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.

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Background: The number of patients demanding endoscopic neck surgery is rising. The access trauma of the axillary, breast and chest approaches is bigger than in open or video assisted surgery. We tested the feasibility of he sublingual transoral access which is in our opinion the only real minimally...-invasive extracollar endoscopic access to the thyroid gland Methods: We performed an experimental investigation in a porcine model. In 10 pigs we made 10 endoscopic transoral thyroidectomys with a modified axilloscope with the help of ultrasonic scissors and a neuro-monitoring system for identification of the recurrent laryngeal nerve. Results: The average operation time from the introduction to the removal of the obturator just above the larynx was 57 seconds. The mean operation time was 43 minutes. With the help of the neuro-monitoring system we proved in all cases the function of the recurrent laryngeal nerve on both sides. The pigs were observed for another two hours after operation. During and after the operation no complications appeared. Conclusions: We could show that the endoscopic transoral thyroid resection in pigs is possible and save. Our results might be useful for using this access for endoscopic thyroid resection in humans.

Liver Metastasis Resection. A Technique That Makes It Easier. Authors: de Santibañes E, Sánchez Clariá R, Palavecino M, Beskow A, Pekolj J. Background: Liver resection is the only therapeutic option that achieves long-term survival for patients with hepatic metastases. We propose a tech...nique that causes traction and counter traction on the resection area, thus easily exposing the structures to be ligated. Since the parenchyma protrudes like a cork from a bottle we named this procedure “Corkscrew Technique”. Objective: To describe an original surgical technique to resect liver metastases. Technique: We delimite the resection area at 2 cm from the tumor. We place separated stitches, in a radiate way. The needle diameter must allow passing far from the deepest margin of the tumor. The stitches must be tractioned all together to separate the tumor from the normal parenchyma. Material and Methods: Between years 1983 and 2006, we perform 1270 liver resection. We used the corkscrew technique like only procedure in 612 patients whereas in 129 patients we associated it to an anatomic resection. Results: Mortality was 1%. Morbidity was 16% with a reoperation rate of 3%. Conclusions: The Corkscrew Technique is simple and safe, it spares surgical time, avoids blood loss, ensures free tumor margins and it is easy to perform.

The trypan blue-stained viscoelastic is removed in its entirety using a Simcoe cannula. A stream of Healonid GV can be seen flowing into the cannula with some residual viscoelastic remaning, which is subsequently removed. Without the dye, much of the viscoelastic might have been left in the anterior... chamber – a risk factor for an acute rise in intra ocular pressure.

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Subtotal Thyroidectomy

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