Nuclear Medicine Practice Questions

Q: A long distance runner complains of pain in the foot causing reduction in his performance. His X-ray and MRI foot are normal. He was advised to undergo a nuclear scan as shown below. Which tracer is used in this scan? (Recent NEET Pattern 2016-17)

18-F Fluoride. ***18-F Fluoride*** - Among the listed PET tracers, **18-F Fluoride** is the bone-seeking radiotracer used for bone imaging - 18-F Fluoride PET provides high-resolution imaging of bone turnover and blood flow, and can detect stress fractures with high sensitivity - It localizes to areas of increased bone metabolism and osteoblastic activity, making it effective for detecting subtle stress injuries - **Note:** In routine clinical practice, **Tc-99m MDP (methylene diphosphonate)** is the standard tracer for conventional bone scintigraphy to detect stress fractures; however, among the PET tracers listed here, 18-F Fluoride is the appropriate bone imaging agent *FMISO (Fluoromisonidazole)* - **FMISO** is a **hypoxia tracer** used in PET imaging to identify areas of low oxygen tension - Primarily used in oncology to assess tumor hypoxia, not for bone or musculoskeletal imaging - Not indicated for evaluating stress fractures or bone metabolism *FLT (Fluorothymidine)* - **FLT** is a **proliferation tracer** that measures cellular DNA synthesis and proliferation - Mainly used in oncology to assess tumor growth and treatment response - Does not assess bone metabolism or detect stress fractures *64-Cu-ATSM* - **64-Cu-ATSM** is another **hypoxia tracer** used in PET imaging, similar to FMISO - Used to evaluate tissue hypoxia in cancer imaging - Not indicated for musculoskeletal injuries or bone metabolism assessment

Q: The following image shows: (Recent NEET Pattern 2016-17)

PET-CT scan. ***PET-CT scan*** - The image displays a **fusion of anatomical detail** (like bone and organ outlines, typical of CT) and **metabolic activity** (represented by areas of increased tracer uptake, characteristic of PET). - The anatomical structures are visible in grayscale/darker tones, while areas of high metabolic activity (e.g., in the brain, heart, and liver) are shown in vivid colors (red, orange, yellow), indicating the combined nature of PET-CT. *PET scan* - A standalone PET scan would primarily show areas of **metabolic activity** and tracer uptake, but with significantly **less anatomical detail** and structural context compared to the image provided. - While it would show areas of high activity in colors, the underlying structural images (like rib cage, outline of organs) would be absent or very blurred. *MUGA scan* - A MUGA scan (Multi-Gated Acquisition scan) is used to assess **cardiac function** and primarily shows the heart chambers in motion to calculate ejection fraction. - The image provided is a whole-body scan, not focused on cardiac motion, and displays different imaging modalities. *HIDA scan* - A HIDA scan (Hepatobiliary Iminodiacetic Acid scan) is a nuclear medicine imaging test used to diagnose problems of the **liver, gallbladder, and bile ducts**. - This scan would exclusively show the hepatobiliary system and its function, which is not what is depicted in this comprehensive whole-body image.

Q: A patient was started on RCHOP regimen for NHL. The investigation shown below was done to monitor response to treatment. What is the investigation?

PET scan. ***PET scan*** - The image displays a **whole-body imaging technique** with areas of increased **radiotracer uptake**, characteristic of **PET-CT (positron emission tomography) scans** using **FDG (fluorodeoxyglucose)**. - **FDG-PET-CT** is the **gold standard** for **staging and monitoring treatment response** in lymphomas, including NHL treated with RCHOP regimen. - It detects areas of **high metabolic activity** typical of viable tumor cells, and response is assessed using **Deauville criteria** or **Lugano classification**. - Post-treatment PET-CT helps differentiate between **residual viable tumor** and **fibrotic tissue**, which is crucial for management decisions. *HIDA scan* - A HIDA (hepatobiliary iminodiacetic acid) scan primarily evaluates the **hepatobiliary system** (gallbladder and bile ducts) for conditions like **acute cholecystitis** or bile duct obstruction. - It uses Tc-99m labeled radiopharmaceutical and does not produce a whole-body image with generalized metabolic uptake as shown. *MUGA scan* - A MUGA (multi-gated acquisition) scan is used to assess **cardiac function**, specifically the **left ventricular ejection fraction (LVEF)**. - It's often performed **before and during anthracycline therapy** (like doxorubicin in RCHOP) to monitor for cardiotoxicity. - It focuses on the heart and does not provide a whole-body metabolic assessment for tumor response. *Bone scintigraphy* - **Bone scintigraphy** (bone scan) uses Tc-99m MDP to visualize **bone metabolism** and detect fractures, infections, or skeletal metastases. - While it uses a radiotracer, the uptake pattern is limited to the skeletal system and shows **osteoblastic activity**, unlike PET-CT which shows soft tissue and nodal metabolic activity throughout the body.

Q: Comment on the diagnosis from the thyroid scan shown below. (AIIMS May 2017)

Hypersecreting adenoma. ***Hypersecreting adenoma*** - The thyroid scan shows a **single, intensely "hot" nodule**, indicating increased uptake of the radioactive tracer in a localized area. - This pattern is characteristic of a **hyperfunctioning thyroid adenoma**, where the adenoma produces hormones independently, leading to suppression of the rest of the normal thyroid tissue (which appears "cold" or has reduced uptake). *Papillary cancer thyroid* - Papillary thyroid cancer typically appears as a **"cold" nodule** on a thyroid scan, meaning it has reduced or no tracer uptake. - Malignant nodules generally do **not accumulate iodine** as efficiently as normal thyroid tissue or hyperfunctioning benign nodules. *Grave's disease* - Grave's disease presents with **diffuse uptake of the tracer** throughout the entire thyroid gland, not a single localized hot nodule. - The entire gland is generally enlarged and hyperactive, showing **symmetrically increased uptake**. *Lateral aberrant thyroid* - A lateral aberrant thyroid refers to **ectopic thyroid tissue** usually found in the neck, often in lymph nodes due to metastatic papillary carcinoma. - While it involves thyroid tissue outside the normal gland, it wouldn't typically manifest as a single hyperfunctioning nodule within the main thyroid gland, and most ectopic thyroid tissue would show varying uptake depending on its function or if it's metastatic cancer.

Q: Positron Emission Tomography (PET) used in Preoperative staging of Gastro Oesophageal tumours is to detect

Distant metastatic disease. ***Distant metastatic disease*** - **PET scans** are highly sensitive for detecting metabolically active lesions, making them excellent for identifying **distant metastases** in organs such as the liver, lungs, and bone, which significantly impacts surgical planning. - Identifying **distant metastatic disease** with PET helps in determining if the patient is a candidate for curative surgery or if palliative treatment is more appropriate. *Local spread* - While PET can show increased metabolic activity in the primary tumor, its resolution is often insufficient to precisely delineate the **local extent** of tumor invasion into adjacent tissues, which is better evaluated by **endoscopic ultrasound (EUS)** or **CT scan**. - Assessing local invasion is crucial for determining resectability, but PET's primary role isn't detailed local staging. *Lymph node status* - **PET scans** can detect metabolically active lymph nodes, but they have limitations in differentiating between inflammatory and malignant nodes, especially for very small metastases, leading to potential false positives or negatives. - **Endoscopic ultrasound (EUS)** with fine-needle aspiration (FNA) is generally considered superior for accurate regional **lymph node staging** in gastroesophageal cancer. *Extension into stomach* - The precise **intramural extension** of the tumor within the esophagus and into the stomach is often difficult to determine accurately with PET due to its relatively poor spatial resolution compared to other imaging modalities like **endoscopic ultrasound (EUS)** and **CT**. - **Endoscopic assessment** directly visualizes the tumor and can determine its macroscopic extent into the stomach more precisely than PET.

Q: Best way to localize extra-adrenal pheochromocytoma:

Nuclear medicine scan (MIBG scan). ***Nuclear medicine scan (MIBG scan)*** - **Iodine-131-metaiodobenzylguanidine (MIBG) scan** is the imaging modality of choice for localizing extra-adrenal pheochromocytomas due to its high specificity for **neuroendocrine tumors** like pheochromocytomas and paragangliomas. - MIBG is structurally similar to **norepinephrine** and is actively taken up by adrenergic neurons, allowing visualization of hypersecreting chromaffin cells wherever they are located in the body. *X-ray* - **X-rays** provide limited soft tissue detail and are generally not useful for localizing pheochromocytomas, especially extra-adrenal ones. - They may show calcifications in some tumors but lack the sensitivity and specificity needed for definitive localization. *Clinical examination* - A **clinical examination** can identify signs and symptoms suggestive of pheochromocytoma (e.g., hypertension, palpitations, sweating) but cannot localize the tumor itself. - Localization requires **imaging studies** due to the variable and often deep-seated location of these tumors. *VMA excretion* - **Vanillylmandelic acid (VMA) excretion** is a biochemical test used to diagnose pheochromocytoma by measuring catecholamine metabolites in urine. - While it confirms the presence of a catecholamine-secreting tumor, it provides **no information about the tumor's location**.

Q: Radiopharmaceutical used for phagocyte study scan:

Sulfur colloid scan. ***Sulfur colloid scan*** - **Sulfur colloid** is readily phagocytosed by **Kupffer cells** in the liver and spleen, making it useful for evaluating their function. - This scan allows for the assessment of the **reticuloendothelial system's phagocytic activity**, which involves various phagocytes. *MDP scan* - **MDP (methylene diphosphonate)** is used primarily for **bone scans** to detect bone abnormalities, infections, or tumors. - It accumulates in areas of increased **osteoblastic activity**, not phagocytic activity. *Thallium 201* - **Thallium 201** is largely used in **myocardial perfusion imaging** to assess blood flow to the heart muscle. - It acts as a potassium analog and is taken up by viable myocardial cells, not phagocytes. *Technetium pertechnetate scan* - **Technetium pertechnetate** is commonly used for **thyroid scans**, Meckel's diverticulum scans, and brain scans. - It accumulates in glandular tissues with active transport mechanisms involving iodide, and is not involved in phagocyte studies.

Q: Hot spot in heart is seen in which scan

Tc pyrophosphate scan. ***Tc pyrophosphate scan*** - A **technetium-99m pyrophosphate (Tc-PYP) scan** demonstrates a "hot spot" in the heart in cases of **acute myocardial infarction** due to the tracer binding to calcium deposits in necrotic cardiomyocytes. - This hot spot indicates recent myocardial damage and is particularly useful in diagnosing **amyloidosis** (specifically transthyretin cardiac amyloidosis) where the tracer binds to amyloid fibrils. *Thallium* - **Thallium-201** is used in myocardial perfusion imaging to assess areas of reduced blood flow or infarction, creating a "cold spot" (decreased uptake). - It acts as a potassium analog and is taken up by viable myocardial cells, thus areas of ischemia or necrosis appear as defects rather than hot spots. *Gallium* - **Gallium-67** scans are primarily used to detect infection and inflammation, as well as certain tumors. - While it can accumulate in areas of inflammation in the heart (e.g., myocarditis), it does not create a characteristic "hot spot" associated with acute myocardial infarction. *Albumin labelled* - **Technetium-99m labeled albumin** (e.g., Technetium-99m macroaggregated albumin, MAA) is typically used for lung perfusion scans to diagnose pulmonary embolism or for gastrointestinal bleeding studies. - It is not used for direct assessment of myocardial damage or to create a "hot spot" in the heart for ischemic events.

Q: Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?

Tc-99m Pyrophosphate. ***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.

Q: Isotope used in ventriculography is

Technetium (Tc). ***Technetium (Tc)*** - **Technetium-99m** is the most commonly used radioisotope in nuclear medicine for various imaging studies, including **ventriculography**. - It is preferred due to its short half-life (6 hours), favorable energy emission (140 keV), and availability, making it ideal for tracking blood flow within the **cardiac ventricles**. *Diatrizoate* - **Diatrizoate** is an **iodinated contrast medium** primarily used in conventional X-ray angiography and computed tomography (CT) scans. - It is not a radioisotope and therefore cannot be used for nuclear medicine procedures like **radionuclide ventriculography**. *Gallium* - **Gallium (Ga-67)** is a radioisotope used in nuclear medicine, but its primary application is in **tumor and infection imaging**, particularly for inflammatory conditions and lymphomas. - It is not suitable for **ventriculography** as it localizes in different tissues and organs, not specifically in cardiac chambers for blood pool imaging. *Lipoidate* - **Lipoidate (Ethiodized oil)** is an **iodinated oil-based contrast agent** historically used for lymphangiography and myelography. - It is not a radioisotope and is not used for **cardiac ventriculography**.

Question 1

A long distance runner complains of pain in the foot causing reduction in his performance. His X-ray and MRI foot are normal. He was advised to undergo a nuclear scan as shown below. Which tracer is used in this scan? (Recent NEET Pattern 2016-17)

Accepted Answer

18-F Fluoride

Answer

FMISO (Fluoromisonidazole)

Answer

FLT (Fluorothymidine)

Answer

64-Cu-ATSM

Question 2

The following image shows: (Recent NEET Pattern 2016-17)

Accepted Answer

PET-CT scan

Answer

PET scan

Answer

MUGA scan

Answer

HIDA scan

Question 3

A patient was started on RCHOP regimen for NHL. The investigation shown below was done to monitor response to treatment. What is the investigation?

Accepted Answer

PET scan

Answer

HIDA scan

Answer

MUGA scan

Answer

Bone scintigraphy

Question 4

Comment on the diagnosis from the thyroid scan shown below. (AIIMS May 2017)

Accepted Answer

Hypersecreting adenoma

Answer

Papillary cancer thyroid

Answer

Grave's disease

Answer

Lateral aberrant thyroid

Question 5

Positron Emission Tomography (PET) used in Preoperative staging of Gastro Oesophageal tumours is to detect

Accepted Answer

Distant metastatic disease

Answer

Local spread

Answer

Lymph node status

Answer

Extension into stomach

Question 6

Best way to localize extra-adrenal pheochromocytoma:

Accepted Answer

Nuclear medicine scan (MIBG scan)

Answer

X-ray

Answer

Clinical examination

Answer

VMA excretion

Question 7

Radiopharmaceutical used for phagocyte study scan:

Accepted Answer

Sulfur colloid scan

Answer

MDP scan

Answer

Thallium 201

Answer

Technetium pertechnetate scan

Question 8

Hot spot in heart is seen in which scan

Accepted Answer

Tc pyrophosphate scan

Answer

Thallium

Answer

Gallium

Answer

Albumin labelled

Question 9

Which radioisotope is PRIMARILY used for detecting acute myocardial infarction rather than assessing myocardial perfusion?

Accepted Answer

Tc-99m Pyrophosphate

Answer

Thallium 201

Answer

Tc-99m Sestamibi

Answer

18-FDG PET

Question 10

Isotope used in ventriculography is

Accepted Answer

Technetium (Tc)

Answer

Diatrizoate

Answer

Gallium

Answer

Lipoidate

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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