyroid cells.

Q: Which investigation is best for assessing the proper functioning of the biliary system?

HIDA scan. ***HIDA scan*** - A **HIDA scan** (hepatobiliary iminodiacetic acid scan) evaluates the patency of the **biliary ducts** and assesses gallbladder function accurately. - It involves injecting a **radioactive tracer** that is taken up by the liver and excreted into the bile, allowing visualization of bile flow from the liver to the duodenum. - This is the **gold standard functional test** for assessing biliary system dynamics, cystic duct patency, and gallbladder ejection fraction. *USG* - **Ultrasound** is excellent for visualizing gallstones and assessing the size of the bile ducts but provides limited information about **biliary function** or the specific rate of bile flow. - It cannot reliably detect **biliary leaks** or assess functional aspects like **biliary dyskinesia** or **sphincter of Oddi dysfunction**. *CT scan* - A **CT scan** is useful for identifying structural abnormalities, tumors, or strictures within the biliary system. - However, it does not assess the **dynamic flow of bile** or the functional aspects of gallbladder emptying, which are crucial for proper functioning. - CT is better suited for anatomical evaluation rather than functional assessment.

Q: Which radioisotope is used for treating bone cancer?

Sr-89. ***Sr-89*** - **Strontium-89** (Sr-89) is a **beta-emitting radioisotope** commonly used for the palliative treatment of **bone pain** in patients with metastatic bone cancer. - It is chemically similar to **calcium** which allows it to be preferentially incorporated into areas of increased bone turnover, such as **bone metastases**, delivering therapeutic radiation directly to the cancerous sites. *I-123* - **Iodine-123** (I-123) is a **gamma-emitting radioisotope** primarily used in **diagnostic imaging**, particularly for **thyroid scans** and functional brain imaging. - It is not used therapeutically for bone cancer. *Ga-67* - **Gallium-67** (Ga-67) is a **gamma-emitting radioisotope** used in **diagnostic imaging** to detect **inflammation**, infection, and certain types of cancer, including lymphoma. - It is not a primary treatment agent for bone cancer. *Tc-99m* - **Technetium-99m** (Tc-99m) is the most common **diagnostic radioisotope** used in nuclear medicine, primarily for **bone scans** (when complexed with diphosphonates), cardiac imaging, and various other organ studies. - While integral for diagnosing bone metastases, it is **not used therapeutically** to treat bone cancer.

Q: Distant bone metastases can be best detected by which of the following imaging techniques?

Bone scan. ***Bone scan*** - A **bone scan** is highly sensitive for detecting **osteoblastic activity**, which is characteristic of most bone metastases. - It involves injecting a **radioactive tracer** (usually technetium-99m methylene diphosphonate) that accumulates in areas of increased bone turnover, making it excellent for surveying the entire skeletal system. *PET scan* - While a **PET scan** (Positron Emission Tomography) can detect bone metastases, especially with **FDG-PET**, it is generally more expensive and may not be as sensitive for purely **osteoblastic lesions** as a bone scan. - Its primary role is often in assessing metabolic activity of the primary tumor and other distant soft tissue metastases. *CT* - **CT scans** (Computed Tomography) are excellent for assessing bone anatomy, cortical destruction, and soft tissue involvement, but they are generally less sensitive for detecting early or widespread **osseous metastatic disease** compared to a bone scan. - CT provides detailed anatomical information but may miss early **marrow involvement** that alters bone metabolism. *Intravenous venogram* - An **intravenous venogram** is an imaging technique used to visualize veins, primarily for detecting **thrombosis** or venous insufficiency. - It has no role in the detection of **bone metastases**, as it provides no information about bone structure or metabolic activity.

Q: This technetium-99m sulfur colloid scan was performed after the patient presented with abdominal pain. Howell-Jolly bodies were present on a peripheral blood smear. What is the diagnosis?

Pelvic spleen. ***Pelvic spleen*** - The presence of **Howell-Jolly bodies** indicates splenic dysfunction or absence, suggesting the spleen is not in its usual location or is non-functional. - A **technetium-99m sulfur colloid scan** localizes reticuloendothelial tissue, and if it shows intense uptake in the pelvis, it indicates an **ectopic pelvic spleen**. *Hemochromatosis* - This is a disorder of **iron overload**, leading to iron deposition in organs but does not typically cause an ectopic spleen or Howell-Jolly bodies. - Diagnosis involves **elevated ferritin** and transferrin saturation, and sometimes a liver biopsy, not typically a sulfur colloid scan for splenic localization. *Hydatidiform mole* - This is an **abnormal pregnancy** characterized by the abnormal growth of trophoblasts; it is completely unrelated to splenic function or location. - It presents with symptoms like **vaginal bleeding** and an enlarged uterus, and is diagnosed by ultrasound and hCG levels. *Multiple myeloma* - This is a **plasma cell malignancy** affecting bone marrow, leading to bone lesions, renal failure, and hypercalcemia. - It does not involve splenic ectopia or splenic dysfunction leading to Howell-Jolly bodies.

Q: Isotopes used in the relief of metastatic bone pain include – a) Strontium–89 b) I–131 c) Gold–198 d) P–32 e) Rhenium–186

ade. ***Strontium-89, Phosphorus-32, and Rhenium-186 (ade)*** - **Strontium-89**, **Phosphorus-32**, and **Rhenium-186** are all **beta-emitting radioisotopes** with bone-seeking properties that selectively localize to areas of increased osteoblastic activity in bone metastases. - These isotopes are **FDA-approved** and widely used for **metastatic bone pain relief**, delivering targeted radiation therapy to reduce pain while minimizing systemic toxicity. *Strontium-89, Gold-198, and Phosphorus-32 (acd)* - While **Strontium-89** and **Phosphorus-32** are correct, **Gold-198** is primarily used for **localized brachytherapy** applications rather than systemic bone pain management. - **Gold-198** does not have the same bone-seeking properties and is not commonly indicated for widespread metastatic bone pain relief. *Strontium-89, Iodine-131, and Phosphorus-32 (abd)* - **Strontium-89** and **Phosphorus-32** are appropriate choices, but **Iodine-131** is primarily used for **thyroid cancer treatment** and **hyperthyroidism**. - **Iodine-131** lacks bone-seeking properties and is not indicated for metastatic bone pain management. *Strontium-89 and Phosphorus-32 (ad)* - This option correctly identifies **Strontium-89** and **Phosphorus-32** as effective radioisotopes for bone pain relief. - However, it omits **Rhenium-186**, which is another well-established and **FDA-approved** isotope for metastatic bone pain, making this option incomplete.

Q: Which radiopharmaceutical is commonly used in positron emission tomography (PET) imaging?

18F-FDG (Fluorodeoxyglucose). ***18F-FDG (Fluorodeoxyglucose)*** - **18F-FDG** is the most widely used radiopharmaceutical in PET imaging, particularly for **oncology**, as it's a glucose analog that accumulates in metabolically active cells. - Its widespread use is due to its favorable physical properties for PET and its ability to reflect **tumor metabolism**. *Carbon-11 acetate* - **Carbon-11 acetate** is used in specific PET applications, primarily for **cardiac imaging** to assess myocardial oxidative metabolism. - It has a very short half-life (around 20 minutes) which limits its availability to centers with on-site cyclotrons. *Oxygen-15 (used in specific PET scans)* - **Oxygen-15** (e.g., O-15 water) is used in highly specialized PET scans for measuring **blood flow** and oxygen metabolism, especially in brain studies. - Its extremely short half-life (approximately 2 minutes) necessitates an on-site cyclotron and immediate use. *Nitrogen-13 ammonia* - **Nitrogen-13 ammonia** is a common radiopharmaceutical for **myocardial perfusion imaging** with PET, reflecting regional blood flow to the heart. - Like other C-11 and O-15 tracers, its short half-life (about 10 minutes) requires proximity to a cyclotron facility.

Question 1

Half-life of iodine-131 is

Accepted Answer

8 days

Answer

8 hours

Answer

8 weeks

Answer

8 months

Question 2

Which radionuclide is best suited for measuring glomerular filtration rate (GFR)?

Accepted Answer

DTPA

Answer

DMSA

Answer

EDTA

Answer

Ortho-Iodohippurate

Question 3

What is the primary function of a gamma camera?

Accepted Answer

To image radioactivity emitted from organs

Answer

Measuring contamination on surfaces

Answer

Detecting background radiation levels

Answer

Scanning the surface of a tumor

Question 4

Which of the following is used in the treatment of well-differentiated thyroid carcinoma?

Accepted Answer

I131

Answer

99m Tc

Answer

32p

Answer

MIBG

Question 5

Which investigation is best for assessing the proper functioning of the biliary system?

Accepted Answer

HIDA scan

Answer

CT scan

Answer

Ultrasonography (USG)

Question 6

Which radioisotope is used for treating bone cancer?

Accepted Answer

Sr-89

Answer

I-123

Answer

Ga-67

Answer

Tc-99m

Question 7

Distant bone metastases can be best detected by which of the following imaging techniques?

Accepted Answer

Bone scan

Answer

CT

Answer

Intravenous venogram

Answer

PET scan

Question 8

This technetium-99m sulfur colloid scan was performed after the patient presented with abdominal pain. Howell-Jolly bodies were present on a peripheral blood smear. What is the diagnosis?

Accepted Answer

Pelvic spleen

Answer

Hydatidiform mole

Answer

Hemochromatosis

Answer

Multiple myeloma

Question 9

Isotopes used in the relief of metastatic bone pain include – a) Strontium–89 b) I–131 c) Gold–198 d) P–32 e) Rhenium–186

Accepted Answer

ade

Answer

acd

Answer

abd

Answer

ad

Question 10

Which radiopharmaceutical is commonly used in positron emission tomography (PET) imaging?

Accepted Answer

18F-FDG (Fluorodeoxyglucose)

Answer

Oxygen-15 (used in specific PET scans)

Answer

Carbon-11 acetate

Answer

Nitrogen-13 ammonia

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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