Initial study of stability and repeatability of measuring R2 ' and oxygen extraction fraction values in the healthy brain with gradient-echo sampling of spin-echo sequence / 中华放射学杂志

ABSTRACT

Objective To evaluate the stability and repeatability of gradient-echo sampling of spinecho (GESSE) sequence in measuring the R2'value in volunteers, by comparison with traditional GRE sequence (T2* map and T2 map). Methods Eight normal healthy volunteers were enrolled in this study and written informed consents were obtained from all subjects. MR scanning including sequences of GESSE,T2 map and T2 * map were performed in these subjects at resting status. The same protocol was repeated one day later. Raw data from GESSE sequence were transferred to PC to conduct postprocessing with the software built in house. R2'map and OEF map were got consequently. To obtain quantitative R2'and OEF values in the brain parenchyma, six ROIs were equally placed in the anterior, middle and posterior part of bilateral hemispheres. Both mean and standard deviation of R2 'and OEF were recorded. All images from T2 * map and T2 map were transferred to the Workstation for postprocessing. The ROIs were put at the same areas as those for GESSE sequence. R2'is defined as R2' = R2 * -R2,R2* = 1/T2*. The R2'value of GESSE sequence were compared with that of GRE sequence. Results The mean R2 'values of GESSE at the first and second scan and those of the GRE were (4.21 ±0.92),(4.45 ±0. 94) Hz and (7.37 ±1.47), (6. 42 ±2. 33) Hz 0. 035 respectively. The R2'value and OEF value obtained from GESSE were not significantly different between the first and second scan ( t = - 0. 83, - 1.48, P ＞ 0. 05 ). The R2' value of first GRE imaging had significantly statistical difference from that of second GRE inaging ( t = 1.80, P ＜ 0. 05 ). The R2' value of GESSE sequence was less than that of GRE sequence, and there was significantly statistical difference between them(t = 1.71 ,P＜0. 05). Conclusion The GESSE sequence has good stability and repeatability with promising clinical practicability.