Nuclear Medicine Practice Questions

Q: Tc HMPAO SPECT is used for what type of imaging?

Cerebral perfusion imaging. **Explanation:** **Tc-99m HMPAO** (Hexamethylpropyleneamine oxime), also known as **Exametazime**, is a lipophilic radiopharmaceutical used primarily for **Cerebral Perfusion Imaging**. Because it is lipophilic, it can cross the intact blood-brain barrier (BBB) via passive diffusion. Once inside the brain cells, it is converted into a hydrophilic form that becomes "trapped," allowing for SPECT (Single Photon Emission Computed Tomography) imaging that reflects regional cerebral blood flow (rCBF). This is clinically vital for evaluating stroke, dementia (e.g., Alzheimer’s), and localizing epileptic foci. **Analysis of Incorrect Options:** * **B. Renal imaging:** Common agents include **Tc-99m DTPA** (for GFR) and **Tc-99m MAG3** (for tubular secretion). **Tc-99m DMSA** is used for renal cortical mapping. * **C. Parathyroid imaging:** The gold standard is **Tc-99m Sestamibi** (MIBI) using a dual-phase technique, as it washes out slower from parathyroid adenomas than from thyroid tissue. * **D. Thyroid imaging:** Primarily uses **Iodine-131**, **Iodine-123**, or **Tc-99m Pertechnetate**, which is trapped by the thyroid gland via the sodium-iodide symporter. **High-Yield Clinical Pearls for NEET-PG:** * **Brain Death:** Tc-99m HMPAO is a confirmatory test; a "hollow skull sign" (absence of tracer uptake in the cerebrum) indicates brain death. * **WBC Labeling:** Apart from brain imaging, Tc-99m HMPAO is used to label **leukocytes** (WBCs) to localize sites of occult infection or inflammatory bowel disease. * **ECD (Ethyl Cysteinate Dimer):** Another lipophilic agent used for brain perfusion, often preferred over HMPAO due to faster blood clearance and better stability.

Q: Which of the following agents does not increase the sensitivity of a Tc-pertechnetate scan?

Metoclopramide. **Explanation:** The **Tc-99m Pertechnetate scan** (Meckel’s scan) is the investigation of choice for detecting a Meckel’s diverticulum containing ectopic gastric mucosa. The pertechnetate ion is actively taken up by the **mucoid cells** of the gastric mucosa. To improve the sensitivity of the scan (i.e., the target-to-background ratio), pharmacological adjuncts are used to either increase uptake or delay the clearance of the tracer. **Why Metoclopramide is the correct answer:** Metoclopramide is a prokinetic agent that increases gastrointestinal motility. By stimulating peristalsis, it promotes the rapid washout of the radiopharmaceutical from the ectopic gastric mucosa into the distal bowel. This **decreases** the scan's sensitivity by blurring the focal "hot spot" and increasing background activity. **Analysis of Incorrect Options:** * **Pentagastrin (Option D):** A potent stimulator of gastric secretions. It increases the metabolic activity and uptake of Tc-99m pertechnetate by the gastric mucosa, making the diverticulum more visible. * **Cimetidine (Option C):** An H2-receptor blocker. It does not prevent uptake but inhibits the *release* of pertechnetate from the mucosal cells into the intestinal lumen, thereby retaining the tracer within the ectopic tissue for longer. * **Glucagon (Option A):** An anti-peristaltic agent. It induces intestinal hypotonia, which minimizes the "washout" of the tracer and keeps it localized at the site of the diverticulum. **High-Yield Clinical Pearls for NEET-PG:** * **Meckel’s Diverticulum Rule of 2s:** 2% of population, 2 inches long, 2 feet from ileocecal valve, 2 types of ectopic tissue (Gastric > Pancreatic). * **Most common presentation:** Painless lower GI bleeding in a child. * **False Negatives:** Can occur if there is insufficient gastric mucosa (<1.8 cm²) or rapid transit. * **False Positives:** Intussusception, inflammatory bowel disease, or vascular malformations.

Q: Radionuclide scans are useful in all of the following except:

Local staging of tumors. **Explanation:** Radionuclide scans (Nuclear Medicine) are functional imaging modalities that rely on the physiological activity of tissues rather than detailed anatomical structure. **Why "Local staging of tumors" is the correct answer:** Local staging (T-staging) requires high **spatial resolution** to determine the exact depth of invasion, involvement of adjacent layers, and precise anatomical boundaries. Radionuclide scans (like PET or Bone scans) have poor spatial resolution compared to **MRI or CT**, making them unsuitable for local staging. While PET-CT is excellent for *distant* metastasis (M-staging), it cannot replace MRI/CT for assessing the local extent of a primary tumor. **Why the other options are incorrect:** * **Gastrointestinal bleed:** **99mTc-labeled RBC scans** are highly sensitive for detecting active GI bleeds, capable of detecting rates as low as 0.1 mL/min (more sensitive than angiography). * **Cholecystitis:** **HIDA scan** (Cholescintigraphy) is the **gold standard** for diagnosing acute calculous cholecystitis. Non-visualization of the gallbladder indicates cystic duct obstruction. * **Intraabdominal abscess:** **Gallium-67** or **In-111 labeled Leukocyte (WBC) scans** are specifically used to localize occult infections and abscesses by targeting inflammatory activity. **High-Yield Clinical Pearls for NEET-PG:** * **Meckel’s Diverticulum:** Diagnosed using **99mTc-Pertechnetate** (Meckel’s scan), which targets ectopic gastric mucosa. * **Bone Scan (99mTc-MDP):** Most sensitive for early bone metastasis (except in Multiple Myeloma, where it is often negative). * **Renal Scans:** **DTPA** (Glomerular filtration), **MAG3** (Tubular secretion), and **DMSA** (Renal cortical scarring—the gold standard).

Q: A patient presented with right upper quadrant pain and dyspepsia. Ultrasound showed an edematous gallbladder wall. What is the most sensitive investigation to confirm the suspected diagnosis?

Hepatobiliary iminodiacetic acid (HIDA) scan. **Explanation:** The clinical presentation of right upper quadrant pain, dyspepsia, and an edematous gallbladder wall on ultrasound strongly suggests **Acute Cholecystitis**. **Why HIDA Scan is the Correct Answer:** While Ultrasonography (USG) is the initial investigation of choice due to its availability and lack of radiation, the **Hepatobiliary iminodiacetic acid (HIDA) scan** is the **most sensitive (97%) and specific (90%)** investigation for confirming acute cholecystitis. * **Mechanism:** The HIDA scan (Cholescintigraphy) involves the intravenous injection of a radioactive tracer that is excreted by the liver into the bile. In a healthy individual, the tracer fills the gallbladder. * **Diagnostic Finding:** In acute cholecystitis, the cystic duct is typically obstructed by a stone. Therefore, the **non-visualization of the gallbladder** after 60 minutes (or up to 4 hours) despite visualization of the common bile duct and duodenum confirms the diagnosis. **Why Other Options are Incorrect:** * **CECT (A):** Useful for identifying complications like gangrene, perforation, or abscess, but it is less sensitive than USG or HIDA for early acute cholecystitis. * **MRI/MRCP (C):** Highly accurate for detecting choledocholithiasis (CBD stones) but is not the primary or most sensitive tool for confirming simple acute cholecystitis. * **ERCP (D):** An invasive procedure used primarily for therapeutic intervention (e.g., stone extraction from the CBD), not for diagnosing cholecystitis. **NEET-PG High-Yield Pearls:** * **IOC (Investigation of Choice):** USG Abdomen (shows wall thickening >4mm, pericholecystic fluid, and sonographic Murphy’s sign). * **Gold Standard/Most Sensitive:** HIDA Scan. * **Rim Sign on HIDA:** Increased tracer uptake in the liver parenchyma surrounding the gallbladder fossa; suggests gangrenous cholecystitis.

Q: In which position should a renal scan be performed?

Prone. **Explanation:** The correct answer is **Prone (Option B)**. This is primarily due to the anatomical location of the kidneys. **1. Why Prone is Correct:** The kidneys are **retroperitoneal organs** located closer to the posterior abdominal wall than the anterior wall. In nuclear medicine renal scans (using tracers like DTPA, MAG3, or DMSA), a gamma camera is used to detect radiation. To minimize **attenuation** (absorption of gamma rays by overlying tissues), the detector should be as close to the kidneys as possible. Placing the patient in a **prone position** (or using a posterior detector in a supine patient) ensures the shortest distance between the kidneys and the camera, resulting in better image resolution and more accurate quantification of renal function. **2. Why Other Options are Incorrect:** * **Supine (A):** In this position, the anterior abdominal contents (bowel, fat, liver) lie between the kidneys and the camera, causing significant photon attenuation and poor image quality. *Exception:* Supine is used for transplanted kidneys (located in the iliac fossa) or horseshoe kidneys. * **Sitting (C) & Left Lateral (D):** These positions are unstable for the duration of a dynamic scan and do not provide the optimal posterior proximity required for standard native kidney imaging. **3. High-Yield Clinical Pearls for NEET-PG:** * **Transplanted Kidney:** Always scanned in the **Supine** position because the graft is placed anteriorly in the iliac fossa. * **Horseshoe Kidney:** Best imaged **Anteriorly (Supine)** because the isthmus crosses anterior to the spine. * **Radiopharmaceuticals:** * **DTPA:** Used for GFR estimation. * **MAG3:** Best for ERPF (Effective Renal Plasma Flow), especially in neonates or renal failure. * **DMSA:** The "Gold Standard" for cortical scarring and ectopic kidneys.

Q: Following RAIU studies demonstrate which of the following conditions?

Lingual Thyroid. ***Lingual Thyroid*** - **RAIU (Radioactive Iodine Uptake)** studies show uptake at the **base of the tongue** with **absence of uptake** in the normal cervical thyroid location. - This pattern is **pathognomonic** for lingual thyroid, where thyroid tissue fails to descend during embryological development and remains at the **tongue base**. *Graves Disease* - Shows **diffusely increased uptake** throughout an **enlarged thyroid gland** in the normal cervical location. - **RAIU values** are typically **elevated (>35%)** with **homogeneous distribution** across both thyroid lobes. *Toxic Adenoma* - Demonstrates a **single hot nodule** with **suppressed uptake** in the surrounding normal thyroid tissue. - The **autonomous nodule** shows intense uptake while the rest of the gland appears **photopenic** due to TSH suppression. *Multinodular Goiter (MNG)* - Exhibits **multiple areas** of increased and decreased uptake creating a **heterogeneous pattern** within an enlarged gland. - Shows **patchy uptake distribution** with both **hot and cold nodules** throughout the cervical thyroid region.

Q: What is the best diagnostic modality for pelvi-ureteric junction obstruction presenting as hydronephrosis?

Nuclear imaging. **Explanation:** The gold standard for diagnosing and assessing the functional significance of **Pelvi-Ureteric Junction Obstruction (PUJO)** is **Nuclear Imaging**, specifically **Diuretic Renography (DTPA or MAG3 scan)**. 1. **Why Nuclear Imaging is Correct:** While anatomical imaging can show dilatation, it cannot reliably differentiate between a "dilated but non-obstructed" system and a "true mechanical obstruction." Nuclear medicine provides a **functional assessment**. By administering a diuretic (Furosemide), clinicians can observe the "washout" rate of the radiotracer. A **T½ (half-life of drainage) > 20 minutes** is diagnostic of true mechanical obstruction. MAG3 is generally preferred over DTPA in patients with impaired renal function. 2. **Why other options are incorrect:** * **Ultrasound:** This is the **initial screening modality** of choice. It identifies hydronephrosis but cannot confirm if the cause is an active obstruction or a functional delay. * **Excretory Urogram (IVP):** Historically used to show the "Pelvic Box" deformity, it is now largely obsolete due to radiation and the inability to quantify the degree of obstruction or differential renal function. * **Retrograde Pyelography (RGP):** This is an invasive procedure used to delineate anatomy before surgery or if the site of obstruction is unclear; it is not the primary diagnostic tool. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of neonatal hydronephrosis:** PUJO. * **Best initial test:** Ultrasound. * **Best confirmatory/functional test:** Diuretic Renography (MAG3/DTPA). * **Dietl’s Crisis:** Episodic loin pain after fluid intake (alcohol/caffeine) associated with PUJO. * **Crossing Vessel:** An aberrant lower pole renal artery is a common extrinsic cause of PUJO.

Q: In the diagnosis of acute myocardial infarction, a hot spot is seen with which imaging modality?

Technetium-99m scan. **Explanation:** The correct answer is **Technetium-99m scan** (specifically **Tc-99m Pyrophosphate**). **1. Why Technetium-99m is correct:** In the setting of an acute myocardial infarction (AMI), irreversible cell damage leads to an influx of calcium into the necrotic myocytes. **Tc-99m Pyrophosphate (PYP)** has a high affinity for these calcium deposits. When injected, the radiopharmaceutical accumulates in the infarcted area, creating a **"Hot Spot"** (increased uptake) on imaging. This scan is typically positive between 24 and 72 hours after the onset of an infarct. **2. Why other options are incorrect:** * **Thallium-201 scan:** Thallium is a potassium analog that is taken up by *viable* myocardium. In an MI, the dead tissue cannot take up the tracer, resulting in a **"Cold Spot."** It is used for viability and stress testing, not for "hot spot" imaging of an acute infarct. * **Strontium-90:** This is a pure beta-emitter used primarily in radiotherapy (e.g., for pterygium or bone pain palliation), not for diagnostic cardiac imaging. * **Iodine-127:** This is the stable, non-radioactive isotope of Iodine. Radioactive isotopes like I-123 or I-131 are used for thyroid imaging, but not for acute MI diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Hot Spot Imaging:** Tc-99m Pyrophosphate (detects necrosis). * **Cold Spot Imaging:** Thallium-201 or Tc-99m Sestamibi (detects ischemia/infarction as a perfusion defect). * **PET Scan:** The "Gold Standard" for myocardial viability is **FDG-PET**, which identifies "hibernating myocardium." * **Rule of Thumb:** "Hot" means the tracer goes to the pathology; "Cold" means the tracer goes to healthy tissue and avoids the pathology.

Q: What is the scan used to estimate collecting system dilatation?

99mTc-DTPA scan. **Explanation:** The correct answer is **99mTc-DTPA scan**. To estimate collecting system dilatation and differentiate between obstructive and non-obstructive hydronephrosis, a **dynamic renal scintigraphy (Diuretic Renogram)** is performed. **1. Why 99mTc-DTPA is correct:** 99mTc-DTPA (Diethylene Triamine Penta-acetic Acid) is an agent that is handled almost exclusively by **glomerular filtration** (not secreted or reabsorbed). Because it stays within the tubular lumen and follows the flow of urine, it is the gold standard for calculating the **Glomerular Filtration Rate (GFR)** and visualizing the drainage pattern of the collecting system. When combined with a diuretic (Furosemide), it helps determine if a dilated renal pelvis is due to mechanical obstruction or simple stasis. **2. Why other options are incorrect:** * **MAG 3 (Mercaptoacetyltriglycine):** While also used for dynamic renography, it is primarily secreted by the renal tubules. It is the agent of choice in patients with **renal failure** or pediatric cases due to better extraction, but DTPA remains the classic answer for GFR-based drainage studies in standard exams. * **DMSA (Dimercaptosuccinic Acid):** This is a **static** renal scan. It binds to the proximal convoluted tubules and is used to identify **renal scars**, ectopic kidneys, or pyelonephritis. It cannot evaluate the collecting system or drainage. * **Hippuran (I-131 OIH):** An older agent used for Effective Renal Plasma Flow (ERPF). It is rarely used now due to high radiation doses and poor imaging quality. **Clinical Pearls for NEET-PG:** * **Best agent for GFR:** 99mTc-DTPA. * **Best agent for Renal Scarring:** 99mTc-DMSA. * **Best agent for Renal Function in Neonates/Renal Failure:** 99mTc-MAG3. * **Whitaker Test:** The invasive gold standard for differentiating obstructive from non-obstructive dilatation (pressure-flow study).

Question 1

Tc HMPAO SPECT is used for what type of imaging?

Accepted Answer

Cerebral perfusion imaging

Answer

Renal imaging

Answer

Parathyroid imaging

Answer

Thyroid imaging

Question 2

Positron emission tomographic (PET) scanning is useful in the evaluation of which of the following conditions?

Accepted Answer

Mycotic aortic aneurysm

Answer

Solitary pulmonary nodules

Answer

Staging lung cancer

Answer

Lymph node involvement by malignancy

Question 3

Which of the following agents does not increase the sensitivity of a Tc-pertechnetate scan?

Accepted Answer

Metoclopramide

Answer

Glucagon

Answer

Cimetidine

Answer

Pentagastrin

Question 4

Radionuclide scans are useful in all of the following except:

Accepted Answer

Local staging of tumors

Answer

Gastrointestinal bleed

Answer

Cholecystitis

Answer

Intraabdominal abscess

Question 5

A patient presented with right upper quadrant pain and dyspepsia. Ultrasound showed an edematous gallbladder wall. What is the most sensitive investigation to confirm the suspected diagnosis?

Accepted Answer

Hepatobiliary iminodiacetic acid (HIDA) scan

Answer

Contrast-enhanced computed tomography (CECT)

Answer

Magnetic resonance imaging (MRI)

Answer

Endoscopic retrograde cholangiopancreatography (ERCP)

Question 6

In which position should a renal scan be performed?

Accepted Answer

Prone

Answer

Supine

Answer

Sitting

Answer

Left lateral

Question 7

Following RAIU studies demonstrate which of the following conditions?

Accepted Answer

Lingual Thyroid

Answer

Graves Disease

Answer

Toxic Adenoma

Answer

Multinodular Goiter (MNG)

Question 8

What is the best diagnostic modality for pelvi-ureteric junction obstruction presenting as hydronephrosis?

Accepted Answer

Nuclear imaging

Answer

Ultrasound

Answer

Excretory urogram

Answer

Retrograde pyelography

Question 9

In the diagnosis of acute myocardial infarction, a hot spot is seen with which imaging modality?

Accepted Answer

Technetium-99m scan

Answer

Thallium-201 scan

Answer

Strontium-90 scan

Answer

Iodine-127 scan

Question 10

What is the scan used to estimate collecting system dilatation?

Accepted Answer

99mTc-DTPA scan

Answer

MAG 3 scan

Answer

DMSA scan

Answer

Hippuran scan

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

On this page

Practice by Chapter

Want unlimited practice?