Nuclear Medicine — MCQs

Nuclear Medicine Indian Medical PG Practice Questions and MCQs

Question 221: Which of the following statements about hepatic adenoma is true?

A. Associated with OCP use
B. Common in young females (Correct Answer)
C. Cold on isotope scan
D. Typically malignant tumor

Explanation: ***Older females*** - Hepatic adenomas are primarily seen in **younger females** of childbearing age, often linked to **oral contraceptive pill (OCP)** usage [1]. - This statement is **incorrect** as hepatic adenomas are not typically associated with older females. *OCP use* - Hepatic adenomas are **strongly associated** with the **use of oral contraceptive pills**, especially in young women [1]. - They may regress or resolve after discontinuation of OCPs, indicating a clear relationship [1]. *Cold on isotope scan* - Hepatic adenomas generally appear as **hot lesions** on imaging, meaning they take up more radioisotope than surrounding liver tissue. - A "cold" appearance would be atypical and may suggest malignancy or other liver lesions. *Benign lesion* - Hepatic adenomas are classified as **benign tumors** [2][3], although they have risks of complications like **hemorrhage** or malignant transformation [3]. - Even though they are benign, they require careful monitoring depending on size and symptoms. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, p. 874. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 398-399. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 874-875.

Question 222: Investigation of choice for studying Renal Cortical mass

A. 99mTc DTPA
B. 53Cr Study
C. 99mTc DMSA (Correct Answer)
D. 99mTc Pyrophosphate

Explanation: ***99mTc DMSA*** - **99mTc DMSA** (Technetium-99m dimercaptosuccinic acid) is the radiopharmaceutical of choice for imaging the **renal cortex** and assessing **renal cortical mass** and scarring. - It binds preferentially to the cells of the **renal tubules**, allowing for excellent visualization of cortical tissue. *99mTc DTPA* - **99mTc DTPA** (Technetium-99m Diethylenetriaminepentaacetic acid) is primarily used to assess **glomerular filtration rate (GFR)** and renal blood flow. - It is filtered by the **glomeruli** but not reabsorbed or secreted by the tubules, making it suitable for functional studies rather than morphological assessment of cortical mass. *53Cr Study* - **53Cr** (Chromium-51) is used in studies to measure **red blood cell mass**, survival, or gastrointestinal protein loss. - It has no role in the direct assessment of **renal cortical mass** or function. *99mTc Pyrophosphate* - **99mTc Pyrophosphate** is primarily used to evaluate **myocardial infarction** (hot spots) or detect bone lesions. - It is not indicated for, nor does it provide useful information about, **renal cortical mass**.

Question 223: Half-life of iodine-131 is

A. 8 days (Correct Answer)
B. 8 hours
C. 8 weeks
D. 8 months

Explanation: ***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.

Question 224: 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

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.

Question 225: Which investigation is best for assessing the proper functioning of the biliary system?

A. CT scan
B. HIDA scan (Correct Answer)
C. Ultrasonography (USG)

Explanation: ***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.

Question 226: 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

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.

Question 227: Which radioisotope is used for treating bone cancer?

A. I-123
B. Sr-89 (Correct Answer)
C. Ga-67
D. Tc-99m

Explanation: ***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.

Question 228: 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

A. ade (Correct Answer)
B. acd
C. abd
D. ad

Explanation: ***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.

Question 229: Which radiopharmaceutical is commonly used in positron emission tomography (PET) imaging?

A. 18F-FDG (Fluorodeoxyglucose) (Correct Answer)
B. Oxygen-15 (used in specific PET scans)
C. Carbon-11 acetate
D. Nitrogen-13 ammonia

Explanation: ***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 230: 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?

A. Paraneoplastic syndrome with muscle involvement
B. Recent physical trauma
C. Recent viral respiratory infection
D. Increased brown adipose tissue activity (Correct Answer)

Explanation: ***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.

Practice by Chapter

Physics of Nuclear Medicine

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Radiopharmaceuticals

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Radiation Detection in Nuclear Medicine

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Thyroid Scintigraphy

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Bone Scintigraphy

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Renal Nuclear Medicine

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Cardiac Nuclear Medicine

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Pulmonary Nuclear Medicine

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Neurological Nuclear Medicine

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PET/CT Principles and Applications

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Radionuclide Therapy

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Radiation Safety in Nuclear Medicine

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