Examination of the heart and lungs with heart sounds

Examination of the hip

Lasik correction of vision of a 26 years old male patient

A very bad lasik eye surgery duringwhich the surgeon messed everything

Examination of the Shoulder and Elbow

One of the various variations of trabeculectomy...

Measurement of pulse and respiratory rate

This video demonstrates how to treat venereal warts or condyloma using a cryosurgery technique.

A video showing the insertion of chest tube

basic subcutaneous (SQ) injection techniques

Two methods to reduce the shoulder are demonstrated and the need for analgesia or anesthesia discussed

Surgery video of transgastric cholecystectomy

26 week uterus using Gyrus PKS Cutting Forcep, PKS Lyons Dissecting Forceps & PKS Needle.

Laparoscopic Colon Resection video

A video showing Cystocele Repair

A dermatologist explains how this skin condition is recognised and treated and the challenging effects it can have on an individual.

Incision of the bladder neck for a small prostate

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.

Examination of the knee from Loyola medical school, Chicago

A video from Loyola medical school, Chicago showing the cardiovascular medical and clinical examination