The application of susceptibility weighted imaging to traumatic brain injury.

摘要

Traumatic brain injury (TBI) is an important public health issue worldwide. It has been around since the beginning of time but only recently become a specialized focus of clinical care and research. Diffuse axonal injury (DAI) as the cause of mortality and morbidity in TBI has been well recognized. CT is the only imaging method that has been widely used in the clinical scenario for acute TBI patients. However CT has difficulties in showing DAI. The discrepancy between normal CT findings and severe neurological symptoms, or between severe outcome and less severe outcome predicted from current imaging models have called for more powerful imaging two hospitals (Beijing Taintan Hospital and Tianjin Huanhu Hospital) with TBI centers two years ago and have collected 63 acute TBI cases. All of them underwent both CT and MRI scans. The initial Glasgow Coma methods. Susceptibility weighted imaging (SWI) is a new neuroimaging technique which uses tissue magnetic susceptibility differences to generate a unique contrast, different from spin density, T1, T2 or T2*. SWI offers information about any tissue that has a different susceptibility than its surrounding structures such as deoxygenated blood, hemosiderin, ferritin and calcium. Its high sensitivity to hemorrhage makes SWI a great method in imaging TBI.;In the process of analyzing the SWI data of this group of patients, we found that SWI could be used to identify subarachnoid hemorrhage (SAH). We compared CT and SWI on 20 TBI cases that had SAH. Our conclusions were that SAH can be recognized by SWI through its signal intensity and unique morphology. SWI has the potential to provide complementary information to CT in imaging SAH.;One thing that needs to be differentiated from hemorrhage on MRI is calcification. We studied one patient who had a partially calcified oligodendroglioma, multiple calcified cysticercosis lesions, and multiple physiologic calcifications with CT and SWI. Our results showed that SWI filtered phase images can accurately detect very small amounts of calcification. However aliasing makes it difficult for SWI to show the exact shape of the calcification of a large area or high concentration.;In summary, SWI is a sensitive method with which to image TBI, especially for patients with DAI. The SWI scoring scale we developed provides a promising direction for the application of SWI in TBI. More TBI cases are needed to validate the reliability and accuracy of this scale. Combining SWI with other advanced imaging methods such as DWI/DTI, MRSI and PWI might lead to more refined and better scoring scales.;We started this study in China from Scale (GCS) score when the patients presented to the hospital and the GCS score when the patients were discharged from the hospital were recorded. The Glasgow Outcome Scale (GOS) score roughly 6 months after the injury was obtained by telephone interview. One neuroradiologist and the author analyzed SWI data without knowing any clinical information about the patients. The brain injuries were separated into two general types: focal (hematoma and contusion) and DAI lesions. The brain was divided into 15 regions. An imaging result form was designed for the imaging readers to fill out. A SWI imaging score was calculated by adding up the number of affected regions weighted by the levels of severity. The imaging scores were correlated with GCS and GOS scores. Our results showed that 21 cases had only "DAI" lesions, 24 cases had only "hematoma and contusion" lesions, 11 had both types of injuries, and 7 cases were normal. SWI showed a particularly interesting characteristic of DAI lesions: linear hemorrhagic lesions that followed the white matter fiber tracts. Among the 32 cases that had DAI lesions, 15 had an unfavorable outcome. All of them had had brainstem lesions and subcortical WM lesions in at least one lobe. For the 24 cases that only had focal lesions, they all had a good outcome. The scatterplot between SWI imaging scores and long term outcomes showed there were no SWI score overlaps between the group of patients that had favorable outcome and the group of patients that had unfavorable outcome. The scatterplot between initial GCS and outcome, or discharge GCS and outcome showed there were GCS overlaps between the favorable and unfavorable outcome groups. Our conclusions were that SWI can help identify DAI lesions by their characteristic morphology and typical locations. This SWI scoring system can be used to predict favorable and unfavorable outcome in the acute stage of TBI. However this scoring system has to be tested on a larger number of patients to validate its efficacy.