Bone Scintigraphy — MCQs
99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of
Earliest investigation for diagnosis of Ankylosing spondylitis:
Distant bone metastases can be best detected by which of the following imaging techniques?
Most sensitive imaging modality for detecting early osteomyelitis
What type of lesions in the skull bones can be identified on this X-ray?
Which one of the following conditions is diagnosed by Tc99m Pertechnetate Scintigraphy?
Which of the following bone lesions is characterized by the 'fallen fragment sign,' a radiological feature seen in lytic bone lesions with fluid-filled cavities?
Which artificial radioisotopes are used in nuclear medicine?
Which radiopharmaceutical is used for a liver scan?
What is the investigation of choice for whole-body imaging in metastasis?
Bone Scintigraphy Indian Medical PG Practice Questions and MCQs
Question 1: 99m Technetium labeled RBC scintigraphy is PRIMARILY used in the diagnosis of
- A. Hepatoma
- B. Left ventricular function wall motion
- C. Hepatic hemangioma
- D. GI Bleeding (Correct Answer)
Explanation: ***GI Bleeding*** - Technetium-99m labeled RBC scintigraphy (**<sup>99m</sup>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, <sup>99m</sup>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., <sup>99m</sup>Tc-Sestamibi or Thallium-201). - <sup>99m</sup>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 **<sup>99m</sup>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.
Question 2: Earliest investigation for diagnosis of Ankylosing spondylitis:
- A. CT scan
- B. Bone scan
- C. X-ray
- D. MRI STIR sequence (Correct Answer)
Explanation: ***MRI STIR sequence*** - An **MRI STIR (Short Tau Inversion Recovery) sequence** is highly sensitive for detecting early inflammatory changes in the **sacroiliac joints** and spine, such as **bone marrow edema**, which is a hallmark of early ankylosing spondylitis. - It can identify disease activity and structural changes *before* they are visible on conventional X-rays, making it the earliest diagnostic tool. *CT scan* - While a **CT scan** provides excellent detailed images of bone, it is not as sensitive as MRI for detecting early inflammatory changes like **bone marrow edema** in the sacroiliac joints. - It involves significant **radiation exposure** and is typically used for more advanced structural assessment rather than early diagnosis. *Bone scan* - A **bone scan** (scintigraphy) shows areas of increased bone turnover but is **not specific** for ankylosing spondylitis and has lower spatial resolution compared to MRI. - It can indicate inflammation or increased metabolic activity but cannot differentiate specific causes or provide detailed anatomical information as effectively as MRI. *X-ray* - **X-rays** are often the initial imaging modality due to their accessibility, but they only show **structural changes** (like erosions, sclerosis, or fusion) in the sacroiliac joints and spine at a later stage of the disease. - Early inflammatory changes, such as **bone marrow edema**, are typically not visible on plain radiographs, leading to a delay in diagnosis compared to MRI.
Question 3: Distant bone metastases can be best detected by which of the following imaging techniques?
- A. Bone scan (Correct Answer)
- B. CT
- C. Intravenous venogram
- D. PET scan
Explanation: ***Bone scan*** - A **bone scan** is highly sensitive for detecting **osteoblastic activity**, which is characteristic of most bone metastases. - It involves injecting a **radioactive tracer** (usually technetium-99m methylene diphosphonate) that accumulates in areas of increased bone turnover, making it excellent for surveying the entire skeletal system. *PET scan* - While a **PET scan** (Positron Emission Tomography) can detect bone metastases, especially with **FDG-PET**, it is generally more expensive and may not be as sensitive for purely **osteoblastic lesions** as a bone scan. - Its primary role is often in assessing metabolic activity of the primary tumor and other distant soft tissue metastases. *CT* - **CT scans** (Computed Tomography) are excellent for assessing bone anatomy, cortical destruction, and soft tissue involvement, but they are generally less sensitive for detecting early or widespread **osseous metastatic disease** compared to a bone scan. - CT provides detailed anatomical information but may miss early **marrow involvement** that alters bone metabolism. *Intravenous venogram* - An **intravenous venogram** is an imaging technique used to visualize veins, primarily for detecting **thrombosis** or venous insufficiency. - It has no role in the detection of **bone metastases**, as it provides no information about bone structure or metabolic activity.
Question 4: Most sensitive imaging modality for detecting early osteomyelitis
- A. Nuclear bone scan
- B. CT scan
- C. MRI (Correct Answer)
- D. Plain radiograph
Explanation: **MRI** - **MRI** is the most sensitive imaging modality for detecting **early osteomyelitis** due to its superior ability to visualize **bone marrow edema** and soft tissue changes, which are the earliest signs of infection. - It can differentiate between **bone infection** and other processes like inflammation or tumor, even before cortical bone changes are evident. *Nuclear bone scan* - **Nuclear bone scans** (e.g., technetium-99m) are highly sensitive for detecting **increased bone turnover** but lack specificity for infection. - They can identify areas of **inflammation** or injury but cannot reliably distinguish between osteomyelitis and other conditions like **fractures** or **tumors**. *CT scan* - **CT scans** are excellent for visualizing **cortical bone destruction**, **sequestra**, and **involucrum** in later stages of osteomyelitis. - However, **CT scans** are not as sensitive as MRI for detecting early bone marrow changes and soft tissue involvement, making them less ideal for **early diagnosis**. *Plain radiograph* - **Plain radiographs** are often the first imaging study for suspected osteomyelitis but have **low sensitivity** in the early stages, with changes typically not visible until 10-14 days after infection onset. - Early findings may include **periosteal elevation** or soft tissue swelling, but **bone destruction** or new bone formation is usually required for a definitive diagnosis.
Question 5: What type of lesions in the skull bones can be identified on this X-ray?
- A. Paget's disease (Correct Answer)
- B. Multiple myeloma
- C. Osteosarcoma
- D. Osteomyelitis
Explanation: ***Paget's disease*** - An X-ray of the skull in Paget's disease typically shows **thickening of the skull vault** and areas of both **osteolysis** and **osteosclerosis**, leading to a characteristic "cotton wool" appearance. - The disease involves abnormal bone remodeling, leading to enlarged and weakened bones susceptible to deformity and fracture. *Multiple myeloma* - On a skull X-ray, multiple myeloma usually presents as multiple, sharply-defined, **"punched-out" lytic lesions** without a sclerotic border. - These lesions reflect areas where malignant plasma cells have destroyed bone, which is distinct from the mixed lytic and sclerotic changes of Paget's disease. *Osteosarcoma* - Osteosarcoma is a **primary bone malignancy** that typically presents as a solitary lesion with a mixture of lytic and sclerotic areas, often with a **sunburst or Codman's triangle** periosteal reaction. - It most commonly affects long bones in younger individuals and is a much less common presentation in the skull compared to other bone conditions. *Osteomyelitis* - Osteomyelitis is an **infection of the bone** that would appear on an X-ray as areas of bone destruction (lysis) and new bone formation (sclerosis), often with **sequestrum** (dead bone) and **involucrum** (new bone formation around the infection). - While it can affect the skull, its imaging features would typically be localized signs of infection rather than the widespread, generalized changes seen in Paget's disease.
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
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.
Question 7: Which of the following bone lesions is characterized by the 'fallen fragment sign,' a radiological feature seen in lytic bone lesions with fluid-filled cavities?
- A. Adamantinoma
- B. Aneurysmal bone cyst
- C. Simple bone cyst (Correct Answer)
- D. Osteosarcoma
Explanation: ***Simple bone cyst*** - The **'fallen fragment sign'** is a **pathognomonic radiological feature** of simple bone cysts (unicameral bone cysts). - This sign occurs when a **pathological fracture** through the cyst allows a fragment of cortical bone to fall into the fluid-filled cavity and settle dependently at the bottom, visible on upright radiographs. - Simple bone cysts are benign, fluid-filled lesions commonly affecting the **proximal humerus and proximal femur** in children and adolescents. *Aneurysmal bone cyst* - This is a **benign, blood-filled, expansile lesion** with multiple septated compartments. - Characteristic radiological feature is **fluid-fluid levels** on MRI or CT due to blood products of different densities. - Does NOT typically demonstrate the 'fallen fragment sign' - the multi-loculated nature prevents free-floating bone fragments. *Adamantinoma* - This rare **malignant bone tumor** primarily affects the **tibia** and presents as a lytic lesion, often with sclerotic borders. - It is a solid tumor that does not form simple fluid-filled cavities or demonstrate the 'fallen fragment sign.' *Osteosarcoma* - This is a **highly malignant bone tumor** characterized by osteoid production and bone destruction. - Often presents with periosteal reaction like a **'sunburst' pattern or Codman's triangle**. - It is a solid, aggressive tumor that does not form fluid-filled cavities that would exhibit a 'fallen fragment sign.'
Question 8: Which artificial radioisotopes are used in nuclear medicine?
- A. Radium
- B. Uranium
- C. Plutonium (Correct Answer)
- D. Iridium
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.
Question 9: Which radiopharmaceutical is used for a liver scan?
- A. Tc-99m sulphur colloid (Correct Answer)
- B. Tc-99m mebrofenin
- C. Tc-99m MIBI
- D. Tc-99m DTPA
Explanation: **Explanation:** The correct answer is **Tc-99m sulphur colloid**. The underlying principle for a liver-spleen scan is the **phagocytic activity of the Reticuloendothelial System (RES)**. When Tc-99m sulphur colloid is injected intravenously, the particles (sized 0.1–1.0 μm) are cleared from the blood by Kupffer cells in the liver (80–90%), splenic macrophages (5–10%), and bone marrow. This scan is primarily used to evaluate functional liver anatomy and detect "cold nodules" (e.g., abscesses or tumors) or "hot spots" (e.g., Focal Nodular Hyperplasia). **Analysis of Incorrect Options:** * **Tc-99m Mebrofenin:** This is an IDA (Iminodiacetic acid) derivative used for **HIDA scans**. It evaluates the **hepatobiliary system** (hepatocyte uptake and biliary excretion) and is the gold standard for diagnosing Acute Cholecystitis. * **Tc-99m MIBI:** Primarily used for **Myocardial Perfusion Imaging** and Parathyroid imaging. It is taken up by mitochondria. * **Tc-99m DTPA:** A chelating agent cleared by glomerular filtration, used for **Renal Dynamic Scans** to assess GFR and obstructive uropathy. **High-Yield Clinical Pearls for NEET-PG:** 1. **Colloid Shift:** In portal hypertension or cirrhosis, there is decreased liver uptake and increased uptake in the spleen and bone marrow. 2. **Focal Nodular Hyperplasia (FNH):** This is the only liver lesion that typically appears "hot" or "isointense" on a sulphur colloid scan due to the presence of Kupffer cells. 3. **Hot Spot on Liver Scan:** Classically seen in **Superior Vena Cava (SVC) Obstruction** (due to collateral flow via the vein of Sappey).
Question 10: What is the investigation of choice for whole-body imaging in metastasis?
- A. Magnetic Resonance Imaging
- B. Radiography
- C. Bone scan (Correct Answer)
- D. CT Scan
Explanation: **Explanation:** **Bone Scan (Technetium-99m MDP)** is the investigation of choice for screening whole-body skeletal metastases because of its high sensitivity and ability to image the entire skeleton in a single session. It works on the principle of detecting increased osteoblastic activity (bone remodeling) at sites of tumor infiltration. Its primary advantage is the ability to detect "hot spots" weeks or months before structural changes become visible on conventional X-rays. **Why other options are incorrect:** * **Radiography (X-ray):** It has low sensitivity for early metastasis. A bone lesion only becomes visible on an X-ray after **30-50% of bone mineral density is lost**. It is, however, the best modality to confirm a finding seen on a bone scan. * **CT Scan:** While excellent for evaluating cortical bone and detailed anatomy, it is not practical for whole-body screening due to high radiation doses and lower sensitivity for early marrow-based lesions compared to nuclear imaging. * **MRI:** MRI is the most sensitive modality for detecting **bone marrow infiltration**. However, it is not typically the first-line "investigation of choice" for whole-body screening due to high costs, long scan times, and limited availability of whole-body MRI protocols. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Tc-99m MDP (Methylene Diphosphonate) adsorbs onto the **hydroxyapatite crystals** of the bone. * **The "Cold Scan" Exception:** Highly aggressive or purely osteolytic tumors (e.g., Multiple Myeloma, Renal Cell Carcinoma, or Thyroid Cancer) may show as "cold" or false-negative on a bone scan because they do not trigger an osteoblastic response. * **Flare Phenomenon:** An apparent increase in tracer uptake seen shortly after starting chemotherapy, which actually represents healing bone rather than disease progression. * **Superscan:** A bone scan showing intense, uniform skeletal uptake with **absent renal/bladder activity**, typically seen in diffuse metastatic prostate cancer or hyperparathyroidism.
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