Ultrasound Practice Questions

Q: What is the most sensitive investigation for a thyroid nodule?

USG. **Explanation:** **Ultrasound (USG)** is the investigation of choice and the most sensitive modality for evaluating thyroid nodules [1, 2]. Its high sensitivity stems from its ability to detect non-palpable nodules as small as 2 mm and accurately characterize their internal architecture (solid vs. cystic) [1]. It is essential for risk stratification using the **TI-RADS** (Thyroid Imaging Reporting and Data System) criteria and serves as the gold standard for guiding **Fine Needle Aspiration Cytology (FNAC)** [1, 5]. **Analysis of Incorrect Options:** * **Clinical Examination:** While the first step, it is highly insensitive. It often misses nodules smaller than 1 cm or those located posteriorly within the gland [3]. * **MRI:** Although useful for assessing local invasion into the esophagus or trachea in advanced malignancies, it is expensive, lacks the spatial resolution of USG for small nodules, and cannot reliably differentiate between benign and malignant lesions [2]. * **PET Scan:** This is a functional imaging modality used primarily for detecting metastases or recurrence in known cases of thyroid cancer. It is not a primary screening or diagnostic tool for thyroid nodules due to low specificity. **High-Yield Clinical Pearls for NEET-PG:** * **Best Initial Test:** USG [1]. * **Most Accurate/Definitive Test:** FNAC (Gold Standard for diagnosis) [5]. * **Hot vs. Cold Nodule:** Evaluated via **Radionuclide (Iodine-123/Technetium-99m) Scan** [3]. Cold nodules have a higher risk of malignancy (~15-20%), while hot nodules are rarely malignant [3]. * **USG Features suggestive of Malignancy:** Microcalcifications (Psammoma bodies), hypoechogenicity, irregular margins, and a "taller-than-wide" shape [4].

Q: Which of the following is a sonographic finding of a fetus with Down's syndrome?

All of the above. In prenatal screening, Down’s syndrome (Trisomy 21) is associated with several "soft markers" on ultrasound. These markers are not necessarily structural malformations but are minor anatomical variants that increase the probability of chromosomal abnormalities. **Explanation of Findings:** * **Nasal Bone Absence/Hypoplasia:** This is one of the most specific second-trimester markers. Approximately 60-70% of fetuses with Trisomy 21 have an absent or short nasal bone due to delayed ossification. * **Mild Renal Pelvis Dilation (Pyelectasis):** Defined as an anteroposterior diameter of ≥4 mm in the second trimester. While often transient and benign, it is found in roughly 17-25% of Down’s syndrome cases. * **Sandal Gap:** This refers to an increased space between the first and second toes. It is a classic dysmorphic feature seen in Trisomy 21 and can be visualized on a dedicated fetal foot view. **Why "All of the Above" is Correct:** Since all three findings—Sandal gap, Pyelectasis, and Nasal bone absence—are recognized sonographic markers for Trisomy 21, Option D is the correct choice. **High-Yield NEET-PG Pearls:** * **Nuchal Translucency (NT):** The most important **first-trimester** (11–13.6 weeks) marker. An increased NT (>3mm or >95th percentile) is highly suggestive of Trisomy 21. * **Nuchal Fold Thickness:** Measured in the **second trimester** (15–20 weeks); a value ≥6 mm is considered abnormal. * **Echogenic Intracardiac Focus (EIF):** A "bright spot" in the heart (usually left ventricle) is another common soft marker. * **Duodenal Atresia:** A structural defect ("Double Bubble sign") strongly associated with Down's syndrome.

Q: What is the frequency range of sound waves typically used for transabdominal ultrasonography?

3.5-5.0 MHz. **Explanation:** The choice of ultrasound frequency involves a fundamental trade-off between **penetration depth** and **axial resolution**. Lower frequencies penetrate deeper into tissues but offer lower resolution, while higher frequencies provide superior detail but cannot travel deep into the body. * **Correct Answer (B) 3.5-5.0 MHz:** This is the standard frequency range for **transabdominal ultrasonography**. In an adult, abdominal organs (liver, kidneys, spleen, gravid uterus) are located several centimeters deep. This range provides the optimal balance, allowing the sound waves to penetrate the abdominal wall and reach deep structures while maintaining sufficient image quality for diagnosis. **Analysis of Incorrect Options:** * **(A) 2.5-3.5 MHz:** These very low frequencies are typically reserved for **deep obstetric scanning** in obese patients or for **echocardiography**, where penetration through thick chest walls or deep pelvic structures is the primary requirement. * **(C) 5.0-7.5 MHz:** This range is used for **transvaginal (TVS)** or **transrectal (TRS)** probes. Since the transducer is placed closer to the organs of interest (uterus/prostate), less penetration is needed, allowing for higher resolution. * **(D) 7.5-10 MHz:** These high frequencies are used for **superficial structures** such as the thyroid, breast, testes, and musculoskeletal (MSK) imaging. They provide excellent resolution but have very poor penetration. **High-Yield Clinical Pearls for NEET-PG:** * **Piezoelectric Effect:** The conversion of electrical energy into mechanical (sound) energy by crystals (e.g., Lead Zirconate Titanate) is the basis of USG. * **A-Mode:** Used in ophthalmology for axial length measurement. * **M-Mode:** Used for assessing moving structures (fetal heart rate, cardiac valves). * **Doppler Effect:** Used to measure the velocity and direction of blood flow.

Q: Comment on the provided ultrasound image?

FAST positive. ***FAST positive*** - The ultrasound shows **free anechoic fluid** in **Morrison's pouch** (hepatorenal space), indicating **hemoperitoneum**. - A **FAST positive** result suggests significant intra-abdominal bleeding requiring immediate surgical evaluation in trauma patients. *FAST inconclusive* - This term indicates **technical difficulties** or **suboptimal visualization** preventing proper assessment of fluid collections. - Requires **repeat examination** or alternative imaging modalities like **CT scan** for definitive evaluation. *FAST negative* - A negative FAST shows **no free fluid** in any of the **four standard views** (pericardial, right upper quadrant, left upper quadrant, pelvis). - Does **not rule out** all intra-abdominal injuries, as **retroperitoneal bleeding** may not be detected. *FAST equivocal* - Refers to **borderline findings** where fluid presence is **uncertain** or **minimal amounts** are detected. - Requires **clinical correlation** and often **serial examinations** or **CT imaging** for clarification.

Q: Which of the following probes is used for transcranial ultrasonography?

Sectoral probe. **Explanation:** The correct answer is **C. Sectoral probe** (also known as a Phased Array probe). **Why Sectoral Probe is Correct:** Transcranial Doppler (TCD) or ultrasonography requires imaging the brain through narrow "acoustic windows" in the skull (such as the temporal bone, orbit, or foramen magnum) where the bone is thinnest. A **Sectoral probe** has a small footprint but produces a wide, fan-shaped field of view. This allows the ultrasound beam to be steered through a small physical gap while still visualizing deep intracranial structures and vasculature. Furthermore, it uses **low frequencies (typically 1–3 MHz)**, which are essential for better penetration through the dense cortical bone of the skull. **Why Other Options are Incorrect:** * **Linear Probe:** These use high frequencies (5–15 MHz) for high resolution but have poor penetration. They produce a rectangular image and are used for superficial structures like the thyroid, breast, or scrotum. * **Curvilinear Probe:** These have a large footprint and are used primarily for abdominal and obstetric imaging. Their size makes them unsuitable for the small acoustic windows of the skull. * **Endocavitary Probe:** These are specialized high-frequency probes designed for insertion into body cavities (transvaginal or transrectal) and are not used for cranial imaging. **High-Yield Clinical Pearls for NEET-PG:** * **Acoustic Windows:** The four standard windows for TCD are Transtemporal (most common), Transorbital, Transforaminal (Suboccipital), and Submandibular. * **Clinical Use:** TCD is the gold standard for monitoring **vasospasm** following Subarachnoid Hemorrhage (SAH) and for screening stroke risk in children with **Sickle Cell Anemia**. * **Frequency Rule:** Lower frequency = Higher penetration (used for deep/bony structures); Higher frequency = Higher resolution (used for superficial structures).

Q: The 'Filaria dance' sign is observed in which imaging modality?

Ultrasonography. **Explanation:** The **'Filaria Dance' sign** is a classic pathognomonic finding on **Ultrasonography (USG)**. It refers to the characteristic undulating, high-velocity, twirling movement of live adult filarial worms (typically *Wuchereria bancrofti*) within dilated lymphatic vessels. **1. Why Ultrasonography is correct:** High-frequency ultrasonography (usually 7.5–10 MHz) allows for real-time visualization of the lymphatic channels. In patients with lymphatic filariasis, the adult worms reside in the scrotal lymphatics (most common site) or the breast. Their continuous, irregular thrashing motion appears as curvilinear echogenic structures moving rapidly within an anechoic (fluid-filled) dilated space. This "dance" is a definitive sign of active infection. **2. Why other options are incorrect:** * **Radiography (X-ray):** Cannot visualize soft tissue parasites or lymphatics in real-time. It may only show calcified dead worms (Rice-grain calcifications), but not the "dance." * **HRCT:** While excellent for lung parenchyma, it lacks the real-time temporal resolution required to observe the rapid movement of parasites. * **Nuclear Scan:** Lymphoscintigraphy is used to assess lymphatic flow and obstruction (showing "hot spots" or delayed clearance), but it cannot visualize individual worm movement. **Clinical Pearls for NEET-PG:** * **Most common site:** Scrotal lymphatics (filarial scrotal dance). * **Doppler finding:** On Color Doppler, the movement produces a characteristic **optical flow artifact** (random color signals) due to the high velocity of the worms, not blood flow. * **Treatment:** Diethylcarbamazine (DEC) is the drug of choice; the "dance" typically disappears after successful treatment as the worms die. * **Associated finding:** Tropical Pulmonary Eosinophilia (TPE) is a systemic manifestation often tested alongside filariasis.

Q: What is the commonly used frequency range in obstetrical ultrasonography?

3.5-5 MHz. **Explanation:** In obstetrical ultrasonography, the choice of frequency is a balance between **penetration depth** and **axial resolution**. 1. **Why 3.5–5 MHz is correct:** Standard transabdominal ultrasound (TAS) for pregnancy requires the sound waves to travel through the maternal abdominal wall, subcutaneous fat, and uterine wall to reach the fetus. Frequencies in the **3.5–5 MHz** range provide the optimal penetration depth (up to 20 cm) necessary to visualize deep pelvic structures while maintaining sufficient resolution to assess fetal anatomy and growth. 2. **Why the other options are incorrect:** * **A & B (KHz range):** These are audible sound frequencies (20 Hz to 20 KHz). Diagnostic ultrasound operates in the **Megahertz (MHz)** range (millions of cycles per second), which is well above the human hearing threshold. * **D (20–25 MHz):** High-frequency waves provide excellent resolution but have very poor penetration. These frequencies are used for superficial structures (e.g., ophthalmology or intravascular USG) and cannot reach the depth required for obstetrics. **High-Yield Clinical Pearls for NEET-PG:** * **Transvaginal Sonography (TVS):** Uses higher frequencies (**5–10 MHz**) because the probe is closer to the target organs. This offers superior resolution for early pregnancy (first trimester) and cervical assessment. * **The Inverse Relationship:** Frequency is inversely proportional to penetration but directly proportional to resolution. (↑ Frequency = ↑ Resolution but ↓ Penetration). * **Safety:** Ultrasound is the preferred modality in pregnancy because it uses non-ionizing radiation, following the **ALARA** (As Low As Reasonably Achievable) principle.

Q: Endoscopic ultrasound is extremely useful in staging which tumour?

Carcinoma of the Esophagus. **Explanation:** **Endoscopic Ultrasound (EUS)** is considered the "gold standard" for the **locoregional staging (T and N staging)** of esophageal carcinoma. Its high-frequency transducer allows for detailed visualization of the individual layers of the esophageal wall, making it superior to CT and MRI for determining the depth of tumor invasion (T-stage) and identifying periesophageal lymphadenopathy (N-stage). * **Why Esophagus is the Correct Answer:** In **Carcinoma of the Esophagus**, EUS is the most accurate modality to differentiate between T1, T2, and T3 lesions. This is critical for clinical decision-making, specifically in determining whether a patient is a candidate for primary surgery or requires neoadjuvant chemoradiotherapy. * **Why other options are incorrect:** * **Carcinoma of the Colon:** Conventional colonoscopy and CT/MRI are preferred. EUS is technically difficult in the proximal colon and is primarily reserved for **Rectal Cancer** (Endorectal US). * **Carcinoma of the Stomach:** While EUS is used, CT is often the initial staging tool for distant metastasis. EUS is less accurate here than in the esophagus due to the larger lumen and gastric folds. * **Carcinoma of the Head of Pancreas:** EUS is excellent for biopsy (EUS-FNA) and detecting small tumors, but **Contrast-Enhanced CT (CECT) - Pancreatic Protocol** is the primary modality for staging and assessing vascular resectability. **High-Yield NEET-PG Pearls:** * **T-Staging:** EUS is the most sensitive tool for T-staging in esophageal and rectal cancers. * **M-Staging:** EUS is **not** used for distant metastasis (M-stage); PET-CT or CECT is required. * **EUS-FNA:** It is the investigation of choice for tissue diagnosis of pancreatic masses and mediastinal lymph nodes.

Q: Ultrasonogram is not useful in which of the following conditions?

Distal common bile duct stones. **Explanation:** The correct answer is **Distal common bile duct (CBD) stones**. **1. Why Distal CBD stones?** Ultrasound (USG) is the initial investigation of choice for the biliary tree; however, its sensitivity significantly decreases in the **distal (intrapancreatic) portion of the CBD**. This is primarily due to **overlying bowel gas** from the duodenum and stomach, which reflects sound waves and creates acoustic shadowing, obscuring the view. While USG is excellent at detecting proximal ductal dilation, it often misses the specific causative stone in the distal segment. For this reason, **Endoscopic Ultrasound (EUS)** or **MRCP** are the gold standards for visualizing distal CBD pathology. **2. Analysis of Incorrect Options:** * **Breast Cyst:** USG is the definitive tool to differentiate between solid and cystic breast masses. Cysts appear as well-defined, anechoic (black) structures with posterior acoustic enhancement. * **Ascites:** USG is highly sensitive and can detect as little as **5–10 mL** of peritoneal fluid. It is the standard procedure for identifying and marking fluid for paracentesis. * **Full Bladder:** A distended bladder acts as an **"acoustic window,"** displacing gas-filled bowel loops and allowing the ultrasound beam to travel through fluid to visualize pelvic organs like the uterus, ovaries, and prostate. **Clinical Pearls for NEET-PG:** * **IOC (Investigation of Choice)** for Gallstones/Cholelithiasis: Ultrasound. * **Gold Standard** for CBD stones: ERCP (Therapeutic) or MRCP (Diagnostic). * **Acoustic Shadowing:** Seen behind dense structures (stones/calcification). * **Acoustic Enhancement:** Seen behind fluid-filled structures (cysts/bladder).

Question 1

What is the most sensitive investigation for a thyroid nodule?

Accepted Answer

USG

Answer

MRI

Answer

PET Scan

Answer

Clinical examination

Question 2

Which of the following is a sonographic finding of a fetus with Down's syndrome?

Accepted Answer

All of the above

Answer

Sandal gap

Answer

Mild renal pelvis dilation

Answer

Nasal bone absence

Question 3

What is the frequency range of sound waves typically used for transabdominal ultrasonography?

Accepted Answer

3.5-5.0 MHz

Answer

2.5-3.5 MHz

Answer

5.0-7.5 MHz

Answer

7.5-10 MHz

Question 4

Comment on the provided ultrasound image?

Accepted Answer

FAST positive

Answer

FAST inconclusive

Answer

FAST negative

Answer

FAST equivocal

Question 5

Which of the following probes is used for transcranial ultrasonography?

Accepted Answer

Sectoral probe

Answer

Linear probe

Answer

Curvilinear probe

Answer

Endocavitary probe

Question 6

The 'Filaria dance' sign is observed in which imaging modality?

Accepted Answer

Ultrasonography

Answer

Radiography

Answer

HRCT

Answer

Nuclear scan

Question 7

What is the commonly used frequency range in obstetrical ultrasonography?

Accepted Answer

3.5-5 MHz

Answer

3.5-5 KHz

Answer

20-25 KHz

Answer

20-25 MHz

Question 8

Endoscopic ultrasound is extremely useful in staging which tumour?

Accepted Answer

Carcinoma of the Esophagus

Answer

Carcinoma of the Colon

Answer

Carcinoma of the Stomach

Answer

Carcinoma of the Head of the Pancreas

Question 9

Which of the following is NOT a feature of a normal venous Doppler study?

Accepted Answer

Triphasic pattern

Answer

Flow ceases with Valsalva maneuver

Answer

Flow augmentation with distal compression

Answer

Compressibility

Question 10

Ultrasonogram is not useful in which of the following conditions?

Accepted Answer

Distal common bile duct stones

Answer

Breast cyst

Answer

Ascites

Answer

Full bladder

Ultrasound — MCQs

Ultrasound — MCQs

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