OBJECTIVES: The authors assessed the effects of varying one extracellular component (fibrinogen concentration) and one cellular component (hematocrit) on magnetic resonance (MR) T1 and T2 relaxation times of in vitro blood clots. METHODS: Blood from six male subjects was collected into sodium citrate anticoagulant (3.8%) and the whole blood was separated into platelet-rich plasma and packed erythrocytes. Subsequently, in vitro blood clots were made from varying concentrations of fibrinogen (1, 10, and 100 microM) in Tyrode's solution and washed, packed erythrocytes (hematocrit levels: 0%, 10%, 40%, and 80%). T1 and T2 measurements were completed at 20 MHz within 8 hours of initiating clotting. RESULTS: Significant shortening of MR relaxation times occurred with increasing fibrinogen concentration for hematocrit values of 0% and 10%. Extracellular fibrinogen concentration did not contribute significantly to variation in relaxation times at hematocrit values of 40% and 80%. For any given fibrinogen level, significant shortening occurred in T1 and T2 values for each successive increase in hematocrit values. CONCLUSIONS: Both extracellular (fibrinogen) and cellular (erythrocyte concentration) factors are significant determinants of thrombus T1 and T2 relaxation times.
OBJECTIVES: The authors assessed the effects of varying one extracellular component (fibrinogen concentration) and one cellular component (hematocrit) on magnetic resonance (MR) T1 and T2 relaxation times of in vitro blood clots. METHODS: Blood from six male subjects was collected into sodium citrate anticoagulant (3.8%) and the whole blood was separated into platelet-rich plasma and packed erythrocytes. Subsequently, in vitro blood clots were made from varying concentrations of fibrinogen (1, 10, and 100 microM) in Tyrode's solution and washed, packed erythrocytes (hematocrit levels: 0%, 10%, 40%, and 80%). T1 and T2 measurements were completed at 20 MHz within 8 hours of initiating clotting. RESULTS: Significant shortening of MR relaxation times occurred with increasing fibrinogen concentration for hematocrit values of 0% and 10%. Extracellular fibrinogen concentration did not contribute significantly to variation in relaxation times at hematocrit values of 40% and 80%. For any given fibrinogen level, significant shortening occurred in T1 and T2 values for each successive increase in hematocrit values. CONCLUSIONS: Both extracellular (fibrinogen) and cellular (erythrocyte concentration) factors are significant determinants of thrombus T1 and T2 relaxation times.