Diagnostics & Imaging

On March 20, 2007, in Diagnostics Imaging

The proliferation of 7-Tesla MRI scanners for research is putting pressure on their adoption for clinical (diagnostic) purposes as well. Already, the US Food and Drug Administration has categorized MRI up to 8T as not a significant health risk, and a clinical trial of a 7T MRI to detect amyloid plaques in Alzheimer’s patients is under way. Clinical adoption of 7T MRI (which is already being planned at the University of Pennsylvania) will likely lead to another arms race among hospitals seeking to poach patients from competitors by offering better technologies. But 7Ts are roughly quadruple the price of today’s standard 3T machines. And that’s hardly the end of it: A 9.4T MRIhas been developed. It can track the firing of individual neurons in the brain and watch thoughts forming in real time. It is expected to provide deeper insight into neurological diseases.


Further evidence that MRI may ultimately supplant CT (for all but the relatively few patients for whom strong magnetic fields pose a danger) is the finding that MRI beats CT for stroke detection. Still, MRI is far from becoming the only imaging game in town and is as susceptible to disruptive innovation as CT is. For instance, a battery of inexpensive eye tests may replace or augment MRI as the best way to diagnose multiple sclerosis in some patients. Then there’s PET, which has already been found to accurately and reliably detect small amounts of amyloid plaques and tangles in the brain. It will be interesting to compare results with the 7T MRI trial just mentioned.

Speaking of disruptive innovation: A palmtop lab that appears to be rapidly approaching commercialization would seem to have disruptive potential, to say the least, for the diagnostic labs business.


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Vanderbilt University’s Institute of Imaging Sciences’ new 7-tesla (7-T) MRI scanner will enable researchers “to better understand and treat everything from learning disabilities to addiction” and “see brain activity much more clearly than has previously been possible,” writes Claudia Pinto in the Tennessean . She quotes institute professor Dr. Calum Avison as calling it “the equivalent of going from regular-resolution TV to HDTV.” The 7-T MRI will help pinpoint the molecular and structural basis for different disorders, quickly establish the effect of a drug on a patient, and lead to early detection of disorders, he said.

Cell-level 9T MRI

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A new 9.4 tesla MRI machine currently undergoing safety tests at the University of Illinois at Chicago can track “the firing of individual neurons in the brain – that is, to watch thoughts form in real time,” says Chicago Tribune reporter Ronald Kotulak. Indeed, while it will have great benefit in understanding neurological disorders, “help people become smarter” by discovering how the brain learns best, and even “aid scientists in building intelligent computers that function more along the lines of the brain,” its ultimate goal “is to be able to find out what people are thinking.”

The director of the institute that houses the machine told Kotulak: “We’d like to get to the stage of reading thoughts. At the moment, all we can do is look at the response of the brain to a particular stimulus. The next step, which we’d all like to get to, is what actually has been processed. Is it the time of day? Is he actually reading a sentence? Which word in the sentence is he understanding?” In time, he believes, the new MRI will reveal some of the mind’s deepest secrets: how we make decisions, how we perceive things, how we process language, how memories are formed, stored, and recalled, and “where they go to be analyzed for their emotional significance.”

Another functional MRI expert said: “That obviously has implications for an understanding of what it is to be a human being, what it is about our brains that makes us the way we are. And it obviously has important implications for an understanding of why different kinds of disease processes give rise to impairments in these everyday functions.”

“If it lives up to its promise,” writes Kotulak, “the machine will spot the first neurons that fire almost instantaneously and track where the communication links go from there.” The magnet weighs 40 tons, is 100,000 times the strength of the Earth’s magnetic field, and is encased in a 520-ton steel shield. It is the first MRI to be able to follow the flow of sodium (other MRIs track water in the blood), which gives it the unique ability to capture the firing of individual brain cells. The magnetic field is so great that sudden movement of the subject’s head inside the machine can stimulate the brain cells, causing the subject to see flashing lights, sense a metallic taste, or feel dizzy.

MRI vs. CT

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CT scans are the most common method of diagnosing a stroke in hospital ERs, notes AP medical writer Maria Cheng, yet they catch only about one out of every four cases. A US government-funded study has caused some experts to declare in The Lancet that MRI scans should replace CT as the standard of care. Of 356 patients studied, 217 were ultimately diagnosed with an acute stroke. Patients were scanned both by CT and MRI, and the scans were independently interpreted by four experts, who had no other patient information. They accurately diagnosed acute strokes 83 percent of the time from the MRI scans, but only 26 percent of the time from CT.

MRI scans were also better at detecting blood clots and bleeding in the brain. In patients scanned within three hours of symptoms, MRIs detected strokes caused by clots in 41 of 90 patients, while CT scans found only six. Since clot-busting drugs must be given within three hours, but can be fatal to the wrong patients, knowing the precise cause of the stroke is vital.

But others counter that MRI results take around 15 to 20 minutes more time, and delay can be deadly to a stroke patient. CT scanners are smaller than MRI, cheaper to operate, relatively ubiquitous in EDs, and produce images in as little as two minutes. MRI scanners are bulky, require patients to lie still for up to 30 minutes, and cannot be used on patients with pacemakers and other implanted metal objects, or who may be pregnant.

MS in the Eyes

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Doctors at a Texas eye center use four different eye examinations to look for abnormalities in the retina and damage to optic-nerve fibers that could indicate the presence of multiple sclerosis, reports Aja Carmichael in the Wall Street Journal . The center uses VEP (visual evoked potential), multifocal VEP, OCT (optical coherence tomography), and visual field tests. In 2006. one-third of the patients who came to the center had beem previously misdiagnosed as having the disease. Currently, MRI scans costing from US$2-4,000 are the primary tests for MS. The Texas center charges $75 to $100 for OCT.

Alzheimers’ Early Diagnosis Possible

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University of California at Los Angeles researchers have discovered a way to highlight distinctive brain changes in patients with early stage Alzheimer’s disease – perhaps long before disabling symptoms emerge. The method involves a new chemical marker that binds to plaques and tangles and is clearly visible on PET scans.

A trial conducted over two years ago involving more than 80 volunteers, some healthy, some with mild cognitive impairments such as memory loss, and 25 already diagnosed with Alzheimer’s showed much higher levels of the chemical among the Alzheimer’s patients compared with the others, and highlighted more subtle differences between the healthy volunteers and those with the mild symptoms. Scans of the same patients two years later revealed that those whose condition had worsened had clear increases in the levels of the chemical in their brain. An autopsy of one of the trial patients who died 14 months after the first scan confirmed the presence of amyloid plaques and tangles in the exact locations revealed by the scan.

Lab Chip

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The Argonne National Laboratory has developed a multipurpose diagnostics chip for infections, based on a concept developed in Russia in the mid-1990s. Hundreds or thousands of wells on the chip can each perform a different test, such as looking for a specific protein or a DNA fragment, to identify a virus or bacterium in a sample. For example, within 15 minutes of a patient arriving at a hospital emergency room with a cough, a credit-card-sized device holding the chip could diagnose strep throat, anthrax, a cold, or other viral or bacterial infection, from a sputum sample.

Three start-up companies have licensed the technology from Argonne, each with a different commercial application in mind: human diagnostics, animal diagnostics, and manufacturing imaging hardware for the system. The entire system [into which the credit-card-sized device would be placed for analysis, presumably] is currently the size of a coffee pot but the developers expect soon to bring it down to palmtop size.

The system will enable doctors to make fast and reliable diagnoses without sending samples to a lab. An Argonne researcher told Chicago Tribune reporter Jon Van: “The beauty of this system is that you can do so many tests in parallel. Most physicians have a pretty good idea what they’re looking for, so you don’t need to run more than 30 or 40 tests usually. But you can do hundreds, which means you can run controls along with diagnostic testing. That increases statistical rigor and the accuracy of your diagnosis.”


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