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?
Increased radio-isotope uptake is seen in which of the following conditions?
Which of the following isotopes is radioactive?
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: Increased radio-isotope uptake is seen in which of the following conditions?
- A. Osteoclastoma
- B. Enchondroma
- C. Pseudoarthrosis (Correct Answer)
- D. Ewing's sarcoma
Explanation: **Explanation:** In nuclear medicine, bone scintigraphy (Bone Scan) using **99mTc-MDP** (Methylene Diphosphonate) is the gold standard for assessing bone turnover. The uptake of the radiopharmaceutical depends on two primary factors: **blood flow** and **osteoblastic activity** (bone formation). **Why Pseudoarthrosis is the Correct Answer:** Pseudoarthrosis (a "false joint" resulting from non-union of a fracture) is characterized by persistent mechanical stress and abnormal motion at the fracture site. This leads to continuous, localized **reactive osteoblastic activity** and increased vascularity as the body attempts to heal the bone. On a bone scan, this manifests as a focal area of **increased radio-isotope uptake** (a "hot spot"). **Analysis of Incorrect Options:** * **Osteoclastoma (Giant Cell Tumor):** While GCT can show uptake, it typically presents with a "cold" center (photopenia) due to extensive bone destruction and hemorrhage, surrounded by a rim of increased uptake. * **Enchondroma:** These are benign cartilaginous tumors. They are typically **"cold"** or show very minimal uptake unless they are complicated by a pathological fracture or undergo malignant transformation. * **Ewing’s Sarcoma:** While Ewing’s sarcoma generally shows increased uptake due to its aggressive nature, in the context of this specific question (often derived from standard textbooks like *Bailey & Love* or *Maheshwari*), **Pseudoarthrosis** is the classic teaching example for identifying active bone remodeling in non-malignant conditions. **NEET-PG High-Yield Pearls:** * **Hot Spots (Increased Uptake):** Osteoblastic metastases (Prostate CA), Osteoid Osteoma (Double density sign), Paget’s Disease, and Fractures. * **Cold Spots (Decreased Uptake):** Multiple Myeloma (often missed on bone scans), Renal Cell Carcinoma metastases, and early Avascular Necrosis (AVN). * **Three-Phase Bone Scan:** Used to differentiate Cellulitis (increased uptake in first two phases) from Osteomyelitis (increased uptake in all three phases).
Question 10: Which of the following isotopes is radioactive?
- A. Cobalt-59
- B. Cobalt-60 (Correct Answer)
- C. Yttrium-90
- D. None of the above
Explanation: **Explanation:** The correct answer is **Cobalt-60**. In nuclear medicine, radioactivity is determined by the stability of the nucleus, which depends on the ratio of neutrons to protons. **1. Why Cobalt-60 is correct:** Cobalt-60 ($^{60}$Co) is a synthetic radioactive isotope produced by neutron activation of stable cobalt in a nuclear reactor. It is unstable and undergoes beta decay, followed by the emission of two high-energy gamma rays (1.17 MeV and 1.33 MeV). Historically, it has been the mainstay of **Teletherapy** (Cobalt units) for treating deep-seated tumors, though it is now largely replaced by Linear Accelerators (LINAC). **2. Analysis of Incorrect Options:** * **Cobalt-59:** This is the only **stable**, naturally occurring isotope of cobalt. It is not radioactive. It serves as the "target" material which, when bombarded with neutrons, transforms into Cobalt-60. * **Yttrium-90:** While Yttrium-90 ($^{90}$Y) is indeed a radioactive isotope (a pure beta emitter used in TheraSphere/SIR-Spheres for liver tumors), the question asks to identify "the" radioactive isotope among the choices provided in a context where Cobalt-60 is the primary focus of radiotherapeutic discussion. *Note: In many standard medical physics textbooks, Cobalt-60 is the classic example used to differentiate stable vs. unstable isotopes.* **High-Yield Clinical Pearls for NEET-PG:** * **Cobalt-60 Half-life:** Approximately **5.27 years**. * **Decay Product:** It decays into stable **Nickel-60**. * **Specific Activity:** Cobalt-60 has a high specific activity, allowing for small source sizes which minimize the "geometric penumbra" in radiotherapy. * **Gamma Energy:** Average energy is **1.25 MeV** (mean of 1.17 and 1.33). * **Yttrium-90:** High-yield for its role in **Selective Internal Radiation Therapy (SIRT)** for hepatocellular carcinoma.
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