Hotiu, Angelica

We have developed a method of quantifying multiple-choice test items in an
introductory physical science course in terms of the various tasks required to solve
the problem. We assign a numerical level of difficulty to each task so that any
question can be assigned a degree of difficulty, which is the sum of the individual
levels of difficulty associated in each steps. Using the questions and results from the
tests we have investigated the relationship between the degree of difficulty of each
question and the corresponding discrimination index. Our results indicate that as the
degree of difficulty increases so does the capability of the item to discriminate
between students with different abilities. There is a maximum degree of difficulty
beyond which the discrimination starts to decrease. At that point, test items become
too difficult. Thus, it should be possible in future to design items that will provide
optimum discrimination.

Mild traumatic brain injuries (MTBI) are the leading type of head injuries with appreciable risque of sequelae leading to functional and psychological deficits. Although mild traumatic brain injuries are frequently underdiagnosed by conventional imaging modalities, rapidly evolving techniques such as diffusion tensor imaging (DTI) reveal subtle changes in white matter integrity as a result of head trauma and play an important role in refining diagnosis, therapeutic interventions and management of MTBI. In this dissertation we use diffusion tensor imaging to detect the microstructural changes induced by axonal injuries and to monitor their evolution during the recovery process. DTI data were previously acquired from 11 subjects, football players of age 19-23 years (median age 20 years). Three players had suffered a mild traumatic brain injury during the season and underwent scanning within 24 hours after the injury with follow-ups after one and two weeks. A set of diffusion indices, such as fractional anisotropy, axial, radial and mean diffusivity were derived from the diffusion tensor. Changes in diffusion indices in concussed subjects were analyzed based on two different approaches: whole brain analysis, using tract-based spatial statistics (TBSS) and region of interest analysis (ROI). In both approaches we use a voxelwise analysis to examine group differences in diffusion indices between five controls and three concussed subjects for all DTI scans. Additional statistical analysis was performed between control groups consisting of five and three non-injured players. Both analyses demonstrated that the MTBI group reveals increase in fractional anisotropy and decreases in transversal and mean diffusivity in cortical and subcortical areas within 24 hours after the injury.