Investigation of the Cerebral Perfusion Changes in Patients with Mild Traumatic Brain Injury Using 3d Bssfp Arterial Spin Labeling Mri

Mild traumatic brain injury (mTBI) accounts for at least 75% of all traumatic brain injuries and is an important public health care problem. Approximate 15% of the mTBI patients have persistent non-specific and non-localizing symptoms including headache, sleep disorders, attention and memory deficits, emotional and behavioral alternations. Despite the persistent post-concussive syndrome (PCS) is observed, there is typically an absence of obvious structural lesions in mTBI, which has made it difficult to understand the pathophysiology. However, reduced brain perfusion has been observed in animal models of concussion and in patients with moderate to severe TBI. Moreover, the importance of vascular damage in mTBI has also been suggested as a mechanistic link between traumatic brain injury and the subsequent development of Alzheimer’s Disease. Functional imaging methods using ASL technique can provide the potential in identifying early changes in neurological diseases such as dementia by imaging regional cerebral blood flow, thus may improve insights in the pathophysiology of mTBI, increase the sensitivity for detecting abnormalities, and hence allow the development of better prognostic indicators. In ASL, 2D EPI is commonly used to take advantage of rapid image acquisition. However, EPI images are prone to susceptibility artifacts resulting in signal drop out and image distortion. 2D multi-slice readout additionally introduces a slice-dependent bias due to the different slice acquisition times and makes it difficult to incorporate background-suppression (BS) technique, which can improve the stability of ASL signal. 3D acquisition schemes such as gradient-and-spin-echo (GRASE) and fast spin-echo (FSE)-spiral have been proposed to overcome these challenges. However, these methods suffer from undesirable imaging blurring in slice direction due to T2 decay during a long echo train. An alternative 3D approach is using balanced steady-state free precession (bSSFP) imaging. The method is known for high SNR efficiency and suitable for a fast, distortion-free, and high-resolution imaging. Moreover, it is a 3D sequence and can be incorporated with BS technique. In this study, we will develop a 3D background-suppressed pCASL-bSSFP pulse sequence with 2D GRAPPA acceleration. The purpose of this study is to explore whether accelerated three-dimensional bSSFP with BS would provide a competitive pCASL imaging with more slice coverage but no severe signal loss and distortion artifacts. We will evaluate the sequence performance by comparing the same pCASL pulse with commonly used 2D EPI (2D pCASL-EPI) and 3D GRASE readouts in baseline perfusion and functional MRI studies. The optimized pCASL-bSSFP technique will be used to quantify CBF changes in patients with mTBI. We hypothesize that perfusion alterations in mTBI would consist in cortical decreases and that those alterations could be detected with this technique. We will integrate these imaging data with the neurocognitive measurements in patient with mTBI to strengthen the understanding of the complex persistent post-concussive syndrome.