Ultrasound Practice Questions

Q: The double bleb sign on ultrasound is indicative of which of the following?

Amniotic sac and yolk sac. **Explanation:** The **"Double Bleb Sign"** is a classic early sonographic marker of an intrauterine pregnancy, typically visible at approximately **5.5 to 6 weeks** of gestation. It describes the visualization of two small cystic structures—the **amniotic sac** and the **yolk sac**—situated side-by-side within the chorionic cavity, with the embryonic disc (the future fetus) sandwiched between them. * **Why Option B is Correct:** The "blebs" represent the developing amniotic sac and the yolk sac. At this early stage, the amniotic sac is very small and roughly equal in size to the yolk sac. Seeing these two structures together confirms the presence of an embryo, even if the embryo itself is too small to be clearly resolved. **Analysis of Incorrect Options:** * **Option A:** Two gestational sacs would indicate a diamniotic-dichorionic twin pregnancy, but they would appear as two separate larger rings rather than two small adjacent blebs within one sac. * **Option C & D:** While ultrasound is used to diagnose ectopic and heterotopic pregnancies, the double bleb sign specifically refers to the internal architecture of a gestational sac, usually implying an intrauterine location. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** The double bleb sign is seen before the amnion expands to fill the chorionic cavity. * **Yolk Sac:** It is the first structure to be seen within the gestational sac (at ~5 weeks). * **Mean Sac Diameter (MSD):** The double bleb sign is usually visible when the MSD is approximately 20 mm. * **Significance:** Its presence is a highly reliable indicator of a true intrauterine pregnancy, helping to differentiate a gestational sac from a "pseudogestational sac" (often seen in ectopic pregnancies).

Q: Which of the following statements regarding Doppler ultrasound is incorrect?

Monophasic tracing indicates abnormal flow.. **Explanation:** The correct answer is **A**, as the statement "Monophasic tracing indicates abnormal flow" is a generalization that is not always true. **1. Why Option A is the correct (incorrect statement):** In Doppler ultrasound, the "phasicity" of a waveform depends on the **vascular resistance** of the organ being supplied. * **Low-resistance vessels** (e.g., Internal Carotid Artery, Renal Artery, Hepatic Artery) normally show **monophasic flow** with continuous forward flow during diastole to ensure constant perfusion to vital organs. * **High-resistance vessels** (e.g., resting Femoral Artery) normally show **triphasic flow**. Therefore, a monophasic tracing is **normal** for certain vessels and only indicates pathology (like proximal stenosis) when found in a vessel that should normally be triphasic. **2. Analysis of other options:** * **Option B:** Doppler measures the frequency shift, which is used to calculate the **velocity** of blood flow using the Doppler equation. * **Option C:** Color Doppler uses a color map (typically BART: Blue Away, Red Towards) to indicate the **direction** of flow relative to the transducer. * **Option D:** By measuring peak systolic velocity (PSV) and end-diastolic velocity (EDV), Doppler is the gold standard for non-invasively assessing the **degree of stenosis** (e.g., Carotid artery stenosis). **High-Yield Clinical Pearls for NEET-PG:** * **BART Sign:** Blue Away, Red Towards (refers to the transducer). * **Spectral Broadening:** Indicates turbulent flow, often seen just distal to a stenosis. * **Tardus Parvus Effect:** A small, late peak (monophasic) seen **distal** to a significant arterial obstruction. * **Aliasing:** An artifact occurring when the Nyquist limit is exceeded; it is corrected by increasing the Pulse Repetition Frequency (PRF).

Q: Evaluation of cardiac valve motion and fetal heart rate is done in which mode of ultrasound?

M-mode. **Explanation:** The correct answer is **M-mode (Motion mode)**. In ultrasound, **M-mode** is used to display the movement of structures over time. It works by taking a single line of a B-mode image and displaying it repeatedly along a time axis. This provides high temporal resolution, making it the gold standard for evaluating rapidly moving structures such as **cardiac valve leaflets** (e.g., mitral valve excursion) and measuring the **fetal heart rate** during early pregnancy. **Analysis of Incorrect Options:** * **A-mode (Amplitude mode):** This is the simplest form where echoes are displayed as vertical spikes on a baseline. The height of the spike represents the amplitude (strength) of the echo. It is primarily used in ophthalmology for axial length measurements of the eye. * **B-mode (Brightness mode):** This is the standard 2D grayscale ultrasound. It converts echo amplitudes into pixels of varying brightness to create a structural image. While it shows anatomy, it lacks the temporal precision of M-mode for tracking rapid motion. * **D-mode (Doppler mode):** This utilizes the Doppler shift to evaluate the velocity and direction of blood flow within vessels, rather than the anatomical motion of valves or heart walls. **High-Yield Clinical Pearls for NEET-PG:** * **M-mode** is essential for calculating **Ejection Fraction (EF)** using the Teichholz formula and diagnosing **cardiac tamponade** (by showing right ventricular collapse). * In lung ultrasound, a normal M-mode shows the **"Seashore sign,"** while a pneumothorax shows the **"Barcode sign" or "Stratosphere sign."** * **Real-time B-mode** is the most commonly used mode in general radiology for abdominal and pelvic imaging.

Q: TI-RADS is a reporting system for thyroid nodules. It is based on the following properties, except:

Vascularity. **Explanation:** The **ACR TI-RADS (Thyroid Imaging Reporting and Data System)** is a standardized scoring system used to assess the risk of malignancy in thyroid nodules and determine the need for Fine Needle Aspiration (FNA). **Why Vascularity is the correct answer:** Unlike the BI-RADS system for breast imaging, the ACR TI-RADS **does not include vascularity** (Doppler findings) in its scoring criteria. While internal vascularity was historically considered a risk factor, large-scale studies have shown it is not a reliable independent predictor of thyroid cancer. Therefore, it is excluded from the point-based calculation. **Analysis of other options (The 5 TI-RADS Categories):** The ACR TI-RADS scores nodules based on five specific ultrasound features: 1. **Composition:** (e.g., cystic, spongiform, or solid). 2. **Echogenicity (Option B):** (e.g., hyperechoic, isoechoic, or highly hypoechoic). 3. **Shape (Option D):** Specifically looking for a **"Taller-than-wide"** orientation (highly suspicious). 4. **Margin (Option A):** (e.g., smooth, ill-defined, lobulated, or extrathyroidal extension). 5. **Echogenic Foci:** (e.g., punctate echogenic foci/microcalcifications). **High-Yield Clinical Pearls for NEET-PG:** * **Most Suspicious Feature:** A "Taller-than-wide" shape and "Punctate echogenic foci" (microcalcifications) carry the highest points (3 points each). * **Highly Hypoechoic:** This is a strong indicator of malignancy compared to simple hypoechogenicity. * **Management:** Points from all five categories are summed to categorize the nodule from TR1 (Benign) to TR5 (Highly Suspicious), which then dictates the size threshold for FNA. * **Note:** If a question mentions **EU-TIRADS** or **K-TIRADS**, vascularity is also generally excluded, making this a consistent high-yield fact across different systems.

Q: On ultrasound, what typically causes dirty shadowing?

Air. **Explanation:** In ultrasonography, shadowing occurs when the sound beam encounters a structure with high attenuation or a significant difference in acoustic impedance, preventing the beam from passing through. **1. Why Air is Correct:** Air has a very low acoustic impedance compared to soft tissue, causing nearly 100% reflection of the ultrasound beam at the tissue-gas interface. This results in **"Dirty Shadowing,"** characterized by a greyish, poorly defined shadow containing internal echoes. These echoes are caused by **reverberation artifacts** and **ring-down artifacts** as the sound bounces between the transducer and the gas bubbles or between the bubbles themselves. **2. Why Incorrect Options are Wrong:** * **Bone & Calcification (Options B & C):** These are dense structures that absorb and reflect sound almost entirely. They produce **"Clean Shadowing,"** which is a crisp, well-defined, and completely black (anechoic) area behind the structure because no sound waves penetrate to create internal echoes. * **Muscle (Option D):** Muscle is a soft tissue with intermediate attenuation. It does not typically cause shadowing unless it is heavily calcified or contains foreign bodies. **3. High-Yield NEET-PG Pearls:** * **Clean Shadow:** Seen in Gallstones (Cholelithiasis), Kidney stones (Nephrolithiasis), and mature bone. * **Dirty Shadow:** Seen in Bowel gas, Emphysematous cholecystitis, and Abscesses containing gas-forming organisms. * **Comet-tail Artifact:** A form of reverberation artifact often seen with metallic foreign bodies or adenomyomatosis of the gallbladder. * **Acoustic Enhancement:** The opposite of shadowing; seen behind fluid-filled structures like simple cysts.

Q: What causes an acoustic shadow in ultrasound imaging?

Reflection. ### Explanation **Correct Answer: C. Reflection** **Why Reflection is Correct:** Acoustic shadowing occurs when an ultrasound beam encounters a structure with high **acoustic impedance** (such as a gallstone or bone). Because the difference in impedance between the structure and the surrounding soft tissue is so vast, the majority of the sound waves are **reflected** back to the transducer. Since very few sound waves can penetrate through the object to reach deeper tissues, a signal-void area (black/anechoic zone) is created behind the object. This is known as "clean" shadowing. **Analysis of Incorrect Options:** * **A. Artifact:** While acoustic shadowing is technically a type of *acoustic artifact*, the question asks for the **physical cause**. Reflection is the mechanism that generates this specific artifact. * **B. Absorption:** While some energy is lost to heat (absorption), it is not the primary cause of the distinct shadow seen behind dense calcifications. Absorption is more relevant to tissue heating and attenuation in soft tissues. * **D. Refraction:** This refers to the bending of the ultrasound beam at an interface. Refraction causes "edge shadows" (narrow shadows at the margins of curved structures like the gallbladder or kidney), but not the dense central shadow of a stone. **High-Yield Clinical Pearls for NEET-PG:** * **Clean Shadowing:** Produced by calcified structures (e.g., gallstones, kidney stones, bone). It indicates high reflection. * **Dirty Shadowing:** Produced by **gas/air** (e.g., bowel gas, emphysematous cholecystitis). It is caused by multiple internal reflections (reverberation) and appears greyish/hazy. * **Acoustic Enhancement:** The opposite of shadowing; it occurs behind fluid-filled structures (like cysts) because fluid attenuates sound less than surrounding tissue, making deeper structures appear brighter.

Q: Sonographic scan shows:

Twins. ***Twins*** - **Two gestational sacs** or **two fetal poles** are clearly visible on the ultrasound scan, confirming twin pregnancy. - Doppler studies may show **two separate fetal heart beats** with distinct rhythms, further supporting twin gestation. *Single fetus* - Would show only **one gestational sac** and **one fetal pole** on ultrasound examination. - **Single fetal heart beat** would be detected, ruling out multiple gestation. *Snow storm appearance* - This is a characteristic finding of **hydatidiform mole** (molar pregnancy), not a normal pregnancy. - Shows **grape-like vesicles** with **hyperechoic areas** and **absent fetal structures**, completely different from twin pregnancy. *Triplets* - Would demonstrate **three gestational sacs** or **three fetal poles** on ultrasound scan. - **Three separate fetal heart beats** would be identifiable, indicating higher-order multiple pregnancy.

Q: What is the smallest size of gallstone that can be confidently diagnosed using ultrasonography?

1.5 mm. **Explanation:** Ultrasonography (USG) is the gold standard for diagnosing cholelithiasis due to its high sensitivity (up to 95%) and specificity. The correct answer is **1.5 mm** because modern high-frequency transducers (5–10 MHz) have excellent axial resolution, allowing for the detection of very small, echogenic foci within the gallbladder lumen. * **Why 1.5 mm is correct:** A gallstone is characterized by an echogenic focus that moves with gravity and typically casts a posterior acoustic shadow. While shadowing is more consistently seen in stones >3 mm, a stone as small as 1.5 mm can be confidently identified if it is highly reflective and the focal zone of the transducer is correctly positioned. * **Why other options are incorrect:** * **3 mm:** While this is often cited as the threshold where **posterior acoustic shadowing** becomes reliably visible, it is not the minimum size for detection. * **5 mm and 10 mm:** These are significantly larger than the technical limit of modern USG. These sizes are more relevant when considering surgical indications (e.g., polyps >10 mm) rather than diagnostic limits. **High-Yield Clinical Pearls for NEET-PG:** * **WES Triad:** Wall-Echo-Shadow (WES) sign is seen when the gallbladder is completely filled with stones. * **Acoustic Shadowing:** Occurs because stones reflect/absorb sound waves. To enhance a shadow from a small stone, use a **higher frequency transducer** and ensure the stone is in the **focal zone**. * **Sludge:** Low-level echoes that do not shadow but move slowly with change in position (precursor to stone formation). * **False Positives:** Polyps (do not move/shadow) and Porcelain Gallbladder (calcified wall).

Q: Ultrasound diagnoses all the following except?

Down syndrome. **Explanation:** The correct answer is **Down Syndrome (Option B)** because ultrasound is a **screening tool**, not a definitive diagnostic tool, for chromosomal abnormalities. 1. **Why Down Syndrome is the correct answer:** While ultrasound can identify "soft markers" associated with Down syndrome (Trisomy 21)—such as increased **Nuchal Translucency (NT)** in the first trimester, an absent nasal bone, or cardiac defects—these findings are only suggestive. A definitive diagnosis requires **karyotyping** or chromosomal analysis via invasive procedures like Amniocentesis or Chorionic Villus Sampling (CVS). 2. **Why the other options are incorrect:** * **Anencephaly:** This is a structural neural tube defect characterized by the absence of the cranial vault and cerebral hemispheres (the "Frog-eye appearance"). It is easily diagnosed via ultrasound as early as 10–12 weeks. * **Placenta Previa:** Ultrasound is the **gold standard** for localizing the placenta. It can clearly visualize the relationship between the placental edge and the internal os of the cervix. * **Hydatidiform Mole:** Ultrasound is diagnostic for molar pregnancies, typically showing a characteristic **"Snowstorm appearance"** (a vesicular mass with multiple small cystic spaces) and the absence of a fetus in a complete mole. **High-Yield Clinical Pearls for NEET-PG:** * **Nuchal Translucency (NT):** Measured between 11 and 13+6 weeks. A value >3mm is highly suspicious for aneuploidy. * **Snowstorm Appearance:** Classic USG sign for Hydatidiform mole. * **Frog-eye/Mickey Mouse Appearance:** Classic USG sign for Anencephaly. * **Double Bubble Sign:** USG finding in Duodenal Atresia, often associated with Down Syndrome.

Question 1

The double bleb sign on ultrasound is indicative of which of the following?

Accepted Answer

Amniotic sac and yolk sac

Answer

Two intrauterine gestational sacs

Answer

Ectopic pregnancy

Answer

Heterotopic pregnancy

Question 2

Which of the following statements regarding Doppler ultrasound is incorrect?

Accepted Answer

Monophasic tracing indicates abnormal flow.

Answer

It provides information about blood velocity.

Answer

It determines the direction of blood flow.

Answer

It assesses the degree of stenosis.

Question 3

Evaluation of cardiac valve motion and fetal heart rate is done in which mode of ultrasound?

Accepted Answer

M-mode

Answer

A-mode

Answer

B-mode

Answer

D-mode

Question 4

TI-RADS is a reporting system for thyroid nodules. It is based on the following properties, except:

Accepted Answer

Vascularity

Answer

Margin

Answer

Echogenicity

Answer

Shape

Question 5

On ultrasound, what typically causes dirty shadowing?

Accepted Answer

Air

Answer

Bone

Answer

Calcification

Answer

Muscle

Question 6

What causes an acoustic shadow in ultrasound imaging?

Accepted Answer

Reflection

Answer

Artifact

Answer

Absorption

Answer

Refraction

Question 7

Sonographic scan shows:

Accepted Answer

Twins

Answer

Single fetus

Answer

Snow storm appearance

Answer

Triplets

Question 8

What is the smallest size of gallstone that can be confidently diagnosed using ultrasonography?

Accepted Answer

1.5 mm

Answer

3 mm

Answer

5 mm

Answer

10 mm

Question 9

Ultrasound diagnoses all the following except?

Accepted Answer

Down syndrome

Answer

Anencephaly

Answer

Placenta previa

Answer

Hydatidiform mole

Question 10

At what gestational week is accurate diagnosis of anencephaly typically seen on ultrasound?

Accepted Answer

14 weeks of gestation

Answer

6 weeks of gestation

Answer

8 weeks of gestation

Answer

10 weeks of gestation

Ultrasound — MCQs

Ultrasound — MCQs

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