Endoscopic measurement of parenchymal near infrared radiation transmittance correlates with HRCT derived lung tissue density in lung fibrosis patients.

Introduction: An accurate diagnosis of interstitial lung disease (ILD) and its severity is crucial for both prognosis and treatment. Aims and objectives: We have attempted to correlate lung tissue density in HU for patients with ILD based on HRCT scans with average absorption of NIR in lung parenchyma measured during bronchoscopy examination. Methods: We have designed the optical probe for measurement of penetrated NIR through the lung tissue. It consists of two fibres contained in one bundle where the indicator fibre is 0.3 cm longer. We have evaluated data form 12 patients with different degree of ILD aged 48-81 years. During bronchoscopy the probe was inserted to the airways via working channel and resulting spectral curve of transmitted NIR in diagnostic window (620-700 nm) was detected. Measured signal was normalised to master signal and based on obtained value and known optical pathlenght, local absorption coefficient was calculated. Average parenchymal density value has been calculated from standard HRCT scans at target lobes. Results: Obtained values for 12 ILD patients showed regression curve with clear linear trend and satisfying correlation R2=0,931 (Figure 1). Conclusions: We proved that our novel method enables to measure lung parenchymal density in real time during bronchoscopic examination and results are in good correlation with CT densitometry.