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From axons to tracts
From axons to tracts Mohamed 21,104 Views • 3 years ago

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.

Simple Skin Suture
Simple Skin Suture Scott 21,025 Views • 3 years ago

A video showing simple skin suture

Nerve Monitoring After Transoral Endoscopic Thyroid Resection
Nerve Monitoring After Transoral Endoscopic Thyroid Resection DrHouse 13,352 Views • 3 years ago

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
Liver Metastasis Resection Mohamed 13,714 Views • 3 years ago

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.

Trypan Blue for Penetrating Keratoplasty
Trypan Blue for Penetrating Keratoplasty DrHouse 11,019 Views • 3 years ago

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.

Appendectomy Operation Video
Appendectomy Operation Video DrHouse 13,484 Views • 3 years ago

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Spread of Prostate Cancer
Spread of Prostate Cancer Mohamed Ibrahim 13,760 Views • 3 years ago

Prostate Cancer spreads in 3 ways. First is spreads by local growth. Second it spreads through the lymphatic system, and lastly, it spreads through the blood stream. Dr. Patrick Swift, a radiation oncologist, discusses how prostate cancer spreads.

Deep Dermal Suture
Deep Dermal Suture DrPhil 17,555 Views • 3 years ago

Demonstration of deep dermal suturing technique for laceration repair or wound closure in the operating room.

The Nose Knows: Sinus Surgery at DMC
The Nose Knows: Sinus Surgery at DMC Emery King 19,816 Views • 3 years ago

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

Infant twins struck with aggressive cancer - Part 2 of 5
Infant twins struck with aggressive cancer - Part 2 of 5 Emery King 10,437 Views • 3 years ago

After their parents were strongly urged by their local hospital to go to Children's Hospital of Michigan, Dr. Jeffrey Taub controls an aggressive cancer in 2 month old twins. ~ Detroit Medical Center

Subtotal Thyroidectomy
Subtotal Thyroidectomy Mohamed 16,210 Views • 3 years ago

Subtotal Thyroidectomy

Tubal Ligation Reversal by Dr. Berger
Tubal Ligation Reversal by Dr. Berger CHTRC Webmaster 11,000 Views • 3 years ago

Dr. Berger, world's leading tubal reversal doctor, performs outpatient tubal ligation reversal and repairs fallopian tubes after a tubal ligation.

Arterial Line Insertion
Arterial Line Insertion Surgeon 20,727 Views • 3 years ago

Arterial line insertion usually involves cannulation of the radial artery with a 20 gauge catheter for the purposes of beat-by-beat blood pressure monitoring all along with arterial blood gas monitoring.

Malar Cheek Pexing Suture  / Surgery Video Vignettes
Malar Cheek Pexing Suture / Surgery Video Vignettes Richard DeAngelis 8,837 Views • 3 years ago

Graphic video demonstrating the reconstruction of a facial cheek defect following the removal of a common skin cancer in a challenging location near the lower eyelid. Visit us @ www.skincancercentre.com.

Surgical Glove Flip How To
Surgical Glove Flip How To Harvard_Student 10,765 Views • 3 years ago

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Meningeococcal Bacterial Maningitis Introduction
Meningeococcal Bacterial Maningitis Introduction Scott 8,654 Views • 3 years ago

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Pterygium Excision with Auto Conjunctival Graft
Pterygium Excision with Auto Conjunctival Graft Alicia Berger 8,574 Views • 3 years ago

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Brain death - Spinal reflex
Brain death - Spinal reflex ericneuro 2,426 Views • 3 years ago

Male 19 y. age victim of penetrating brain injury. All the criteria for the encephalic death diagnosis were present. The presence of this complex spinal reflex doesn't exclude the brain death diagnosis and must be known and understood by the professionals involved in this very important diagnosis

Complete Eye Exam Importance 3D Animation
Complete Eye Exam Importance 3D Animation Scott 8,630 Views • 3 years ago

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Myths about Aging Debunked
Myths about Aging Debunked John Snow 2,669 Views • 3 years ago

Like in any other sector of health, aging come with its myths. These myths can be hurtful to senior citizens and their caretakers if mistaken for truths. Here are some common myths about aging that caregivers should be aware of.

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