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The complex circuitry interconnecting different areas in the brain, known collectively as white matter, is composed of millions of axons organized into fascicles and bundles. Upon macroscopic examination of sections of the brain, it is difficult to discern the orientation of the fibers. The same is true for conventional imaging modalities. However, recent advancements in magnetic resonance imaging (MRI) make such task possible in a live subject. By sensitizing an otherwise typical MRI sequence to the diffusion of water molecules it is possible to measure their diffusion coefficient in a given direction1. Normally, the axonal membrane and myelin sheaths pose barriers to the movement of water molecules and, thus, they diffuse preferentially along the axon2. Therefore, the direction of white matter bundles can be elucidated by determining the principal diffusivity of water. The three-dimensional representation of the diffusion coefficient can be given by a tensor and its mathematical decomposition provides the direction of the tracts3; this MRI technique is known as diffusion tensor imaging (DTI). By connecting the information acquired with DTI, three-dimensional depictions of white matter fascicles are obtained4. The virtual dissection of white matter bundles is rapidly becoming a valuable tool in clinical research.
Our journey begins with a transverse section of tightly packed axons as seen through light microscopy. Although represented as a two-dimensional "slice", we see that these axons in fact resemble tubes. A simulation of water molecules diffusing randomly inside the axons demonstrates how the membranes and myelin hinder their movement across them and shows the preferred diffusion direction --along the axons. The tracts depicted through DTI slowly blend in and we ride along with them. As we zoom out even more, we realize that it is a portion of the corpus callosum connecting the two sides of the brain we were traveling on and the great difference in relative scale of the individual axons becomes evident. The surface of the brain is then shown, as well as the rest of the white matter bundles--a big, apparently chaotic tangle of wires. Finally, the skin covers the brain.
With the exception of the simulated water molecules, all the data presented in the animation is obtained through microscopy and MRI. Computer algorithms for the extraction of the cerebral structures and a custom-built graphics engine make our journey through the brain's anatomy possible in a living person.
Micrograph courtesy of Dr. Christian Beaulieu, University of Alberta.
Music by Mario Mattioli.
References:
1. Stejskal, E.O., et al., J. Chem. Phys., 1965. 42:
2. Beaulieu, C., NMR Biomed., 2002. 15:435-55.
3. Basser, P.J., et al., J. Magn. Reson. B, 1994. 103:247-54.
4. Mori, S., et al., NMR Biomed., 2002. 15:468-80.
A video-animation presentation about sentinel lymph node biopsies for breast cancer diagnosis. 3D graphics are used to explain the process. Topics include the lymphatic system and the methods used. This video is part of the breast cancer education series produced by CancerQuest at Emory University
The colonoscope is slowly withdrawn during this screening colonoscopy down from the transverse colon, back around the splenic flexure, and down the descending colon, and reveals this finding a colonic diverticula. Diverticulosis is a common, acquired, age-related occurrence affecting over 50% of the... western adult population over the age of 50. It is seen rarely in Africa and Asia where the dietary fiber content is traditionally higher. Thus most investigators feel that low fiber diets are related to the development of this condition. Ironically, colonic diverticula are not true diverticula but rather pseudodiverticula in that the sac includes layers of the mucosa and submucosa that push through rather than include the outer muscular layer. As with the small bowel the colon has an inner circular muscular layer, but the outer longitudinal layer is composed of three bands of muscle that run the length of the colon known as teniae. Diverticula occur in rows between the mesenteric and two antimesenteric teniae where the colonic wall is further weakened by the defect caused by the perforating vasa recti artery which supplies the colonic mucosa. Occasionally, the anatomic propensity of diverticula to form in rows is quite apparent as seen when this clip is replayed in slow motion. Most often, however, the arrangement of the diverticula appears random due to the angulation of the bowel and thickening of the semi lunar folds. The conditions that cause these pulsion diverticula are not know with certainty but may include high intrahaustral pressures, muscular hypertrophy, and age related alterations in collagen cross linking. Diverticula can bleed or can abscess and perforate. The incidence of diverticulitis or diverticular bleeding is in the range of 1:1,000 patients with diverticulosis.
University Hospitals Neurological Institute will host a live webcast to demonstrate the removal of a brain tumor that doctors believe is causing epileptic seizures in a middle-aged man.
An MRI showed what appears to be a glioma (tumor) near a part of the brain that controls muscle movement, called the motor strip. Studies have shown that complete removal can cure the seizures and improve quality of life and survival, but this is difficult to do with conventional technology without harming the surrounding normal brain because it's difficult to determine where tumor ends and normal brain begins.
DMC Huron Valley-Sinai Hospital offers hope for severe sinus sufferers through new image-guided surgery that opens up passages, allowing freer breathing and higher quality of life. See two patients who have undergone the procedure and hear about their new lease on life. ~ Detroit Medical Center
In this video, Dr. Joe Bresee, with the CDC Influenza Division, describes swine flu - its signs and symptoms, how it's transmitted, medicines to treat it, steps people can take to protect themselves from it, and what people should do if they become ill.
A closure device and method to close the abdomen between surgical procedures and maintain a normal physiologic tension on the fascia to prevent undue retraction. In one embodiment, the closure device includes a “needled carabiner” attached to a rubberband of specific tension. The rubberband mimics the physiologic tension the abdominal wall normally experiences during daily activities and allows the abdominal compartment to expand as needed to maintain a healthy intra-abdominal pressure. The bands contract to maintain the intra-abdominal pressure and slowly pull the abdominal fascia back to the midline to facilitate surgical closure of the abdomen. In one embodiment, the “needled carabiner” includes a hinged surgical needle with a protected cap. The hinged needle is placed outside the normal suture line, thereby limiting the amount of surgical trauma the fascia endures. The strength of the rubberbands may be varied to accommodate differently sized individuals.
The 3rd Annual W. B. Ingalls Memorial
Prostate Health and Cancer Seminar features nationally renowned physicians and scientists presenting the most current study and practices for the diagnosis and treatment of prostate cancer. This day-long program offers in-depth exploration of prostate issues that range from monitoring PSA counts to cutting-edge research to current treatment trends.