Validation of an automated technique for quantification of pulmonary perfusion territories using computed tomography angiography

Abstract

Background: Computed tomography pulmonary angiography (CTPA) is the primary modality for the detection and diagnosis of pulmonary embolism (PE) while the stratification of PE severity remains challenging using angiography. Hence, an automated minimum-cost path (MCP) technique was validated to quantify the subtended lung tissue distal to emboli using CTPA.Methods: A Swan-Ganz catheter was placed in the pulmonary artery of seven swine (body weight: 42.6±9.6 kg) to produce different PE severities. A total of 33 embolic conditions were generated, where the PE location was adjusted under fluoroscopic guidance. Each PE was induced by balloon inflation followed by computed tomography (CT) pulmonary angiography and dynamic CT perfusion scans using a 320-slice CT scanner. Following image acquisition, the CTPA and the MCP technique were used to automatically assign the ischemic perfusion territory distal to the balloon. Dynamic CT perfusion was used as the reference standard (REF) where the low perfusion territory was designated as the ischemic territory. The accuracy of the MCP technique was then evaluated by quantitatively comparing the MCP-derived distal territories to the perfusion-derived reference distal territories by mass correspondence using linear regression, Bland-Altman analysis, and paired sample t-test. The spatial correspondence was also assessed. Results:The MCP-derived distal territory masses (Mass MCP , g) and the reference standard ischemic territory masses (Mass REF , g) were related by Mass MCP =1.02Mass REF − 0.62 g (r=0.99, paired t-test P=0.51). The mean Dice similarity coefficient was 0.84±0.08. Conclusions:The MCP technique enables accurate assessment of lung tissue at risk distal to a PE using CTPA. This technique can potentially be used to quantify the fraction of lung tissue at risk distal to PE to further improve the risk stratification of PE.

Reproducibility of a semiautomatic lobar lung tissue assignment technique on noncontrast CT scans: a study on swine animal model

“…The MCP technique has undergone previous validation using CT pulmonary angiography images, where a comparative analysis between MCP-derived territories and dynamic CT perfusion-derived territories was conducted [ 11 ]. The results from this validation study revealed a mean Dice similarity coefficient of 0.84 ± 0.08 (mean ± standard deviation) for all tested conditions.…”

“…This coefficient, assessing the spatial overlap between segmented regions, signifies that the MCP technique demonstrates precise spatial correspondence. Furthermore, the validation process also addressed mass correspondence, providing additional confirmation of the accuracy of the MCP technique in assessments related to mass [ 11 ]. These findings support the reliability and validity of the MCP technique, reinforcing its utility in accurately delineating pulmonary arterial territories and associated mass characteristics.…”

“…Moreover, given the adaptability of the MCP technique between noncontrast and contrast images, it holds the potential to generate lobar-specific perfusion maps and perfusion defect maps using whole lung perfusion measurements [14]. Furthermore, the MCP technique has been successfully applied in CT pulmonary angiography to assist in the quantification of lung tissue at-risk distal to a pulmonary embolism [11]. This application enables the calculation of the total mass percentage at risk for the entire lung and specific lobes, thereby enhancing risk stratification for pulmonary embolism.…”

“…Recently, an automated minimum cost path (MCP) technique was utilized for accurate pulmonary lobar segmentation using CT pulmonary angiography images [11]. This method relies on the assumption that the lung tissue is supplied by the nearest arterial tree, facilitating the determination of the minimum distance between a lung tissue voxel and its closest supplying pulmonary artery [12].…”