Voxel-based analysis of diffusion tensor imaging in mild traumatic brain injury in adolescents

BACKGROUND AND PURPOSE

DTI of normal-appearing WM as evaluated by conventional MR imaging in mTBI has the potential to identify important regional abnormalities that relate to PCS. VBA was used to examine WM changes in acute mTBI.

MATERIALS AND METHODS

WM was assessed between 1 and 6 days postinjury with voxel-based DTI analyses in 10 adolescent patients with mTBI and 10 age-matched control participants. In addition to the voxel-based group, analysis used to identify brain pathology across all patients with mTBI, 2 voxel-based linear regressions were performed. These analyses investigated the relation between 1) the ADC and PCS severity scores, and 2) ADC and scores on the BSI of emotional symptoms associated with mTBI. We hypothesized that frontotemporal WM changes would relate to symptoms associated with PCS and endorsed on the BSI.

RESULTS

Patients with mTBI demonstrated significant reductions in ADC in several WM regions and in the left thalamus. As expected, no increases in ADC were found in any region of interest. All injury-affected regions showed decreased radial diffusivity, unchanged AD, and increased FA, which is consistent with axonal cytotoxic edema, reflective of acute injury.

CONCLUSIONS

Whole-brain WM DTI measures can detect abnormalities in acute mTBI associated with PCS symptoms in adolescents.

Performance of QRS detection for cardiac magnetic resonance imaging with a novel vectorcardiographic triggering method

In many cardiac patients, image quality and/or scan efficiency is reduced due to imprecise R-wave ability to trigger the scan due to noise on the electrocardiogram (ECG) caused by the magnetic resonance (MR) environment. We developed a triggering system that uses the spatial information of the vectorcardiogram (VCG) to minimize the effects of MR-related noise on triggering. Fifteen volunteers underwent standard cardiovascular MR exams, and a total of 52,474 R-waves were evaluated with the algorithm, giving a performance index of 99.91%. The mean propagation delay of the system was -10.64 +/- 3.19 msec, which falls within the real-time definition for cardiac MRI triggering. Five patients had arrhythmias consisting of premature ventricular depolarizations (PVDs) and supraventricular extra systoles. For those patients with PVDs, all arrhythmic beats were rejected unless they passed through the algorithm's reference point. The performance index for the arrhythmic patients approached 100%. VCG-based triggering has been demonstrated to provide near 100% triggering performance during cardiac MR examinations.