Nuclear Medicine — MCQs

Nuclear Medicine Indian Medical PG Practice Questions and MCQs

Question 191: What is a radionuclide scan finding in hyperparathyroidism?

A. Panda sign
B. Hot spots (Correct Answer)
C. Hawkin's sign
D. Cold spots

Explanation: ***Hot spots*** - **Hot spots** on a radionuclide scan in hyperparathyroidism indicate areas of **increased metabolic activity** or uptake of the radioactive tracer in the overactive parathyroid glands. - This increased uptake is due to the **overproduction of PTH** by the affected parathyroid glands, leading to their hyperplasia or adenoma. *Panda sign* - A **panda sign** is typically observed on a **gallium scan** or **PET scan** in sarcoidosis or other granulomatous diseases, indicating bilateral symmetric uptake in the parotid and lacrimal glands. - This finding is **not characteristic of hyperparathyroidism**, which involves parathyroid gland abnormalities. *Hawkin's sign* - **Hawkin's sign** is a radiologic finding on a plain X-ray, referring to subchondral lucency in the talar dome, indicating **avascular necrosis of the talus** after ankle fracture. - It is an orthopedic finding and has **no relevance to radionuclide scans** or hyperparathyroidism. *Cold spots* - **Cold spots** on a radionuclide scan indicate areas of **decreased or absent tracer uptake**, suggesting reduced metabolic activity or tissue damage. - While some pathologies can cause cold spots, **hyperfunctioning parathyroid glands** typically show increased, not decreased, uptake.

Question 192: All of the following radioisotopes are used as systemic radionuclides, EXCEPT:

A. Strontium-89
B. Samarium-153
C. Iridium-192 (Correct Answer)
D. Phosphorus32

Explanation: ***Iridium192*** - While a radioisotope, **Iridium-192** is predominantly used in **brachytherapy**, a form of internal radiation therapy where the source is placed directly within or next to the tumor. - It is not typically administered systemically to treat widespread disease. *Strontium89* - **Strontium-89** is a **beta-emitting radionuclide** that mimics calcium and is selectively taken up by areas of increased bone turnover, such as **bone metastases** [1], [2]. - It is used systemically for palliative treatment of **pain from bone metastases** [1], [2]. *Samarium153* - **Samarium-153** is another **beta-emitting radionuclide** that targets bone metastases, similar to Strontium-89 [2]. - It is also administered systemically for **pain palliation** in patients with disseminated bone cancer [2]. *Phosphorus32* - **Phosphorus-32** is a **beta-emitter** used systemically for the treatment of **polycythemia vera** (a myeloproliferative disorder) and **bone metastases** [1]. - It accumulates in areas of rapid cell proliferation, making it effective in these systemic treatments [1].

Question 193: All isotopes are used for thyroid except:

A. I-131
B. I-123
C. I-122 (Correct Answer)
D. All of the options

Explanation: ***I-122*** - **Iodine-122** has an extremely short half-life (around 3.6 minutes) making its clinical utility for most thyroid procedures, which require longer imaging windows or therapeutic effects, impractical. - Due to its short half-life and positron emission, it is primarily used in **positron emission tomography (PET)** imaging, but not routinely for thyroid scans or therapy. *I-131* - **Iodine-131** is widely used in nuclear medicine for both the diagnosis (imaging) and treatment of thyroid diseases, particularly **hyperthyroidism** and **differentiated thyroid cancer**, due to its beta and gamma emissions. - Its relatively long half-life (8 days) allows time for uptake and accumulation in thyroid tissue, making it effective for therapy. *I-123* - **Iodine-123** is an ideal radionuclide for diagnostic thyroid imaging and uptake studies because it emits **gamma rays** suitable for SPECT imaging and has no particulate radiation (beta particles), minimizing patient radiation dose. - Its half-life of 13.2 hours is sufficient for obtaining high-quality images and physiological data. *All of the options* - This option is incorrect because **Iodine-131** and **Iodine-123** are commonly used in various thyroid diagnostic and therapeutic applications. - While Iodine-122 has limited practical use, the statement "All of the options" would imply none are used, which is false.

Question 194: Which technetium is most commonly used in bone pathology?

A. 99mTc-MDP (Correct Answer)
B. 99mTc-Sestamibi
C. 99mTc-Pyrophosphate
D. 99mTc-Exametazime

Explanation: ***99mTc-MDP*** - **Technetium-99m Methylene Diphosphonate (99mTc-MDP)** is the agent of choice for routine **bone scintigraphy** due to its optimal pharmacokinetics and high affinity for bone. - It readily binds to the **hydroxyapatite crystals** of bone, especially in areas of increased osteoblastic activity, making it excellent for detecting bone metastases, fractures, and infections. *99mTc-Sestamibi* - **Technetium-99m Sestamibi (99mTc-Sestamibi)** is primarily used for **myocardial perfusion imaging** to assess cardiac function. - It also has applications in parathyroid imaging for detecting **parathyroid adenomas**, but not for general bone pathology. *99mTc-Pyrophosphate* - **Technetium-99m Pyrophosphate (99mTc-Pyrophosphate)** was an older bone-seeking agent but has largely been replaced by MDP due to MDP's superior imaging characteristics. - Its main current use is in diagnosing **cardiac amyloidosis**, not for routine bone scans. *99mTc-Exametazime* - **Technetium-99m Exametazime (99mTc-Exametazime)**, also known as HMPAO, is specifically used for **leukocyte imaging** to detect infection and inflammation. - It is also used for **brain perfusion imaging** to assess cerebral blood flow, not for direct visualization of bone pathology.

Question 195: Investigation of choice for locating Parathyroid gland:

A. USG
B. CAT Scan
C. Angiography
D. Sestamibi scan (Correct Answer)

Explanation: ***Sestamibi scan*** - The **Sestamibi scan** (Technetium-99m Sestamibi scintigraphy) is the investigation of choice for localizing **hyperfunctioning parathyroid glands**, especially in cases of primary hyperparathyroidism. - This nuclear medicine scan uses a radiotracer that is preferentially taken up and retained by **abnormal (adenomatous or hyperplastic) parathyroid tissue**, allowing for its differentiation from normal thyroid tissue. *USG* - **Ultrasound (USG)** can visualize enlarged parathyroid glands, but its accuracy is highly dependent on the operator and the gland's location. - While useful for initial screening or guiding biopsies, it is less sensitive than Sestamibi for identifying **ectopic or smaller adenomas**. *CAT Scan* - **Computed Tomography (CT) scans** can identify enlarged parathyroid glands and rule out other neck masses, but it is not specific for parathyroid tissue. - CT involves **radiation exposure** and may not reliably distinguish hyperplastic parathyroid tissue from lymph nodes or thyroid nodules without contrast. *Angiography* - **Angiography** is an invasive procedure primarily used to visualize blood vessels and is generally not the primary investigation for locating parathyroid glands. - It might be rarely used in very complex cases to localize **ectopic glands with specific vascular supply**, but it carries higher risks and is less sensitive than nuclear imaging.

Question 196: GFR for assessment of impaired renal function is best measured by

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

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.

Question 197: A dense nephrogram is obtained by

A. Dehydrating the patient
B. Rapid (Bolus) injection of dye (Correct Answer)
C. Using non ionic media
D. Increasing the dose of contrast media

Explanation: ***Rapid (Bolus) injection of dye*** - A **rapid bolus injection** of contrast material ensures a high concentration reaches the kidneys simultaneously, leading to optimal opacification and a **dense nephrogram**. - This method allows for the collection of a **large bolus of undiluted contrast** in the renal vessels and parenchyma, improving visualization of the renal parenchyma during the nephrographic phase. - The dense nephrogram phase occurs when contrast is within the renal tubules and interstitium, producing uniform opacification. *Dehydrating the patient* - **Dehydration** would concentrate the urine in the collecting system, but it does not directly contribute to the **dense nephrogram** appearance of the renal parenchyma. - While dehydration may improve visualization of the pelvicalyceal system on delayed images, it can increase the risk of **contrast-induced nephropathy**. *Using non ionic media* - **Non-ionic contrast media** are associated with fewer adverse reactions and greater patient safety compared to ionic media due to their lower osmolality. - However, the type of contrast media (ionic vs. non-ionic) does not primarily determine the **density of the nephrogram** itself, but rather patient tolerability and safety profile. *Increasing the dose of contrast media* - While increasing the dose might provide more contrast overall, it does not guarantee a **dense nephrogram**, which requires a high concentration of contrast to be present acutely in the renal parenchyma. - A dense nephrogram is better achieved by **rapid bolus injection technique** rather than simply increasing the total dose. - Excessive contrast increases the risk of **adverse reactions** and contrast-induced nephropathy without necessarily improving nephrographic density proportionally.

Question 198: Which one of the following hepatic lesions can be diagnosed with high accuracy by using nuclear imaging?

A. Cholangiocarcinoma
B. Hepatocellular carcinoma
C. Hepatic adenoma
D. Focal nodular hyperplasia (Correct Answer)

Explanation: ***Focal nodular hyperplasia*** - **Focal nodular hyperplasia** (FNH) contains functioning Kupffer cells, which take up **Technetium-99m sulfur colloid** used in nuclear imaging. - FNH typically shows **normal or increased uptake** on sulfur colloid scans, which distinguishes it from other hepatic lesions with high accuracy. - The presence of functional **Kupffer cells and hepatocytes** allows FNH to be diagnosed with high specificity using nuclear imaging. *Cholangiocarcinoma* - **Cholangiocarcinoma** is a malignant tumor of the bile ducts and does not contain Kupffer cells. - It appears as a **photopenic defect** (decreased or absent uptake) on nuclear scans due to its lack of functional liver cells. *Hepatocellular carcinoma* - **Hepatocellular carcinoma** (HCC) is a primary liver malignancy that typically lacks functional Kupffer cells. - HCC usually shows **decreased or absent uptake** on **Technetium-99m sulfur colloid scans**, appearing as a cold lesion. *Hepatic adenoma* - A **hepatic adenoma** is a benign liver tumor that lacks Kupffer cells and thus does not take up the tracer in nuclear imaging. - Adenomas appear as **photopenic defects** on sulfur colloid scans and are better characterized by their enhancement patterns on MRI or CT.

Question 199: Isotope selectively concentrated in abscess cavities:

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

Explanation: ***Gallium*** - **Gallium-67 citrate** is incorporated into lactoferrin and transferrin, proteins that are drawn to inflammatory sites, including abscesses. - Its accumulation reflects the cellular activity and **increased vascular permeability** at the site of infection. *Technetium* - **Technetium-99m** is widely used in many different imaging studies, but it is not specifically concentrated in abscess cavities. - While it can be used to label white blood cells for infection imaging, it's not the isotope itself that is selectively concentrated in an abscess. *Chromium* - **Chromium-51** is primarily used for imaging related to red blood cell survival or gastrointestinal bleeding. - It does not have a mechanism for selective accumulation in abscess cavities. *Selenium* - **Selenium-75** is used in imaging, primarily for pancreatic or adrenal gland studies, and for assessing protein-losing enteropathy. - It does not show selective concentration in abscess cavities.

Question 200: Which of the following isotopes is not commonly used as a radioisotope in medical or industrial applications?

A. Iodine-135 (Correct Answer)
B. Iridium-192
C. Iodine-131
D. Caesium-137

Explanation: ***Iodine-135*** - **Iodine-135** has a very short half-life of 6.6 hours and decays into Xenon-135, which is a potent neutron absorber. - Its rapid decay and the problematic daughter product make it **unsuitable for routine medical or industrial applications** requiring sustained radioactivity or safe handling. *Iridium-192* - **Iridium-192** is a widely used gamma-emitting radioisotope in **brachytherapy** for cancer treatment and in **industrial radiography** for non-destructive testing of materials. - It has a half-life of 73.8 days, which is long enough for practical applications. *Iodine-131* - **Iodine-131** is a well-established radioisotope used in medicine for both **diagnosis and therapy of thyroid conditions**, including hyperthyroidism and thyroid cancer. - Its half-life of 8 days is appropriate for these clinical applications. *Caesium-137* - **Caesium-137** is used in **radiotherapy for external beam treatments**, in industrial gauges (e.g., for density and fill level measurements), and as a calibration source. - It has a relatively long half-life of 30 years, making it useful where a consistent and long-lasting gamma source is needed.

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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