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MRI: Alzheimer’s, OCD & Spine – Vol. 2, Number 23

Tuesday, September 16th, 2008

MRI: ALZHEIMER’S

Brain MRI Temporoparietal Measurements in Prodromal Alzheimer’s Disease
The National Institute for Aging estimates that up to 4.5 million Americans suffer from Alzheimer’s disease.  To assess the early imaging appearance of the disease, researchers in a multicenter prospective trial led by Boston University followed the brain MRI measurements of various anatomic brain locations over time and correlated them with metal status.  As reported in Neurology, 16 brain regions of interest underwent MRI scrutiny in 66 subjects.  The people who developed Alzheimer’s disease over the course of the study displayed greater atrophy rates in six brain areas, compared to those individuals who showed stable, mild cognitive impairment throughout the study.  These areas included the hippocampus, entorhinal cortex, temporal lobe, middle temporal gyrus, fusiform gyrus, and inferior temporal gyrus.  Those subjects who advanced to Alzheimer’s disease over the time frame demonstrated differentially greater rates of atrophy, compared to normal cognitive controls in five of these areas and in the inferior parietal lobe.  Correlation occurred between the rate of mental status change and rates of atrophy in these areas.

Conclusion:  Brain MRI exams in podromal Alzheimer’s disease show differential rates of atrophy in the temporoparietal regions that correlate with cognitive decline, and carry potential for use as markers in early Alzheimer’s disease.

MRI: OCD

Obsessive-Compulsive Disorder Patients and Their Close Relatives Displayed Functional MRI Signs
Obsessive-compulsive disorder (OCD) is an anxiety disorder described by the National Institute of Mental Health (NIMH) as recurrent, unwanted thoughts and/ore repetitive behaviors.  The number of affected American adults age 18 or over approaches 2.2 million, representing roughly 1 percent of people in this age range per year.  Symptoms frequently commence in childhood or adolescence, with a mean age of 19.  The condition displays a familial link, though studies to investigate the inheritance pattern, thought to be complex and involving multiple genes, have been ongoing in the U.S.  In light of this complicated genetic puzzle, researchers at the University of Cambridge (England) sought to identify alternative disease markers using functional brain MRI.  The study examined 14 patients with OCD, 12 of their unaffected first-degree relatives, and 15 unaffected matched controls.  The participants underwent visual tasks to elicit different components of behavioral flexibility.  A recent report in Science examines their findings, reporting abnormally decreased activation in several cortical regions, including the lateral orbito-frontal cortex, in OCD patients and their unaffected close relatives.  The authors conclude that such brain-based markers may provide powerful assistance in solving the genetic basis of the disorder.

Conclusion:  Functional brain MRI demonstrated markers for obsessive compulsive disorder.

MRI: SPINAL CORD

First Spinal Cord Genetic Atlas Released
The National Spinal Cord Injury Statistical Center (NSCISC) estimates that as of 2007, approximately 255,702 people in the United States were living with spinal cord injuries.  The current widely available imaging methods for such individuals can display their macroscopic cord findings.  Such findings reflect the cord’s anatomy and histology, the foundation of which ultimately occurs at the molecular level.  The more refined imaging can become, the further it can delve into the microscopic cellular and subcellular milieu.  As reported in Nature News, an ambitious project to map the expression patterns of 18,500 genes in the mouse spinal cord has released data on the first 2,000 of these genes.  Ultimately, the Allen Institute for Brain Science plans to release the Allen Spinal Cord Atlas, created from 20-micrometer thick sections at millimeter intervals.  The journal explains that pictures will be “resolvable down to one micrometer per pixel of screen – individual nerve cells are upwards of 10 micrometers in diameter.

Conclusion:  A new atlas of mouse spinal cord genetic expression holds promise as a reference f0r normal anatomy, with detail never heretofore accomplished.

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Posted in Brain, Neuro | No Comments »

MRI: Brain & Contrast and Cardiac CT – Vol. 2, Number 22

Thursday, September 4th, 2008

MRI: BRAIN

Imaging Reveals Astrocytes Can Respond to Visual Stimuli
Neurons are known as the principal functioning cells in the brain, receiving, storing, and transmitting information.  Higher-order functions such as sight, therefore, rely on neurons.  The brain’s star-shaped astrocyte cells are thought to perform functions for neurons, metabolically buffering, detoxifying, supplying nutrients, and electrically insulating them.  Astrocytes also contribute to brain barriers and play a principal role in brain repair and brain scar formation.  Until now, the ability to see had not been a role ascribed (in part) to astrocytes.  Yet researchers at the Massachusetts Institute of Technology recently documented that astrocytes do indeed respond to visual stimuli.  The authors used two-photon imaging of calcium signals in vivo, employing a ferret visual cortex model.  As reported in Science, astrocytes displayed distinct spatial receptive fields, as well as orientation and spatial associations.  The finding suggests the role of both neurons and astrocytes in vision.  This holds implications for non-invasive imaging techniques that study brain activity, such as functional MRI.

Conclusion:  Imaging shows that astrocytes join neurons as cells known to respond to visual stimuli.

MRI: CONTRAST

Alternative MRI Contrast Agent Can Deliver Therapeutic Drugs
Gadolinium has dominated the MRI contrast market since it was approved for human use 20 years ago.  More than 85 million doese had been administered by 2007, about 5 million annually.  A recent study in the Journal of the American Chemical Society reports the creation of a novel MRI contrast agent that is not gadolinium-based, but rather manganese-labeled, toroidal (doughnut-shaped) nanoparticles.  This new molecular agent can target fibrin, a constituent of a clot.  The authors, from Washington University School of Medicine, Philips HealthCare, and St. Thomas Hospital (London), state that the agent can also incorporate chemotherapeutic compounds, raising the possibility of its exhibiting both diagnostic and therapeutic utilities.

Conclusion:  A novel MRI contrast agent can not only target the fibrin in thrombus, but also deliver therapeutic compounds.

CARDIAC CT

Pericardial Fat Is Related to Calcified Coronary Artery Plaque
The U.S. Centers for Disease Control (CDC) report that an estimated 66 percent of U.S. adults and 17 percent of children and adolscents are overweight.  Inflammatory cytokines exist at higher levels in pericardial fat than in subcutaneous fat.  To assess whether pericardial fat is associated with calcified coronary artery plaque, researchers for the Multiethnic Study of Atherosclerosis examined the volume of pericardial fat on cardiac CT in 159 patients in Forsythe County, NC, and evaluated for calcified coronary artery plaque.  As reported in the research journal Obesity, pericardial fat proved significantly associated with calcified coronary artery plaque, even when adjusting for other cardiovascular risk factors, and was independent of gender and ethnicity.

Conclusion:  Pericardial fat is associated with calcified coronary artery plaque, independent of gender and ethnicity.

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Posted in Brain, Obesity, Oncology, Visual Stimuli | No Comments »

MRI: Lymphoma, Cardiac & Lead Exposure – Vol. 2, Number 20

Friday, August 1st, 2008

MRI: LYMPHOMA

Imaging of pH Change in Cancer Accomplished in Mice
A change in the acid/base milieu accompanies a variety of pathologic conditions, including cancer, ischemia, and inflammation.  Cancer commonly has an acidic pH and will turn bicarbonate into carbon dioxide.  By harnessing this reaction, lead researchers at Cambridge Research Institute and University of Cambridge accomplished in vivo imaging of the pH alteration in lymphoma.  In a study published in the June 12 issue of Nature, the authors report that they were able to create nontoxic, labeled bicarbonate by utilizing dynamic nuclear polarization (DNP).  The ratio of signal intensities in hyperpolarized bicarbonate into mice with subcutaneous lymphoma revealed that the average interstitial pH in the lymphoma was significantly lower than in the surrounding tissue.  The authors present MRI images of this signal difference.

Conclusion:  In vivo imaging of pH alteration in lymphoma has been achieved in a mouse model using labeled bicarbonate.

MRI: CARDIAC

Late MRI Gadolinium Enhancement Portends Higher Risk of Cardiac Event in Patients with Nonischemic Cardiomyophathy
Patients with nonischemic cardiomyophathy (NICM) underwent gadolinium-enhanced cardiovascular MRI to assess whether the presence and extent of late enhancement correlated with adverse outcomes.  As published in the Journal of the American College of Cardiology, authors from John Hopkins prospectively assessed 65 NICM patients with left ventricular ejection fractions of less than 35%.  The cohort had the MRI examinations prior to receiving implantable cardioverter-defibrillators (ICD).  The results showed that 42% of the group had late gadolinium enhancement.  Of these, 44% had either hospitalization for heart failure, appropriate ICD firing, or cardiac death, compared to 8% of those patients who did not have late enhancement.

Conclusion:  Late gadolinium enhancement correlates with increased risk of cardiac events in patients with nonischemic cardiomyopathy.

MRI: LEAD EXPOSURE

Childhood Lead Exposure Associated with Decreased Brain Volume in Adults
The Centers for Disease Control (CDC) report that approximately 310,000 U.S. children between the ages of one and five have current elevated blood levels greater than the level at which action is recommended – 10 micrograms of lead per deciliter of blood.  Lead causes a variety of toxicities, central nervous system injury being dominant among them.

A recent study led by researchers at Cincinnati Children’s Hospital examined young adults who had experienced elevated childhood lead levels and enrolled in a long-term follow-up study.  The cohort had detailed pre- and postnatal low to moderate lead exposure, with behavioral outcomes monitored over 25 years.  The group underwent whole-brain, high-resolution MRI imaging with assessment of global and regional brain changes using voxel-based morphometry.

The results showed significant reductions in gray-matter volume for several cortical regions in individuals with higher mean childhood lead levels.  As published online at PLoS Medicine, the greatest areas affected included the frontal gray matter, specifically the anterior cingulate cortex.  The lead-associated brain volume loss proved much larger in men than women.  Fine-motor scores correlated positively with the gray-matter volume.

Conclusion:  Childhood lead toxicity is associated with region-specific diminished adult brain volume in areas responsible for mood and decision making, and adversely affects males more than females.

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Posted in Brain, Cancer, Cardiac, Disease Control | No Comments »

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