Assessment of post-PTE pulmonary reperfusion using automatic segmentation and quantitative analysis of lung perfusion SPECT/CT

Abstract

Objective

To assess the diagnostic impact of using automatic segmentation and quantitative analysis of lung perfusion SPECT/CT in the evaluation of pulmonary reperfusion in patients undergoing follow-up for pulmonary thromboembolism (PTE).

Materials and methods

A prospective study was conducted from October 2021 to October 2024. We included 132 patients with PTE diagnosed by lung perfusion scintigraphy with SPECT/CT, who underwent a follow-up scan at 6 months.

Reperfusion was assessed visually and quantitatively. Three grades were visually established: no reperfusion, partial reperfusion, and complete reperfusion. For quantitative analysis, automatic segmentation was performed, obtaining volumes and total counts in the baseline and follow-up SPECT/CT scans. Two parameters were established for comparison: the relative decrease in defect volume (RDV) and the relative increase in total perfused volume counts (RIC). Reperfusion was classified as: no reperfusion, partial reperfusion (minor and major), and complete reperfusion.

The scintigraphic results were correlated with demographic variables, extension and size of the PTE and other complementary diagnostic tools (pulmonary function tests and echocardiogram).

Results

82 patients were women (mean age 70 ± 16 years) and 50 were men (64 ± 15 years).

Comparing the agreement between visual and quantitative analysis (weighted Cohen's Kappa index), a slight, but non-statistically significant, agreement was demonstrated between evaluators (κ = 0.04; p = 0.464).

Pearson's assessment revealed a very high and positive assessment between RDV and RIC (r = 0.77; p < 0.001).

Patients with abnormal complementary diagnostics tools at follow-up were not more likely to have residual thrombosis (p > 0.05 in the visual and quantitative analyses). The remaining variables also did not show statistical significance in the persistence of PTE.

Conclusions

In the assessment of post-PTE pulmonary reperfusion, quantitative analysis of lung perfusion SPECT/CT is superior to visual analysis. Furthermore, it suggests that it is a particularly useful tool in patients in whom visual analysis does not show improvement, as it could prevent unnecessary and prolonged treatment if reperfusion is observed through quantification.