Posts tagged MRI
Articles and news from the latest research reports.
MRIs Reveal Signs of Brain Injuries Not Seen in CT Scans
Hospital MRIs may be better at predicting long-term outcomes for people with mild traumatic brain injuries than CT scans, the standard technique for evaluating such injuries in the emergency room, according to a clinical trial led by researchers at UCSF and the San Francisco General Hospital and Trauma Center (SFGH).
Published this month in the journal Annals of Neurology, the study led by UCSF neuroradiologist Esther Yuh, MD, PhD, followed 135 people treated for mild traumatic brain injuries over the past two years at one of three urban hospitals with level-one trauma centers: SFGH, the University of Pittsburgh Medical Center and University Medical Center Brackenridge in Austin, Texas. The study was called the NIH-funded TRACK-TBI (Transforming Research and Clinical Knowledge in Traumatic Brain Injury).
All 135 patients with mild traumatic brain injuries received CT scans when they were first admitted, and all were given MRIs about a week later. Most of them (99) had no detectable signs of injury on a CT scan, but more than a quarter (27/99) who had a “normal” CT scans also had detectable spots on their MRI scans called “focal lesions,” which are signs of microscopic bleeding in the brain.
Spotting these focal lesions helped the doctors predict whether the patients were likely to suffer persistent neurological problems. About 15 percent of people who have mild traumatic brain injuries do suffer long-term neurological consequences, but doctors currently have no definitive way of predicting whether any one patient will or not.
“This work raises questions of how we’re currently managing patients via CT scan,” said the study’s senior author Geoff Manley, MD, PhD, the chief of neurosurgery at SFGH and vice-chair of the Department of Neurological Surgery at UCSF. “Having a normal CT scan doesn’t, in fact, say you’re normal,” he added.
Better Precision Tools Needed for Head Injuries
At least 1.7 million Americans seek medical attention every year for acute head injuries, and three-quarters of them have mild traumatic brain injuries – which generally do not involve skull fractures, comas or severe bleeding in the brain but have a variety of more mild symptoms, such as temporary loss of consciousness, vomiting or amnesia.
The U.S. Centers for Disease Control and Prevention estimates that far more mild traumatic brain injuries may occur each year in the United States but the true number is unknown because only injuries severe enough to bring someone to an emergency room are counted.
Most of those who do show up at emergency rooms are treated and released without being admitted to the hospital. In general, most people with mild traumatic brain injuries recover fully, but about one in six go on to develop persistent, sometimes permanent, disability.
The problem, Manley said, is that there is no way to tell which patients are going to have the poor long-term outcomes. Some socioeconomic indicators can help predict prolonged disability, but until now there were no proven imaging features, or blood tests for predicting how well or how fast a patient will recover. Nor is there a consensus on how to treat mild traumatic brain injuries.
“The treatment’s all over the place – if you’re getting treatment at all,” Manley said.
The new work is an important step toward defining a more quantitative way of assessing patients with mild traumatic brain injuries and developing more precision medical tools to detect, monitor and treat them, he added.
If doctors knew which patients were at risk of greater disabilities, they could be followed more closely. Being able to identify patients at risk of long-term consequences would also speed the development of new therapeutics because it would allow doctors to identify patients who would benefit the most from treatment and improve their ability to test potential new drugs in clinical trials.
Researchers Find Evidence That Brain Compensates After Traumatic Injury
Researchers at Albert Einstein College of Medicine of Yeshiva University and Montefiore Medical Center have found that a special magnetic resonance imaging (MRI) technique may be able to predict which patients who have experienced concussions will improve. The results, which were presented at the annual meeting of the Radiological Society of North America (RSNA), suggest that, in some patients, the brain may change to compensate for the damage caused by the injury.
“This finding could lead to strategies for preventing and repairing the damage that accompanies traumatic brain injury,” said Michael Lipton, M.D., Ph.D., who led the study and is associate director of the Gruss Magnetic Resonance Research Center at Einstein and medical director of MRI services at Montefiore, the University Hospital and academic medical center for Einstein.
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“In a traumatic brain injury, it’s not one specific area that is affected but multiple areas of the brain which are interconnected by axons,” said Dr. Lipton, who is also associate professor of radiology, of psychiatry and behavioral sciences, and in the Dominick P. Purpura Department of Neuroscience at Einstein. “Abnormally low FA within white matter has been correlated with cognitive impairment in concussion patients. We believe that high FA is evidence not of axonal injury, but of brain changes that are occurring in response to the trauma.”
Researchers in the voice, speech, and language branch of the National Institute on Deafness and Other Communication Disorders (NIDCD) at the National Institutes of Health (NIH) have used functional magnetic resonance imaging to study the brain activity of rappers when they are “freestyling”—spontaneously improvising lyrics in real time. The findings, published online in the November 15 issue of the journal Scientific Reports, reveal that this form of vocal improvisation is associated with a unique functional reallocation of brain activity in the prefrontal cortex and proposes a novel neural network that appears to be intimately involved in improvisatory and creative endeavors.
The researchers, led by Siyuan Liu, Ph.D., scanned the brains of 12 freestyle rap artists (who had at least 5 years of rapping experience) while they performed two tasks using an identical 8-bar musical track. For the first task, they improvised rhyming lyrics and rhythmic patterns guided only by the beat. In the second task, they performed a well-rehearsed set of lyrics.
During freestyle rapping, the researchers observed increases in brain activity in the medial prefrontal cortex, a brain region responsible for motivation of thought and action, but decreased activity in dorsolateral prefrontal regions that normally play a supervisory or monitoring role. Like an experienced parent who knows when to lay down the law and when to look the other way, these shifts in brain function may facilitate the free expression of thoughts and words without the usual neural constraints.
Freestyling also increased brain activity in the perisylvian system (involved in language production), the amygdala (an area of the brain linked to emotion), and cingulate motor areas, suggesting that improvisation engages a brain network that links motivation, language, mood, and action. Further studies of this network in other art forms that involve the innovative use of language, such as poetry and storytelling, could offer more insights into the initial, improvisatory phase of the creative process.
After nearly 10 years of follow-up of study participants who experienced migraines and who had brain lesions indentified via magnetic resonance imaging, women with migraines had a higher prevalence and greater increase of deep white matter hyperintensities (brain lesions) than women without migraines, although the number, frequency, and severity of migraines were not associated with lesion progression, according to a study appearing in the November 14 issue of JAMA. Also, increase in deep white matter hyperintensity volume was not significantly associated with poorer cognitive performance at follow-up.
Migraine affects up to 15 percent of the general population. “A previous cross-sectional study showed an association of migraine with a higher prevalence of magnetic resonance imaging (MRI)-measured ischemic lesions in the brain,” according to background information in the article. White matter hyperintensities are associated with atherosclerotic disease risk factors, increased risk of ischemic stroke, and cognitive decline.
Learning who’s the top dog: Study reveals how the brain stores information about social rank
Researchers supported by the Wellcome Trust have discovered that we use a different part of our brain to learn about social hierarchies than we do to learn ordinary information. The study provides clues as to how this information is stored in memory and also reveals that you can tell a lot about how good somebody is likely to be at judging social rank by looking at the structure of their brain.
Primates (and people) are remarkably good at ranking each other within social hierarchies, a survival technique that helps us to avoid conflict and select advantageous allies. However, we know surprisingly little about how the brain does this.
The team at the UCL Institute for Cognitive Neuroscience used brain imaging techniques to investigate this in twenty six healthy volunteers.
Participants were asked to play a simple science fiction computer game where they would be acting as future investors. In the first phase they were told they would first need to learn about which individuals have more power within a fictitious space mining company (the social hierarchy), and then which galaxies have more precious minerals (non-social information).
Whilst they were taking part in the experiments, the team used functional magnetic resonance imaging (fMRI) to monitor activity in their brains. Another MRI scan was also taken to look at their brain structure.
Their findings reveal a striking dissociation between the neural circuits used to learn social and non-social hierarchies. They observed increased neural activity in both the amygdala and the hippocampus when participants were learning about the hierarchy of executives within the fictitious space mining company. In contrast, when learning about the non-social hierarchy, relating to which galaxies had more mineral, only the hippocampus was recruited.
(Source: eurekalert.org)
Brain and brain waves in epilepsy
Caption: 3D magnetic resonance imaging (MRI) scan of a brain (seen from the front), overlaid with an electroencephalogram (EEG) of a 17-year-old’s brain during an epileptic episode (chaotic brain activity). This EEG shows generalized epilepsy, where the whole brain cortex is affected: all the EEG traces show chaotic brain waves. Epilepsy can have many causes, but when the cause is unknown, as here, it is called essential epilepsy. An EEG measures the electrical activity of the brain using electrodes attached to the scalp. The electrode locations are labelled at far left, on diagrams of the head seen from above, with the front of the head at left.
3D fetus fly-through peers inside abnormal bodies
Thanks to MRI techniques, you can see what a baby looks like before it’s born. But now these images can also be used to peer inside the body of a fetus, generating a fly-through of internal tissues that rivals the view you would get from a video.
Developed by Jorge Lopes from the National Institute of Technology (INT) in Rio de Janeiro, Brazil, and colleagues, the system can quickly produce a 3D virtual tour through a region of interest, usually to examine congenital anomalies. Using a combination of software, a doctor can produce a reconstruction after an MRI scan by selecting the camera angle and movement desired. In this video, a view into the lungs and airways of two unborn babies with tumours helped determine if their breathing would be affected after birth.
In addition to virtual models, the team can also produce 3D printed versions of an unborn child (see image above). According to Lopes, physical models can help describe a condition to expectant parents and illustrate surgical procedures required, as well as being useful for blind mothers to get a sense of their baby’s appearance.
MRI research sheds new light on nerve fibres in the brain
World-leading experts in Magnetic Resonance Imaging from The University of Nottingham’s Sir Peter Mansfield Magnetic Resonance Centre have made a key discovery which could give the medical world a new tool for the improved diagnosis and monitoring of neuro-degenerative diseases like multiple sclerosis.
The new study, published in the Proceedings of the National Academy of Science, reveals why images of the brain produced using the latest MRI techniques are so sensitive to the direction in which nerve fibres run.
The white matter of the brain is made up of billions of microscopic nerve fibres that pass information in the form of tiny electrical signals. To increase the speed at which these signals travel, each nerve fibre is encased by a sheath formed from a fatty substance, called myelin. Previous studies have shown that the appearance of white matter in magnetic resonance images depends on the angle between the nerve fibres and the direction of the very strong magnetic field used in an MRI scanner.
Is this the most unpleasant sound in the world?
The ear-splitting screech of a knife on a glass bottle has been identified as the worst sound to the human ear by scientists who studied the brain’s response to unpleasant noises.
People who listened to a series of 74 recordings while having their brain activity measured by an MRI scanner rated the sound of a fork on a glass as the second worst noise, followed by chalk on a blackboard.
The scans revealed that unpleasant sounds provoked a stronger response in the brain than pleasant ones such as the noise of blubbing water. While sounds are processed in the brain’s auditory cortex, uncomfortable noises activate the amygdala, a separate brain region which processes emotions.
The researchers studied a group of 13 volunteers and found that sounds with a frequency of between 2,000 and 5,000 Hz, the range at which our ears are the most sensitive, were the hardest to bear.
Although it remains unclear why our ears are most sensitive to this type of sound, researchers noted that screams, which we naturally find uncomfortable, fall within the same range.
Dr Sukhbinder Kumar of Newcastle University, author of the study, which was published in the Journal of Neuroscience, said: “It appears there is something very primitive kicking in. It’s a possible distress signal from the amygdala to the auditory cortex.”
His colleague Prof Tim Griffiths added: “This might be a new inroad into emotional disorders and disorders like tinnitus and migraine, in which there seems to be heightened perception of the unpleasant aspects of sounds.”
Imaging the network traffic in our brains
MRI brain scans no longer just show the various regions of brain activity; nowadays the networks in the brain can now be imaged with ever greater precision. This will make functional MRI (fMRI) increasingly powerful in the coming years, leading to tools that can be used in cognitive neuroscience. This is the claim made by Prof. David Norris in his inaugural lecture as Professor of Neuroimaging at the University of Twente on 13 September.
During the twenty years since the invention of fMRI (functional Magnetic Resonance Imaging) developments have come thick and fast, from initially identifying active brain regions to more complex analysis of the connections and hubs in the brain. In his inaugural lecture Norris describes how this has been achieved thanks to not only a growing understanding of the underlying biophysics but also rapid technological developments: scanners with larger magnetic fields, better image-processing techniques and algorithms. His aim is to go beyond merely localizing which parts of the brain are active. The challenge is to answer two questions: How are the various regions interconnected, structurally and functionally? What do the networks in our brains look like?
Faster and more powerful
Back in the 19th century scientists observed increased blood flow in brain regions that are functionally active. fMRI enables the change in oxygen content to be seen. Haemoglobin, the substance that transports oxygen in the blood, can take the form of oxyhaemoglobin (when it is still combined with oxygen) and deoxyhaemoglobin (when the oxygen has been released), each of which has different magnetic properties. One of the complicating factors when interpreting the scans is that various physiological mechanisms are at work simultaneously, causing the deoxyhaemoglobin level to rise and fall. One of the remedies to increase accuracy, Norris explains, has been to increase the magnetic field strength: there are now MRI scanners operating at 7 Tesla. At the same time the speed at which laminae can be imaged has gone up by leaps and bounds: the entire brain can be scanned in three seconds with a precision of 1 millimetre.
Hubs
The functional connections between parts of the brain can be registered by means of blood flow, but MRI also enables the structural and anatomical connections to be seen. This involves measuring the movement of water molecules caused by the ‘white matter’ in nerve fibres. This technology is known as diffusion-weighted imaging (DWI). Combining these technologies provides a wealth of fresh information on the networks in the brain and the places where many connections come together, the ‘hubs’. Not only have ‘known networks’ thus been proven, so have networks that neuroscience posits as plausible but that have never been measured.
Image showing the distribution of connector hubs on the surface of a flattened brain. The top two figures show the medial views of each hemisphere, the bottom two show the external views.
CMI
The new Centre for Medical Imaging that is to come to the University of Twente campus will soon provide extensive facilities for collaborating in the field of fMRI, says Norris, who is also on the staff of the Donders Institute in Nijmegen.
(Source: utwente.nl)