Multiparametric MRI in characterizing venous thrombi and pulmonary thromboemboli acquired from patients with pulmonary embolism.

BACKGROUND: The structure of thrombi plays an important role in delaying reperfusion and re-occlusion after intravenous thrombolysis and could influence the performance of mechanical thrombectomy devices. This study aims to distinguish various thrombi groups based on their T2 and apparent diffusion coefficient (ADC) properties.

METHODS: 26 venous thrombi (VT), 28 acute (aPTE) and 18 chronic pulmonary thromboemboli (cPTE) and 18 sedimented clots (SC) were scanned by a three-dimensional T1 -weighted spin-echo sequence and by T2 and ADC mapping. Immunohistochemical analysis was used as a reference. Differences in the ADC, T2 and paired ADC-T2 distributions between the various thrombi group pairs were analyzed by standard statistics as well as by overlap integrals.

RESULTS: Paired ADC-T2 distribution enabled the most efficient discrimination of structural changes between pairs of thrombi. For thrombi pairs VT-cPTE, VT-SC, aPTE-cPTE, aPTE-SC, cPTE-SC differences were statistically significant (pADC , pT 2 , pADC-T 2 < 0.05) and the values of the overlap integrals were low (OIADC ≤ 0.505, OIT2 ≤ 0.823, OIADC-T2 ≤ 0.379). Least efficient was the structural discrimination for the VT-aPTE pair (pT 2 = 0.877, OIT2 = 0.940).

CONCLUSION: Multiparametric MRI is an efficient method for discriminating different thrombi groups at various stages of organization.