Thyroid Scintigraphy Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Thyroid Scintigraphy. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Thyroid Scintigraphy Indian Medical PG Question 1: Investigation of choice for locating Parathyroid gland:
- A. USG
- B. CAT Scan
- C. Angiography
- D. Sestamibi scan (Correct Answer)
Thyroid Scintigraphy Explanation: ***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.
Thyroid Scintigraphy Indian Medical PG Question 2: Which of the following conditions is the most common complication of radioiodine treatment for Graves' disease?
- A. Hypothyroidism (Correct Answer)
- B. Thyroid cancer
- C. Thyroid storm
- D. Subacute thyroiditis
Thyroid Scintigraphy Explanation: ***Hypothyroidism***
- **Radioiodine (RAI) therapy** destroys overactive thyroid cells, making it highly effective for Graves' disease but often leading to a permanent state of **hypothyroidism** post-treatment.
- The goal of RAI is to eliminate the source of excess hormone production, and while effective, it frequently necessitates lifelong **thyroid hormone replacement**.
*Thyroid storm*
- **Thyroid storm** is a rare, life-threatening complication, usually seen in untreated or undertreated hyperthyroidism or during acute stress, not typically a direct outcome of effective RAI.
- While a transient increase in thyroid hormones can occur shortly after RAI, a full-blown thyroid storm is infrequent with proper preparation and management.
*Thyroid cancer*
- There is no significant evidence to suggest an increased risk of **thyroid cancer** in adults following therapeutic doses of radioiodine for Graves' disease [1].
- The radiation dose is targeted primarily at the thyroid gland, and studies have shown no clear link to increased malignancy [1].
*Subacute thyroiditis*
- **Subacute thyroiditis** (also known as de Quervain's thyroiditis) is typically a post-viral inflammatory condition of the thyroid, characterized by pain and tenderness in the thyroid gland [2].
- It does not directly result from radioiodine treatment; however, some patients may experience a transient inflammatory response (radiation thyroiditis) after RAI, which is usually mild and self-limiting, not true subacute thyroiditis.
Thyroid Scintigraphy Indian Medical PG Question 3: A 26-year-old male presents to the outpatient department with a discrete thyroid swelling. On neck ultrasound, an isolated cystic swelling of the gland is seen. What is the risk of malignancy associated with this finding?
- A. 48%
- B. 12%
- C. 24%
- D. 3% (Correct Answer)
Thyroid Scintigraphy Explanation: ***3%***
- **Purely cystic thyroid nodules** (as described in this case with "isolated cystic swelling") have a **very low risk of malignancy**, typically **2-3%** or less.
- According to **ATA guidelines** and **TIRADS classification**, purely cystic nodules are considered **low suspicion** lesions.
- The cystic nature suggests a **benign process** such as a degenerated adenoma, colloid cyst, or simple cyst.
- **Fine needle aspiration (FNA)** may still be considered if the nodule is >2 cm or has any suspicious solid components, but is often not required for purely cystic lesions.
*48%*
- This percentage is **significantly higher** than the actual malignancy risk for a purely cystic thyroid swelling.
- Such a **high risk** would typically be associated with **solid nodules** exhibiting highly suspicious ultrasound features such as:
- Microcalcifications
- Irregular or spiculated margins
- Taller-than-wide shape
- Marked hypoechogenicity
- Extrathyroidal extension
*24%*
- This percentage represents a **moderate to high risk** of malignancy, which is **not characteristic** of an isolated purely cystic thyroid swelling.
- A risk in this range might be seen with:
- **Mixed solid-cystic nodules** with predominantly solid components
- Solid nodules with **intermediate suspicious features** on ultrasound
*12%*
- While lower than 24% or 48%, 12% is still **considerably higher** than the generally accepted malignancy risk for purely cystic thyroid nodules.
- This risk level could be plausible for:
- **Predominantly cystic nodules** with some eccentric solid components
- Solid nodules with **mildly suspicious** features on ultrasound
Thyroid Scintigraphy Indian Medical PG Question 4: What is a gamma camera used for?
- A. Measuring radioactivity
- B. RIA (Radioimmunoassay)
- C. Monitoring surface contamination
- D. Organ imaging (Correct Answer)
Thyroid Scintigraphy Explanation: ***Organ imaging***
- A **gamma camera**, also known as a Anger camera, is a device used in **nuclear medicine** to image the distribution of gamma-emitting radioisotopes within the body.
- This allows for the visualization and assessment of organ function and structure, such as in **bone scans** or **myocardial perfusion studies**.
*Measuring radioactivity*
- While a gamma camera detects gamma rays, its primary function is **spatial imaging** of radiotracer distribution, not simply quantifying general radioactivity levels.
- Devices like **Geiger counters** or **scintillation counters** are more commonly used for general measurement of radioactivity.
*RIA (Radioimmunoassay)*
- **Radioimmunoassay (RIA)** is an in vitro technique used for measuring the concentration of specific substances (like hormones or drugs) in a sample, often using gamma-emitting tracers.
- RIA primarily uses **beta counters** or **gamma counters** sensitive to small samples, not large-field-of-view gamma cameras.
*Monitoring surface contamination*
- Monitoring surface contamination typically involves handheld detectors like **Geiger-Müller counters** or **portable survey meters**.
- These devices are designed for detecting radiation on surfaces, whereas a gamma camera is optimized for **internal imaging** within a patient.
Thyroid Scintigraphy Indian Medical PG Question 5: Most sensitive investigation for preoperative localization of abnormal parathyroid glands is
- A. Neck ultrasound
- B. (99mTc) labelled Sestamibi isotope scan (Correct Answer)
- C. CT scan
- D. MRI
Thyroid Scintigraphy Explanation: ***(99mTc) labelled Sestamibi isotope scan***
- This scan uses a **radioactive tracer** that is preferentially taken up and retained by hyperfunctioning parathyroid tissue, making it highly sensitive for identifying **abnormal parathyroid glands**, especially parathyroid adenomas.
- It is particularly useful for detecting **ectopic parathyroid glands** and in cases of persistent or recurrent hyperparathyroidism.
*Neck ultrasound*
- While useful for localizing parathyroid glands, its sensitivity can be limited by **operator dependence**, gland size, and location (e.g., retrosternal).
- It is generally good for initial screening but not as sensitive as Sestamibi for identifying all abnormal glands, especially those located in challenging areas.
*CT scan*
- CT scans can visualize larger parathyroid adenomas, but their sensitivity is lower than Sestamibi scans for smaller lesions or those with **atypical locations**.
- It is often used as a **second-line imaging modality** when Sestamibi is inconclusive or to complement findings.
*MRI*
- MRI can provide detailed anatomical information and identify parathyroid glands, but its sensitivity for detecting abnormal parathyroid tissue is generally **comparable to or slightly less** than CT and inferior to Sestamibi scanning.
- It may be considered in cases of unclear findings from other modalities or when radiation exposure is a concern.
Thyroid Scintigraphy Indian Medical PG Question 6: Which one of the following conditions is diagnosed by Tc99m Pertechnetate Scintigraphy?
- A. Meckel's diverticulum (Correct Answer)
- B. Pharyngeal diverticulum
- C. Duodenal diverticulum
- D. Colonic diverticulum
Thyroid Scintigraphy Explanation: ***Meckel's diverticulum***
- **Meckel's diverticulum** often contains **ectopic gastric mucosa**, which has parietal cells that secrete acid.
- **Tc99m Pertechnetate** is taken up by these gastric parietal cells, allowing visualization of the diverticulum on scintigraphy.
*Pharyngeal diverticulum*
- A **pharyngeal diverticulum**, such as **Zenker's diverticulum**, is a pouch-like herniation of the pharyngeal mucosa; it does not contain ectopic gastric mucosa.
- Diagnosis is typically made through **barium swallow studies** or **endoscopy**, not scintigraphy.
*Duodenal diverticulum*
- A **duodenal diverticulum** is a common pouch-like protrusion in the duodenum and usually lacks ectopic gastric mucosa.
- It is often asymptomatic and diagnosed incidentally on **upper endoscopy** or **cross-sectional imaging** (CT, MRI).
*Colonic diverticulum*
- **Colonic diverticula** are small, bulging pouches common in the large intestine that do not contain gastric tissue.
- They are typically diagnosed with **colonoscopy** or **CT colonography**, particularly in cases of diverticulitis.
Thyroid Scintigraphy Indian Medical PG Question 7: A thyroid FNA shows 'bubble gum' colloid. Which nuclear feature would best support papillary thyroid carcinoma?
- A. Nuclear grooves
- B. Ground glass nuclei (Correct Answer)
- C. Prominent nucleoli
- D. Salt and pepper chromatin
Thyroid Scintigraphy Explanation: ***Ground glass nuclei***
- **Ground glass nuclei**, also known as **Orphan Annie eye nuclei** [1][2], are the most **characteristic and recognized nuclear feature** of **papillary thyroid carcinoma (PTC)** on FNA cytology. [1]
- This appearance results from **fine, evenly dispersed chromatin** that gives the nucleus a clear, empty, or translucent appearance with a prominent nuclear membrane. [1]
- Among the given options, this is the **single best feature** that would support a PTC diagnosis when 'bubble gum' colloid is present.
*Nuclear grooves*
- **Nuclear grooves** are a common and highly supportive feature of PTC, particularly when **prominent and numerous**.
- However, as a **single finding**, they are less definitive than ground glass nuclei, as grooves can occasionally be seen in benign conditions (though usually less prominent).
- In combination with other features, nuclear grooves are highly specific for PTC.
*Prominent nucleoli*
- **Prominent nucleoli** are more frequently associated with **follicular neoplasms**, **medullary thyroid carcinoma**, or anaplastic thyroid carcinoma.
- Classical PTC typically has **inconspicuous nucleoli**, so prominent nucleoli would suggest an alternative diagnosis or a tall cell variant of PTC.
*Salt and pepper chromatin*
- **Salt and pepper chromatin** (finely stippled chromatin) is a classic cytological feature of **medullary thyroid carcinoma** (MTC).
- This chromatin pattern reflects neuroendocrine differentiation and is distinct from the nuclear characteristics of PTC.
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1098-1100.
[2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 429-430.
Thyroid Scintigraphy Indian Medical PG Question 8: A 45-year-old female presents with a 2 cm thyroid nodule. Which TIRADS category has >95% risk of malignancy?
- A. TIRADS 4
- B. TIRADS 2
- C. TIRADS 5 (Correct Answer)
- D. TIRADS 3
Thyroid Scintigraphy Explanation: ***TIRADS 5***
- A **TIRADS 5** classification indicates a **highly suspicious** nodule with features strongly suggestive of **malignancy**.
- This category corresponds to a **>95% risk of malignancy**, necessitating further investigation such as fine-needle aspiration (FNA).
*TIRADS 4*
- **TIRADS 4** nodules are classified as **moderately suspicious** for malignancy, with a risk ranging from **5% to 50%**.
- While requiring follow-up and often FNA, the risk is significantly lower than for TIRADS 5.
*TIRADS 2*
- **TIRADS 2** nodules are considered **benign**, with a **0% risk of malignancy** (or extremely low).
- These nodules typically have features like **spongiform appearance** or purely cystic composition.
*TIRADS 3*
- **TIRADS 3** nodules are classified as **mildly suspicious**, with a malignancy risk between **0% and 5%**.
- They often have some indeterminate features but are predominantly considered to be low risk.
Thyroid Scintigraphy Indian Medical PG Question 9: Which of the following ultrasound features of a thyroid nodule is not suggestive of malignancy?
- A. Hypoechogenicity
- B. Hyperechogenicity (Correct Answer)
- C. Microcalcification
- D. Nonhomogeneous
Thyroid Scintigraphy Explanation: ***Hyperechogenicity***
- A **hyperechoic** thyroid nodule appears brighter than the surrounding parenchyma on ultrasound, typically indicating a benign lesion, such as a **colloid nodule**.
- This feature suggests a higher reflection of sound waves, characteristic of tissues rich in **fluid or colloid material**.
*Hypoechogenicity*
- **Hypoechoic** nodules appear darker than the surrounding thyroid tissue, which is a strong indicator of malignancy due to their often dense cellular structure.
- This feature is associated with a higher risk of thyroid cancer and often prompts further investigation with **fine-needle aspiration (FNA)**.
*Microcalcification*
- The presence of **microcalcifications** (tiny, bright spots) within a thyroid nodule is one of the most specific ultrasound signs of **papillary thyroid carcinoma**.
- These calcifications, often punctate, represent psammoma bodies, which are a histopathological hallmark of this common thyroid cancer.
*Nonhomogeneous*
- A **nonhomogeneous** (heterogeneous) echotexture within a thyroid nodule, characterized by irregular internal architecture, can be suggestive of malignancy.
- This often indicates disorganized cellular growth, fibrosis, or cystic degeneration with solid components, which are features seen in various thyroid cancers.
Thyroid Scintigraphy Indian Medical PG Question 10: Which artificial radioisotopes are used in nuclear medicine?
- A. Radium
- B. Uranium
- C. Plutonium (Correct Answer)
- D. Iridium
Thyroid Scintigraphy Explanation: ### Explanation
**Correct Answer: C. Plutonium**
In nuclear medicine, radioisotopes are categorized as either **natural** (found in nature) or **artificial** (man-made via nuclear reactors or cyclotrons).
**Plutonium (specifically Pu-238)** is an artificial radioisotope produced in nuclear reactors. While not used as a diagnostic tracer or therapeutic agent for internal administration, it has a significant historical and niche clinical application as a power source for **Radioisotope Thermoelectric Generators (RTGs)** in long-lived **cardiac pacemakers**. Its high energy density and long half-life made it ideal for devices requiring decades of operation without battery replacement.
**Analysis of Incorrect Options:**
* **A. Radium:** This is a **naturally occurring** radioactive metal found in uranium ores. While Radium-223 is used in treating bone metastases (Xofigo), the element itself is classified as natural.
* **B. Uranium:** This is a **naturally occurring** heavy metal. It is the raw material used to produce artificial isotopes but is not used directly in clinical nuclear medicine.
* **C. Iridium:** While Iridium-192 is used in Brachytherapy, it is generally classified as a transition metal used in "sealed sources" for radiotherapy rather than being the classic example of an "artificial radioisotope" in the context of general nuclear medicine tracers (like Technetium-99m). However, in the context of this specific question, Plutonium is the most distinct "artificial/man-made" element.
**High-Yield Clinical Pearls for NEET-PG:**
* **Technetium-99m (Tc-99m):** The most commonly used artificial radioisotope in diagnostic nuclear medicine (produced in a Mo-99/Tc-99m generator).
* **Cyclotron-produced isotopes:** Include F-18 (used in PET scans), I-123, and Thallium-201.
* **Reactor-produced isotopes:** Include I-131, Mo-99, and Xenon-133.
* **Therapeutic Alpha Emitter:** Radium-223 is the first alpha-emitting radiopharmaceutical approved to improve survival in castration-resistant prostate cancer with bone metastases.
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