L1 (Basic)

L1 Question 1: What defines an acinar nodule radiologically?

• a) A nodule larger than 3 cm with calcification
• b) A small, round opacity (5-10 mm) representing alveolar filling
• c) A solitary peripheral lesion with pleural effusion
• d) A centrally located mass with necrosis

Answer: b) A small, round opacity (5-10 mm) representing alveolar filling

Comments

Acinar nodules are small, round opacities measuring 5-10 mm, often indicating alveolar filling with fluid, cells, or other material. “Acinar nodules represent small round opacities due to alveolar filling, typically ranging from 5-10 mm in diameter.” Radiopaedia

Incorrect Answers

• a) Nodules >3 cm are classified as masses, not acinar nodules. Radiopaedia
• c) A solitary lesion with pleural effusion does not fit the definition of acinar nodules. Fleischner Society Guidelines
• d) Centrally located masses are more typical of malignancy or abscesses rather than acinar nodules. Radiopaedia

L1 Question 2: What is the most common infectious cause of acinar nodules?

• a) Fungal infections
• b) Viral infections
• c) Bacterial pneumonia
• d) Tuberculosis

Answer: c) Bacterial pneumonia

Comments

Bacterial pneumonia is the most common infectious cause of acinar nodules due to alveolar filling with pus and inflammatory cells. “Bacterial pneumonia commonly presents with acinar nodules due to alveolar consolidation.” Radiopaedia

Incorrect Answers

• a) Fungal infections are less common and often present with larger nodules or mass-like lesions. RadiologyKey
• b) Viral infections can cause acinar nodules but are less frequent compared to bacterial infections. Radiopaedia
• d) Tuberculosis often presents with centrilobular nodules and cavitation rather than acinar nodules. Radiographics

L1 Question 3: What imaging modality is most sensitive for detecting acinar nodules?

• a) Chest X-ray
• b) MRI
• c) CT scan
• d) PET-CT

Answer: c) CT scan

Comments

CT scan is the most sensitive imaging modality for detecting acinar nodules, as it provides high-resolution cross-sectional imaging of the lung parenchyma. “CT scan remains the gold standard for evaluating lung nodules due to its high sensitivity and spatial resolution.” Radiopaedia

L1 Question 4: What histopathological feature is commonly seen in acinar nodules caused by infection?

• a) Caseating granulomas
• b) Alveolar consolidation with neutrophilic infiltration
• c) Fibrosis with collagen deposition
• d) Hemorrhage with hemosiderin-laden macrophages

Answer: b) Alveolar consolidation with neutrophilic infiltration

L1 Question 5: What is the difference between an acinar nodule and an acinar shadow on imaging?

• a) Acinar nodules are small, discrete round opacities, while acinar shadows refer to clusters of nodules creating alveolar filling
• b) Acinar nodules and acinar shadows are identical terms used interchangeably
• c) Acinar shadows are larger lesions greater than 3 cm
• d) Acinar nodules are always malignant, while acinar shadows are always benign

Answer: a) Acinar nodules are small, discrete round opacities, while acinar shadows refer to clusters of nodules creating alveolar filling

L2 (Advanced)

L2 Question 6: A 40-year-old male presents with multiple acinar nodules, ground-glass opacities, and multicentric consolidation in the right upper lobe following a motor vehicle accident. Which of the following is the most likely cause based on this CT presentation?

• a) Diffuse alveolar hemorrhage
• b) Aspiration pneumonia
• c) Bacterial infection
• d) Pulmonary edema

Answer: a) Diffuse alveolar hemorrhage

Comments

The most likely cause in this trauma context is diffuse alveolar hemorrhage (DAH), as the presentation includes ground-glass opacities and multicentric consolidation following trauma, which is typical of hemorrhagic processes. “Trauma with ground-glass opacities and acinar nodules suggests alveolar hemorrhage rather than infection or aspiration.” Radiopaedia

L2 Question 7: Which of the following conditions is least likely to present with acinar nodules?

• a) Bacterial pneumonia
• b) Diffuse alveolar hemorrhage
• c) Lung adenocarcinoma
• d) Hypersensitivity pneumonitis

Answer: c) Lung adenocarcinoma

L2 Question 8: What is the most appropriate next step in a patient with multiple bilateral acinar nodules and hemoptysis?

• a) Empiric antibiotics
• b) Bronchoscopy with lavage
• c) PET-CT
• d) Observation with repeat imaging

Answer: b) Bronchoscopy with lavage

Comments

Bronchoscopy with lavage is the most appropriate next step in a patient with multiple acinar nodules and hemoptysis, as it helps identify diffuse alveolar hemorrhage (DAH) and can provide diagnostic information through fluid analysis. “Bronchoscopy with bronchoalveolar lavage is essential in cases of suspected diffuse alveolar hemorrhage, aiding in both diagnosis and exclusion of infection.” Radiopaedia

Incorrect Answers

• a) Empiric antibiotics are not recommended without clear evidence of infection. Hemoptysis with acinar nodules is more suggestive of hemorrhage than bacterial pneumonia. Radiopaedia
• c) PET-CT is less useful in cases of acute hemorrhage as it evaluates metabolic activity rather than structural findings. RadiologyKey
• d) Observation without intervention can delay the diagnosis and treatment of potentially life-threatening alveolar hemorrhage. Radiographics

L2 Question 9: Which infection is most commonly associated with acinar nodules on chest CT?

• a) Tuberculosis
• b) Bacterial pneumonia
• c) Pneumocystis pneumonia (PCP)
• d) Viral infections (e.g., influenza)

Answer: b) Bacterial pneumonia

Comments

Bacterial pneumonia is the most common infectious cause of acinar nodules due to alveolar filling with pus and inflammatory cells. “Bacterial pneumonia often presents with acinar nodules due to alveolar consolidation and inflammatory infiltrates.” Radiopaedia

Incorrect Answers

• a) Tuberculosis more commonly presents with cavitary lesions or centrilobular nodules. Radiopaedia
• c) PCP often presents with ground-glass opacities rather than discrete acinar nodules. Radiopaedia
• d) Viral infections typically present with diffuse ground-glass opacities rather than focal acinar nodules. Radiopaedia

L2 Question 10: A 50-year-old male with a history of Wegener’s granulomatosis presents with acute hemoptysis and multiple bilateral acinar nodules on chest CT. What is the most likely diagnosis?

• a) Diffuse alveolar hemorrhage
• b) Pulmonary embolism
• c) Bacterial pneumonia
• d) Sarcoidosis

Answer: a) Diffuse alveolar hemorrhage

Comments

In a patient with Wegener’s granulomatosis and acute hemoptysis, diffuse alveolar hemorrhage (DAH) is the most likely cause, often presenting with acinar nodules and ground-glass opacities. “DAH is a known complication of Wegener’s granulomatosis, presenting with acinar nodules and ground-glass opacities on imaging.” Radiopaedia

Incorrect Answers

• b) Pulmonary embolism typically presents with wedge-shaped infarcts rather than acinar nodules. Radiographics
• c) Bacterial pneumonia would be less likely without fever or consolidation. Radiopaedia
• d) Sarcoidosis generally presents with perilymphatic nodules and mediastinal lymphadenopathy rather than acinar nodules. Radiopaedia