Boujraf Saïd, Summers Paul, Belahsen Faouzi, Prüssmann Klaas, Kollias Spyros
Department of Biophysics and Clinical MRI Methods, Faculty of Medicine and Pharmacy, University of Fez, Fez, Morocco.
J Med Phys. 2009 Jan;34(1):37-42. doi: 10.4103/0971-6203.48719.
The choice of imaging parameters for functional MRI can have an impact on the accuracy of functional localization by affecting the image quality and the degree of blood oxygenation-dependent (BOLD) contrast achieved. By improving sampling efficiency, parallel acquisition techniques such as sensitivity encoding (SENSE) have been used to shorten readout trains in single-shot (SS) echo planar imaging (EPI). This has been applied to susceptibility artifact reduction and improving spatial resolution. SENSE together with single-shot spin-echo (SS-SE) imaging may also reduce off-resonance artifacts. The goal of this work was to investigate the BOLD response of a SENSE-adapted SE-EPI on a three Tesla scanner. Whole-brain fMRI studies of seven healthy right hand-dominant volunteers were carried out in a three Tesla scanner. fMRI was performed using an SS-SE EPI sequence with SENSE. The data was processed using statistical parametric mapping. Both, group and individual subject data analyses were performed. Individual average percentage and maximal percentage signal changes attributed to the BOLD effect in M1 were calculated for all the subjects as a function of echo time. Corresponding activation maps and the sizes of the activated clusters were also calculated. Our results show that susceptibility artifacts were reduced with the use of SENSE; and the acquired BOLD images were free of the typical quadrature artifacts of SS-EPI. Such measures are crucial at high field strengths. SS SE-EPI with SENSE offers further benefits in this regard and is more specific for oxygenation changes in the microvasculature bed. Functional brain activity can be investigated with the help of single-shot spin echo EPI using SENSE at high magnetic fields.
功能磁共振成像（fMRI）成像参数的选择会影响图像质量和所实现的血氧水平依赖（BOLD）对比度，进而对功能定位的准确性产生影响。通过提高采样效率，诸如灵敏度编码（SENSE）等并行采集技术已被用于缩短单次激发（SS）回波平面成像（EPI）中的读出序列。这已被应用于减少磁化率伪影和提高空间分辨率。SENSE与单次激发自旋回波（SS-SE）成像相结合还可能减少失谐伪影。本研究的目的是在3特斯拉扫描仪上研究采用SENSE的SE-EPI的BOLD响应。对7名惯用右手的健康志愿者进行了全脑fMRI研究，研究在3特斯拉扫描仪上进行。使用带有SENSE的SS-SE EPI序列进行fMRI。数据使用统计参数映射进行处理。进行了组分析和个体受试者数据分析。计算了所有受试者M1区归因于BOLD效应的个体平均百分比和最大百分比信号变化，并将其作为回波时间的函数。还计算了相应的激活图和激活簇的大小。我们的结果表明，使用SENSE可减少磁化率伪影；所采集的BOLD图像没有SS-EPI典型的正交伪影。这些措施在高场强下至关重要。带有SENSE的SS SE-EPI在这方面具有更多优势，并且对微血管床中的氧合变化更具特异性。在高磁场下，借助使用SENSE的单次激发自旋回波EPI可以研究脑功能活动。
