Ultrasound Practice Questions

Q: Which of the following conditions cannot be diagnosed by Ultrasound (USG)?

Down's syndrome. **Explanation:** The correct answer is **D. Down’s syndrome**. **1. Why Down’s syndrome is the correct answer:** Down’s syndrome (Trisomy 21) is a **genetic/chromosomal diagnosis**, not a structural one. While Ultrasound (USG) can identify "soft markers" or associated structural anomalies (like an absent nasal bone or endocardial cushion defects), it cannot provide a definitive diagnosis. A definitive diagnosis of Down’s syndrome requires **Karyotyping** or chromosomal analysis via invasive procedures like Amniocentesis or Chorionic Villus Sampling (CVS). **2. Analysis of Incorrect Options:** * **Anencephaly:** This is a major structural defect characterized by the absence of the cranial vault and cerebral hemispheres. It is easily diagnosed on USG (often called the "Frog-eye appearance") as early as the late first trimester. * **Neural Tube Defects (NTDs):** USG is the gold standard for screening structural anomalies like Spina Bifida. Findings such as the "Lemon sign" (scalloping of frontal bones) and "Banana sign" (curved cerebellum) are classic sonographic markers. * **Placenta Previa:** USG is the investigation of choice for placental localization. It accurately identifies the relationship between the placenta and the internal cervical os. **3. Clinical Pearls for NEET-PG:** * **First Trimester Screening for Down’s:** Increased **Nuchal Translucency (NT)** >3mm between 11–13.6 weeks is a high-yield USG marker, but it is a *screening* tool, not diagnostic. * **Combined Test:** Includes NT scan + PAPP-A + β-hCG. * **Level II Scan (Anomaly Scan):** Performed at **18–20 weeks** to detect structural malformations. * **Safe Modality:** USG is preferred in pregnancy because it uses non-ionizing radiation (mechanical sound waves).

Q: "Lemon sign" and "Banana sign" on Antenatal Ultrasound are seen in which condition?

Chiari Malformation. ### Explanation The "Lemon" and "Banana" signs are classic sonographic markers of **Neural Tube Defects (NTDs)**, specifically associated with **Arnold-Chiari Malformation Type II**. **1. Why Chiari Malformation is Correct:** These signs occur due to the downward displacement of the hindbrain through the foramen magnum, which creates a pressure gradient: * **Lemon Sign:** The frontal bones of the fetal skull collapse inward (scalloping), giving the head a shape resembling a lemon. This is due to low intracranial pressure. While it is highly sensitive for spina bifida, it often disappears after 24 weeks as the skull bones ossify. * **Banana Sign:** The cerebellum is pulled downward and wrapped around the brainstem, losing its typical "dumbbell" shape and appearing curved like a banana. This also leads to the obliteration of the **Cisterna Magna**. **2. Why Other Options are Incorrect:** * **Down Syndrome (Trisomy 21):** Associated with an increased **Nuchal Translucency (NT)**, absent nasal bone, echogenic intracardiac focus, and duodenal atresia ("Double bubble sign"). * **Turner Syndrome (45, XO):** Characterized by **Cystic Hygroma** (posterior neck fluid collection) and coarctation of the aorta. * **Klinefelter Syndrome (47, XXY):** Usually does not present with specific structural anomalies detectable on routine antenatal ultrasound. **Clinical Pearls for NEET-PG:** * **Banana sign** is more specific for spina bifida than the lemon sign. * The presence of these signs should prompt a meticulous search for **Spina Bifida Aperta** (Meningomyelocele). * **Strawberry skull** is associated with **Trisomy 18** (Edwards Syndrome). * **Cisterna Magna measurement:** Normal is **2–10 mm**. If 10 mm, suspect Dandy-Walker malformation.

Q: All of the following are ultrasonographic fetal growth parameters except?

Transcerebeller diameter. **Explanation:** In fetal ultrasonography, **fetal growth parameters** are specific biometric measurements used to estimate the **Estimated Fetal Weight (EFW)** and assess for conditions like Intrauterine Growth Restriction (IUGR) or macrosomia. 1. **Why Transcerebellar Diameter (TCD) is the correct answer:** While TCD is a vital biometric measurement, it is primarily used for **dating the pregnancy (gestational age)** rather than assessing growth. The cerebellum is relatively resistant to growth restriction (the "brain-sparing effect"), meaning its size remains consistent even if the fetus is malnourished. Therefore, it serves as a reliable baseline to determine the actual age of the fetus when other parameters are lagging. 2. **Analysis of Incorrect Options (Standard Growth Parameters):** * **Biparietal Diameter (BPD) & Head Circumference (HC):** These measure the fetal head. HC is considered more reliable than BPD in cases of abnormal head shapes (dolichocephaly/brachycephaly). * **Femur Length (FL):** This measures the longitudinal growth of the skeletal system. * **Abdominal Circumference (AC):** (Though not listed, it is the most sensitive indicator of fetal growth/nutrition). * *Note:* The combination of BPD, HC, FL, and AC is used in the **Hadlock Formula** to calculate EFW. **High-Yield Clinical Pearls for NEET-PG:** * **Most sensitive parameter for IUGR:** Abdominal Circumference (AC). * **Best parameter for dating in the 1st Trimester:** Crown-Rump Length (CRL). * **TCD Rule of Thumb:** Between 14 and 20 weeks, the TCD in millimeters is roughly equal to the gestational age in weeks. * **Brain-Sparing Effect:** In asymmetrical IUGR, the head and cerebellum are preserved while the AC decreases.

Q: Which of the following is not a prerequisite for transvaginal sonography?

Full bladder. **Explanation:** In Transvaginal Sonography (TVS), the ultrasound probe is placed in the vaginal fornix, directly adjacent to the pelvic organs (uterus and ovaries). Because the probe is in close proximity to these structures, it uses higher-frequency transducers which provide superior resolution compared to transabdominal scans. **1. Why "Full Bladder" is the Correct Answer (Not a Prerequisite):** A **full bladder** is a prerequisite for **Transabdominal Sonography (TAS)**, where it acts as an "acoustic window" to push bowel loops away and transmit sound waves to the pelvic organs. In TVS, however, a full bladder is a hindrance. It pushes the uterus and ovaries too far away from the high-frequency probe (which has limited depth penetration) and can cause patient discomfort during probe manipulation. Therefore, a full bladder is contraindicated for TVS. **2. Analysis of Other Options:** * **Consent:** Essential for any invasive or semi-invasive procedure. Since TVS involves internal probe insertion, informed verbal or written consent is mandatory. * **Empty Bladder:** This is a strict prerequisite for TVS. It ensures the pelvic organs are as close to the vaginal vault as possible for optimal imaging. * **Lithotomy Position:** The patient must be in a lithotomy or modified lithotomy position (often using a pelvic wedge) to allow the sonographer the necessary range of motion to tilt the probe and visualize the adnexa. **High-Yield Clinical Pearls for NEET-PG:** * **TVS vs. TAS:** TVS offers better resolution (high frequency) but less depth; TAS offers better "field of view" (low frequency) but less resolution. * **First Trimester:** TVS can detect a gestational sac as early as **4.5–5 weeks**, whereas TAS usually requires **5.5–6 weeks**. * **Beta-hCG Discriminatory Zone:** A gestational sac should be visible via TVS when serum Beta-hCG levels reach **1500–2000 mIU/mL**.

Q: Distal acoustic shadow is seen in?

All of the above. **Explanation:** **Acoustic Shadowing** is a common ultrasound artifact that occurs when the ultrasound beam encounters a structure with a very high **attenuation coefficient** or high **acoustic impedance**. When the beam hits such a structure, most of the sound waves are either reflected or absorbed, leaving a signal-void (black) area distal to the object. **Why "All of the Above" is correct:** * **Calculi (Gallstones/Renal stones):** These are dense structures that reflect and absorb sound waves significantly. They typically produce "clean" shadows (sharp, black borders). * **Bone:** Bone has the highest acoustic impedance in the body. It reflects the majority of the ultrasound beam at the soft tissue-bone interface, preventing deeper penetration and creating a dense distal shadow. * **Air (Gas):** Air has extremely low acoustic impedance compared to soft tissue, causing a massive mismatch. This results in nearly total reflection of the sound beam. Air often produces "dirty" shadows (shadows containing internal echoes or reverberations). **Clinical Pearls for NEET-PG:** 1. **Clean vs. Dirty Shadowing:** * **Clean Shadow:** Characterized by an absence of echoes. Seen in **Calculi** and **Bone**. * **Dirty Shadow:** Characterized by internal echoes/reverberations. Seen in **Air/Bowel Gas** and **Emphysematous Cholecystitis**. 2. **Acoustic Enhancement:** The opposite of shadowing. It occurs distal to fluid-filled structures (e.g., simple cysts, gallbladder) because fluid attenuates sound much less than surrounding tissue. 3. **Edge Shadowing:** A specific type of shadowing seen at the curved edges of cystic structures due to refraction of the beam.

Q: Harmonic imaging is related to which of the following imaging modalities?

Sonography. **Explanation:** **Tissue Harmonic Imaging (THI)** is a specialized ultrasound technique based on the principle of non-linear propagation of sound waves through tissues. When an ultrasound pulse travels, it undergoes distortion, generating frequencies that are integer multiples of the original (fundamental) frequency. The ultrasound machine filters out the fundamental frequency and processes only these "harmonics" (usually the second harmonic) to create an image. **Why Sonography is correct:** In sonography, THI significantly improves image quality by: * **Reducing artifacts:** It minimizes side-lobe artifacts and reverberations (e.g., "sludge" in the gallbladder). * **Improving resolution:** It provides better lateral resolution and improved contrast-to-noise ratios, making it easier to visualize small lesions or cysts in technically difficult patients (e.g., obese patients). **Why other options are incorrect:** * **Digital Radiography:** Uses X-rays and digital detectors; it does not utilize wave harmonics. * **MRCP (Magnetic Resonance Cholangiopancreatography):** Uses MRI sequences (T2-weighted) based on proton spin and relaxation times, not acoustic harmonics. * **Nuclear Imaging:** Relies on the detection of gamma rays emitted from radiopharmaceuticals injected into the body. **High-Yield Clinical Pearls for NEET-PG:** * **Contrast-Enhanced Ultrasound (CEUS):** Uses microbubble contrast agents which are highly non-linear, making harmonic imaging essential for visualizing blood flow and tumor vascularity. * **Key Advantage:** THI is particularly useful for clearing "pseudo-sludge" in the gallbladder and improving the visualization of the endocardial border in echocardiography. * **Trade-off:** While THI improves resolution, it may result in a slight loss of penetration depth compared to fundamental imaging.

Q: What is the preferred non-invasive imaging modality for screening carotid artery stenosis?

Doppler Ultrasound. **Explanation:** **Doppler Ultrasound** is the preferred non-invasive screening modality for carotid artery stenosis because it provides both anatomical and functional data. It combines high-resolution B-mode imaging (to visualize plaque morphology) with spectral Doppler (to measure blood flow velocities). According to the NASCET criteria, peak systolic velocity (PSV) is the primary parameter used to grade the severity of stenosis. It is cost-effective, portable, and lacks ionizing radiation or nephrotoxic contrast. **Why other options are incorrect:** * **Ultrasound (USG):** While B-mode ultrasound visualizes the vessel wall and plaque, it cannot assess the hemodynamic significance (flow velocity) of the stenosis. "Doppler" is the specific functional component required for diagnosis. * **Computed Tomography (CT):** CT Angiography (CTA) is highly accurate for surgical planning but is not used for *screening* due to radiation exposure and the need for iodinated contrast. * **Magnetic Resonance Imaging (MRI):** MR Angiography (MRA) is excellent for visualizing the carotids but is expensive, time-consuming, and less accessible than Doppler, making it unsuitable for initial screening. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Digital Subtraction Angiography (DSA) remains the gold standard but is invasive. * **Key Parameter:** A **Peak Systolic Velocity (PSV) >230 cm/s** typically correlates with >70% stenosis. * **Plaque Characterization:** Ultrasound is superior for identifying "vulnerable plaques" (hypoechoic/ulcerated), which carry a higher risk of embolic stroke. * **ICA/CCA Ratio:** A ratio >4.0 is highly suggestive of significant internal carotid artery stenosis.

Q: What is the earliest fetal anomaly detectable by ultrasound?

Anencephaly. **Explanation:** **Anencephaly** is the correct answer because it is a lethal neural tube defect characterized by the absence of the cranial vault (acrania) and cerebral hemispheres. This structural defect is established very early in embryogenesis (failure of the rostral neuropore to close by day 25-27). With high-resolution transvaginal sonography (TVS), it can be diagnosed as early as **10–14 weeks** of gestation. The classic ultrasound findings include the "Frog-eye appearance" or "Mickey Mouse sign" due to the absence of the calvarium and bulging orbits. **Why the other options are incorrect:** * **Hydrocephalus:** Ventriculomegaly is typically not diagnosed until the **second trimester** (usually after 18 weeks), as the choroid plexus normally fills the lateral ventricles in the first trimester, making early detection unreliable. * **Achondroplasia:** This is the most common non-lethal skeletal dysplasia, but it typically manifests in the **third trimester** (after 26 weeks) when rhizomelic (proximal) limb shortening becomes sonographically evident. * **Spina Bifida:** While screening begins in the late first trimester via "intracranial translucency," a definitive diagnosis is usually made during the **level II anomaly scan (18–20 weeks)** by visualizing the vertebral defect or secondary cranial signs (Lemon/Banana signs). **High-Yield Clinical Pearls for NEET-PG:** * **Acrania-Anencephaly Sequence:** Acrania (absent skull with present brain) is the precursor to anencephaly; the unprotected brain tissue eventually degenerates due to exposure to amniotic fluid (exencephaly). * **Biochemical Marker:** Anencephaly is associated with markedly elevated **Maternal Serum Alpha-Fetoprotein (MSAFP)**. * **Associated Finding:** Polyhydramnios is common in the late second/third trimester due to the fetus's inability to swallow.

Question 1

Which of the following conditions cannot be diagnosed by Ultrasound (USG)?

Accepted Answer

Down's syndrome

Answer

Anencephaly

Answer

Neural tube defect

Answer

Placenta previa

Question 2

In colour Doppler, the colour displayed depends upon which of the following?

Accepted Answer

The relation of the transducer to the direction of blood flow

Answer

The strength of the returning echo

Answer

The frequency of the Doppler used

Answer

The type of Doppler machine used

Question 3

"Lemon sign" and "Banana sign" on Antenatal Ultrasound are seen in which condition?

Accepted Answer

Chiari Malformation

Answer

Down syndrome

Answer

Turner syndrome

Answer

Klinefelter syndrome

Question 4

All of the following are ultrasonographic fetal growth parameters except?

Accepted Answer

Transcerebeller diameter

Answer

Biparietal diameter

Answer

Head circumference

Answer

Femur length

Question 5

Which of the following is not a prerequisite for transvaginal sonography?

Accepted Answer

Full bladder

Answer

Consent

Answer

Empty bladder

Answer

Lithotomy position

Question 6

Distal acoustic shadow is seen in?

Accepted Answer

All of the above

Answer

Air

Answer

Calculi

Answer

Bone

Question 7

USG is/are based on which of the following principles?

Accepted Answer

Piezoelectric effect

Answer

Diamagnetic effect

Answer

Paramagnetic effect

Answer

Ferromagnetic effect

Question 8

Harmonic imaging is related to which of the following imaging modalities?

Accepted Answer

Sonography

Answer

Digital radiography

Answer

MRCP

Answer

Nuclear imaging

Question 9

What is the preferred non-invasive imaging modality for screening carotid artery stenosis?

Accepted Answer

Doppler Ultrasound

Answer

Ultrasound (USG)

Answer

Computed Tomography (CT)

Answer

Magnetic Resonance Imaging (MRI)

Question 10

What is the earliest fetal anomaly detectable by ultrasound?

Accepted Answer

Anencephaly

Answer

Hydrocephalus

Answer

Achondroplasia

Answer

Spina bifida

Ultrasound — MCQs

Ultrasound — MCQs

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