Nuclear Medicine — MCQs

Nuclear Medicine Indian Medical PG Practice Questions and MCQs

Question 181: In the evaluation of a suspected hepatic hemangioma, what is the expected behavior of Tc-99m labeled RBCs during scintigraphy?

A. Increased uptake on delayed images (Correct Answer)
B. Decreased uptake on delayed images
C. No uptake
D. Diffuse uptake

Explanation: ***Increased uptake on delayed images*** - Hepatic hemangiomas are vascular malformations with **slow blood flow** within their extensive sinusoidal spaces. - This slow flow causes the **Tc-99m labeled RBCs** to accumulate gradually and remain trapped within the lesion, leading to characteristic increased uptake on delayed images (typically 1-2 hours after injection). *Decreased uptake on delayed images* - This pattern would suggest **washout** of the tracer, which is not characteristic of hemangiomas where the tracer is retained due to sluggish flow. - It could be seen in highly vascular but non-hemangioma lesions where tracer clearance is rapid. *No uptake* - Lack of uptake would indicate a **non-vascular lesion** or a lesion with very poor perfusion, which is not consistent with a hemangioma's highly vascular nature. - While initial images might show less uptake than surrounding liver due to slow flow, delayed images will show accumulation. *Diffuse uptake* - **Diffuse uptake** throughout the liver would indicate normal liver parenchyma or a condition affecting the entire organ, not a localized benign tumor like a hemangioma. - Hemangiomas are typically discrete lesions that show focal uptake.

Question 182: A lady presented with a 4 cm tumor in the left parietal lobe for which she underwent surgery and radiotherapy. After 3 months she presented with headache and vomiting. Which of the following would characterize the lesion in the patient?

A. Digital subtraction angiography with dual source CT scan
B. Gd-enhanced MRI
C. 99Tc-HMPAO SPECT brain
D. 18FDG PET Scan (Correct Answer)

Explanation: ***18FDG PET Scan*** - This patient, presenting with new neurological symptoms after **surgery and radiotherapy** for a cerebral tumor, faces a diagnostic dilemma: differentiating between **tumor recurrence** and **radiation necrosis**. - **18FDG PET scans** effectively distinguish between these two conditions because viable tumor cells exhibit high metabolic activity and thus actively take up **fluorodeoxyglucose (FDG)**, while radiation necrosis is metabolically inactive and shows little to no FDG uptake. *Digital subtraction angiography with dual source CT scan* - **Digital subtraction angiography (DSA)** is primarily used to visualize **vascular structures** and is not the modality of choice for differentiating tumor recurrence from radiation necrosis. - A **dual-source CT scan** is useful for rapid imaging and dynamic studies but lacks the metabolic information needed for this specific differentiation. *Gd-enhanced MRI* - While **Gd-enhanced MRI** is excellent for detecting **structural changes** and **blood-brain barrier disruption**, it often cannot definitively differentiate between **tumor recurrence** and **radiation necrosis**. - Both conditions can present with similar **enhancement patterns** on MRI, making differentiation challenging without additional metabolic information. *99Tc-HMPAO SPECT brain* - **99mTc-HMPAO SPECT** measures **regional cerebral blood flow (rCBF)**, which can be altered in both tumors and areas of radiation injury. - However, it does not provide the specific metabolic information (glucose metabolism) needed to reliably distinguish between **viable tumor cells** and **radiation necrosis** as effectively as FDG PET.

Question 183: Tc-labeled RBCs are used for all except:

A. Liver adenoma (Correct Answer)
B. LV function
C. GI bleeding
D. Liver hemangioma

Explanation: ***Liver adenoma*** - Tc-labeled RBCs are primarily used to highlight a specific type of tissue or process. **Liver adenomas** do not typically show an affinity for **Tc-labeled RBCs**, as they are benign epithelial tumors with a different vascular composition. - While adenomas can be vascular, they do not inherently contain the **vascular pooling** or blood volume characteristics that would be specifically targeted by **Tc-labeled RBCs** for diagnostic imaging. *LV function* - **Tc-labeled RBCs** (or Tc-99m-pertechnetate) are commonly used in **gated blood pool imaging** (MUGA scan) to assess **left ventricular (LV) function**, including **ejection fraction** and wall motion abnormalities. - This technique directly visualizes the blood pool within the cardiac chambers, making it suitable for assessing functional parameters of the heart. *GI bleeding* - **Tc-labeled RBCs** are a standard imaging agent for detecting and localizing **active gastrointestinal (GI) bleeding**, especially when the bleeding rate is intermittent or slow. - The labeled RBCs extravasate at the site of hemorrhage, creating a 'hot spot' that can be identified over time. *Liver hemangioma* - **Tc-labeled RBCs** are highly effective in diagnosing **liver hemangiomas**, which are benign vascular tumors composed of large, dilated blood vessels. - These lesions show characteristic uptake and retention of **labeled RBCs** due to their slow blood flow and large intravascular space, appearing as early peripheral enhancement with subsequent centripetal filling.

Question 184: In a patient presenting with jaundice, the HIDA scan would be most useful for which of the following:

A. Biliary atresia (Correct Answer)
B. Cholelithiasis
C. Benign biliary disease
D. Bile duct carcinoma

Explanation: ***Biliary atresia*** - A **HIDA scan** (hepatobiliary iminodiacetic acid scan) is instrumental in diagnosing biliary atresia by demonstrating the **absence of bile flow** into the duodenum. - In infants with persistent jaundice, the failure of the tracer to appear in the small bowel after a prolonged period strongly suggests this condition, indicating **obstructed or absent bile ducts**. *Cholelithiasis* - While HIDA scans can detect **cystic duct obstruction** in acute cholecystitis, they are less definitive for uncomplicated cholelithiasis (gallstones without acute inflammation). - **Ultrasound** is typically the primary imaging modality for diagnosing gallstones due to its non-invasiveness and ability to visualize stones directly. *Benign biliary disease* - This is a broad category, and while a HIDA scan can assess bile flow, it's not the **primary diagnostic tool** for all benign biliary conditions. - For most benign biliary diseases (e.g., choledocholithiasis without acute cholecystitis), **ultrasound, ERCP, or MRCP** often provide more detailed anatomical information. *Bile duct carcinoma* - A HIDA scan might show **obstructed bile flow** in bile duct carcinoma (cholangiocarcinoma), but it does not provide the detailed anatomical information or staging necessary for diagnosis and treatment planning. - **CT, MRI, MRCP, or ERCP** with biopsy are far more effective for identifying, characterizing, and staging bile duct malignancies.

Question 185: All the following radioisotopes are used in painful body metastasis except

A. Tin-117
B. Samarium-153
C. Strontium-89
D. Yttrium (Correct Answer)

Explanation: ***Yttrium*** - **Yttrium-90 (⁹⁰Y)** is a pure **beta-emitter** primarily used for **radioembolization of liver tumors** (selective internal radiation therapy) and **radiosynovectomy** for joint inflammation. - It is **NOT a standard radioisotope for treating painful bone metastases**, unlike the other options listed. - Its high-energy beta particles and specific applications make it unsuitable for the palliative treatment of bone pain from metastases. *Tin-117* - **Tin-117m (¹¹⁷ᵐSn-DTPA)** is a **conversion electron emitter** that has been studied and used for palliation of painful bone metastases. - It localizes to areas of increased osteoblastic activity and provides localized radiation therapy. - Though less commonly used than Samarium-153 or Strontium-89, it is still a therapeutic option for bone pain. *Samarium-153* - **Samarium-153 (¹⁵³Sm-EDTMP)** is a commonly used **beta-emitting radioisotope** for the treatment of painful bone metastases. - It selectively binds to areas of increased bone turnover, such as metastases, and its beta emissions provide **localized pain relief**. - FDA-approved and widely used for bone pain palliation. *Strontium-89* - **Strontium-89 (⁸⁹Sr)** is another highly effective **beta-emitting radioisotope** used for palliation of painful bone metastases. - It is a **calcium analog** and is preferentially incorporated into bone mineral at sites of increased osteoblastic activity. - FDA-approved and considered a gold standard for bone pain treatment.

Question 186: Radio-isotope of iodine used for thyroid tissue destruction:

A. I-132
B. I-123
C. I-125
D. I-131 (Correct Answer)

Explanation: ***I-131*** - **Iodine-131** is widely used in nuclear medicine for the **destruction of thyroid tissue** in conditions like hyperthyroidism (Graves' disease) and differentiated thyroid cancer due to its emission of both beta and gamma radiation. - The **beta particles** emitted by I-131 have a short tissue penetration range, allowing for localized destruction of thyroid cells while minimizing damage to surrounding tissues. *I-132* - **Iodine-132** has a very short half-life (2.3 hours) and a lower energy beta emission compared to I-131, making it less suitable for sustained tissue destruction. - It is not commonly used for thyroid ablation due to its **less favorable decay characteristics** for therapeutic applications. *I-123* - **Iodine-123** is primarily a **gamma emitter** with a half-life of 13.2 hours, making it ideal for diagnostic imaging of the thyroid (e.g., thyroid scans). - It delivers a low radiation dose and is not used for tissue destruction because it lacks the **destructive beta particle emission** required for therapeutic effects. *I-125* - **Iodine-125** is a gamma emitter with a longer half-life (59.4 days) and is predominantly used in brachytherapy for some cancers and occasionally for **diagnostic imaging and research**. - While it has limited therapeutic uses, its primary application is not for widespread thyroid tissue ablation due to its **different decay mode** compared to I-131.

Question 187: Gamma camera in Nuclear Medicine is used for –

A. Organ imaging (Correct Answer)
B. Measuring the radioactivity
C. RIA
D. Monitoring the surface contamination

Explanation: ***Organ imaging*** - A **gamma camera** is primarily used to detect gamma rays emitted from **radiopharmaceuticals** introduced into the body. - This detection allows for the creation of 2D images or 3D tomographic images (SPECT) of organ function and structure. *Measuring the radioactivity* - While radioactivity is measured by the gamma camera, its primary purpose is not just to quantify dps/Bq, but to create a **spatial distribution** of this radioactivity. - Dedicated **dosimeters** or **activity meters** are used for precise measurement of radioactivity. *RIA* - **Radioimmunoassay (RIA)** is a laboratory technique used to measure the concentration of substances (e.g., hormones, drugs) in a sample, not a function of the gamma camera. - RIA utilizes **radioactively labeled antibodies** and antigens but does not involve imaging the body. *Monitoring the surface contamination* - **Geiger counters** or specific contamination meters are used for monitoring surface contamination. - A gamma camera is designed for internal imaging and is not practical or optimized for detecting external surface contamination.

Question 188: MUGA scan is not useful in:

A. Stroke volume
B. Regional wall perfusion (Correct Answer)
C. Left ventricular ejection fraction
D. Regional wall motion

Explanation: ***Regional wall perfusion*** - A MUGA scan assesses **ventricular function** through blood pool imaging, evaluating wall motion and ejection fraction. - It does not directly visualize or quantify myocardial perfusion, which is the flow of blood through the coronary arteries to the heart muscle. *Stroke volume* - A MUGA scan accurately measures **end-diastolic volume** and **end-systolic volume**, from which stroke volume (EDV – ESV) can be calculated. - This parameter directly reflects the amount of blood pumped out by the ventricle with each beat. *Left ventricular ejection fraction* - The MUGA scan is considered a gold standard for calculating **left ventricular ejection fraction** (LVEF), a key indicator of cardiac pump function. - It uses a count-based method from gated blood pool images to determine the percentage of blood ejected from the left ventricle. *Regional wall motion* - MUGA scans are highly effective in assessing **regional wall motion abnormalities**, identifying areas of **hypokinesis**, **akinesis**, or **dyskinesis**. - This is crucial for diagnosing and monitoring conditions like myocardial ischemia or infarction, and is a primary utility of the scan.

Question 189: Radioactive isotope of which of the following is used in bone scans?

A. Iodine
B. Gallium
C. Phosphorus
D. Technetium (Correct Answer)

Explanation: ***Technetium*** - **Technetium-99m** (**Tc-99m**) is the most commonly used radioisotope for **bone scans** due to its favorable decay characteristics and ability to be chelated with phosphates. - When injected, **Tc-99m**-labeled phosphates are incorporated into areas of **increased osteoblastic activity**, highlighting regions of bone remodeling, trauma, infection, or malignancy. *Iodine* - **Iodine radioisotopes** (e.g., **Iodine-123**, **Iodine-131**) are primarily used for imaging and treating **thyroid conditions** because the thyroid gland actively absorbs iodine. - They are not used in bone scans as iodine does not accumulate significantly in bone tissue. *Gallium* - **Gallium-67** (**Ga-67**) is used in scans for detecting **inflammation**, **infection**, and some **tumors**, particularly lymphomas. - While it can sometimes enhance in areas of bone infection, it is not the primary or preferred agent for general **bone scintigraphy**. *Phosphorus* - While **phosphate compounds** are used as carriers for the radioactive isotope in bone scans, elemental **phosphorus** itself is not used as a radioactive isotope for imaging. - The **phosphate** ligands are labeled with **Technetium-99m** to create the radiopharmaceutical.

Question 190: Which of the following is not an artificial radio isotope element?

A. CO 60
B. Ra226 (Correct Answer)
C. 1-125
D. Tc-99m

Explanation: ***Ra-226*** * **Radium-226** (Ra-226) is a **naturally occurring radioactive isotope** of radium, found in the uranium decay chain. * It is not artificially produced but rather exists in nature as a product of the **radioactive decay of uranium-238**. *Co-60* * **Cobalt-60** is a **synthetic radioactive isotope** produced by neutron activation of cobalt-59. * It is widely used in **radiation therapy** and industrial applications, making it an artificial radioisotope. *I-125* * **Iodine-125** is an **artificially produced radioisotope** commonly used in brachytherapy and diagnostic imaging. * It is created in a nuclear reactor by bombarding tellurium-124 with neutrons, making it not naturally occurring. *Tc-99m* * **Technetium-99m** is the most widely used **artificial radioisotope** in nuclear medicine for diagnostic imaging. * It is produced artificially from molybdenum-99 generators and does not occur naturally, making it an ideal choice for medical imaging due to its short half-life and gamma emission.

Practice by Chapter

Physics of Nuclear Medicine

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Radiopharmaceuticals

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Radiation Detection in Nuclear Medicine

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Thyroid Scintigraphy

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Bone Scintigraphy

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Renal Nuclear Medicine

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Cardiac Nuclear Medicine

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Pulmonary Nuclear Medicine

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Neurological Nuclear Medicine

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PET/CT Principles and Applications

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Radionuclide Therapy

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Radiation Safety in Nuclear Medicine

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