X-ray principles and interpretation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for X-ray principles and interpretation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
X-ray principles and interpretation US Medical PG Question 1: A 57-year-old man presents to his family physician for a routine exam. He feels well and reports no new complaints since his visit last year. Last year, he had a colonoscopy which showed no polyps, a low dose chest computerized tomography (CT) scan that showed no masses, and routine labs which showed a fasting glucose of 93 mg/dL. He is relatively sedentary and has a body mass index (BMI) of 24 kg/m^2. He has a history of using methamphetamines, alcohol (4-5 drinks per day since age 30), and tobacco (1 pack per day since age 18), but he joined Alcoholics Anonymous and has been in recovery, not using any of these for the past 7 years. Which of the following is indicated at this time?
- A. Colonoscopy
- B. Chest computerized tomography (CT) scan (Correct Answer)
- C. Abdominal ultrasound
- D. Chest radiograph
- E. Fasting glucose
X-ray principles and interpretation Explanation: ***Chest computerized tomography (CT) scan***
- This patient has a significant **smoking history** (1 pack per day since age 18 = **39 pack-years**) and is 57 years old, placing him in a high-risk group for **lung cancer**.
- Annual low-dose CT screening for lung cancer is recommended for individuals aged 50-80 with a 20 pack-year smoking history who currently smoke or have quit within the past 15 years.
- He meets all criteria: age 57, 39 pack-years, and quit only 7 years ago (within the 15-year window).
- Since he had screening **last year** with no masses, this year's visit represents the appropriate time for his **annual follow-up screening**.
*Colonoscopy*
- The patient had a colonoscopy last year with **no polyps**, suggesting he is at average risk for colorectal cancer.
- For individuals at average risk with normal findings, repeat screening colonoscopy is typically recommended every **10 years** (or every 5 years for flexible sigmoidoscopy), not annually.
*Abdominal ultrasound*
- One-time abdominal ultrasound screening for **abdominal aortic aneurysm (AAA)** is recommended for men aged 65-75 who have ever smoked.
- This patient is only 57 years old and does not yet meet the age criteria for AAA screening.
*Chest radiograph*
- While a chest radiograph can identify some lung abnormalities, a **low-dose CT scan** is far more sensitive and specific for detecting early-stage lung cancer in high-risk populations.
- Chest radiography is **not recommended** as a screening tool for lung cancer due to its lower sensitivity and lack of mortality benefit in trials.
*Fasting glucose*
- The patient had a **normal fasting glucose** of 93 mg/dL last year, and there are no new symptoms suggestive of diabetes.
- For asymptomatic adults with normal glucose, diabetes screening is typically repeated every **3 years**.
- Annual re-screening is not indicated without new risk factors or symptoms.
X-ray principles and interpretation US Medical PG Question 2: A 60-year-old man comes to the physician for an examination prior to a scheduled cholecystectomy. He has hypertension treated with hydrochlorothiazide. His mother had chronic granulomatous disease of the lung. He works in a glass manufacturing plant. He has smoked two packs of cigarettes daily for 38 years. His vital signs are within normal limits. Examination shows no abnormalities. Laboratory studies are within the reference range. An x-ray of the chest is shown. Which of the following is the most appropriate next step in management?
- A. Perform diffusion capacity of the lung for carbon monoxide
- B. Perform arterial blood gas analysis
- C. Request previous chest x-ray (Correct Answer)
- D. Perform CT-guided biopsy
- E. Measure angiotensin-converting enzyme
X-ray principles and interpretation Explanation: ***Request previous chest x-ray***
- Comparing the current chest X-ray with previous ones is crucial to determine if the findings are **new or chronic**, which significantly impacts further management.
- Given the patient's age, smoking history, and occupational exposure, a nodule or infiltrates could be present for a long time without causing symptoms, and a **stable finding** would alleviate immediate concern.
*Perform diffusion capacity of the lung for carbon monoxide*
- **DLCO** measures the lung's ability to transfer gas from inhaled air to the bloodstream and is primarily used to assess **interstitial lung disease** or emphysema.
- While the patient has risk factors for lung disease (smoking, occupational exposure), without a specific indication of interstitial lung disease or significant respiratory symptoms, it is not the most immediate next step, especially before understanding the chronicity of any X-ray findings.
*Perform arterial blood gas analysis*
- **ABG analysis** assesses oxygenation, ventilation, and acid-base balance, typically performed in patients with acute respiratory distress, significant dyspnea, or to monitor severe lung pathology.
- The patient is **asymptomatic** with normal vital signs, and there is no indication that his gas exchange is compromised, making ABG analysis premature.
*Perform CT-guided biopsy*
- A **CT-guided biopsy** is an invasive procedure used to obtain tissue for histological diagnosis, typically reserved when a lesion is highly suspicious for malignancy or infection and non-invasive methods are insufficient.
- It is an aggressive initial step without first characterizing the X-ray findings further or determining if the lesion is new or chronic.
*Measure angiotensin-converting enzyme*
- **ACE levels** are primarily used in the diagnosis and monitoring of **sarcoidosis**, a granulomatous disease.
- While the patient's mother had "chronic granulomatous disease of the lung," implying a possible genetic link or predisposition to granulomatous conditions, there are no specific findings on the history or presentation to directly suggest sarcoidosis, and it would be a secondary investigation after initial X-ray comparison.
X-ray principles and interpretation US Medical PG Question 3: A 36-year-old male is taken to the emergency room after jumping from a building. Bilateral fractures to the femur were stabilized at the scene by emergency medical technicians. The patient is lucid upon questioning and his vitals are stable. Pain only at his hips was elicited. Cervical exam was not performed. What is the best imaging study for this patient?
- A. AP and lateral radiographs of hips
- B. Lateral radiograph (x-ray) of hips
- C. Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area
- D. Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area
- E. Computed tomography (CT) scan of cervical spine, hips, and lumbar area (Correct Answer)
X-ray principles and interpretation Explanation: ***Computed tomography (CT) scan of cervical spine, hips, and lumbar area***
- In **high-energy trauma** (fall from height), a CT scan is the **gold standard** for evaluating the **spine and pelvis**, providing detailed cross-sectional images superior to plain radiographs.
- Since the **cervical exam was not performed**, cervical spine imaging is **mandatory** per ATLS (Advanced Trauma Life Support) protocols. High-energy falls carry significant risk of **cervical spine injury** even without obvious neurological symptoms.
- CT allows comprehensive assessment of **hip fractures, pelvic injuries, and the entire spine** (cervical, thoracic, lumbar), identifying both obvious and **subtle fractures** that may be missed on plain films.
- This approach provides the most **efficient and thorough evaluation** in the acute trauma setting, allowing for appropriate surgical planning and ruling out life-threatening spinal instability.
*AP and lateral radiographs of hips*
- Plain radiographs provide **limited detail** and may **miss subtle fractures**, particularly in complex areas like the pelvis and acetabulum.
- This option **fails to address cervical spine clearance**, which is essential in all high-energy trauma patients, especially when cervical exam has not been performed.
- Radiographs are insufficient for **comprehensive trauma evaluation** after a fall from height.
*Lateral radiograph (x-ray) of hips*
- A single lateral view is **grossly insufficient** for evaluating hip and pelvic fractures, providing only a **two-dimensional perspective** that can miss significant injuries.
- This option **completely neglects spinal evaluation**, which is dangerous in an uncleared trauma patient with a high-energy mechanism.
*Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area*
- While MRI excels at evaluating **soft tissues, ligaments, and bone marrow**, it is **not the initial imaging modality** for acute bony trauma due to longer scan times and lower sensitivity for acute fractures compared to CT.
- MRI is **time-consuming and impractical** in the emergency setting for initial fracture assessment, potentially delaying definitive treatment.
- CT is superior for evaluating **acute skeletal injuries** in the trauma bay.
*Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area*
- Multiple plain radiographs have **limited sensitivity** for complex or non-displaced fractures, particularly in the **spine and pelvis**, making them inadequate for high-energy trauma evaluation.
- Obtaining multiple radiographic views requires **numerous patient repositionings**, which risks further injury if **spinal instability** is present.
- Plain films provide significantly **less diagnostic information** than CT scanning for trauma assessment.
X-ray principles and interpretation US Medical PG Question 4: A 45-year-old man in respiratory distress presents to the emergency department. He sustained a stab to his left chest and was escorted to the nearest hospital. The patient appears pale and has moderate difficulty with breathing. His O2 saturation is 94%. The left lung is dull to percussion. CXRs are ordered and confirm the likely diagnosis. His blood pressure is 95/57 mm Hg, the respirations are 22/min, the pulse is 87/min, and the temperature is 36.7°C (98.0°F). His chest X-ray is shown. Which of the following is the next best step in management for this patient?
- A. ABG
- B. Needle aspiration
- C. CT scan
- D. Thoracotomy
- E. Chest tube insertion (Correct Answer)
X-ray principles and interpretation Explanation: ***Chest tube insertion***
- The patient presents with **respiratory distress**, a **stab wound to the chest**, and the chest X-ray likely shows a **hemothorax** or **pneumothorax**, as indicated by the dullness to percussion and the imaging description.
- **Chest tube insertion** is the definitive treatment for significant hemothorax or pneumothorax, allowing for drainage of blood/air and lung re-expansion.
*ABG*
- While an **arterial blood gas (ABG)** can provide information about oxygenation and ventilation, it is a diagnostic test and not a primary therapeutic intervention for acute respiratory distress due to chest trauma.
- Addressing the underlying cause (hemothorax/pneumothorax) is paramount before detailed physiologic assessment, which might delay life-saving treatment.
*Needle aspiration*
- **Needle aspiration** (thoracentesis or needle decompression) can be used for simple pneumothorax or small effusions but is generally insufficient for a large hemothorax or tension pneumothorax, especially in a patient with signs of hypovolemic shock (low BP).
- Given the stab wound and patient's unstable status, a more definitive and continuous drainage method is required.
*CT scan*
- A **CT scan** provides detailed imaging but is generally not indicated in an unstable patient with acute chest trauma who likely has a life-threatening condition like hemothorax or pneumothorax.
- Delaying definitive treatment for further imaging in an unstable patient can be detrimental.
*Thoracotomy*
- **Thoracotomy** is an invasive surgical procedure indicated for massive hemothorax (e.g., >1500 mL blood drainage immediately or >200 mL/hr for 2-4 hours) or ongoing hemorrhage not controlled by a chest tube.
- It is a more aggressive step and not the first-line intervention in this scenario, where a chest tube is typically needed first to assess the extent of bleeding and lung re-expansion.
X-ray principles and interpretation US Medical PG Question 5: A tall, slender 32-year-old man comes to the emergency room because of sudden chest pain, cough, and shortness of breath. On physical examination, he has decreased breath sounds on the right. Chest radiography shows translucency on the right side of his chest. His pCO2 is elevated and pO2 is decreased. What is the most likely cause of his symptoms?
- A. Spontaneous pneumothorax (Correct Answer)
- B. Chronic obstructive pulmonary disease
- C. Tension pneumothorax
- D. Asthma
- E. Pneumonia
X-ray principles and interpretation Explanation: ***Spontaneous pneumothorax***
- The patient's presentation with **sudden chest pain**, **cough**, and **shortness of breath** in a **tall, slender young man** is classic for a primary spontaneous pneumothorax.
- **Decreased breath sounds** on the affected side and **translucency on chest X-ray** (indicating air in the pleural space) further support this diagnosis.
*Chronic obstructive pulmonary disease*
- COPD typically affects older individuals with a history of smoking and presents with **chronic progressive dyspnea**, not sudden onset.
- While COPD can lead to secondary spontaneous pneumothorax, the patient's age and lack of pre-existing lung disease make this less likely as the primary cause.
*Tension pneumothorax*
- A tension pneumothorax is a **life-threatening condition causing mediastinal shift** and severe hemodynamic compromise (e.g., hypotension, tracheal deviation) which are not described.
- While it shares some features, the absence of these critical signs means a simple spontaneous pneumothorax is more likely first.
*Asthma*
- Asthma presents with **episodic wheezing**, cough, and shortness of breath, often triggered by allergens or exercise.
- The sudden onset of symptoms with **decreased localized breath sounds** and radiological findings of transparencies do not align with typical asthma exacerbations.
*Pneumonia*
- Pneumonia usually involves **fever, productive cough, and localized crackles** or bronchial breath sounds on examination.
- Chest X-rays in pneumonia show **infiltrates or consolidation**, which contrast with the translucency seen in this case.
X-ray principles and interpretation US Medical PG Question 6: A 64-year-old man presents to the office for an annual physical examination. He has no complaints at this visit. His chart states that he has a history of hypertension, chronic obstructive pulmonary disease (emphysema), Raynaud’s disease, and glaucoma. He is a 30 pack-year smoker. His medications included lisinopril, tiotropium, albuterol, nifedipine, and latanoprost. The blood pressure is 139/96 mm Hg, the pulse is 86/min, the respiration rate is 16/min, and the temperature is 37.2°C (99.1°F). On physical examination, his pupils are equal, round, and reactive to light. The cardiac auscultation reveals an S4 gallop without murmur, and the lungs are clear to auscultation bilaterally. However, the inspection of the chest wall shows an enlarged anterior to posterior diameter. Which of the following is the most appropriate screening test for this patient?
- A. Low-dose CT (Correct Answer)
- B. Bronchoalveolar lavage with cytology
- C. Magnetic resonance imaging
- D. Pulmonary function tests
- E. Chest radiograph
X-ray principles and interpretation Explanation: ***Low-dose CT***
- This patient, a 64-year-old with a 30 pack-year smoking history and current emphysema (COPD), falls precisely within the **high-risk criteria** for lung cancer screening.
- The **USPSTF guidelines** recommend annual **low-dose computed tomography (LDCT)** for individuals aged 50-80 years with a 20 pack-year smoking history who currently smoke or have quit within the past 15 years.
*Bronchoalveolar lavage with cytology*
- This is an **invasive diagnostic procedure** used to collect cells and fluid directly from the airways, typically performed when there is already suspicion of a lung malignancy or infection.
- It is not a recommended **screening test** for asymptomatic individuals due to its invasiveness and the absence of clear evidence of benefit as a primary screening tool.
*Magnetic resonance imaging*
- **MRI** is primarily used for evaluating soft tissue structures, defining tumor extent, and assessing metastatic disease, but it is **not the preferred imaging modality for lung cancer screening** due to its lower spatial resolution for pulmonary nodules compared to CT and higher cost.
- It involves longer scan times and is not routinely used for primary lung screening.
*Pulmonary function tests*
- **PFTs** are used to assess lung function, diagnose and monitor respiratory conditions like COPD, and evaluate the severity of airflow obstruction.
- While important for managing his **emphysema**, PFTs do not directly screen for **lung cancer**; they measure how well the lungs work.
*Chest radiograph*
- A **chest X-ray** is less sensitive than LDCT for detecting small lung nodules and early-stage lung cancer due to its two-dimensional nature and potential for superimposition of structures.
- While readily available and less expensive, it is **not recommended for lung cancer screening** as it has not shown a mortality benefit in randomized controlled trials compared to no screening.
X-ray principles and interpretation US Medical PG Question 7: A 45-year-old man presents for a follow-up visit as part of his immigration requirements into the United States. Earlier this week, he was administered the Mantoux tuberculin skin test (TST). Today’s reading, 3 days after being administered the test, he shows an induration of 10 mm. Given his recent immigration from a country with a high prevalence of tuberculosis, he is requested to obtain a radiograph of the chest, which is shown in the image. Which of the following is true regarding this patient’s chest radiograph (CXR)?
- A. Posterior ribs 9 and 10 are visible only in an expiratory film.
- B. The right lower boundary of the mediastinal silhouette belongs to the right ventricle.
- C. If the spinous process is not in-between the two clavicular heads, the image is repeated. (Correct Answer)
- D. The film is taken in a supine position.
- E. The view is anteroposterior (AP).
X-ray principles and interpretation Explanation: ***If the spinous process is not in-between the two clavicular heads, the image is repeated.***
- Proper patient positioning is crucial for an accurate chest X-ray; **rotation of the patient** can distort the appearance of the heart and lungs, simulating pathology or obscuring real findings.
- Symmetrical positioning, indicated by the **spinous process being equidistant from the medial ends of the clavicles**, ensures an ideal posteroanterior (PA) view for interpretation.
*Posterior ribs 9 and 10 are visible only in an expiratory film.*
- In a properly **inspired chest X-ray**, at least 9 or 10 posterior ribs (or 5-6 anterior ribs) should be visible above the diaphragm.
- If fewer ribs are visible on a standard PA film, it indicates a **poor inspiratory effort**, which can compress lung fields and mimic pathology.
*The right lower boundary of the mediastinal silhouette belongs to the right ventricle.*
- The **right lower boundary of the mediastinal silhouette** is formed by the right atrium, not the right ventricle.
- The right ventricle forms part of the **anterior cardiac border** and is typically not seen as a distinct border on a standard PA chest X-ray.
*The film is taken in a supine position.*
- The presence of the **gastric bubble visible below the left hemidiaphragm** confirms an upright position, as gas rises in the stomach.
- A supine film would typically result in a **magnified cardiac silhouette** and less prominent gastric air.
*The view is anteroposterior (AP).*
- In an AP view, the **medial ends of the clavicles overlay the lung apices**, and the scapulae are often within the lung fields; this image shows the scapulae largely clear of the lung fields, consistent with a PA view.
- AP films also tend to **magnify the heart shadow** due to the divergent X-ray beam, which is not evident here.
X-ray principles and interpretation US Medical PG Question 8: During an evaluation of a new diagnostic imaging modality for detecting salivary gland tumors, 90 patients tested positive out of the 100 patients who tested positive with the gold standard test. A total of 80 individuals tested negative with the new test out of the 100 individuals who tested negative with the gold standard test. What is the positive likelihood ratio for this test?
- A. 80/90
- B. 90/100
- C. 90/20 (Correct Answer)
- D. 90/110
- E. 10/80
X-ray principles and interpretation Explanation: ***90/20***
- The **positive likelihood ratio (LR+)** is calculated as **sensitivity / (1 - specificity)**. To calculate this, we first need to determine the values for true positives (TP), false positives (FP), true negatives (TN), and false negatives (FN).
- Given that 90 out of 100 actual positive patients tested positive, **TP = 90** and **FN = 100 - 90 = 10**. Also, 80 out of 100 actual negative patients tested negative, so **TN = 80** and **FP = 100 - 80 = 20**.
- **Sensitivity** is the true positive rate (TP / (TP + FN)) = 90 / (90 + 10) = 90 / 100.
- **Specificity** is the true negative rate (TN / (TN + FP)) = 80 / (80 + 20) = 80 / 100.
- Therefore, LR+ = (90/100) / (1 - 80/100) = (90/100) / (20/100) = **90/20**.
*80/90*
- This option incorrectly represents the components for the likelihood ratio. It seems to misinterpret the **true negative** count and the **true positive** count.
- It does not follow the formula for LR+ which is **sensitivity / (1 - specificity)**.
*90/100*
- This value represents the **sensitivity** of the test, which is the proportion of true positives among all actual positives.
- It does not incorporate the **false positive rate** (1 - specificity) in the denominator required for the positive likelihood ratio.
*90/110*
- This option incorrectly combines different values, possibly by confusing the denominator for sensitivity or specificity calculations.
- It does not correspond to the formula for the **positive likelihood ratio**.
*10/80*
- This value seems to relate to the inverse of the **false negative rate** (10/100) or misrepresents the relationship between false negatives and true negatives.
- It is not correctly structured to represent the **positive likelihood ratio (LR+)**.
X-ray principles and interpretation US Medical PG Question 9: A 6-month-old boy is brought to the emergency department by his mother, who informs the doctor that her alcoholic husband hit the boy hard on his back. The blow was followed by excessive crying for several minutes and the development of redness in the area. On physical examination, the boy is dehydrated, dirty, and irritable and when the vital signs are checked, they reveal tachycardia. He cries immediately upon the physician touching the area around his left scapula. The doctor strongly suspects a fracture of the 6th, 7th, or 8th retroscapular posterior ribs. Evaluation of his skeletal survey is normal. The clinician is concerned about child abuse in this case. Which of the following is the most preferred imaging technique as the next step in the diagnostic evaluation of the infant?
- A. Bedside ultrasonography
- B. Magnetic resonance imaging
- C. Babygram
- D. Chest computed tomography scan
- E. Skeletal survey in 2 weeks (Correct Answer)
X-ray principles and interpretation Explanation: ***Skeletal survey in 2 weeks***
- A repeat **skeletal survey in 2 weeks** is the most appropriate next step in suspected child abuse cases with an initial normal survey, as it allows for the detection of **healing fractures** that may not be apparent immediately after injury.
- New bone formation and callus development around a fracture site become radiographically visible after approximately 7 to 14 days, improving the detection rate of subtle or undisplaced fractures.
*Bedside ultrasonography*
- While **ultrasonography** can detect acute fractures, especially in cartilage and non-ossified bones, its utility in a comprehensive assessment for multiple non-displaced rib fractures as part of a child abuse workup is limited.
- It is highly **operator-dependent** and may not provide the full skeletal overview required in suspected child abuse.
*Magnetic resonance imaging*
- **MRI** is excellent for evaluating soft tissue injuries, bone marrow edema, and non-ossified cartilaginous structures. However, it is not the primary imaging modality for detecting acute or subacute fractures of ossified bone and requires **sedation** in infants, making it less practical for routine skeletal screening.
- The **high cost** and limited availability of MRI also make it less suitable as a first-line diagnostic tool for rib fractures in this context.
*Babygram*
- A **babygram** is a single large radiograph of an infant's entire body, often used to rapidly assess for gross developmental anomalies or immediate concerns.
- It provides **less detailed imaging** of individual bones compared to a standard skeletal survey and is insufficient for reliably detecting subtle or non-displaced rib fractures.
*Chest computed tomography scan*
- A **chest CT scan** is highly sensitive for detecting acute rib fractures, even subtle ones. However, it exposes the infant to **significant radiation** and is usually reserved for specific clinical indications, such as suspected internal organ injury, rather than as a primary screening tool for rib fractures in child abuse in an otherwise stable patient.
- It does not provide a comprehensive view of the entire skeleton, which is crucial for identifying other potential abuse-related injuries elsewhere.
X-ray principles and interpretation US Medical PG Question 10: A 2-year-old child is brought to the emergency department with rapid breathing and a severe cyanotic appearance of his lips, fingers, and toes. He is known to have occasional episodes of mild cyanosis, especially when he is extremely agitated. This is the worst episode of this child’s life, according to his parents. He was born with an APGAR score of 8 via a normal vaginal delivery. His development is considered delayed compared to children of his age. History is significant for frequent squatting after strenuous activity. On auscultation, there is evidence of a systolic ejection murmur at the left sternal border. On examination, his oxygen saturation is 71%, blood pressure is 81/64 mm Hg, respirations are 42/min, pulse is 129/min, and temperature is 36.7°C (98.0°F). Which of the following will most likely be seen on chest x-ray (CXR)?
- A. Egg on a string
- B. Boot-shaped heart (Correct Answer)
- C. Increased pulmonary vascular markings
- D. Cardiomegaly with globular heart
- E. Figure-3 sign
X-ray principles and interpretation Explanation: ***Boot-shaped heart***
- The patient's presentation with **cyanosis**, **squatting spells**, and a **systolic ejection murmur** is classic for **Tetralogy of Fallot** (TOF).
- A **boot-shaped heart** (Coeur en sabot) on chest X-ray is a characteristic finding in TOF, caused by **right ventricular hypertrophy** and an upturned cardiac apex, leading to a concave pulmonary artery segment.
*Egg on a string*
- This CXR finding is characteristic of **Transposition of the Great Arteries (TGA)**, where the aorta and pulmonary artery are switched, creating an "egg" outline with a narrow vascular pedicle ("string").
- TGA typically presents with severe **cyanosis** from birth and does not usually involve squatting spells or a loud systolic murmur from a prominent **right ventricular outflow tract obstruction**.
*Increased pulmonary vascular markings*
- This finding is common in conditions with **left-to-right shunting** or **increased pulmonary blood flow**, such as a **ventricular septal defect (VSD)** or **patent ductus arteriosus (PDA)**.
- In Tetralogy of Fallot, there is typically **decreased pulmonary blood flow** due to **pulmonic stenosis**, leading to *decreased* pulmonary vascular markings.
*Cardiomegaly with globular heart*
- A **globular heart** is a non-specific finding often associated with **pericardial effusion** or **dilated cardiomyopathy**, where the heart appears enlarged and rounded.
- While TOF can cause cardiomegaly (specifically **right ventricular hypertrophy**), the characteristic shape is "boot-shaped," not globally enlarged or globular.
*Figure-3 sign*
- The **figure-3 sign** on CXR is pathognomonic for **aortic coarctation**, caused by indentation of the aorta at the coarctation site and post-stenotic dilation.
- This condition presents with signs of **heart failure**, **differential cyanosis** (if preductal), and **blood pressure discrepancies** between upper and lower extremities, not the cyanotic spells and squatting seen in this case.
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