Nuclear Medicine Practice Questions

Q: A bone scan in multiple myeloma typically shows which of the following?

Cold spot. **Explanation:** In **Multiple Myeloma (MM)**, the characteristic bone lesions are purely **osteolytic**. The pathophysiology involves the activation of osteoclasts by myeloma cells (via RANKL expression) and the simultaneous inhibition of osteoblasts. A standard **Technetium-99m MDP Bone Scan** relies on osteoblastic activity (bone formation) to show "hot spots." Because MM lacks a reactive osteoblastic response, the lesions do not take up the tracer. Instead, they appear as **"Cold spots"** (areas of decreased or absent uptake) or may even appear normal, leading to a high false-negative rate (approx. 30-50%). **Analysis of Options:** * **A. Hot spot:** This is the typical finding for osteoblastic or mixed lesions (e.g., Prostate cancer metastases, Paget’s disease, or healing fractures). It is rarely seen in MM unless a pathological fracture is actively healing. * **C & D. Diffuse uptake patterns:** "Diffusely increased uptake" (Super scan) is characteristic of metabolic bone diseases (Hyperparathyroidism) or widespread osteoblastic metastases. MM does not present with diffuse metabolic alterations of the entire skeleton in this manner. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Imaging MM:** Whole-body Low-Dose CT (WBLDCT) or MRI is now preferred over the traditional skeletal survey. * **Bone Scan vs. Skeletal Survey:** A skeletal survey (X-ray) is more sensitive than a bone scan for MM, but even X-rays require 30-50% bone mineral loss to be visible. * **Punch-out Lesions:** The classic radiographic description of MM on X-ray. * **Exception:** If a bone scan *is* positive (hot) in a suspected MM patient, always rule out a pathological fracture.

Q: Which statement is true regarding Strontium-89 when compared to Phosphorus-32?

Strontium-89 has less toxicity.. **Explanation:** Both Strontium-89 ($^{89}$Sr) and Phosphorus-32 ($^{32}$P) are beta-emitting radionuclides used for the palliative treatment of painful bone metastases. However, their pharmacological profiles differ significantly. **Why Option B is Correct:** Strontium-89 is a calcium analog that selectively localizes to areas of high osteoblastic activity (bone metastases). In contrast, Phosphorus-32 is a phosphate analog that incorporates into the hydroxyapatite crystal of the bone but also into the **rapidly dividing cells of the bone marrow**. Consequently, $^{32}$P causes significant and prolonged **myelosuppression** (leukopenia and thrombocytopenia). Strontium-89 has a more targeted uptake, resulting in **less hematologic toxicity** compared to $^{32}$P. **Analysis of Incorrect Options:** * **Option A:** Strontium-89 has a **longer** physical half-life (~50.5 days) compared to Phosphorus-32 (~14.3 days). * **Option C:** Phosphorus-32 actually has a higher maximum beta energy (1.71 MeV) compared to Strontium-89 (1.46 MeV). Therefore, $^{32}$P generally has a slightly **deeper** tissue penetration (average 3.0 mm) than $^{89}$Sr (average 2.4 mm). **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Both are pure beta emitters (ideal for therapy, not imaging). * **Indications:** Primarily used for osteoblastic metastases (e.g., Prostate and Breast cancer). * **Samarium-153 ($^{153}$Sm):** Another common agent; unlike the others, it also emits a small amount of gamma radiation, allowing for post-therapy scintigraphic imaging. It has the shortest half-life (approx. 1.9 days). * **Flare Phenomenon:** Patients may experience a transient increase in bone pain 2–3 days after injection before relief begins.

Q: Radioisotopes emit all the following types of radiation except?

X-rays. ### Explanation The core concept behind this question lies in the **origin of the radiation**. Radioisotopes (radionuclides) are unstable atoms that undergo **nuclear decay** to reach a stable state. Therefore, the radiation they emit originates from the **nucleus**. **Why X-rays is the correct answer:** X-rays are **extranuclear** in origin. They are produced when electrons transition between atomic shells (Characteristic X-rays) or when high-speed electrons are decelerated near a nucleus (Bremmstrahlung radiation). Since X-rays do not originate from the radioactive decay of the nucleus itself, they are not considered a primary emission of radioisotopes. **Analysis of incorrect options:** * **Alpha Rays (α):** These consist of two protons and two neutrons (Helium nucleus). They are emitted by heavy unstable nuclei (e.g., Radium-226) during alpha decay. * **Beta Rays (β):** These are high-speed electrons ($\beta^-$) or positrons ($\beta^+$) emitted from the nucleus when a neutron converts to a proton or vice versa. * **Gamma Rays (γ):** These are high-energy electromagnetic photons emitted from an excited nucleus as it transitions to a lower energy state. This is the most common emission used in diagnostic Nuclear Medicine (e.g., Technetium-99m). **High-Yield Clinical Pearls for NEET-PG:** * **Technetium-99m (Tc-99m):** The most widely used radioisotope in diagnostic imaging; it is a pure **Gamma** emitter with a half-life of 6 hours and energy of 140 keV. * **Therapeutic Isotopes:** Usually emit **Beta particles** (e.g., I-131 for hyperthyroidism, Yttrium-90 for radioembolization) because they have a short path length and cause local tissue destruction. * **PET Scans:** Utilize **Positron ($\beta^+$) emitters** like Fluorine-18 (F-18). * **Alpha emitters:** Used in targeted alpha therapy (e.g., Radium-223 for bone metastases) due to high linear energy transfer (LET).

Q: Which radionucleotide is used in Scintimammography?

Sestamibi (MIBI). **Explanation:** **Scintimammography** (also known as Molecular Breast Imaging) is a functional imaging technique used to detect breast cancer, particularly in women with dense breast tissue where traditional mammography may be less sensitive. **Why Sestamibi (MIBI) is correct:** **Technetium-99m Sestamibi** is a lipophilic cationic compound. It is taken up by breast cancer cells due to their high metabolic activity and increased mitochondrial density. The tracer crosses the cell membrane and accumulates within the mitochondria via a passive transport mechanism driven by the negative transmembrane potential. Malignant cells, having higher metabolic demands, show significantly higher uptake compared to normal breast tissue. **Analysis of Incorrect Options:** * **A. HIDA (Hepatic Iminodiacetic Acid):** Used for **Cholescintigraphy** to evaluate the gallbladder and biliary tree (e.g., diagnosing acute cholecystitis). * **B. MIBG (Metaiodobenzylguanidine):** An analogue of norepinephrine used to image neuroendocrine tumors like **Pheochromocytoma** and Neuroblastoma. * **D. DTPA (Diethylene Triamine Pentaacetic Acid):** Primarily used for **Renal Scintigraphy** to assess Glomerular Filtration Rate (GFR) and evaluate obstructive uropathy. **High-Yield Clinical Pearls for NEET-PG:** * **Sestamibi** is also the gold standard for **Parathyroid Scintigraphy** (to locate adenomas) and **Myocardial Perfusion Imaging** (Stress Thallium/MIBI). * **Washout phenomenon:** Sestamibi is a substrate for the **P-glycoprotein (Pgp)** pump. Rapid washout of the tracer from a breast lesion is often associated with multidrug resistance (MDR) in tumors. * Scintimammography is particularly useful when mammography is inconclusive due to breast implants or severe scarring.

Q: Hot rim sign on hepatobiliary scintigraphy (Tc99m-HIDA) is seen in which of the following conditions?

Gangrenous Cholecystitis. **Explanation:** The **Hot Rim Sign** (also known as the "Rim Sign") on Tc99m-HIDA scintigraphy refers to a curvilinear area of increased radioactivity in the liver parenchyma immediately adjacent to the gallbladder fossa. **1. Why Gangrenous Cholecystitis is correct:** The Hot Rim Sign is a highly specific indicator of **acute severe cholecystitis**, often associated with complications like **gangrenous cholecystitis** or perforation. The underlying mechanism is increased blood flow (hyperemia) and inflammatory changes in the liver bed surrounding the inflamed gallbladder. While HIDA scans typically show non-visualization of the gallbladder in acute cholecystitis, the presence of this "rim" of activity suggests a more advanced or necrotic disease process. **2. Why the other options are incorrect:** * **Chronic Cholecystitis:** Typically shows delayed visualization of the gallbladder (after 1–4 hours) rather than a hot rim sign. * **Biliary Atresia:** Characterized by good hepatic uptake of the tracer but a total **absence of excretion** into the small intestine, even on delayed 24-hour images. * **Porcelain Gallbladder:** This is a surgical/radiological diagnosis (calcification of the gallbladder wall) seen on X-ray or CT; it is not a primary finding on HIDA scans. **Clinical Pearls for NEET-PG:** * **Gold Standard:** HIDA scan is the most sensitive imaging modality for diagnosing **Acute Cholecystitis** (due to cystic duct obstruction). * **Normal HIDA:** Visualization of the gallbladder, common bile duct, and duodenum within 60 minutes. * **False Positives:** Can occur in patients with prolonged fasting (>24 hours), total parenteral nutrition (TPN), or severe liver disease. * **Morphine Augmentation:** Used to differentiate acute from chronic cholecystitis by increasing sphincter of Oddi pressure to force tracer into the gallbladder.

Q: The Panda sign in a gallium scan is characteristic of which condition?

Sarcoidosis. **Explanation:** The **Panda sign** is a classic nuclear medicine finding on a **Gallium-67 (Ga-67) citrate scan**. It occurs due to bilateral, symmetrical uptake of the radiotracer in the **lacrimal glands, parotid glands, and nasopharyngeal mucosa**. When these areas of uptake are visualized together on an anterior head/neck image, they resemble the face of a giant panda. 1. **Why Sarcoidosis is correct:** Sarcoidosis is a multisystem granulomatous disease. Gallium-67 is an iron analog that binds to lactoferrin and accumulates in areas of active inflammation and granuloma formation. The Panda sign specifically indicates bilateral dacryoadenitis and parotitis. When combined with the **"Lambda sign"** (symmetrical uptake in the hilar and paratracheal lymph nodes), the specificity for Sarcoidosis increases significantly. 2. **Why other options are incorrect:** * **SLE, Rheumatoid Arthritis, and Seronegative Spondyloarthropathy:** While these are systemic inflammatory conditions, they do not typically cause the specific pattern of symmetrical lacrimal and salivary gland inflammation required to produce the Panda sign. While Gallium scans may show joint or visceral uptake in these diseases, the findings are non-specific. **High-Yield Clinical Pearls for NEET-PG:** * **Panda Sign:** Seen in Sarcoidosis, Sjögren’s syndrome, and occasionally after neck irradiation or in lymphoma (post-treatment). * **Lambda Sign:** Symmetrical uptake in right paratracheal and bilateral hilar lymph nodes (resembling the Greek letter $\lambda$). * **Gallium-67:** It has a physical half-life of **78 hours** and emits four photopeaks (approx. 93, 184, 300, and 394 keV). * **Hot Potato Sign:** Another name sometimes used for the combination of Panda and Lambda signs in Sarcoidosis.

Q: Renal cortical imaging is done by which of the following modalities?

DMSA (Dimercaptosuccinic acid). **Explanation:** **DMSA (Dimercaptosuccinic acid)** is the gold standard for **renal cortical imaging**. The underlying mechanism involves its accumulation in the **proximal convoluted tubules** of the renal cortex. Approximately 40-50% of the injected dose is bound to the cortical tubular cells and remains there for several hours, allowing for high-resolution static imaging. It is primarily used to detect **renal scarring** (post-pyelonephritis), ectopic kidneys, and to calculate **differential renal function**. **Analysis of Incorrect Options:** * **DTPA (Diethylene triamine pentaacetic acid):** This is a glomerular agent. It is filtered solely by the **glomerulus** and is not reabsorbed or secreted. It is used for measuring **GFR** and dynamic renography to assess obstructive uropathy. * **MAG3 (Mercaptoacetyltriglycine):** This is a tubular secretion agent. It is primarily secreted by the **proximal tubules** and rapidly excreted into the urine. It is the agent of choice for **dynamic renography** (diuretic renogram) to evaluate drainage and renal perfusion, especially in patients with impaired renal function. * **UIH:** This is likely a distractor or a typo for OIH (Ortho-iodohippurate), which was historically used for effective renal plasma flow (ERPF) but has been largely replaced by MAG3. **High-Yield Clinical Pearls for NEET-PG:** * **Static Imaging:** DMSA (Think "S" for Static/Scarring). * **Dynamic Imaging:** DTPA and MAG3 (Think "D" for Drainage/Dynamic). * **Best agent for Neonates/Renal Failure:** MAG3 (due to high extraction fraction). * **Glucoheptonate (GHA):** A unique agent that can be used for both cortical imaging and GFR estimation.

Question 1

A bone scan in multiple myeloma typically shows which of the following?

Accepted Answer

Cold spot

Answer

Hot spot

Answer

Diffusely increased uptake

Answer

Diffusely decreased uptake

Question 2

Distant metastasis of bone can be best detected by?

Accepted Answer

Bone scan

Answer

NMI

Answer

CT

Answer

Intravenous venogram

Question 3

What does 18-FDG stand for?

Accepted Answer

18-Fluorodeoxy glucose

Answer

18-Fluorodioxy glucose

Answer

18-Fluorodeoxy galactose

Answer

18-Fluorodioxy galactose

Question 4

Which statement is true regarding Strontium-89 when compared to Phosphorus-32?

Accepted Answer

Strontium-89 has less toxicity.

Answer

Strontium-89 has a shorter half-life.

Answer

Strontium-89 has deeper penetration.

Answer

None of the above.

Question 5

Radioisotopes emit all the following types of radiation except?

Accepted Answer

X-rays

Answer

Alpha Rays

Answer

Beta Rays

Answer

Gamma Rays

Question 6

Which radionucleotide is used in Scintimammography?

Accepted Answer

Sestamibi (MIBI)

Answer

HIDA

Answer

MIBG

Answer

DTPA

Question 7

Which of the following factors contribute to the development of duodenal ulcer?

Accepted Answer

I-131

Answer

I-125

Answer

Tc-99

Answer

P-32

Question 8

Hot rim sign on hepatobiliary scintigraphy (Tc99m-HIDA) is seen in which of the following conditions?

Accepted Answer

Gangrenous Cholecystitis

Answer

Chronic cholecystitis

Answer

Biliary Atresia

Answer

Porcelain Gallbladder

Question 9

The Panda sign in a gallium scan is characteristic of which condition?

Accepted Answer

Sarcoidosis

Answer

Systemic lupus erythematosus

Answer

Rheumatoid arthritis

Answer

Seronegative spondyloarthropathy

Question 10

Renal cortical imaging is done by which of the following modalities?

Accepted Answer

DMSA (Dimercaptosuccinic acid)

Answer

DTPA (Diethylene triamine pentaacetic acid)

Answer

MAG3 (Mercaptoacetyltriglycine)

Answer

UIH (Unknown abbreviation - likely incorrect)

Nuclear Medicine — MCQs

Nuclear Medicine — MCQs

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