Nuclear Medicine Practice Questions

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: 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: 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: 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.

Q: What is the most likely explanation for symmetrical uptake in bilateral supraclavicular areas with no uptake on paratracheal nodes on PET-CT in a patient diagnosed with esophageal carcinoma?

Increased brown adipose tissue activity. ***Increased brown adipose tissue activity*** - **Symmetrical supraclavicular uptake** with no paratracheal node involvement is the **classic pattern** for metabolically active **brown adipose tissue (BAT)** on FDG-PET/CT. - BAT is commonly seen in younger patients and can be activated by **cold exposure, anxiety, or sympathomimetic medications**, causing physiologic FDG uptake that may mimic pathology. - The **absence of paratracheal node uptake** effectively excludes metastatic lymphadenopathy, which would be expected in esophageal carcinoma spread. *Paraneoplastic syndrome with muscle involvement* - Paraneoplastic myositis would typically present with **asymmetrical or diffuse muscle uptake** with associated clinical symptoms (weakness, elevated muscle enzymes). - Would not explain the **specific symmetrical supraclavicular pattern** or the absence of paratracheal involvement. *Recent physical trauma* - Trauma causes **localized, asymmetrical uptake** at injury sites due to inflammation and healing. - Bilateral symmetrical supraclavicular uptake without history of trauma to those specific areas is inconsistent with this diagnosis. *Recent viral respiratory infection* - Viral infections typically cause **reactive lymphadenopathy** involving cervical and **paratracheal nodes**. - The **absence of paratracheal uptake** and the diffuse symmetrical pattern in supraclavicular fossae favor BAT rather than inflammatory lymph nodes.

Question 1

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

Accepted Answer

DTPA

Answer

DMSA

Answer

EDTA

Answer

Ortho-Iodohippurate

Question 2

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 3

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 4

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

Accepted Answer

HIDA scan

Answer

CT scan

Answer

Ultrasonography (USG)

Question 5

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 6

Which radioisotope is used for treating bone cancer?

Accepted Answer

Sr-89

Answer

I-123

Answer

Ga-67

Answer

Tc-99m

Question 7

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 8

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 9

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

Question 10

What is the most likely explanation for symmetrical uptake in bilateral supraclavicular areas with no uptake on paratracheal nodes on PET-CT in a patient diagnosed with esophageal carcinoma?

Accepted Answer

Increased brown adipose tissue activity

Answer

Paraneoplastic syndrome with muscle involvement

Answer

Recent physical trauma

Answer

Recent viral respiratory infection

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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