Dynamic Contrast-Enhanced Imaging Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Dynamic Contrast-Enhanced Imaging. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 1: Volume of distribution of a drug is 500 ml and target concentration of drug in blood is 5 g/L. 20% of administered drug is reached to systemic circulation. What will be the loading dose of that drug -
- A. 1 gm
- B. 5 gm
- C. 25 gm
- D. 12.5 gm (Correct Answer)
Dynamic Contrast-Enhanced Imaging Explanation: ***12.5 gm***
- The formula for loading dose (LD) is: LD = (Target Concentration × Volume of Distribution) / Bioavailability.
- Given: Target Concentration = 5 g/L, Volume of Distribution = 500 mL = 0.5 L, Bioavailability = 20% = 0.2.
- So, LD = (5 g/L × 0.5 L) / 0.2 = 2.5 g / 0.2 = **12.5 g**.
*1 gm*
- This value would be obtained if the target concentration was 2 g/L with 100% bioavailability, or if the calculation incorrectly handled the volume or bioavailability factor.
- It does not account for the specified **bioavailability of 20%** or the given target concentration and volume of distribution.
*5 gm*
- This result would be obtained if the bioavailability was assumed to be 50% (LD = 2.5 g / 0.5 = 5 g), or if the volume of distribution was incorrectly used in the calculation.
- This option does not correctly factor in the **20% bioavailability** of the administered drug.
*25 gm*
- This value would result from mistakes such as dividing by bioavailability of 10% instead of 20% (LD = 2.5 g / 0.1 = 25 g), or by multiplying bioavailability instead of dividing by it.
- This answer significantly **overestimates** the required dose, which could lead to drug toxicity.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 2: Gadolinium is a contrast agent used for:
- A. CT - angiography
- B. Bronchography
- C. MRI - Imaging (Correct Answer)
- D. Contrast Sonography
Dynamic Contrast-Enhanced Imaging Explanation: ***MRI - Imaging***
- **Gadolinium** is a paramagnetic substance commonly used as a contrast agent in **Magnetic Resonance Imaging (MRI)**.
- It works by altering the **T1 relaxation times** of protons in tissues, enhancing the signal and improving the visibility of certain structures or pathologies like **tumors** or **inflammation**.
*CT - angiography*
- **CT angiography** typically uses **iodine-based contrast agents**, not gadolinium, to visualize blood vessels.
- Iodine contrast agents work by absorbing X-rays, making blood vessels appear bright on CT images.
*Bronchography*
- **Bronchography** is an older imaging technique that involved introducing an **iodinated contrast medium** directly into the bronchial tree.
- It has largely been replaced by **high-resolution CT scans** for evaluating airways.
*Contrast Sonography*
- **Contrast-enhanced ultrasound (CEUS)**, or contrast sonography, primarily uses **microbubble contrast agents** made of inert gas.
- These microbubbles enhance the reflectivity of blood, improving visualization of blood flow and organ perfusion.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 3: 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
Dynamic Contrast-Enhanced Imaging 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.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 4: Best investigation to detect rupture of silicone breast implants is-
- A. Mammography
- B. X-ray
- C. MRI (Correct Answer)
- D. USG
Dynamic Contrast-Enhanced Imaging Explanation: ***MRI***
- **Magnetic Resonance Imaging (MRI)** is considered the **gold standard** for detecting silicone breast implant ruptures due to its superior soft tissue contrast and ability to differentiate silicone from other tissues.
- It can accurately identify both **intracapsular** (linguine sign) and **extracapsular** ruptures, as well as associated silicone granulomas.
*Mammography*
- While useful for breast cancer screening, **mammography** has limited sensitivity for detecting silicone implant ruptures, especially subtle ones.
- It can show indirect signs like implant contour abnormalities or increased implant density but is often inconclusive for rupture diagnosis.
*X-ray*
- **X-rays** provide very little information regarding the integrity of silicone breast implants because silicone is radiolucent and does not show up clearly on standard radiographs.
- Its utility is primarily for detecting calcifications or foreign bodies, not implant rupture.
*USG*
- **Ultrasound (USG)** can be a useful initial screening tool for detecting implant ruptures, showing signs like the **"stepladder sign"** for intracapsular rupture or anechoic collections (silicone outside the capsule).
- However, its accuracy is highly operator-dependent, and it may miss subtle ruptures or be limited by poor visualization due to scar tissue, making MRI a more definitive choice.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 5: Most common benign tumor of the liver is:
- A. Focal nodular hyperplasia (FNH)
- B. Hepatic adenoma
- C. Hepatic hemangioma (Correct Answer)
- D. Angiomyolipoma of the liver
Dynamic Contrast-Enhanced Imaging Explanation: ***Hepatic hemangioma***
- **Hepatic hemangiomas** are the **most common benign solid tumors of the liver**, often discovered incidentally [1].
- They are composed of a tangled mass of **blood vessels** and are generally asymptomatic [1].
*Focal nodular hyperplasia (FNH)*
- FNH is the **second most common benign liver tumor**, characterized by a central scar on imaging [1].
- While benign, it is less common than hepatic hemangioma [1].
*Hepatic adenoma*
- Hepatic adenomas are benign tumors with a higher risk of **hemorrhage** and **malignant transformation** compared to hemangiomas [1], [2].
- Their incidence is linked to oral contraceptive use or anabolic steroid use.
*Angiolipoma of the liver*
- **Angiomyolipomas** are rare benign tumors, more commonly found in the kidney, and are not the most frequent benign liver tumor.
- They are composed of varying amounts of **fat**, **smooth muscle**, and **blood vessels**.
**References:**
[1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 398-399.
[2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 874-875.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 6: A man comes to the emergency department with stab injury to left flank. He has stable vitals. What would be the next step in management?
- A. Diagnostic peritoneal lavage
- B. Laparotomy
- C. CECT (Correct Answer)
- D. Laparoscopy
Dynamic Contrast-Enhanced Imaging Explanation: ***CECT***
- A **Contrast-Enhanced Computed Tomography (CECT)** scan is the preferred initial diagnostic step for a hemodynamically stable patient with a stab wound to the flank.
- It effectively assesses the **depth of penetration** and identifies potential internal organ injuries in the abdomen or retroperitoneum, guiding further management.
*Diagnostic peritoneal lavage*
- **Diagnostic peritoneal lavage (DPL)** is less commonly used for stab wounds in hemodynamically stable patients due to its **invasiveness** and lower specificity compared to CT scans.
- While it can detect peritoneal penetration or significant hemorrhage, it often leads to **unnecessary laparotomies** and is not as precise in identifying specific organ injuries.
*Laparotomy*
- **Laparotomy** (surgical exploration) is indicated for **hemodynamically unstable** patients or those with definitive signs of peritonitis or evisceration.
- Since the patient has **stable vitals**, immediate laparotomy is not the next step, as diagnostic imaging is needed first.
*Laparoscopy*
- **Laparoscopy** is a minimally invasive surgical procedure that can be used diagnostically or therapeutically in stable patients.
- However, in the initial assessment of a flank stab wound, a **CECT scan** is typically performed first to get a comprehensive view of potential organ damage before considering a more invasive procedure like laparoscopy.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 7: A 48-year-old woman presents with suspected myocardial ischemia. Pharmacologic stress myocardial perfusion SPECT with Tc-99m sestamibi shows reversible perfusion defect in the inferior wall. Evaluate the optimal management approach based on this functional imaging finding.
- A. Reassure patient as findings represent artifact
- B. Start medical management without further investigation
- C. Recommend coronary angiography for further evaluation and potential revascularization (Correct Answer)
- D. Proceed directly to coronary artery bypass grafting
Dynamic Contrast-Enhanced Imaging Explanation: ***Recommend coronary angiography for further evaluation and potential revascularization***
- A **reversible perfusion defect** on SPECT denotes **stress-induced ischemia** with viable myocardium, characterized by reduced tracer uptake during stress that normalizes at rest.
- This finding indicates significant **coronary artery stenosis** (often >70%) and requires **coronary angiography** to define the anatomy and plan possible **percutaneous coronary intervention (PCI)**.
*Reassure patient as findings represent artifact*
- While **diaphragmatic attenuation** can cause inferior wall artifacts, a truly **reversible defect** (normal rest scan) is diagnostic of ischemia rather than a permanent artifact.
- Attenuation artifacts typically present as **fixed defects** or are clarified using **ECG-gated SPECT** to check for normal wall motion.
*Start medical management without further investigation*
- Although medical therapy is a pillar of CAD treatment, a documented **reversible defect** in a symptomatic patient warrants anatomical assessment to evaluate the risk of **major adverse cardiovascular events (MACE)**.
- Management solely with drugs is insufficient for patients with high-risk ischemia patterns on **functional imaging** who may benefit from revascularization.
*Proceed directly to coronary artery bypass grafting*
- **Coronary artery bypass grafting (CABG)** is a surgical intervention that requires prior visualization of coronary anatomy via angiography to determine the extent of disease (e.g., **triple-vessel** or **left main disease**).
- It is premature to provide surgical referral before confirming the **syntax score** or the suitability of the lesions for less invasive procedures like **angioplasty**.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 8: A 70-year-old male with recurrent prostate cancer post-prostatectomy has rising PSA (4.2 ng/mL) but negative conventional imaging. Which functional imaging modality would provide the highest detection rate for disease localization in this clinical scenario?
- A. 68Ga-PSMA PET-CT (Correct Answer)
- B. In-111 Capromab pendetide scan
- C. 18F-FDG PET-CT
- D. Tc-99m MDP bone scan
Dynamic Contrast-Enhanced Imaging Explanation: ***68Ga-PSMA PET-CT***
- **68Ga-PSMA PET-CT** is currently the gold standard for detecting **biochemical recurrence** of prostate cancer, showing a detection rate of over 90% when PSA levels are >2 ng/mL.
- It targets the **Prostate-Specific Membrane Antigen**, which is significantly overexpressed in prostate cancer cells, allowing for precise localization of both local recurrence and **distant metastases**.
*In-111 Capromab pendetide scan*
- This older imaging modality (ProstaScint) targets an **intracellular epitope** of PSMA, which is less accessible in viable, non-necrotic cells compared to the extracellular targets of modern tracers.
- It has a much lower **sensitivity and specificity** compared to 68Ga-PSMA PET-CT and is rarely used in contemporary clinical practice.
*18F-FDG PET-CT*
- **18F-FDG** is generally not useful for prostate cancer because these tumors are typically slow-growing and have **low glucose metabolism** (low glycolytic rate).
- It is primarily reserved for **aggressive, high-grade**, or neuroendocrine-differentiated prostate cancers that have lost the ability to express PSMA.
*Tc-99m MDP bone scan*
- This is a conventional imaging modality that detects **osteoblastic activity** rather than the cancer cells themselves, often resulting in low sensitivity at low PSA levels.
- It is specifically limited to detecting **bone metastases** and cannot identify soft tissue recurrence or lymph node involvement in the pelvis.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 9: A 58-year-old presents with progressive cognitive decline. MRI brain is unremarkable. FDG-PET shows bilateral temporoparietal and posterior cingulate hypometabolism with relative sparing of sensorimotor cortex. Analyze these findings to determine the most likely diagnosis.
- A. Normal pressure hydrocephalus
- B. Frontotemporal dementia
- C. Alzheimer's disease (Correct Answer)
- D. Vascular dementia
Dynamic Contrast-Enhanced Imaging Explanation: ***Alzheimer's disease***
- The classic FDG-PET findings for this condition involve bilateral **temporoparietal** and **posterior cingulate** hypometabolism while typically sparing the **sensorimotor cortex**.
- This metabolic signature often appears during the **prodromal phase**, frequently preceding the structural **atrophy** seen on traditional MRI scans.
*Normal pressure hydrocephalus*
- On imaging, this condition is characterized by **ventriculomegaly** disproportionate to the degree of cortical atrophy, which is not described here.
- Clinically, it presents with the classic triad of **gait disturbance**, **urinary incontinence**, and **dementia**, rather than isolated metabolic patterns on PET.
*Frontotemporal dementia*
- FDG-PET would typically demonstrate hypometabolism localized to the **frontal** and **anterior temporal lobes**, which differs from the posterior pattern seen in this case.
- Early symptoms usually include significant **personality changes** or **behavioral disturbances** rather than generalized progressive cognitive decline alone.
*Vascular dementia*
- PET scanning usually shows a **focal or multifocal** "patchy" pattern of hypometabolism corresponding to areas of prior **infarction** or chronic ischemia.
- Diagnosis is generally supported by MRI evidence of **lacunar infarcts**, **extensive white matter disease**, or territorial strokes.
Dynamic Contrast-Enhanced Imaging Indian Medical PG Question 10: A 62-year-old male with lung cancer undergoes baseline PET-CT showing a 4 cm right upper lobe mass with SUVmax of 8.5. After 2 cycles of chemotherapy, repeat PET-CT shows the mass measures 3.5 cm with SUVmax of 3.2. Analyze the metabolic response according to PERCIST criteria.
- A. Progressive metabolic disease
- B. Stable metabolic disease
- C. Partial metabolic response (Correct Answer)
- D. Complete metabolic response
Dynamic Contrast-Enhanced Imaging Explanation: ***Partial metabolic response***
- According to **PERCIST** criteria, a reduction in **SULpeak** or **SUVmax** of **≥30%** is classified as a partial metabolic response.
- In this case, the SUVmax decreased from **8.5 to 3.2**, which is a **62% reduction**, far exceeding the 30% threshold for response.
*Progressive metabolic disease*
- Defined by a **>30% increase** in SUVmax or the appearance of **new metabolic lesions**.
- This patient showed a significant decrease in metabolic activity, contradicting a diagnosis of progression.
*Stable metabolic disease*
- This category applies when the change in SUVmax falls between a **30% decrease and a 30% increase**.
- Since the metabolic activity dropped by 62%, the response is too significant to be labeled as stable.
*Complete metabolic response*
- Requires a total **disappearance of metabolic uptake** in all lesions, ideally dropping below the level of **background liver activity**.
- While the uptake decreased significantly, a residual **SUVmax of 3.2** indicates persistent metabolic activity, preventing a classification of complete response.
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