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Objective: To discuss the trends about the phase value, T2* and R2* value of susceptibility weighted imaging (SWI) with the arterial oxygen level, and analyze the accuracy about the thrombus volume measurement using SWI.Methods: 12 cases of human arterial blood were collected. They were scanned using MR SWI according to 6 time point of 1,3,5,7,9,11 days. During each time, the cases was measured about the phase value, T2* and R2* value, meanwhile, the backup samples were sent to the laboratory to test the blood gas, including oxygen partial pressure, oxyhemoglobin, deoxyhemoglobin and methemoglobin. By spearman correlation test, analyze the relationship between the arterial phase value, T2* value, R2* value and blood gas index. In addition, 7 specimens of patients about lower extremity arterial thrombosis were collected. They were fixed by 10% formalin solutioin, and then scanned by MR SWI, after that measured the volume. The actual volume was measured by a 5 millilitre graduatd cylinder. Using the paired t test, analysis the difference between the method of graduatd cylinder and the SWI images.Results: The phase value of SWI in the arterial blood was positively correlated with oxygen partial pressure and oxyhemoglobin(r=0.390,p= 0.009;r=0.589,p=0.000), and negative correlated with deoxygenated hemoglobin and methemoglobin(r=-0.332,p=0.033;r=-0.337,p-0.025). T2* value was positive correlated with oxygen partial pressure and oxyhemoglobin(r=0.321,p=0.034;r=0.416,p=0.005), and negative correlated with deoxygenated hemoglobin and methemoglobin(r=-0.314,p=0.038;r=-0.479,p=0.001). R2* value was negative correlated with oxyhemoglobin (r=-0.439,p=0.003),and positive correlated with methemoglobin (r= 0.454,p=0.002). R2* value was no significant correlation with the oxygen partial pressure and the deoxygenated hemoglobin (r=- 0.252,p=0.098;r=0.234,p=0.127). In addition, compared with the graduated cylinder measurement, the volume measurement with phase image was significantly increased. For phase image measurment the average value was 0.71±0.26 cm~3, and for the graduated cylinder measurement the value was 0.28±0.10 cm~3.There was significant difference with the two measurements.Conclusion: SWI can sensitively reflect the change in the composition of blood, and was particularly in close contact with the oxygen changes. Using phase map、T2* map and R2* map of SWI can better show the changes of oxygen and hemoglobin. It exists over-evaluation about the measurement of thrombus volume by the phase map of SWI, and it is some guiding value to the clinical work.
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