Doppler Ultrasound Principles and Applications — MCQs
The intensity of colour in Doppler is determined by-
A woman with an obstetric score of G2P1 comes to the clinic at 14 weeks of gestation for her antenatal checkup. A uterine artery doppler was suggested by the doctor. What would it detect?
What is the most specific use of Doppler ultrasound in twin pregnancies?
In current obstetrics practice, what is the best test for monitoring sensitized Rh negative mother?
On Doppler, the most ominous sign indicating fetal compromise is:
Following are the ultrasound parameters used in the diagnosis of intrauterine growth restriction except?
Which of the following is the best in-vivo screening choice for carotid artery stenosis?
How does 'hepatic vein thrombosis' present on Doppler ultrasound?
Causes of thickened gallbladder wall on ultrasound examination are all except:
Which is not echogenic while doing ultrasonography:
Doppler Ultrasound Principles and Applications Indian Medical PG Practice Questions and MCQs
Question 1: The intensity of colour in Doppler is determined by-
- A. Strength of returning echo
- B. Velocity of flow (Correct Answer)
- C. Direction of flow
- D. None of the options
Explanation: ***Velocity of flow*** - The **intensity of color** in Doppler ultrasound is directly related to the **velocity of blood flow**; faster flow typically results in a brighter or more intense color display. - This is because the Doppler shift, which the ultrasound system uses to calculate velocity and assign color, is proportional to the speed of the moving blood cells. *Strength of returning echo* - The **strength of the returning echo** (amplitude) primarily determines the **brightness** of the B-mode image (grayscale), not the intensity of the color Doppler signal. - It relates to the density and acoustic properties of the tissue or blood, not its motion. *Direction flow* - The **direction of flow** relative to the ultrasound beam determines the **hue** of the color displayed (e.g., red for flow towards the transducer, blue for flow away). - It does not influence the intensity or brightness of that color.
Question 2: A woman with an obstetric score of G2P1 comes to the clinic at 14 weeks of gestation for her antenatal checkup. A uterine artery doppler was suggested by the doctor. What would it detect?
- A. Risk of early-onset preeclampsia (Correct Answer)
- B. Risk of late-onset preeclampsia
- C. Risk of placenta accreta
- D. Fetal growth restriction risk
Explanation: **Risk of early-onset preeclampsia** - **Uterine artery Doppler** at 11-14 weeks of gestation is used to screen for **preeclampsia risk**, particularly **early-onset preeclampsia**, which is associated with impaired placental development. - An increased **pulsatility index (PI)** or presence of **bilateral notching** in the uterine arteries indicates high resistance to blood flow, suggesting a higher risk of developing this condition. *Risk of late-onset preeclampsia* - While uterine artery Doppler can indicate a general risk for preeclampsia, its predictive value is significantly lower for **late-onset preeclampsia** (after 34 weeks). - Late-onset preeclampsia often has different underlying causes, not solely related to abnormal **trophoblast invasion** detectable by early Doppler. *Risk of placenta accreta* - **Placenta accreta** is typically associated with previous **cesarean sections** or other uterine surgeries, leading to abnormal placental implantation. - It is diagnosed by the absence of a clear retroplacental hypoechoic zone and features such as **lacunae** on **ultrasound**, not primarily by uterine artery Doppler. *Fetal growth restriction risk* - Uterine artery Doppler at 11-14 weeks can offer some indication of **fetal growth restriction (FGR)** risk, particularly if severe and related to **placental insufficiency**. - However, the primary surveillance for FGR later in pregnancy often involves **umbilical artery Doppler** and fetal biometry, not solely early uterine artery Doppler.
Question 3: What is the most specific use of Doppler ultrasound in twin pregnancies?
- A. Evaluating conjoined twins
- B. Monitoring fetal well-being in twins
- C. Assessing twin-to-twin transfusion syndrome (Correct Answer)
- D. All of the options
Explanation: ***Assessing twin-to-twin transfusion syndrome (TTTS)*** - Doppler ultrasound is crucial for diagnosing and monitoring **TTTS** by evaluating blood flow in the umbilical arteries and veins, and assessing fetal cardiac output and venous flow patterns. - It helps detect the characteristic signs of **TTTS**, such as unequal blood flow between twins and abnormal Doppler indices in the umbilical and middle cerebral arteries, guiding timely intervention. *Evaluating conjoined twins* - While ultrasound identifies **conjoined twins** and their anatomical connections, Doppler primarily assesses blood flow, not the structural fusion itself. - 2D and 3D ultrasound are more directly used for the anatomical evaluation of the degree and type of organ sharing in **conjoined twins**. *Monitoring fetal well-being in twins* - Though Doppler can contribute to **fetal well-being assessment** through blood flow analysis, its primary and most specific role in twin pregnancies is the diagnosis and management of **TTTS**. - Other parameters like **biophysical profile** and growth scans are also vital for general fetal well-being in twins. *All of the options* - This option is incorrect because while Doppler ultrasound might be part of a broader assessment in some scenarios, its most significant and specific application in twin pregnancies is for **TTTS**. - Its role in the direct evaluation of conjoined twin anatomy or general fetal well-being is secondary to specialized applications like **TTTS** diagnosis.
Question 4: In current obstetrics practice, what is the best test for monitoring sensitized Rh negative mother?
- A. Biophysical profile
- B. Amniotic fluid spectrophotometry
- C. Middle cerebral artery Doppler wave forms (Correct Answer)
- D. Fetal blood sampling
Explanation: ***Middle cerebral artery Doppler wave forms*** - This is currently the most widely accepted and **non-invasive** method for monitoring **fetal anemia** in Rh-sensitized pregnancies. - An increase in the **peak systolic velocity (PSV)** in the middle cerebral artery indicates that the fetus is increasing cardiac output to compensate for a reduced oxygen-carrying capacity due to anemia. *Biophysical profile* - The biophysical profile assesses various fetal parameters like **movement**, **tone**, **breathing**, and **amniotic fluid volume**, which are often altered late in the course of severe fetal anemia. - It is a **less sensitive** indicator of early or moderate fetal anemia compared to MCA Doppler. *Amniotic fluid spectrophotometry* - This method measures the **bilirubin levels** in amniotic fluid, which correlates with the severity of hemolysis. - It is an **invasive procedure** (amniocentesis) and has largely been replaced by non-invasive MCA Doppler due to associated risks and better predictive value of Doppler. *Fetal blood sampling* - Fetal blood sampling (cordocentesis) provides a direct measurement of **fetal hemoglobin** and other blood parameters. - While definitive, it is a **highly invasive procedure** with significant risks, reserved primarily for confirmation of severe anemia or for direct transfusion, not for routine monitoring.
Question 5: On Doppler, the most ominous sign indicating fetal compromise is:
- A. ↑ pulsatility index in umbilical artery
- B. ↑ S/D blood flow ratio
- C. ↑ Cerebral artery flow
- D. Absent diastolic flow (Correct Answer)
Explanation: ***Absent diastolic flow*** - This indicates a severe increase in **vascular resistance** within the placental circulation, signifying significant fetal compromise. - The absence of forward flow during diastole means the fetus is receiving **minimal blood supply** during relaxation, leading to hypoxia and acidosis. *↑ pulsatility index in umbilical artery* - An elevated pulsatility index (PI) suggests increased resistance to blood flow in the **placental circulation**, indicating compromise. - However, it is generally less severe than absent or reversed diastolic flow, which are later stages of fetal compromise. *↑ S/D blood flow ratio* - An increased S/D ratio in the umbilical artery signifies **higher resistance** to blood flow, often due to placental insufficiency. - While concerning, it is considered an earlier indicator of compromise compared to the complete absence of diastolic flow. *↑ Cerebral artery flow* - Increased cerebral artery flow (often decreased PI in the middle cerebral artery) is a sign of **brain-sparing effect**, where the fetus redistributes blood flow to essential organs. - This is a compensatory mechanism and, while indicating compromise, means the fetus is still able to adapt to some extent, unlike absent diastolic flow which represents decompensation.
Question 6: Following are the ultrasound parameters used in the diagnosis of intrauterine growth restriction except?
- A. Doppler velocimetry
- B. Increased diastolic velocity in middle cerebral artery
- C. Abdominal circumference
- D. Ponderal index (Correct Answer)
Explanation: ***Ponderal index*** - The **ponderal index** is a measure of proportionality (weight/length³) used to assess fetal body proportions and nutritional status, but it is calculated **after birth** using the newborn's weight and length. - It is **not an ultrasound parameter** used during prenatal diagnosis of intrauterine growth restriction (IUGR). - While it can identify asymmetric growth patterns postnatally, it has no role in prenatal IUGR assessment. *Abdominal circumference* - **Fetal abdominal circumference (AC)** is a key **biometric ultrasound parameter** that is essential in diagnosing IUGR. - It reflects fetal liver size and subcutaneous fat stores, making it the **most sensitive single parameter** for detecting IUGR. - Serial AC measurements below the 10th percentile or showing poor growth velocity are diagnostic criteria for IUGR. *Doppler velocimetry* - **Doppler velocimetry**, particularly of the **umbilical artery**, is crucial for assessing placental vascular resistance and diagnosing IUGR. - Abnormal findings include **increased pulsatility index (PI)**, **absent end-diastolic flow (AEDF)**, or **reversed end-diastolic flow (REDF)**. - These findings indicate placental insufficiency and help classify IUGR severity. *Increased diastolic velocity in middle cerebral artery* - **Increased diastolic velocity** in the middle cerebral artery (leading to **decreased PI/RI**) indicates the **brain-sparing effect** (cerebrovasodilation). - This is a fetal compensatory response to chronic hypoxemia in IUGR. - The **cerebroplacental ratio (CPR)** (umbilical artery PI / MCA PI) is a sensitive marker for adverse perinatal outcomes in IUGR.
Question 7: Which of the following is the best in-vivo screening choice for carotid artery stenosis?
- A. Digital Subtraction Angiography (DSA)
- B. CT
- C. MRI
- D. USG (Correct Answer)
Explanation: ***USG*** - **Ultrasound** (USG), specifically **carotid duplex ultrasonography**, is the **safest**, most cost-effective, and readily available initial screening tool for carotid artery stenosis due to its non-invasive nature and ability to visualize blood flow and vessel morphology. - It combines **B-mode imaging** with **Doppler flow analysis** to provide real-time images and flow velocity measurements, allowing for assessment of the degree of **stenosis** and plaque characteristics without radiation or contrast agents. - Sensitivity and specificity exceed 85-90% for detecting significant stenosis, making it the preferred first-line screening modality. *Digital Subtraction Angiography (DSA)* - **DSA** is the **gold standard** for anatomical detail and remains the most accurate method for quantifying carotid stenosis, but it is **invasive** and requires arterial catheterization. - It involves **ionizing radiation** and **iodinated contrast agents**, carrying risks of stroke (0.5-1%), arterial dissection, nephrotoxicity, and contrast allergic reactions. - Due to its invasive nature and associated risks, DSA is reserved for **pre-surgical planning** or when non-invasive imaging is inconclusive, not for initial screening. *CT* - **Computed tomography angiography (CTA)** involves **ionizing radiation** and typically requires an **iodinated contrast agent**, which carries risks of allergy and nephrotoxicity. - Though CTA provides excellent anatomical detail and can visualize vessel wall calcification, it is generally reserved for confirmation or surgical planning rather than initial screening due to its higher cost, radiation exposure, and contrast-related risks. *MRI* - **Magnetic resonance angiography (MRA)** can visualize carotid arteries well but is more expensive, less accessible than ultrasound, and may require a **gadolinium-based contrast agent**, which can have adverse effects (nephrogenic systemic fibrosis in renal impairment). - It is often used when ultrasound findings are equivocal or in cases where CTA is contraindicated, but it's not the preferred initial screening method due to its complexity, cost, longer examination time, and contraindications (pacemakers, metallic implants).
Question 8: How does 'hepatic vein thrombosis' present on Doppler ultrasound?
- A. Absent or reversed flow (Correct Answer)
- B. Anechoic appearance
- C. Increased flow
- D. Normal triphasic flow
Explanation: ***Absent or reversed flow*** - **Hepatic vein thrombosis** directly obstructs blood flow, leading to either an absence of detectable flow or, in some cases, reversal of flow due to high downstream pressure and collateral formation. - This finding on **Doppler ultrasound** is a key indicator of **Budd-Chiari syndrome**, caused by the obstruction of hepatic venous outflow. *Anechoic appearance* - An **anechoic appearance** on ultrasound typically refers to a fluid-filled structure, such as a cyst or gallbladder, which allows sound waves to pass through without reflection. - While thrombosis can affect the lumen of a vessel, the thrombus itself often has some echogenicity, and the primary Doppler finding relates to flow dynamics, not simply the anechoic nature of the vessel. *Increased flow* - **Increased flow** in the hepatic veins would suggest a hyperdynamic state or shunting, which is not characteristic of venous thrombosis. - Thrombosis causes obstruction, leading to a reduction or cessation of flow, not an increase. *Normal triphasic flow* - **Normal triphasic flow** in the hepatic veins is characterized by three distinct phases corresponding to cardiac cycles: antegrade flow during systole and diastole, and a brief period of reversed flow during atrial contraction. - The presence of thrombosis would disrupt this normal pattern, making it an unlikely finding in **hepatic vein thrombosis**.
Question 9: Causes of thickened gallbladder wall on ultrasound examination are all except:
- A. Congestive cardiac failure
- B. Postprandial state
- C. Kawasaki disease (Correct Answer)
- D. Cholecystitis
Explanation: ***Kawasaki disease*** (Correct Answer) - While Kawasaki disease can cause **gallbladder hydrops** (distension with bile), the primary ultrasound finding is an **enlarged, distended gallbladder** rather than isolated wall thickening. - When gallbladder involvement occurs in Kawasaki disease, it manifests as **acalculous cholecystitis** with hydrops, but this is **not a typical or common presentation** compared to the other causes listed. - The hallmark features of Kawasaki disease are **coronary artery aneurysms** and systemic vasculitis, not primary gallbladder pathology. - In clinical practice, gallbladder wall thickening would **not be attributed to Kawasaki disease** as a primary differential diagnosis. *Incorrect: Congestive cardiac failure* - **Systemic fluid overload** and venous congestion in CHF leads to gallbladder wall thickening due to **transudative edema**. - This is a **common cause** of non-inflammatory gallbladder wall thickening (>3mm). - The wall appears thickened, hypoechoic, and **edematous** without pericholecystic fluid. *Incorrect: Postprandial state* - After eating, the gallbladder **contracts to release bile**, causing the wall to appear thicker on ultrasound due to **accordion-like folding** of the mucosa. - This is a **normal physiological finding** and typically resolves within 1-2 hours. - Scanning should ideally be done after **6-8 hours of fasting** to avoid this pseudo-thickening. *Incorrect: Cholecystitis* - **Acute cholecystitis** is the **classic cause** of gallbladder wall thickening (>3mm, often >5mm). - Associated findings include **gallstones, pericholecystic fluid, positive sonographic Murphy's sign**, and wall edema. - The wall shows **layering** (subserosal edema) and hyperemia on Doppler imaging.
Question 10: Which is not echogenic while doing ultrasonography:
- A. Bile (Correct Answer)
- B. Bone
- C. Gas
- D. Gall stones
Explanation: ***Bile*** - Bile is largely composed of **water**, which allows ultrasound waves to pass through it with minimal reflection, appearing **anechoic** (black) on ultrasound. - This property makes the gallbladder lumen, when filled with bile, appear anechoic, which is crucial for identifying structures like gallstones. *Bone* - **Bone** is highly dense and reflects a significant portion of ultrasound waves, making it appear very **echogenic** (bright) on ultrasonography. - Due to its high reflectivity, bone often produces a strong **acoustic shadow** behind it, obscuring deeper structures. *Gas* - **Gas** (air) is a strong reflector of ultrasound waves and appears brightly echogenic, often with a characteristic **dirty shadowing** or **reverberation artifact**. - The presence of gas can significantly hinder visualization of underlying tissues due to its strong reflection and scatter of the ultrasound beam. *Gall stones* - **Gallstones** are solid concretions that are highly reflective of ultrasound waves, appearing as bright, **echogenic foci** within the gallbladder lumen. - A classic ultrasound sign of gallstones is an echogenic structure with strong **posterior acoustic shadowing**.
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