MCQ Mosaic Attenuation Caused by Small Blood Vessel Disease

Which of the following is the most common cause of mosaic attenuation caused by vascular disease?
- A) Chronic thromboembolic pulmonary hypertension (CTEPH)
- B) Pulmonary vasculitis
- C) Pulmonary arteriovenous malformations (PAVMs)
- D) Sickle cell disease
Answer: A) Chronic thromboembolic pulmonary hypertension (CTEPH)
Comment (Correct Answer): CTEPH is the most frequent vascular cause of mosaic attenuation due to regional perfusion defects caused by chronic thromboemboli.
“CTEPH is characterized by chronic thromboemboli causing regional hypoperfusion, leading to mosaic attenuation on imaging.” (Radiopaedia)

Incorrect Answers:
- B) Pulmonary vasculitis
  “Pulmonary vasculitis can cause perfusion defects, but it is a less common cause compared to CTEPH.” (Radiology Key)
- C) Pulmonary arteriovenous malformations (PAVMs)
  “PAVMs can lead to focal perfusion defects but are less prevalent compared to thromboembolic causes.” (Radiopaedia)
- D) Sickle cell disease
  “Sickle cell disease can cause microvascular occlusion but is a rare contributor to mosaic attenuation.” (AJR)

What imaging modality is most sensitive for detecting perfusion abnormalities in vascular causes of mosaic attenuation?
- A) Expiratory CT
- B) VQ Scan
- C) Pulmonary function tests (PFTs)
- D) Chest X-ray
Answer: B) VQ Scan
Comment (Correct Answer): VQ scans are highly sensitive for identifying perfusion abnormalities caused by vascular diseases like CTEPH.
“VQ scanning is the imaging modality of choice for detecting perfusion defects in suspected CTEPH.” (Radiopaedia)

Incorrect Answers:
- A) Expiratory CT
  “Expiratory CT is useful for detecting air trapping but not perfusion defects.” (Radiology Key)
- C) Pulmonary function tests (PFTs)
  “PFTs are non-specific and do not provide direct information about perfusion defects.” (AJR)
- D) Chest X-ray
  “Chest X-rays lack the sensitivity to detect subtle perfusion abnormalities.” (Radiopaedia)

Which of the following findings helps distinguish mosaic attenuation caused by vascular disease from airway disease?
- A) Air trapping on expiratory CT
- B) Enlarged pulmonary arteries
- C) Bronchial wall thickening
- D) Ground-glass opacities
Answer: A) Air trapping on expiratory CT
Comment (Correct Answer): Air trapping is absent in vascular causes of mosaic attenuation and is a key distinguishing feature from airway diseases.
“Air trapping is indicative of small airway diseases and can be excluded in vascular causes using expiratory CT imaging.” (Radiopaedia)

Incorrect Answers:
- B) Enlarged pulmonary arteries
  “Enlarged pulmonary arteries are a common finding in vascular diseases but do not directly differentiate from airway disease.” (Radiology Key)
- C) Bronchial wall thickening
  “Bronchial wall thickening is a feature of airway diseases, not vascular conditions.” (AJR)
- D) Ground-glass opacities
  “Ground-glass opacities are more commonly associated with interstitial or inflammatory lung diseases.” (Radiology Key)

Which condition is most associated with mosaic attenuation and pulmonary venous congestion?
- A) Chronic thromboembolic pulmonary hypertension (CTEPH)
- B) Congestive heart failure (CHF)
- C) Pulmonary vasculitis
- D) Sickle cell disease
Answer: B) Congestive heart failure (CHF)
Comment (Correct Answer): CHF causes pulmonary venous congestion, leading to regional mosaic attenuation patterns due to redistribution of blood flow and elevated venous pressures.
“Pulmonary venous hypertension in CHF contributes to mosaic attenuation by altering perfusion and increasing lung water content.” (Radiopaedia)

Incorrect Answers:
- A) Chronic thromboembolic pulmonary hypertension (CTEPH)
  “CTEPH primarily results in pulmonary arterial obstruction rather than venous congestion.” (Radiology Key)
- C) Pulmonary vasculitis
  “Vasculitis causes arterial inflammation and occlusion but does not lead to venous congestion.” (Radiopaedia)
- D) Sickle cell disease
  “Sickle cell disease may lead to microvascular occlusion but rarely causes venous congestion.” (AJR)

What distinguishes mosaic attenuation due to CHF from CTEPH on imaging?
- A) Air trapping
- B) Redistribution of blood flow and interstitial edema
- C) Enlarged pulmonary arteries
- D) Hypodense regions on inspiratory CT
Answer: B) Redistribution of blood flow and interstitial edema
Comment (Correct Answer): CHF is characterized by redistribution of pulmonary blood flow and interstitial edema, which differentiate it from perfusion defects seen in CTEPH.
“Pulmonary venous hypertension in CHF leads to blood flow redistribution and interstitial changes, distinguishing it from CTEPH.” (Radiopaedia)

Incorrect Answers:
- A) Air trapping
  “Air trapping is absent in both CHF and CTEPH, being more indicative of airway diseases.” (Radiology Key)
- C) Enlarged pulmonary arteries
  “Enlarged pulmonary arteries may be seen in both CHF and CTEPH but are not distinguishing.” (AJR)
- D) Hypodense regions on inspiratory CT
  “Hypodense regions can be present in both conditions and require additional findings to differentiate.” (Radiopaedia)