3D-EIT for Diagnosis and Monitoring of Pulmonary Embolism (TIDE-PE)

Pulmonary embolism (PE) is a major cause of morbidity and mortality. Computed tomography pulmonary angiography (CTPA) is the current reference standard for PE diagnosis, but it is limited by radiation exposure, contrast administration, and poor suitability for bedside or repeated dynamic assessment. Three-dimensional electrical impedance tomography (3D-EIT) is a non-invasive, radiation-free imaging technique that enables bedside evaluation of regional lung ventilation and perfusion.

The objective of this study is to validate the clinical utility of 3D-EIT for the diagnosis, risk stratification, and longitudinal monitoring of PE. The study will focus on EIT-derived ventilation-perfusion parameters, including the Matching Index (MI), Dead Space Index (DI), and Shunt Index (SI).

This is a prospective, single-center, observational case-control study conducted at Beijing Tsinghua Changgung Hospital. Two cohorts will be enrolled:

1. A control cohort without PE or VTE, recruited from patients scheduled for saphenous vein radiofrequency ablation for varicose veins who meet predefined screening criteria.
2. A PE cohort including patients with a first episode of PE confirmed by CTPA. Participants in the control cohort will undergo one 3D-EIT examination to establish reference ranges for MI, DI, and SI. Participants in the PE cohort will undergo 3D-EIT within 24 hours after diagnostic CTPA. Repeated EIT examinations will be performed after thrombolytic therapy when applicable, at hospital discharge, and at 1-month follow-up to evaluate dynamic changes over time.

The primary objective is to assess the diagnostic performance of MI and DI for identifying PE using CTPA as the reference standard. Secondary objectives include evaluating the association of EIT-derived indices with PE severity, CTPA-based obstruction burden, risk stratification category, and temporal changes following treatment.

Statistical analyses will include estimation of reference ranges in the control cohort, receiver operating characteristic (ROC) analysis for diagnostic performance, correlation analyses between EIT and CTPA-derived parameters, and longitudinal analyses of repeated EIT measurements in the PE cohort.