Renal Nuclear Medicine — MCQs
In the context of bilateral renal artery stenosis, which antihypertensive drug is considered contraindicated?
Tc-labeled RBCs are used for all except:
A dense nephrogram is obtained by
The T1/2 of Iodine-131 is:
Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?
In a child, non-functioning kidney is best diagnosed by
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?
Precautions advised after outpatient Radioiodine (I-131) therapy are all, EXCEPT:
Renal Nuclear Medicine Indian Medical PG Practice Questions and MCQs
Question 1: In the context of bilateral renal artery stenosis, which antihypertensive drug is considered contraindicated?
- A. Beta-blockers
- B. Calcium channel blockers
- C. ACE inhibitors (Correct Answer)
- D. Diuretics
Explanation: ***ACE inhibitors*** - In bilateral renal artery stenosis, ACE inhibitors can precipitate **acute kidney injury** by severely reducing **glomerular filtration pressure**, as both kidneys rely on **angiotensin II** for maintaining this pressure [1]. - They inhibit the production of **angiotensin II**, leading to **efferent arteriolar dilation** and a drop in glomerular hydrostatic pressure, which is critical for filtration in stenosed kidneys [2]. *Beta-blockers* - Beta-blockers are generally considered safe and effective in treating hypertension associated with renal artery stenosis, as they do not directly interfere with **renal autoregulation** in the same critical way as ACE inhibitors. - They lower blood pressure by reducing **cardiac output** and inhibiting renin release but do not acutely compromise **glomerular filtration** in the presence of stenosis. *Calcium channel blockers* - Calcium channel blockers are safe to use in bilateral renal artery stenosis and are often effective in controlling blood pressure. - They dilate **afferent arterioles**, which can actually help maintain or improve **glomerular filtration rate** by increasing blood flow to the glomerulus. *Diuretics* - Diuretics can be used cautiously in renal artery stenosis to manage blood pressure and fluid overload. - However, aggressive diuresis can lead to intravascular volume depletion, which might exacerbate **renal hypoperfusion** in already stenosed kidneys.
Question 2: 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 3: A dense nephrogram is obtained by
- A. Dehydrating the patient
- B. Rapid (Bolus) injection of dye (Correct Answer)
- C. Using non ionic media
- D. Increasing the dose of contrast media
Explanation: ***Rapid (Bolus) injection of dye*** - A **rapid bolus injection** of contrast material ensures a high concentration reaches the kidneys simultaneously, leading to optimal opacification and a **dense nephrogram**. - This method allows for the collection of a **large bolus of undiluted contrast** in the renal vessels and parenchyma, improving visualization of the renal parenchyma during the nephrographic phase. - The dense nephrogram phase occurs when contrast is within the renal tubules and interstitium, producing uniform opacification. *Dehydrating the patient* - **Dehydration** would concentrate the urine in the collecting system, but it does not directly contribute to the **dense nephrogram** appearance of the renal parenchyma. - While dehydration may improve visualization of the pelvicalyceal system on delayed images, it can increase the risk of **contrast-induced nephropathy**. *Using non ionic media* - **Non-ionic contrast media** are associated with fewer adverse reactions and greater patient safety compared to ionic media due to their lower osmolality. - However, the type of contrast media (ionic vs. non-ionic) does not primarily determine the **density of the nephrogram** itself, but rather patient tolerability and safety profile. *Increasing the dose of contrast media* - While increasing the dose might provide more contrast overall, it does not guarantee a **dense nephrogram**, which requires a high concentration of contrast to be present acutely in the renal parenchyma. - A dense nephrogram is better achieved by **rapid bolus injection technique** rather than simply increasing the total dose. - Excessive contrast increases the risk of **adverse reactions** and contrast-induced nephropathy without necessarily improving nephrographic density proportionally.
Question 4: The T1/2 of Iodine-131 is:
- A. 8 days (Correct Answer)
- B. 12 hours
- C. 13 days
- D. 2 days
Explanation: ***8 days*** - Iodine-131 (¹³¹I) has a relatively short half-life of **8.02 days**, making it suitable for diagnostic and therapeutic uses with a controlled radiation exposure window. - This **half-life** allows for effective patient monitoring and targeted treatment while minimizing long-term radiation risks. *12 hours* - This is an incorrect value; 12 hours is a significantly shorter half-life than that of **Iodine-131**. - Other isotopes, such as **Iodine-123**, have a half-life of 13.2 hours, which is closer to this value but still distinct from **Iodine-131**. *13 days* - This value is close but incorrect; the correct half-life for **Iodine-131** is approximately **8 days**. - A 13-day half-life would imply a longer period of radioactivity, altering its clinical applications. *2 days* - This is an incorrect half-life for **Iodine-131**, which has a significantly longer half-life of approximately 8 days. - A 2-day half-life would mean the isotope decays much faster than it actually does.
Question 5: Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?
- A. Iodohippurate
- B. Tc99m-DTPA (Correct Answer)
- C. Tc99m-MAG3
- D. Tc99m-DMSA
Explanation: ***Tc99m-DTPA*** - Technetium-99m-Diethylenetriaminepentaacetic acid (**Tc99m-DTPA**) is a radiopharmaceutical that is cleared almost exclusively by **glomerular filtration** (~98%), making it the ideal agent for measuring GFR. - Its **renal clearance rate** directly correlates with the GFR, providing an accurate, non-invasive assessment of kidney function. - Used for dynamic renal scintigraphy to calculate GFR quantitatively. *Iodohippurate* - **Iodohippurate (OIH)** is primarily cleared by **tubular secretion** (~80%), similar to Para-aminohippuric acid (PAH). - It is used to measure **renal plasma flow (RPF)** or **effective renal plasma flow (ERPF)**, not GFR. - Not suitable for GFR measurement due to its tubular handling mechanism. *Tc99m-MAG3* - Technetium-99m-Mercaptoacetyltriglycine (**Tc99m-MAG3**) is predominantly handled by **tubular secretion** (~90%). - Used to assess **effective renal plasma flow (ERPF)** and is preferred in patients with impaired renal function due to its high extraction efficiency. - Has largely replaced OIH in clinical practice but does not measure GFR. *Tc99m-DMSA* - Technetium-99m-Dimercaptosuccinic acid (**Tc99m-DMSA**) binds to the **proximal tubular cells** in the renal cortex (~40-50% accumulation). - Used for **static renal cortical scintigraphy** to evaluate renal morphology, differential renal function, and detect cortical scarring. - Not cleared by glomerular filtration and unsuitable for GFR measurement.
Question 6: In a child, non-functioning kidney is best diagnosed by
- A. Creatinine clearance
- B. Ultrasonography
- C. IVU
- D. DTPA renogram (Correct Answer)
Explanation: ***DTPA renogram*** - A **DTPA renogram** (diethylene triamine pentaacetic acid scan) is a nuclear medicine study that assesses **renal blood flow** and **glomerular filtration rate (GFR)**. - It is highly effective in determining if a kidney is non-functioning because it directly measures the **uptake and excretion of a radiotracer** by the kidney, providing quantitative data on its functional capacity. *Creatinine clearance* - **Creatinine clearance** is a measure of overall kidney function, reflecting the GFR of **both kidneys combined**. - It cannot specifically identify a non-functioning individual kidney, as the other kidney might compensate for the non-functioning one, leading to a near-normal overall creatinine clearance. *Ultrasonography* - **Ultrasonography** is excellent for evaluating **renal anatomy**, such as size, shape, and presence of cysts, hydronephrosis, or stones. - While it can show structural abnormalities, it provides limited direct information about the **functional status** of the kidney, and a structurally normal kidney can still be non-functional. *IVU (Intravenous Urography)* - **Intravenous Urography (IVU)** uses contrast dye injected intravenously to visualize the kidneys, ureters, and bladder, assessing both anatomy and some aspects of function. - If a kidney is non-functioning, it would show **no uptake or excretion of the contrast dye**, but IVU involves radiation exposure and nephrotoxic contrast, making DTPA renogram often preferred in children for functional assessment.
Question 7: 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 8: 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 9: 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.
Question 10: Precautions advised after outpatient Radioiodine (I-131) therapy are all, EXCEPT:
- A. Carry treatment certificate for 90 days.
- B. Maintain a distance of 2 meters from children and pregnant women.
- C. Avoid using household chlorine bleaches for cleaning. (Correct Answer)
- D. Use contraception for three months.
Explanation: **Explanation:** Radioiodine (I-131) therapy is commonly used for hyperthyroidism and thyroid carcinoma. Post-therapy precautions are designed to minimize radiation exposure to others (ALARA principle) and prevent environmental contamination. **Why Option C is the Correct Answer:** Patients are actually **encouraged** to use household chlorine bleach to clean toilets and sinks after use. I-131 is excreted primarily through urine and saliva. Chlorine bleach effectively decontaminates the surfaces by chemically reacting with the radioiodine, reducing the risk of indirect exposure to family members. Therefore, "avoiding" it is incorrect advice. **Analysis of Other Options:** * **Option A (Treatment Certificate):** Patients must carry a treatment certificate for up to **90 days**. Modern security sensors (e.g., at airports or international borders) are highly sensitive and can detect residual gamma radiation from the patient’s body for several weeks. * **Option B (Social Distancing):** Patients are advised to maintain a distance of **2 meters (6 feet)** from others, especially children and pregnant women, for a specified period (usually 3–7 days depending on the dose) to minimize external gamma radiation exposure. * **Option C (Contraception):** Female patients must avoid pregnancy for at least **6 months**, and males should use contraception for **3–4 months** (to allow for one full cycle of spermatogenesis) to prevent potential genetic damage to the fetus. **Clinical Pearls for NEET-PG:** * **Mechanism:** I-131 emits both **Beta particles** (therapeutic effect/tissue destruction) and **Gamma rays** (diagnostic/safety concern). * **Half-life:** The physical half-life of I-131 is **8.02 days**. * **Contraindication:** Radioiodine is strictly **contraindicated in pregnancy** (crosses the placenta and destroys the fetal thyroid) and **breastfeeding**. * **Hydration:** Patients are advised to increase fluid intake to facilitate the renal clearance of unbound I-131.
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