Analysis of Diffuse Axonal Injury Using Diffusion Tensor Imaging in Traumatic Brain Injury Patients

Disruption of the cytoskeletal network and axonal membranes characterizes diffuse axonal injury (DAI) after traumatic brain injury. Histologic abnormalities seen in DAI hypothetically decrease the diffusion along axons and increase the diffusion in directions perpendicular to them. We tested this hypothesis by measuring the diffusion characteristics of traumatized brain tissue with use of diffusion tensor imaging (DTI). Two patients with traumatic brain injuries and five control subjects were studied with DTI. Mechanisms of change in fractional anisotropy maps of DTI were explored using an eigenvalue analysis of the diffusion tensor. Axial diffusivity (λ1) were decreased and radial diffusivity ((λ2+λ3)/2) were increased in both caudal middle frontal gyri, pars orbitalis gyri, fusiform gyri, parahippocampal gyri (patient 1), caudal middle frontal gyri, precentral gyri, middle temporal gyri (patient 2). Both axial and radial diffusivity were increased in most of the frontal lobe gyri. We applied new analytic methods for DAI in traumatic brain injury.

Validity of the Prediction Equation of the Maximal OxygenConsumption in Submaximal Exercise Test

OBJECTIVE: To explore accuracy and validity of a VO2max prediction equation of the multistage model using by modified Bruce protocol submaximal exercise test in healthy subjects. METHOD: Thirty three healthy subjects (age: 44.0+/-12.9) were recruited. VO2max was measured during treadmill by direct gas analysis from a maximal incremental test. VO2max was then predicted from multistage model equation with age, measured oxygen consumption and heart rate during a maximal incremental treadmill test. And the predicted VO2max values from equation were compared with the measured VO2max values. RESULTS: The predicted VO2max values and the measured VO2max values were highly correlated (r=0.9, p<0.001). The predicted VO2max values (2,285.3+/-536.0 ml/min) were not significantly different from the measured VO2max values (2,285.5+/-598.5 ml/min). CONCLUSION: In healthy subjects, the multistage model equation offers a fairly accurate VO2max prediction. Therefore the equation can be used in the estimation of VO2max at modified Bruce protocol in an aerobic exercise program.