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 showing the correct way to hold a forceps

This endoscopy shows a patient with cancer of the larynx, Laryngeal cancer is the most common cancer of the upper respiratory tract. The incidence of laryngeal tumors is closely correlated with smoking, as head and neck tumors occur 6 times more often among cigarette smokers than among nonsmokers. The age-standardized risk of mortality from laryngeal cancer appears to have a linear relationship with increasing cigarette consumption. Death from laryngeal cancer is 20 times more likely for the heaviest smokers than for nonsmokers. It should be suspected in any patient with hoarseness of the voice for three weeks or longer until proven otherwise.

Polycystic ovary syndrome (PCOS, also known clinically as Stein-Leventhal syndrome), which is an endocrine disorder that affects 5--10% of women. It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility. The symptoms and severity of the syndrome vary greatly between women. While the causes are unknown, insulin resistance (often secondary to obesity) is heavily correlated with PCOS.

Axillary Cannulation: Antegrade Flow and Brain Protection

Hand Assisted Nephrectomy

Various laparoscopic techniques have been described for the insertion of peritoneal dialysis catheters. However, most use 3 to 4 ports, thus multiplying the potential risk for abdominal wall complications (hemorrhage, hernia, leaking). With the technique presented herein a Tenckhoff catheter is plac...ed laparoscopically, using just 1 port, in 13 consecutive patients with end-stage renal failure. The catheter is fixed in the abdominal cavity with no additional ports for this purpose. The simplicity and the rapidity of the method justifies serious consideration for its use as the standard Tenckhoff catheter placement.

Repair techniques for various types of asymmetric pectus excavatum are illustrated. Morphology-tailored bar shaping and selecting the hinge points are key elements of the technique. Repair of two cases on an eccentric type and unbalanced type according to "Park Classification" was demonstrated.

Allograft material is placed submucosally to expand tissue to simulate turbinate tissue. It is placed in a location to direct the airstream toward "virgin" tissue that can sense airflow. Empty Nose Syndrome (ENS) is an iatrogenic disease characterized by paradoxical obstruction: a hugely patent no...

se with subjective "blockage" or poor nasal breathing.

Laparoscopy in acute bowel obstruction following previous surgery is a difficult procedure and avoided by most of the surgeons due to the difficulty in obtaining pneumoperitoneum, port placement, lack of working space, adhesions and risk of bowel injury.
Here is a patient who had a previous laparotomy for trauma with a midline incision from xyphysternum to pubis; after unsuccessful conservative management he underwent a laparoscopy; a prior CT scan showed adhesions in the left side and a distal-mid small bowel obstruction. The pneumoperitoneum was obtained with the Visiport placed in the right lower quadrant; although the abdomen was grossly distended, under significant tension and distended loops of small bowel were occupying most the peritoneal cavity, with muscle relaxation there is usually enough space to perform a thorough inspection of the abdominal cavity. Port placement has to be done with special care as there is no room to push and usually a blunt trocar directed away from the bowel is employed in my practice. The collapsed loops of small bowel point quickly to the site of obstruction -- it is better to avoid manipulating the distended bowel as it is heavy, oedematous and prone to be lacerated with the instruments; once the pathology is identified, in this case the obstructive band, light packing is performed in order to expose the working space and protect the bowel from instruments like scissors or diathermy. In this case the band adhesion was slightly more difficult to separate from the bowel and required a combination of sharp and gentle blunt dissection.
Once the obstruction is release and the transit of contents is confirmed in the collapsed bowel the procedure is terminated. No abdominal drainage is usually necessary.

Atrial Fibrillation is the most common heart rythmn abnormatlity and is very common as you age. Atrial fibrillation is a condition in which the top chambers of the heart, the Atrium are fibrillating, rather than having a regular synchronized contraction. One of the worst complications of Atrial Fibrillation can be Stroke. There are very good treatments of Atrial Fibrillation. This animated video is an overview of Atrial Fibrillation.

cardiac catheterization in the work up of heart disease.

Ingrown Toenail

Two Step Adult CPR Video Demonstration

Oral Surgery and Dental Implants

Laparoscopic Sleeve Gastrectomy

Combined Spinal-Epidural Obstetric Anesthesia

A knee replacement operation from India shows a Gender specific knee replacement implanted through a subvastus approach. Surgery performed by Dr.Venkatachalam of Madras Joint Replacement center www.kneeindia.com

Laparoscopic Removal of Ovarian Cyst

Liposuction for weight loss with Abdominoplasty and Body Lifting