Nuclear Medicine Practice Questions

Q: Investigation of choice for locating Parathyroid gland:

Sestamibi scan. ***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.

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

DTPA. ***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.

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

Focal nodular hyperplasia. ***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.

Q: Isotope selectively concentrated in abscess cavities:

Gallium. ***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.

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

Iodine-135. ***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.

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

Warthin tumor. ***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.

Q: Technetium-99m scan is used for diagnosis of -

Meckel's diverticulum. ***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.

Q: Radioisotope used for thyroid treatment of metastasis/ablation

I-131. ***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.

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

DTPA renogram. ***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.

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

Technetium-99m linked to Methylene diphosphonate. ***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 1

Investigation of choice for locating Parathyroid gland:

Accepted Answer

Sestamibi scan

Answer

USG

Answer

CAT Scan

Answer

Angiography

Question 2

GFR for assessment of impaired renal function is best measured by

Accepted Answer

DTPA

Answer

MAG3

Answer

IodoHippurate

Answer

DMSA Scan

Question 3

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

Accepted Answer

Focal nodular hyperplasia

Answer

Cholangiocarcinoma

Answer

Hepatocellular carcinoma

Answer

Hepatic adenoma

Question 4

Isotope selectively concentrated in abscess cavities:

Accepted Answer

Gallium

Answer

Technetium

Answer

Chromium

Answer

Selenium

Question 5

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

Accepted Answer

Iodine-135

Answer

Iridium-192

Answer

Iodine-131

Answer

Caesium-137

Question 6

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

Accepted Answer

Warthin tumor

Answer

Pleomorphic adenoma

Answer

Acinic cell tumor

Answer

Adenoid cystic carcinoma

Question 7

Technetium-99m scan is used for diagnosis of -

Accepted Answer

Meckel's diverticulum

Answer

Obstruction

Answer

Volvulus

Answer

Appendix

Question 8

Radioisotope used for thyroid treatment of metastasis/ablation

Accepted Answer

I-131

Answer

I-90

Answer

I-83

Answer

I-123

Question 9

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

Accepted Answer

DTPA renogram

Answer

Creatinine clearance

Answer

Ultrasonography

Answer

IVU

Question 10

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

Accepted Answer

Technetium-99m linked to Methylene diphosphonate

Answer

Gallium 67

Answer

Technetium-99m

Answer

Technetium-sulfur-colloid

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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