Nuclear Medicine — MCQs

Nuclear Medicine Indian Medical PG Practice Questions and MCQs

Question 201: Hotspot on Tc-99m is seen in which parotid tumor?

A. Pleomorphic adenoma
B. Acinic cell tumor
C. Adenoid cystic carcinoma
D. Warthin tumor (Correct Answer)

Explanation: ***Warthin tumor*** - A **Warthin tumor** (papillary cystadenoma lymphomatosum) is a benign parotid gland tumor characterized by the accumulation of **technetium-99m (Tc-99m)** pertechnetate. - This **hotspot** on Tc-99m scintigraphy is due to the tumor cells' ability to concentrate pertechnetate, similar to the normal salivary gland tissue. *Acinic cell tumor* - **Acinic cell tumors** are malignant parotid gland tumors that typically do not show increased uptake on **Tc-99m scanning**. - They are often described as having a **cold spot** or being isodense to surrounding tissue on imaging. *Pleomorphic adenoma* - **Pleomorphic adenomas** are the most common benign salivary gland tumors and usually appear as **cold lesions** or show normal uptake on **Tc-99m scans**. [1] - They are generally **well-circumscribed** and enhance homogenously on CT or MRI. [1] *Adenoid cystic carcinoma* - **Adenoid cystic carcinomas** are malignant tumors that characteristically present as **cold spots** or areas of decreased uptake on **Tc-99m scintigraphy**. - They are known for **perineural invasion** and can cause significant pain or nerve paralysis.

Question 202: Technetium-99m scan is used for diagnosis of -

A. Meckel's diverticulum (Correct Answer)
B. Obstruction
C. Volvulus
D. Appendix

Explanation: ***Meckel's diverticulum*** - A Technetium-99m pertechnetate scan is used to detect **ectopic gastric mucosa**, which is present in symptomatic Meckel's diverticulum. - The **Technetium-99m pertechnetate** is taken up by the **mucous cells** of the ectopic gastric tissue, making the diverticulum visible on the scan. *Obstruction* - While imaging is crucial for diagnosing obstruction, **Technetium-99m scans** are not the primary modality. - **CT scans** or **abdominal X-rays** are typically used to visualize bowel loops, air-fluid levels, and the point of obstruction. *Volvulus* - Volvulus involves the **twisting of a loop of intestine**, leading to obstruction. - It is diagnosed using imaging techniques like **CT scans** or **barium studies**, which show characteristic features such as the **"whirl sign"**. *Appendix* - Appendicitis, an inflammation of the appendix, is primarily diagnosed with **ultrasound** or **CT scans**. - These modalities help visualize the **inflamed appendix**, periappendiceal fluid, and other signs of inflammation.

Question 203: Radioisotope used for thyroid treatment of metastasis/ablation

A. I-90
B. I-131 (Correct Answer)
C. I-83
D. I-123

Explanation: ***I-131*** - **Iodine-131** is widely used for **thyroid cancer treatment** due to its ability to emit both **beta particles** (for therapeutic ablation) and **gamma rays** (for imaging). - Its therapeutic effect relies on its uptake by thyroid cells and metastatic lesions, leading to **localized radiation damage** and destruction. - **I-131** has a half-life of **8 days**, making it ideal for both treatment and post-therapy imaging. *I-90* - **I-90 is not a recognized or clinically used iodine isotope** in nuclear medicine. - This is not a standard radioisotope for any medical application, including thyroid treatment. *I-83* - **I-83** is not a commonly used or recognized radioisotope in clinical nuclear medicine, particularly not for thyroid treatment. - There is no significant clinical application for this specific iodine isotope in thyroid disease. *I-123* - **Iodine-123** is a **diagnostic radioisotope** used for thyroid imaging (**scans**) due to its **gamma emission** and shorter half-life (13 hours). - It is not used for treatment or ablation of thyroid cancer as it lacks the therapeutic beta particle emission of **I-131**. - **I-123** provides excellent imaging quality with lower radiation dose to the patient compared to I-131.

Question 204: In a child, non-functioning kidney is best diagnosed by

A. Creatinine clearance
B. Ultrasonography
C. IVU
D. DTPA renogram (Correct Answer)

Explanation: ***DTPA renogram*** - A **DTPA renogram** (diethylene triamine pentaacetic acid scan) is a nuclear medicine study that assesses **renal blood flow** and **glomerular filtration rate (GFR)**. - It is highly effective in determining if a kidney is non-functioning because it directly measures the **uptake and excretion of a radiotracer** by the kidney, providing quantitative data on its functional capacity. *Creatinine clearance* - **Creatinine clearance** is a measure of overall kidney function, reflecting the GFR of **both kidneys combined**. - It cannot specifically identify a non-functioning individual kidney, as the other kidney might compensate for the non-functioning one, leading to a near-normal overall creatinine clearance. *Ultrasonography* - **Ultrasonography** is excellent for evaluating **renal anatomy**, such as size, shape, and presence of cysts, hydronephrosis, or stones. - While it can show structural abnormalities, it provides limited direct information about the **functional status** of the kidney, and a structurally normal kidney can still be non-functional. *IVU (Intravenous Urography)* - **Intravenous Urography (IVU)** uses contrast dye injected intravenously to visualize the kidneys, ureters, and bladder, assessing both anatomy and some aspects of function. - If a kidney is non-functioning, it would show **no uptake or excretion of the contrast dye**, but IVU involves radiation exposure and nephrotoxic contrast, making DTPA renogram often preferred in children for functional assessment.

Question 205: In radionuclide imaging, the most useful radiopharmaceutical for skeletal imaging is:

A. Technetium-99m linked to Methylene diphosphonate (Correct Answer)
B. Gallium 67
C. Technetium-99m
D. Technetium-sulfur-colloid

Explanation: ***Technetium-99m linked to Methylene diphosphonate*** - **Technetium-99m MDP** is the most widely used radiopharmaceutical for skeletal imaging due to its **high affinity for hydroxyapatite crystals** in bone and favorable physical properties. - It readily incorporates into areas of **increased bone turnover**, making it excellent for detecting fractures, infections, and metastatic lesions. *Gallium 67* - **Gallium 67** is primarily used for **oncology, infection, and inflammation imaging** and has limited utility for general skeletal imaging. - It accumulates in areas of infection and inflammation, but its **biodistribution is not specific for bone metabolism**. *Technetium-sulfur-colloid* - **Technetium-sulfur-colloid** is mainly used for **liver and spleen imaging** (reticuloendothelial system), not for bone scans. - Its particle size and chemical properties prevent its significant uptake in bone tissue. *Technetium-99m* - **Technetium-99m** is a **radioisotope generator** for many different radiopharmaceuticals, but by itself, it's not directly used for skeletal imaging. - It serves as the **radionuclide scaffold** that is chelated to specific bone-seeking ligands like MDP.

Question 206: Isotope used in bone scans:

A. Technetium (Correct Answer)
B. Chromium
C. Selenium
D. Gallium

Explanation: **Technetium** - **Technetium-99m (Tc-99m)** is the most widely used isotope in bone scans due to its ideal physical characteristics, including a short half-life and suitable gamma energy for imaging. - It rapidly localizes to areas of **increased osteoblastic activity** and blood flow, making it effective for detecting bone pathologies like fractures, infections, and tumors. *Chromium* - **Chromium-51** is primarily used for **red blood cell labeling** to assess red cell mass, survival, and gastrointestinal bleeding. - It is not used for bone imaging because it does not accumulate in bone tissue and has different decay characteristics. *Selenium* - **Selenium-75** is used for imaging the **parathyroid glands** (e.g., in hyperparathyroidism) and in some studies of pancreatic function. - It does not have an affinity for bone tissue and is therefore unsuitable for bone scanning. *Gallium* - **Gallium-67** is primarily used in **inflammation and infection imaging** (Ga-67 scans) and some tumor imaging. - While it can accumulate in some bone pathologies (like osteomyelitis), it is not the primary or preferred isotope specifically for routine bone structural scans.

Question 207: Most sensitive modality for detecting bone metastases

A. Bone scan
B. PET-CT
C. Plain radiograph
D. MRI (Correct Answer)

Explanation: ***MRI*** - **MRI**, especially **whole-body MRI (WB-MRI)**, has the **highest sensitivity (90-100%)** for detecting bone metastases among all imaging modalities. - It directly visualizes **bone marrow changes** before cortical bone destruction occurs, allowing for earlier detection than other modalities. - Excellent for detecting both **lytic and sclerotic lesions** and provides superior soft tissue contrast for assessing marrow involvement. - Particularly sensitive for **spine and pelvic metastases**, and whole-body protocols enable comprehensive skeletal assessment. *PET-CT* - **PET-CT with 18F-FDG** is highly sensitive for detecting metabolically active lesions and provides whole-body assessment with both metabolic and anatomical information. - However, its sensitivity varies by primary tumor type and is **limited for sclerotic/osteoblastic metastases** which may not be FDG-avid. - While excellent for many malignancies, it has **lower sensitivity than MRI** for pure bone metastases detection, particularly in low-metabolism lesions. *Bone scan* - **Bone scan (Tc-99m MDP)** detects increased osteoblastic activity and has been the traditional screening tool with good sensitivity (62-89%). - Effective for detecting osteoblastic lesions and provides whole-body skeletal survey at relatively low cost. - However, it is **less sensitive than MRI** and can miss purely lytic metastases or early marrow involvement before osteoblastic response occurs. *Plain radiograph* - **Plain radiographs** require significant bone mineral loss (30-50%) to visualize lesions, making them the **least sensitive modality** for bone metastases. - Useful for assessing established lesions and complications like pathological fractures, but inadequate for screening or early detection.

Question 208: Which imaging study is preferred for detecting a Meckel's diverticulum?

A. Barium enema
B. CT scan
C. Ultrasound
D. Technetium-99m pertechnetate scan (Correct Answer)

Explanation: ***Technetium-99m pertechnetate scan*** - This scan specifically identifies **ectopic gastric mucosa**, which is present in over 50% of symptomatic Meckel's diverticula. - The **Technetium-99m pertechnetate tracer** is concentrated and secreted by the gastric parietal cells. *Barium enema* - A barium enema is primarily used to visualize the **large intestine** and is generally not effective for small bowel lesions like Meckel's diverticulum. - It has a very low sensitivity for detecting Meckel's diverticulum, especially if the diverticulum is small or not distended. *CT scan* - While a CT scan can sometimes show a Meckel's diverticulum, especially if it's inflamed or complicated, it is **not the preferred initial imaging modality** for uncomplicated cases. - Its sensitivity for detecting Meckel's diverticulum with ectopic gastric mucosa is lower compared to the Technetium-99m scan. *Ultrasound* - Ultrasound can be useful in detecting complications of Meckel's diverticulum, such as **inflammation or intussusception**, but it is generally not reliable for direct visualization of the diverticulum itself. - The small size and often intra-abdominal location of the diverticulum make it difficult to reliably identify with ultrasound.

Question 209: What is the half-life of Technetium-99m?

A. 2 hours
B. 6 hours (Correct Answer)
C. 12 hours
D. 24 hours

Explanation: ***6 hours*** - The **half-life of Technetium-99m (Tc-99m)** is approximately **6 hours**, making it suitable for diagnostic imaging as it allows for sufficient time for imaging while minimizing radiation exposure. - This relatively short half-life ensures that the patient's body is exposed to **radioactivity** for a limited period. *2 hours* - A half-life of **2 hours** would be too short for many diagnostic procedures, as the radioisotope would decay too quickly to complete necessary imaging. - While some isotopes have shorter half-lives, **Technetium-99m** is specifically chosen for its optimal 6-hour half-life. *12 hours* - A half-life of **12 hours** would result in significantly increased radiation exposure to the patient, which is generally undesirable for routine diagnostic imaging. - Longer half-lives typically limit the amount of activity that can be administered safely. *24 hours* - A half-life of **24 hours** would expose the patient to an unacceptably high and prolonged dose of radiation, making it unsuitable for most diagnostic medical imaging applications. - Such long half-lives are typically reserved for therapeutic applications or specialized research, not diagnostic scans.

Question 210: Acute myocarditis scintigraphy is done with -

A. Thallium
B. Technetium
C. Gallium (Correct Answer)
D. None of the options

Explanation: ***Gallium*** - **Gallium-67 citrate** accumulates in areas of inflammation and infection, making it useful in detecting **active inflammatory processes** like myocarditis. - In acute myocarditis, the **inflammatory infiltrates** within the myocardium take up gallium, localizing the areas of disease. *Thallium* - **Thallium-201** is primarily used for **myocardial perfusion imaging** to assess blood flow to the heart muscle, not inflammation. - It reflects **myocyte viability** and is typically used to detect ischemia or infarction. *Technetium* - **Technetium-99m labeled tracers** (e.g., Sestamibi, Tetrofosmin) are also widely used for **myocardial perfusion imaging**. - While other **Technetium-labeled agents** can detect inflammation, these specific perfusion tracers are not the primary choice for acute myocarditis. *None of the options* - This option is incorrect because **Gallium-67 scintigraphy** is a recognized method for detecting myocardial inflammation in acute myocarditis. - Other imaging modalities like **cardiac MRI with gadolinium** are also used, but among the given options, gallium is relevant for scintigraphy.

Practice by Chapter

Physics of Nuclear Medicine

Practice Questions

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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