Nuclear Medicine

Nuclear Medicine Indian Medical PG Question 1: What is the primary function of a gamma camera?

• A. To image radioactivity emitted from organs (Correct Answer)
• B. Measuring contamination on surfaces
• C. Detecting background radiation levels
• D. Scanning the surface of a tumor

Nuclear Medicine Explanation: ***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.

Nuclear Medicine Indian Medical PG Question 2: Distant bone metastases can be best detected by which of the following imaging techniques?

• A. Bone scan (Correct Answer)
• B. CT
• C. Intravenous venogram
• D. PET scan

Nuclear Medicine Explanation: ***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.

Nuclear Medicine Indian Medical PG Question 3: 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

Nuclear Medicine 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.

Nuclear Medicine Indian Medical PG Question 4: Under RNTCP, the target for case detection through quality sputum microscopy is at least:

• A. 70% (Correct Answer)
• B. 95%
• C. 85%
• D. 60%

Nuclear Medicine Explanation: ***70%*** - The **Revised National Tuberculosis Control Programme (RNTCP)** aimed for a minimum of **70% case detection** by identifying infectious smear-positive TB cases. - This target ensures that a significant proportion of **tuberculosis cases** are diagnosed and brought under treatment, thereby reducing transmission. *95%* - While 95% is a very high target, it was not the initial or primary target set by RNTCP for sputum microscopy case detection. - Such a high rate is often an ideal goal for **treatment success** or **cure rates**, rather than initial case detection. *85%* - The **85% target** was set for the **treatment success rate** for smear-positive pulmonary TB cases under RNTCP, not for initial case detection. - Achieving this target ensures effective treatment outcomes and prevents the development of **drug resistance**. *60%* - A 60% detection rate would be considered **insufficient** for effective TB control, as it would leave a large number of infectious individuals undiagnosed. - This low target would not adequately address the public health burden of **tuberculosis**.

Nuclear Medicine Indian Medical PG Question 5: GFR for assessment of impaired renal function is best measured by

• A. MAG3
• B. IodoHippurate
• C. DTPA (Correct Answer)
• D. DMSA Scan

Nuclear Medicine Explanation: ***DTPA*** - **Diethylene Triamine Pentaacetic Acid (DTPA)** is the primary radiopharmaceutical used to measure **glomerular filtration rate (GFR)**, which is the gold standard for quantifying renal function. - DTPA is freely filtered by the glomeruli and not reabsorbed or secreted by the tubules, making it an excellent tracer for evaluating glomerular function and assessing the degree of renal impairment. - **Note:** While MAG3 is often preferred for dynamic renal imaging in patients with severe renal impairment (GFR < 30 ml/min) due to better image quality, DTPA remains the standard for direct GFR measurement. *MAG3* - **Mercaptoacetyltriglycine (MAG3)** is used to assess **effective renal plasma flow (ERPF)** and tubular secretion, not GFR. - MAG3 is actually preferred over DTPA for dynamic renal scintigraphy in patients with poor renal function because of its superior extraction efficiency and image quality. - However, it does not directly measure GFR, which is the primary parameter for quantifying impaired renal function. *IodoHippurate* - **IodoHippurate** (I-123 or I-131 labeled) is used to measure **effective renal plasma flow (ERPF)** through tubular secretion. - While it provides information about renal blood flow, it does not directly measure GFR and is not the primary agent for assessing the degree of renal functional impairment. *DMSA Scan* - **Dimercaptosuccinic acid (DMSA)** is used for **static cortical imaging** to assess renal parenchymal structure and detect abnormalities like renal scarring, differential renal function, or pyelonephritis. - DMSA binds to the proximal tubular cells and provides anatomical information, but does not assess dynamic renal function or measure GFR.

Nuclear Medicine Flashcard 1 of 5

Question: The Renal function is best assessed by which Radionucleide agent?_____

Answer: Tc-99m MAG3

Nuclear Medicine Flashcard 2 of 5

Question: _____-labeled tracers are most commonly used in myocardial perfusion imaging, as they are associated with the best image quality and the lowest radiation dose to the patient

Answer: 99mTc

Nuclear Medicine Flashcard 3 of 5

Question: _____ scan is a nuclear medicine test designed to evaluate the function of right and left ventricles of the heart

Answer: MUGA (multi gated acquisition)

Nuclear Medicine Flashcard 4 of 5

Question: A gamma camera (-camera), also called _____ camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes

Answer: scintillation

Nuclear Medicine Flashcard 5 of 5

Question: Which imaging technique can help in differentiating between radiation necrosis and recurrence?_____

Answer: PET scan