Usage of tilt-in-space, recline, and elevation seating functions in natural environment of wheelchair users.

This study examined the usage of powered seating functions, including tilt-in-space, backrest recline, and seat elevation, among a group of wheelchair users during their typical daily activities. Twelve individuals who used a power wheelchair with seating functions participated in the study. They drove their own wheelchair and used the seating functions as needed in their community environment for about 2 weeks while the seating function usage was recorded with a portable device. We found that subjects occupied their wheelchair for 11.8 +/- 3.4 hours a day (all data shown as mean +/- standard deviation). While occupying their wheelchairs, they accessed tilt-in-space, backrest recline, and seat elevation 19 +/- 14 times a day for 64.1% +/- 36.8%, 12 +/- 8 times for 76.0% +/- 29.8%, and 4 +/- 4 times for 22.5% +/- 34.9%, respectively. Subjects chose to stay in tilted and reclined positions in their wheelchair for 39.3% +/- 36.5% of their time each day. They spent little time in a fully upright position. Subjects changed their seating positions every 53.6 +/- 47.0 minutes. Time spent in positions of different seating pressures varied among subjects. The information collected could enhance clinical practice of wheelchair provision, resulting in better compliance with clinical instructions and appropriate use of seating functions among wheelchair users.

In vivo imaging of rapid deformation and strain in an animal model of traumatic brain injury.

In traumatic brain injury (TBI) rapid deformation of brain tissue leads to axonal injury and cell death. In vivo quantification of such fast deformations is extremely difficult, but important for understanding the mechanisms of degeneration post-trauma and for development of numerical models of injury biomechanics. In this paper, strain fields in the brain of the perinatal rat were estimated from data obtained in vivo during rapid indentation. Tagged magnetic resonance (MR) images were obtained with high spatial (0.2 mm) and temporal (3.9 ms) resolution by gated image acquisition during and after impact. Impacts were repeated either 64 or 128 times to obtain images of horizontal and vertical tag lines in coronal and sagittal planes. Strain fields were estimated by harmonic phase (HARP) analysis of the tagged images. The original MR data was filtered and Fourier-transformed to obtain HARP images, following a method originally developed by Osman et al. (IEEE Trans. Med. Imaging 19(3) (2000) 186). The displacements of material points were estimated from intersections of HARP contours and used to generate estimates of the deformation gradient and Lagrangian strain tensors. Maximum principal Lagrangian strains of >0.20 at strain rates >40/s were observed during indentations of 2 mm depth and 21 ms duration.

A wheelchair usage monitoring/logging system.

Real life information on wheelchair usage is important for investigating the effectiveness of certain features, evaluate users' performance, and eventually improve the safety and reliability of wheelchairs. The purpose of the study is to develop a wheelchair usage monitoring/logging system that travels with wheelchair users in their daily activity settings and collects data independently. The system consists of a wheel rotation logging module, a GPS logging module, and a seating posture logging module. It obtains data on how far wheelchair users drive, where they have been, and how long they spend in various seating positions. The initial testing results showed that the system can be used as a clinical compliance tool to determine how clients are using their wheelchairs, and if they are effectively using seat features to relieve seating pressure.