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.

ENDOSCOPIC (NON-SURGICAL) REMOVAL OF MULTIPLE LARGE TUMORS FROM STOMACH IN A PATIENT WITH PEUTZ-JEGHERS SYNDROME
PEUTZ-JEGHERS SYNDROME: Peutz-Jeghers syndrome (PJS) is a familial syndrome consisting of mucocutaneous pigmentation, gastrointestinal polyposis and cancers of gut & other sites like breast, ovary, and testes. PJS has an autosomal dominant inheritance with variable and incomplete penetrance. Germline mutations of STK11/LKB1 gene on 19p cause this syndrome. Mucocutaneous pigmentation may be noted in early infancy. These deposits of melanin are most commonly found around the mouth, nose, lips, buccal mucosa, hands, and feet, and may also be present in perianal and genital areas. PJS polyps may be found in stomach, small intestine, or colon, but they tend to be prominent in the small intestine. These polyps may increase in size and cause small intestinal obstruction or intussusceptions that may occur in early infancy. Acute upper gastrointestinal bleeding and chronic faecal blood may complicate the disease.
PATIENT: The patient was a 25 yr male who had mucocutaneous pigmentation and multiple polyps in the stomach and duodenum. He presented with bleeding from gastric polyps. As the polyps in stomach were numerous, (more than 20 in number) and were large in size (some equal to small egg size), he had been advised to undergo surgery. Surgery planned was total gastrectomy.
PROCEDURE: The patient underwent video-endoscopy of the esophagus, stomach and duodenum. All polyps were examined for size and presence or absence of stalk. A plan to remove all the gastric polyps at endoscopy was made in the same sitting. He received light conscious sedation. Flat polyps were raised form the gastric wall by injection of saline in to polyp base to let these lesions have a stalk. This was done by needle injector. Each polyp was engaged in a snare and the polyp stalk was cut by coagulation cutting current. The cuts were clean without any bleeding. All polyps were recovered for histology. The histology revealed all polyps to be hamartomous lesions. None of the polyps were cancerous. Patient has been followed up for over one year and is doing fine without any further bleeding or pain.
Video shows the procedure of videoendoscpy and endoscopic removal of polyps.

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Intercostal Tube Insertion in case of pneumothorax

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CD4 T-cells (a type of white blood cell) are important to your body's defence against infections. This animation describes how your immune system is weakened by the HIV virus, which targets CD4 T-cells and leads to their gradual decline in number. Low to very low levels of CD4 cells put you at risk for 'opportunistic infections' that take advantage of the body's weakened immune system.