Song J.,Imaging Research |
Hynynen K.,Sunnybrook Health science Center
IEEE Transactions on Biomedical Engineering | Year: 2010
A hemispherical-focused, ultrasound phased array was designed and fabricated using 1372 cylindrical piezoelectric transducers that utilize lateral coupling for noninvasive transcranial therapy. The cylindrical transducers allowed the electrical impedance to be reduced by at least an order of magnitude, such that effective operation could be achieved without electronic matching circuits. In addition, the transducer elements generated the maximum acoustic average surface intensity of 27 W/cm 2. The array, driven at the low (306-kHz) or high frequency (840-kHz), achieved excellent focusing through an ex vivo human skull and an adequate beam steering range for clinical brain treatments. It could electronically steer the ultrasound beam over cylindrical volumes of 100-mm in diameter and 60-mm in height at 306 kHz, and 30-mm in diameter and 30-mm in height at 840 kHz. A scanning laser vibrometer was used to investigate the radial and length mode vibrations of the element. The maximum pressure amplitudes through the skull at the geometric focus were predicted to be 5.5 MPa at 306 kHz and 3.7 MPa at 840 kHz for RF power of 1 W on each element. This is the first study demonstrating the feasibility of using cylindrical transducer elements and lateral coupling in construction of ultrasound phased arrays. © 2009 IEEE. Source
Boyd N.F.,Campbell University |
Boyd N.F.,Ontario Cancer Institute |
Martin L.J.,Campbell University |
Martin L.J.,Ontario Cancer Institute |
And 2 more authors.
Breast Cancer Research | Year: 2011
Variations in percent mammographic density (PMD) reflect variations in the amounts of collagen and number of epithelial and non-epithelial cells in the breast. Extensive PMD is associated with a markedly increased risk of invasive breast cancer. The PMD phenotype is important in the context of breast cancer prevention because extensive PMD is common in the population, is strongly associated with risk of the disease, and, unlike most breast cancer risk factors, can be changed. Work now in progress makes it likely that measurement of PMD will be improved in the near future and that understanding of the genetics and biological basis of the association of PMD with breast cancer risk will also improve. Future prospects for the application of PMD include mammographic screening, risk prediction in individuals, breast cancer prevention research, and clinical decision making. © 2010 BioMed Central Ltd. Source
Schizophrenia, a severe mental disorder affecting about one in 100 people, is notoriously difficult to diagnose and treat, in large part because it manifests differently in different people. A new study published in Molecular Neuropsychiatry helps explain why. Researchers at the University of North Carolina School of Medicine have created a map that shows how specific schizophrenia symptoms are linked to distinct brain circuits. The findings add to a growing body of evidence that schizophrenia is not a single disease but a complex constellation of neural circuit problems. The study also reinforces the potential value of brain scans for identifying and understanding schizophrenia in individual patients, for finding promising new therapeutic approaches, and for helping clinicians track a patient’s progress during therapy. “For a long time, we’ve thought of brain imaging studies as mainly a way to corroborate or confirm aspects of brain function and pathology that we had already identified from studying a patient’s behavior,” said Aysenil Belger, Ph.D., professor of psychiatry and psychology at UNC and the study’s senior author. “This approach, where we use brain imaging to dissect the specific neural pathways of complex syndromes, is very novel and important. The imaging can help us distinguish between the different brain networks that contribute to distinct sub-symptoms. These distinctions are not recognizable from behavioral observations alone.” Belger, the director of the UNC Neurocognition and Imaging Research Laboratory, and recent UNC graduate student Joseph Shaffer, Ph.D., compared brain scans from more than 100 people with schizophrenia against brain scans from people with no psychiatric diagnoses. The scans were acquired as part of a large multi-site national collaborative research project, the Biomedical Informatics Research Network. Researchers imaged participants during a non-invasive test in which subjects were asked to listen to simple tones and detect changes in pitch. The analysis revealed that people with schizophrenia showed markedly less brain activity during detection of the tonal changes as compared to the control group, a difference that became more apparent as symptoms worsened. The study’s most novel and striking findings emerged when researchers analyzed patterns of brain activity in patients with different types of schizophrenia symptoms. They focused on schizophrenia’s so-called “negative” symptoms, such as problems with speech, blunted emotions, lack of motivation, and an inability to experience pleasure. (“Positive” symptoms include delusions, thought disorders, and hallucinations.) Negative symptoms are the hardest to treat with available medications and can make it difficult to hold a job or form relationships. A close analysis of the brain scans revealed vastly different neural circuitry behind problems that seem similar on the surface. While a clinician may find it difficult to parse whether a patient’s stilted conversational manner is rooted in a lack of emotional connection or problems forming words, a brain scan in Belger’s study made it clear, for example, that particular symptoms were more closely associated with disruption in the brain’s emotional processing areas, whereas other symptoms were more closely associated with regions responsible for language and motor control. “We were surprised by the degree to which these circuits were connected with different sub-symptoms, and by what was, in some cases, almost a complete lack of circuit overlap between these different sub-symptoms,” said Belger. Parsing these complex symptoms could help inform new treatment approaches for schizophrenia and other disorders. “Many of these sub-symptoms are seen in other neuropsychiatric disorders, as well. Therefore, finding the neurological pathway or developing a treatment for that specific symptom could help to address multiple disorders,” Belger said. Also, the findings could help improve the tools available for early detection of risk for schizophrenia and psychosis, which are typically not diagnosed until late adolescence. If clinicians could use brain scans to identify vulnerable high-risk individuals in early adolescence when the brain is still developing, it may be possible to curb the development of the disorder and help prevent its most debilitating effects. Belger also indicated that such “high-risk” mapping studies are currently being conducted at the University of North Carolina in collaboration with Diana Perkins, M.D., and collaborators at multiple institutions across the country under the North American Prodrome Longitudinal Study (NAPLS).
News Article | September 13, 2016
Research from Indiana University has found that structured block-building games improve spatial abilities in children to a greater degree than board games. The study, which appears in the journal Frontiers in Psychology, measured the relative impact of two games -- a structured block-building game and a word-spelling board game -- on children’s spatial processing. Such processing includes mental rotation, which involves visualizing what an object will look like after it is rotated. The research lends new support to the idea that such block games might help children develop spatial skills needed in science- and math-oriented disciplines. It is also the first study to use neuroimaging to explore the effects of block building on brain activity, saidSharlene Newman, a professor in the IU Bloomington College of Arts and Sciences' Department of Psychological and Brain Sciences, who led the research. "Block play changed brain activation patterns," Newman said. "It changed the way the children were solving the mental rotation problems; we saw increased activation in regions that have been linked to spatial processing only in the building blocks group." The structured block-building game used for the study was called "Blocks Rock"; the board game was Scrabble. The research builds upon previous studies that have shown that children who frequently participate in activities such as block play, puzzles and board games have higher spatial ability than those who participate more in activities such as drawing, riding bikes, or playing with trucks and sound-producing toys. It is also demonstrates that training on one visuospatial task can transfer to other tasks. In this instance, training on the structured block-building game resulted in transfer to mental rotation performance. "Other studies look solely at behavioral changes, such as the improved performance on measures of spatial ability," Newman said. "We're actually scanning the brain." To conduct the study, IU researchers placed 28 8-year-olds in a magnetic resonance imaging scanner before and after playing one of the two games. Play sessions were conducted for 30 minutes over the course of five days. To create an equal distribution of spatial ability between the two groups from the start, the children were divided evenly according to several categories that have been linked to differences in spatial ability: gender, age, musical training, mathematical skill and socio-economic status. The two groups of 14 children also took a mental rotation test while inside the scanner, both before and after playing the games. The test -- a longstanding measure of spatial visualization and analysis -- presents two versions of the same letter, and the children had to decide whether the second letter was simply a rotated version of the same letter or a rotated mirror image of that letter. There were no differences in mental rotation performance between the two groups in either the brain activation or performance during the first rotation test and scan. But the block play group showed a change in activation in regions linked to both motor and spatial processing during the second scan. The group who played board games failed to show any significant change in brain activation between the pre- and post-game scans, or any significant improvement on the mental rotation test results. Insofar as the spatial abilities of 8-year-olds are still developing, Newman said the change from the first scan to the second scan might reflect a shift in the strategy used to solve the mental rotation problems. In other words, as children develop their spatial abilities, they may move from a piecemeal strategy in which they analyze the internal relations or parts of an image to a holistic strategy in which the image as a whole is mentally rotated. "The block play group showed a change in activation in regions linked to both motor and spatial processing," Newman added. "This raises the possibility that the block play group changed how they were performing the mental rotation task after training." Ultimately, Newman, who in other work has explored the relationship between math and spatial reasoning, hopes that such findings will help students struggling with math and other disciplines. "Any way you can improve a child's mathematical competence, whether through block-building or any other method, that's where my interest lies," she said. Newman is also the director of the IU Imaging Research Facility and associate vice provost of undergraduate education at IU Bloomington. Other IU researchers on the study were Mitchell Hansen, an undergraduate student, and Arianna Gutierrez, a research associate who was an undergraduate at the time of the study. Both are members of the IU Bloomington Department of Psychological and Brain Sciences.
Chopra R.,Imaging Research |
Chopra R.,University of Toronto |
Vykhodtseva N.,Brigham and Womens Hospital |
Hynynen K.,Imaging Research |
Hynynen K.,University of Toronto
ACS Chemical Neuroscience | Year: 2010
Pulsed ultrasound exposures of brain tissue in the presence of microbubble contrast agents have been shown to achieve transient focal disruption of the blood-brain barrier without significant damage to surrounding brain tissue. The effects of overall exposure duration on the extent of blood-brain barrier disruption was studied in these experiments to determine operating conditions for increasing the amount of therapeutic agents delivered to the brain. Exposures at 1.08 MHz ranging from 0.2 to 0.8 MPa in amplitude were delivered transcranially to the brains of rabbits and rats for durations ranging from 30 to 1200 s. The amount of signal enhancement on contrast-enhanced T1-weighted MR images were used to quantify the extent of blood-brain barrier disruption, and histological evaluation of the exposed regions was performed to evaluate the impact on brain tissue. A subset of four rats underwent weekly exposures for 3 weeks to evaluate the feasibility of repeat sonications to the brain. The results suggest that exposures less than 180 s in duration are associated with a low probability of irreversible damage to brain tissue at pressure amplitudes of 0.38 MPa. Although exposures greater than 300 s were associated with an increase in the proportion of irreversible damage, this may be acceptable for chemotherapy delivery, where the therapeutic goal is tissue destruction. Repeat exposures to the brain were feasible but resulted in evidence of focal brain damage in 50% of animals. © 2010 American Chemical Society. Source