In this study we focus on the problem of segmentation and visualization of soft tissue structures in three-dimensional (3D) magnetic resonance (MR) imaging. We introduce a classification method which is a combination of a recently proposed contour detection algorithm and Haslett's contextual classification method extended to 3D. This classification method is used in the classification step of a rendering model suggested by Drebin et al. for visualizing normal and pathological tissue structures in the brain. We evaluate the combination of these two methodologies, and identify some problems which have to be solved in order to develop a clinical useful tool.

Algorithms↗

PubMedDate not supplied

The identification of cerebral volume changes in treated growth hormone-deficient adults using serial 3D MR image processing.

PURPOSE: A pilot study to detect volume changes of cerebral structures in growth hormone (GH)-deficient adults treated with GH using serial 3D MR image processing and to assess need for segmentation prior to registration was conducted. METHOD: Volume MR scans of the brain were obtained in five patients and six control subjects. Patients were scanned before and after 3 and 6 months of therapy. Control subjects were scanned at the same intervals. A phantom was used to quantify scaling errors. Second and third volumes were aligned with the baseline by maximizing normalized mutual information and transformed using sinc interpolation. Registration was performed with and without brain segmentation and correction of scaling errors. Each registered, transformed image had the original subtracted, generating a difference image. Structural change and effects of segmentation and scaling error correction were assessed on original and difference images. The radiologists' ability to detect volume change was also assessed. RESULTS: Compared with control subjects, GH-treated subjects had an increase in cerebral volume and reduction in ventricular volume (p = 0.91 x 10(-3)). Scale correction and segmentation made no difference (p = 1 and p = 0.873). Structural changes were identified in the difference images but not in the original (p = 0.136). The radiologists detected changes >200 microm. CONCLUSION: GH treatment in deficient patients results in cerebral volume changes detectable by registration and subtraction of serial MR studies but not by standard assessment of images. This registration method did not require prior segmentation.

Adult↗

PubMedDate not supplied

Stabilization of posture by precision contact of the index finger.

Postural sway during quiet stance increases if sight of the surroundings is denied. We studied how sensory-motor information about body displacement provided by contact of the index finger with a stationary bar can be used to stabilize balance in the absence of vision. Stabilization equivalent to the contribution conferred by vision was achieved at contact force levels less than 1 N. This value is much below that necessary to provide significant physical stabilization of the body. We interpret our findings in relation to tactile thresholds for motion detection, "precision grip," and proprioceptive and sensory-motor information about the configuration of the arm to the torso. In conditions allowing higher force levels at the fingertip (5-8 N), subjects assumed a passively stable state to stabilize their stance.

Adult↗