Nuclear Medicine Practice Questions

Q: FDG-PET negative tumor is:

Typical carcinoid. ***Typical carcinoid*** - **Typical carcinoid tumors** generally have a low metabolic rate and thus do not avidly take up **FDG (fluorodeoxyglucose)**, appearing **FDG-PET negative**. - These tumors are characterized by low mitotic activity and lack of necrosis, contributing to their low glucose metabolism. *Atypical carcinoid* - **Atypical carcinoid tumors** have a higher proliferative index and increased metabolic activity compared to typical carcinoids. - They tend to be **FDG-PET positive** due to their higher glucose utilization. *Small cell carcinoma* - **Small cell carcinoma** is a highly aggressive tumor type with rapid proliferation and high metabolic activity. - It is typically **FDG-PET positive**, reflecting its significant glucose uptake. *Large cell neuroendocrine carcinoma* - **Large cell neuroendocrine carcinoma (LCNEC)** is also an aggressive tumor with a high mitotic rate and often exhibits necrosis. - Similar to small cell carcinoma, LCNEC is generally **FDG-PET positive** due to its high metabolic demand.

Q: Which common tracer in PET is usually administered in the form of a glucose sugar?

Fluorine 18. ***Fluorine 18*** - **18F-FDG** (Fluorodeoxyglucose) is the most common PET tracer, utilizing **Fluorine-18** as its radioactive component. - FDG is a glucose analog, meaning it mimics glucose and is taken up by metabolically active cells, allowing for imaging of **glucose metabolism**. *Aluminum - 12* - **Aluminum-12** is not a common radionuclide used in PET imaging. - The most common tracers in PET are **positron emitters** like Fluorine-18, Carbon-11, Nitrogen-13, and Oxygen-15. *Carbon 11* - **Carbon-11** can be used in PET tracers (e.g., 11C-methionine), but it is **less common** than 18F-FDG due to its shorter half-life. - Its short half-life (20 minutes) requires an **on-site cyclotron** for production, limiting its widespread use. *Oxygen 15* - **Oxygen-15** is employed in PET tracers (e.g., 15O-water for cerebral blood flow), but it has an **even shorter half-life** (2 minutes) than Carbon-11. - Its extremely short half-life makes it **impractical** for routine clinical use in the form of a glucose sugar.

Q: 99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of

GI Bleeding. ***GI Bleeding*** - Technetium-99m labeled RBC scintigraphy (** 99m Tc-RBC scan**) is highly sensitive for detecting **active gastrointestinal bleeding**, especially slow or intermittent bleeding. - The labeled red blood cells extravasate at the site of bleeding, accumulating and outlining the bleeding focus over time. *Hepatoma* - **Hepatoma** (hepatocellular carcinoma) is primarily diagnosed using imaging modalities like **CT, MRI**, and **ultrasound**, often with contrast enhancement. - While nuclear medicine scans like **FDG-PET** can be used in some cases for staging or assessing viability, 99m Tc-RBC scans are not a primary diagnostic tool for hepatoma. *Left ventricular function wall motion* - **Left ventricular function** and **wall motion abnormalities** are typically assessed using **echocardiography**, cardiac **MRI**, or **nuclear cardiology studies** like **SPECT** or **PET** using tracers that localize in the myocardium (e.g., 99m Tc-Sestamibi or Thallium-201). - 99m Tc-RBC scans are sometimes used for **gated blood pool scans** to assess global ejection fraction, but not directly for wall motion analysis in the same way as other dedicated cardiac modalities. *Hepatic hemangioma* - **Hepatic hemangiomas** can be characterized by ** 99m Tc-RBC scintigraphy**, which shows **early photopenia** followed by **delayed fill-in and retention** of the tracer due to the characteristic slow blood flow within these benign vascular tumors. - While it can be used for confirmation, it's not the most commonly used primary diagnostic tool (which is often **ultrasound** or **MRI** with specific contrast patterns), and GI bleeding is a more direct application where the scan detects extravasation rather than vascular pooling.

Q: Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?

Meckel's diverticulum. ***Meckel's diverticulum*** - **Meckel's diverticulum** is a **congenital outpouching** of the small intestine that often contains **ectopic gastric mucosa**. - The **Tc-99m pertechnetate scan** identifies the **parietal cells of ectopic gastric mucosa**, which absorb and secrete pertechnetate, making it the diagnostic modality of choice. *Duodenal diverticulum* - A **duodenal diverticulum** is an **outpouching of the duodenum** and typically does not contain ectopic gastric mucosa. - It is usually **asymptomatic** and incidentally found during imaging for other conditions. *Pharyngeal diverticulum* - A **pharyngeal diverticulum**, also known as **Zenker's diverticulum**, is an outpouching of the **posterior hypopharynx**. - It does not contain gastric mucosa and is typically diagnosed with a **barium swallow study**. *Colonic diverticulum* - **Colonic diverticula** are **sac-like protrusions** of the colonic wall, often found in the sigmoid colon. - They are diagnosed with **colonoscopy** or **CT colonography** and do not contain gastric mucosa.

Q: The Renal function is best assessed by:

Tc 99m MAG3. ***Tc 99m MAG3*** - **Technetium-99m mercaptoacetyltriglycine (MAG3)** is the **preferred agent for dynamic renal scintigraphy** and assessment of **overall renal function**. - It is a **renal tubular agent** with a high extraction fraction (40-50%) that assesses **effective renal plasma flow (ERPF)** and **tubular secretion**. - **Superior to DTPA** for functional assessment due to better image quality, faster clearance, and excellent performance even in **impaired renal function**. - Provides comprehensive evaluation of **renal perfusion, function, and excretion** in a single study. *Tc 99m DMSA* - **Technetium-99m dimercaptosuccinic acid (DMSA)** is a **cortical imaging agent** used primarily for **static renal imaging**. - Excellent for assessing **renal anatomy**, detecting **cortical scarring**, **pyelonephritis**, and **differential renal function**. - It binds to the cells of the **proximal tubules** and is retained (40-50% at 6 hours), making it unsuitable for dynamic functional studies or excretion assessment. *Tc 99m DTPA* - **Technetium-99m diethylenetriaminepentaacetic acid (DTPA)** is a **glomerular filtration agent** used to measure **GFR**. - Excreted solely by **glomerular filtration** (no tubular secretion), making it the gold standard for **GFR measurement**. - However, it has a **lower extraction fraction (20%)** compared to MAG3, resulting in poorer image quality and less reliable assessment in patients with **impaired renal function**. - MAG3 has largely replaced DTPA as the preferred agent for routine dynamic renal studies. *Tc 99m pertechnetate* - **Technetium-99m pertechnetate** is primarily used for **thyroid imaging** and detecting **Meckel's diverticulum** (taken up by mucous-secreting cells). - **Not used for renal function assessment** as it does not provide reliable information about glomerular or tubular function.

Q: Isotope used in RAIU (Radioactive Iodine Uptake test) is:

I123. ***I123*** - **Iodine-123 (I-123)** is the preferred isotope for **Radioactive Iodine Uptake (RAIU)** tests due to its ideal physical characteristics. - It emits **gamma rays** suitable for imaging, has a relatively short half-life of 13 hours, and minimal beta emissions, reducing patient radiation exposure. *I131* - **Iodine-131 (I-131)** is primarily used for **thyroid ablation** and treatment of thyroid cancers due to its high-energy beta emissions, which are destructive to tissue. - While it can be used for imaging, its longer half-life and higher radiation dose make it less ideal for diagnostic uptake studies compared to I-123. *I125* - **Iodine-125 (I-125)** has a very long half-life (59 days) and emits low-energy gamma photons and X-rays. - It is often used in **radioimmunoassays (RIAs)** and for brachytherapy, not typically for diagnostic RAIU scans. *I127* - **Iodine-127 (I-127)** is the **stable, non-radioactive** isotope of iodine that is naturally abundant in the body and in nutritional sources. - It is not used in radioactive uptake studies because it does not emit radiation.

Q: In the evaluation of a suspected hepatic hemangioma, what is the expected behavior of Tc-99m labeled RBCs during scintigraphy?

Increased uptake on delayed images. ***Increased uptake on delayed images*** - Hepatic hemangiomas are vascular malformations with **slow blood flow** within their extensive sinusoidal spaces. - This slow flow causes the **Tc-99m labeled RBCs** to accumulate gradually and remain trapped within the lesion, leading to characteristic increased uptake on delayed images (typically 1-2 hours after injection). *Decreased uptake on delayed images* - This pattern would suggest **washout** of the tracer, which is not characteristic of hemangiomas where the tracer is retained due to sluggish flow. - It could be seen in highly vascular but non-hemangioma lesions where tracer clearance is rapid. *No uptake* - Lack of uptake would indicate a **non-vascular lesion** or a lesion with very poor perfusion, which is not consistent with a hemangioma's highly vascular nature. - While initial images might show less uptake than surrounding liver due to slow flow, delayed images will show accumulation. *Diffuse uptake* - **Diffuse uptake** throughout the liver would indicate normal liver parenchyma or a condition affecting the entire organ, not a localized benign tumor like a hemangioma. - Hemangiomas are typically discrete lesions that show focal uptake.

Q: A lady presented with a 4 cm tumor in the left parietal lobe for which she underwent surgery and radiotherapy. After 3 months she presented with headache and vomiting. Which of the following would characterize the lesion in the patient?

18FDG PET Scan. ***18FDG PET Scan*** - This patient, presenting with new neurological symptoms after **surgery and radiotherapy** for a cerebral tumor, faces a diagnostic dilemma: differentiating between **tumor recurrence** and **radiation necrosis**. - **18FDG PET scans** effectively distinguish between these two conditions because viable tumor cells exhibit high metabolic activity and thus actively take up **fluorodeoxyglucose (FDG)**, while radiation necrosis is metabolically inactive and shows little to no FDG uptake. *Digital subtraction angiography with dual source CT scan* - **Digital subtraction angiography (DSA)** is primarily used to visualize **vascular structures** and is not the modality of choice for differentiating tumor recurrence from radiation necrosis. - A **dual-source CT scan** is useful for rapid imaging and dynamic studies but lacks the metabolic information needed for this specific differentiation. *Gd-enhanced MRI* - While **Gd-enhanced MRI** is excellent for detecting **structural changes** and **blood-brain barrier disruption**, it often cannot definitively differentiate between **tumor recurrence** and **radiation necrosis**. - Both conditions can present with similar **enhancement patterns** on MRI, making differentiation challenging without additional metabolic information. *99Tc-HMPAO SPECT brain* - **99mTc-HMPAO SPECT** measures **regional cerebral blood flow (rCBF)**, which can be altered in both tumors and areas of radiation injury. - However, it does not provide the specific metabolic information (glucose metabolism) needed to reliably distinguish between **viable tumor cells** and **radiation necrosis** as effectively as FDG PET.

Q: Tc-labeled RBCs are used for all except:

Liver adenoma. ***Liver adenoma*** - Tc-labeled RBCs are primarily used to highlight a specific type of tissue or process. **Liver adenomas** do not typically show an affinity for **Tc-labeled RBCs**, as they are benign epithelial tumors with a different vascular composition. - While adenomas can be vascular, they do not inherently contain the **vascular pooling** or blood volume characteristics that would be specifically targeted by **Tc-labeled RBCs** for diagnostic imaging. *LV function* - **Tc-labeled RBCs** (or Tc-99m-pertechnetate) are commonly used in **gated blood pool imaging** (MUGA scan) to assess **left ventricular (LV) function**, including **ejection fraction** and wall motion abnormalities. - This technique directly visualizes the blood pool within the cardiac chambers, making it suitable for assessing functional parameters of the heart. *GI bleeding* - **Tc-labeled RBCs** are a standard imaging agent for detecting and localizing **active gastrointestinal (GI) bleeding**, especially when the bleeding rate is intermittent or slow. - The labeled RBCs extravasate at the site of hemorrhage, creating a 'hot spot' that can be identified over time. *Liver hemangioma* - **Tc-labeled RBCs** are highly effective in diagnosing **liver hemangiomas**, which are benign vascular tumors composed of large, dilated blood vessels. - These lesions show characteristic uptake and retention of **labeled RBCs** due to their slow blood flow and large intravascular space, appearing as early peripheral enhancement with subsequent centripetal filling.

Q: In a patient presenting with jaundice, the HIDA scan would be most useful for which of the following:

Biliary atresia. ***Biliary atresia*** - A **HIDA scan** (hepatobiliary iminodiacetic acid scan) is instrumental in diagnosing biliary atresia by demonstrating the **absence of bile flow** into the duodenum. - In infants with persistent jaundice, the failure of the tracer to appear in the small bowel after a prolonged period strongly suggests this condition, indicating **obstructed or absent bile ducts**. *Cholelithiasis* - While HIDA scans can detect **cystic duct obstruction** in acute cholecystitis, they are less definitive for uncomplicated cholelithiasis (gallstones without acute inflammation). - **Ultrasound** is typically the primary imaging modality for diagnosing gallstones due to its non-invasiveness and ability to visualize stones directly. *Benign biliary disease* - This is a broad category, and while a HIDA scan can assess bile flow, it's not the **primary diagnostic tool** for all benign biliary conditions. - For most benign biliary diseases (e.g., choledocholithiasis without acute cholecystitis), **ultrasound, ERCP, or MRCP** often provide more detailed anatomical information. *Bile duct carcinoma* - A HIDA scan might show **obstructed bile flow** in bile duct carcinoma (cholangiocarcinoma), but it does not provide the detailed anatomical information or staging necessary for diagnosis and treatment planning. - **CT, MRI, MRCP, or ERCP** with biopsy are far more effective for identifying, characterizing, and staging bile duct malignancies.

Question 1

FDG-PET negative tumor is:

Accepted Answer

Typical carcinoid

Answer

Atypical carcinoid

Answer

Small cell carcinoma

Answer

Large cell neuroendocrine carcinoma

Question 2

Which common tracer in PET is usually administered in the form of a glucose sugar?

Accepted Answer

Fluorine 18

Answer

Aluminum - 12

Answer

Carbon 11

Answer

Oxygen 15

Question 3

99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of

Accepted Answer

GI Bleeding

Answer

Hepatoma

Answer

Left ventricular function wall motion

Answer

Hepatic hemangioma

Question 4

Which one of the following conditions is diagnosed by Tc-99m Pertechnetate Scintigraphy?

Accepted Answer

Meckel's diverticulum

Answer

Duodenal diverticulum

Answer

Pharyngeal diverticulum

Answer

Colonic diverticulum

Question 5

The Renal function is best assessed by:

Accepted Answer

Tc 99m MAG3

Answer

Tc 99m DMSA

Answer

Tc 99m DTPA

Answer

Tc 99m pertechnetate

Question 6

Isotope used in RAIU (Radioactive Iodine Uptake test) is:

Accepted Answer

I123

Answer

I131

Answer

I125

Answer

I127

Question 7

In the evaluation of a suspected hepatic hemangioma, what is the expected behavior of Tc-99m labeled RBCs during scintigraphy?

Accepted Answer

Increased uptake on delayed images

Answer

Decreased uptake on delayed images

Answer

No uptake

Answer

Diffuse uptake

Question 8

A lady presented with a 4 cm tumor in the left parietal lobe for which she underwent surgery and radiotherapy. After 3 months she presented with headache and vomiting. Which of the following would characterize the lesion in the patient?

Accepted Answer

18FDG PET Scan

Answer

Digital subtraction angiography with dual source CT scan

Answer

Gd-enhanced MRI

Answer

99Tc-HMPAO SPECT brain

Question 9

Tc-labeled RBCs are used for all except:

Accepted Answer

Liver adenoma

Answer

LV function

Answer

GI bleeding

Answer

Liver hemangioma

Question 10

In a patient presenting with jaundice, the HIDA scan would be most useful for which of the following:

Accepted Answer

Biliary atresia

Answer

Cholelithiasis

Answer

Benign biliary disease

Answer

Bile duct carcinoma

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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