Correlation of semi-quantitative analyses and visual scores in pulmonary perfusion SPECT/CT imaging with pulmonary function test parameters in patients with interstitial lung diseases.

Objective: To evaluate the correlation between semi-quantitative analyses and visual scores of pulmonary perfusion Single Photon Emission Computed Tomography (SPECT)/ Computed Tomography (CT) imaging and pulmonary function test parameters (PFTs) in patients with interstitial lung diseases (ILDs).

Methods: This retrospective study included 35 patients with ILDs from China-Japan Friendship Hospital between January 2020 and December 2022. All patients underwent pulmonary perfusion SPECT/CT imaging and a pulmonary function test. Visual scores of pulmonary perfusion SPECT/CT images were determined using the Meyer method, and functional lung volumes of pulmonary perfusion were calculated using various cutoff values (5%-95% of the maximum pixel value). PFTs included forced expiratory volume in the first second (FEV1) and FEV1 as a percentage of the predicted value (FEV1%), forced vital capacity (FVC) and FVC as a percentage of the predicted value (FVC%), one-second rate (FEV1/FVC), pulmonary carbon monoxide dispersion (DLCO) and DLCO as a percentage of the predicted value (DLCO%). Pearson's correlation was calculated to compare visual scores and lung perfusion functional volumes with PFT indices.

Results: Visual scores correlated with FEV1, FEV1%, FVC% and DLCO%, with a significant correlation observed for FEV1% (r = 0.576, P < 0.001). When taking the maximal pixel value of bilateral lung fields or unilateral lung field as 100%, lung perfusion volumes were significantly correlated with FEV1, FEV1%, FVC and FVC% at a threshold of 15%-30% (rs > 0.6, P < 0.001).

Conclusions: Pulmonary perfusion volumes within the threshold of 15%-30% in pulmonary perfusion SPECT/CT imaging reliably reflect lung function and outperform visual scores in patients with ILDs.