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Regional structure-function correlations in chronic obstructive lung disease measured with positron emission
L H Brudin1, C G Rhodes, S O Valind
1Medical Research Council, Royal Postgraduate Medical School, Hammersmith Hospital, London.
Thorax
|November 1, 1992
Summary
Positron emission tomography reveals distinct lung density patterns in chronic airflow obstruction. These patterns correlate with ventilation-perfusion ratios and help differentiate between bronchial inflammation and alveolar destruction.
Area of Science:
- Pulmonary Medicine
- Radiology
- Medical Imaging
Background:
- Positron emission tomography (PET) with short-lived isotopes can assess local lung tissue density in relation to ventilation and ventilation:perfusion (V/Q) ratios.
- This technique was applied to 10 patients diagnosed with severe chronic airflow obstruction, exhibiting varied carbon monoxide transfer factor (TLCO) and transfer coefficient (KCO) values.
Purpose of the Study:
- To investigate the relationship between regional lung tissue density and functional parameters like ventilation, perfusion, and V/Q ratio in patients with chronic airflow obstruction.
- To determine if distinct density patterns correlate with specific underlying pathologies (e.g., bronchial inflammation vs. alveolar destruction) in these patients.
Main Methods:
- Regional lung density, ventilation (VA), and V/Q ratios were measured using PET in a single transaxial section at mid-heart level.
- Alveolar volume, extravascular tissue lung density, and perfusion (Q) were derived, with analysis focused on 25 abnormal ventilation regions.
Main Results:
- Tissue density showed significant correlations with V/Q ratio (negative, r = -0.55), perfusion (Q) (positive, r = 0.59), and blood volume (positive, r = 0.65).
- Patients with low TLCO/KCO (<50% predicted) often displayed low tissue density with normal/high V/Q in low VA regions.
- Conversely, patients with higher TLCO/KCO (>50% predicted) typically showed normal/high tissue density with low V/Q in low VA regions.
- A strong positive correlation (r = 0.79) was observed between the ratio of mean tissue density to V/Q and KCO (% predicted).
Conclusions:
- The study links structural lung density differences to distinct functional patterns in chronic airflow obstruction.
- Findings support the hypothesis that some patients predominantly exhibit bronchial inflammation or edema, while others show significant alveolar destruction.