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Saturday, June 09, 2012

A case of primitive trigeminal artery infarction

Posted by turbospinecho on June 4, 2012
Within minutes following an altercation with police, a 55-year-old man noted onset of speech difficulty and right-sided weakness without headache or neck pain. Dysarthria and right hemiparesis (grade 4/5) without ocular disturbance was found. Left ventral hemipontine infarction was documented from the ipsilateral tortuous primitive trigeminal artery (figure). Cerebral angiogram failed to reveal underlying arterial dissection.

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White arrow points to the primitive trigeminal artery (A–D). MRI, fluid-attenuated inversion recovery sequence, demonstrating the left ventral pontine infarction (A). Magnetic resonance angiography demonstrates proximal hypoplastic-stenotic vertebrobasilar system (B). Selective left internal carotid artery angiogram: lateral (C) and anteroposterior view (D) (same viewing angle as in B). Triangular arrowhead points to the left internal carotid artery (B–D).
Persistent anastomosis from a cavernous portion of internal cerebral artery to rostral basilar artery is unusual, with an estimated incidence of 0.2%.1 Although the artery has been implicated as a conduit of a carotid artery to posterior cerebral artery distribution embolic stroke,2 our case illustrates that localized occlusive process may also occur.

Monday, June 04, 2012

Saturday, June 02, 2012

What are the noises that M.R.I. machines make?

Q. What are the noises that M.R.I. machines make?
A. The banging is the vibration of metal coils in the machine caused by rapid pulses of electricity, said Dr. Keith Hentel, chief of emergency/musculoskeletal imaging at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.
Magnetic resonance imaging produces images of the body by causing shifts in a very strong magnetic field and measuring how tissues react, Dr. Hentel said. The principal magnet of an M.R.I. scanner commonly is strong enough to produce fields 60,000 times the strength of the earth’s natural magnetic field.
Inside the scanner are coils of metal wire called gradient coils. When electricity is passed through such a coil, a magnetic field is created. Rapid pulses of electricity cause predictable changes in the field, resulting in tissue changes that can be measured and transformed into anatomic images.
The pulses cause not just the desired changes but undesired vibrations of the gradient coils, resulting in the banging heard during an M.R.I. examination.
As stronger magnets result in stronger vibrations, the higher the field strength of the M.R.I. scanner, measured in teslas, the louder the banging, Dr. Hentel said.
In a three-tesla system, a strength common in clinical practice, he said, these sounds may be as loud as 125 decibels, equivalent to a rock concert or a balloon popping near the ear. That is why ear protection is recommended.

ViewRay™ MRI-guided radiation therapy system

ViewRay™ Incorporated, a privately held medical device company, has received U.S. FDA 510(k) premarket notification clearance for its MRI-guided radiation therapy system. The ViewRay system features a unique combination of radiotherapy delivery and simultaneous magnetic resonance imaging (MRI) for the treatment of cancer. ViewRay’s treatment planning and delivery software received 510(k) premarket notification clearance in 2011.
“FDA clearance of our integrated system is a major milestone in the development of our technology,” said ViewRay President and CEO Gregory M. Ayers, MD, PhD. “It has already been an exciting year for ViewRay, with an additional round of funding and the installation of our first research systems at major U.S. medical centers. Early clinical imaging studies have verified the quality of the system’s MR images, and now we’re looking forward to clinical applications.” The ViewRay system provides continuous soft-tissue imaging during treatment so that clinicians can see and record precisely where radiation therapy is being delivered, as it’s being delivered.ViewRay’s patented cancer treatment technology was invented by company founder James F. Dempsey, PhD, while he was a member of the radiation oncology faculty at the University of Florida. “ViewRay began with the idea that we need to see what exactly we’re doing when we treat cancer patients with radiation therapy,” said Dempsey, now ViewRay’s chief scientific officer. “Thanks to our clear vision, an outstanding engineering team, and dedicated leadership, we’re now able to bring that idea into the clinic, where it can help cancer patients.”
Potential clinical applications
ViewRay researchers are studying the motion of tumors in lung, prostate, liver, head and neck, and other types of cancer where MRI-guided radiotherapy could offer sophisticated treatments.


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