Stories about: MRI

The future of cardiac MRI: 3-D cine

A 3-D motion-capture MRI of the heart

The heart is a dynamic, beating organ, and until now it has been challenging to fully capture its complexity by magnetic resonance imaging (MRI). In an ideal world, doctors could create a 3-D visual representation of each patient’s unique heart and watch as it pumps, moving through each phase of the cardiac cycle. Andrew Powell, MD, Chief of the Division of Cardiac Imaging at Boston Children’s Hospital, and his physicist colleague Mehdi Hedjazi Moghari, PhD, have taken steps toward realizing this vision.

The standard cardiac MRI includes multiple 2-D image slices stacked next to each other that must be carefully positioned  by the MRI technologist based on a patient’s anatomy. Planning the location and angle for the slices requires a highly-knowledgeable operator and takes time.

Powell and Moghari are working on a new MRI-based technology that can produce moving 3-D images of the heart. It allows cardiologists and cardiac surgeons to see a patient’s heart from any angle and observe its movement throughout the entire cardiac cycle.

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For dyslexia, writing is often on the wall from birth

Writing on the wall-shutterstock_345548735-croppedSome 5 to 17 percent of all children have developmental dyslexia, or unexplained reading difficulty. When a parent has dyslexia, the odds jump to 50 percent. Typically, though, dyslexia isn’t diagnosed until the end of second grade or as late as third grade — when interventions are less effective and self-esteem has already suffered.

“It’s a diagnosis that requires failure,” says Nadine Gaab, PhD, an investigator in Boston Children’s Hospital’s Laboratories of Cognitive Neuroscience.

But a new study led by Gaab and lab members Nicolas Langer, PhD, and Barbara Peysakhovich finds that the writing is on the wall as early as infancy — if only there were a way to read it and intervene before the academic, social and emotional damage is done.

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MRI-powered ‘millirobots’ could swim around the body, drive needles, puncture tissues

(noppasit TH/Shutterstock)
(noppasit TH/Shutterstock)

MRI is a staple of surgical imaging, but it has the potential to do much more than take pictures. In 2011, bioengineer Pierre Dupont, PhD, and colleagues demonstrated that an MRI machine’s magnetic field could power a motor strong enough to control a robotic instrument, in this case driving a needle into an organ to do a biopsy.

But Dupont, head of the Pediatric Cardiac Bioengineering Lab at Boston Children’s Hospital, wants to go further. “We had this idea, admittedly fanciful: What if you could swim robots through the body?” he says. “If you could inject something systemically and steer it to just hit your target, that would be a cool application.”

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Brain structural imaging: Gleaning more with math

MRI images showing isotropic diffusion in autism
A new MRI computational technology (above right) captures differences in water diffusion in the brain across a population of children with autism as compared with controls. This non-directional, “isotropic” diffusion pattern, not evident with conventional diffusion tensor imaging (DTI), may be an indicator of brain inflammation.

Diffusion tensor imaging (DTI), a form of magnetic resonance imaging, has become popular in neuroscience. By analyzing the direction of water diffusion in the brain, it can reveal the organization of bundles of nerve fibers, or axons, and how they connect—providing insight on conditions such as autism.

But conventional DTI has its limits. For example, when fibers cross, DTI can’t accurately analyze the signal: the different directions of water flow effectively cancel each other out. Given that an estimated 60 to 90 percent of voxels (cubic-millimeter sections of brain tissue) contain more than one fiber bundle, this isn’t a minor problem. In addition, conventional DTI can’t interpret water flow that lacks directionality, such as that within the brain’s abundant glial cells or the freely diffusing water that results from inflammation—so misses part of the story.

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Bringing MRI to vulnerable newborns

Premature newborn in small-bore MRI magnet-courtesy Cincinnati Children's
A 4.2-lb baby girl in the new 1.5 Tesla MRI magnet, designed for use in the NICU. (Images courtesy of Cincinnati Children’s Hospital Medical Center)
Charles Dumoulin, PhD, is the director of the Imaging Research Center at Cincinnati Children’s Hospital Medical Center (CCHMC) and a professor of pediatric radiology at University of Cincinnati College of Medicine. He led the team of scientists and engineers from CCHMC’s Imaging Research Center who won the Clinical Innovation Award at Boston Children’s Hospital’s National Innovation Pediatric Summit + Awards in September.

Experience suggests that magnetic resonance imaging (MRI) and advanced MR techniques such as spectroscopy and diffusion imaging offer substantial benefits when diagnosing problems in premature babies. However, today’s MR systems poses significant logistical barriers to imaging these infants. We have been working to change that.

MRI provides an unparalleled ability to visualize anatomy without the hazards of ionizing radiation. Yet premature and sick babies in neonatal intensive care units (NICUs) are usually too delicate to leave the unit. The few babies who receive MRI today must be accompanied by NICU staff during transport to and from the Radiology Department. This process is often a multi-hour ordeal and reduces the staff available to care for other babies in the NICU. Moreover, infants must be imaged in an adult-sized MRI scanner

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Has lung MRI for children come of age?

Chest MRI and CT scans from a child
With the latest technologies and techniques, MRI (bottom) is in many cases just as good as, if not better than, CT (top) when taking images of a child's chest. (Courtesy Edward Y. Lee, MD, MPH)

Magnetic resonance imaging, or MRI, can produce stunningly detailed images of the body’s tissues and structures. Historically, however, the chest—and in particular, the lungs and airway—has proven challenging for radiologists to clearly visualize through MR images.

Why is that? Unlike most other solid organs, the lung and trachea aren’t really solid. The air spaces within them do not absorb the magnetic fields or produce the radio signals needed to generate high-quality diagnostic images. Also, they are in constant motion—we have to breathe, after all.

For these reasons, radiologists have long relied on x-rays and computed tomography (CT) scans to take pictures of the lungs. Both can produce very good, highly detailed diagnostic images, but both also come with risks related to their reliance on ionizing radiation.

The lung MRI’s time may now have come. In a review paper in Radiologic Clinics of North America (RCNA), an international team of radiologists led by Simon Warfield, PhD, and Edward Y. Lee, MD, MPH, of Boston Children’s Department of Radiology outlines several recent advances that have made MRI a more viable—radiation-free—alternative for diagnostic imaging of children’s lungs and airway.

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Mapping the wiring of the developing brain in 3D

Ed. note: Last week we wrote about Jurriaan Peters, MD’s brain network analysis in children with autism. In the second of our two part series on brain mapping, we talk about ways of mapping the brain’s physical wiring.

(AMagill/Flickr)

At the most basic level, the brain is a collection of wires, albeit a really complex one.

But how during development do nerve fibers thread their way through the growing brain and make the right connections?

The answer to that question could reveal more about the nature of conditions like autism spectrum disorders—which, as we reported about a year and a half ago, seem to have their roots in structurally altered brain pathways.

“We know very little about what’s happening in the developing brain in three dimensions,” says Emi Takahashi, PhD, a researcher in the Fetal-Neonatal Neuroimaging & Developmental Science Center (FNNDSC) at Boston Children’s Hospital. “With histology techniques, we can achieve a two-dimensional view over small areas, but it’s hard to know which fiber bundles are growing in which ways during different stages of development in the whole brain.”

But new MRI-based technologies are quickly closing that knowledge gap, giving us our first high-resolution peek into how the developing brain wires itself up.

Using something called high angular resolution diffusion imaging (HARDI) MRI, Takahashi and her colleagues (including neuroradiologist and FNNDSC director P. Ellen Grant, MD) can trace the three-dimensional pathways within the growing brain via stunning images like these:

Courtesy Cerebral Cortex (Takahashi et al., 2012)

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MRI-powered medical robots are coming

It began as a proof-of-principle demonstrated with LEGOs – a surgical biopsy needle whose motor is driven solely by a clinical MRI scanner:

The above demo shows that an MRI machine’s magnetic field can be programmed to produce enough force to control a robotic instrument — an accomplishment with broad potential in medicine. In the demo, the scanner’s magnetic field swings a rotating arm, and a set of gears convert that motion into the motion of a biopsy needle, strong enough to puncture the tough outer tissue of an animal heart and then withdraw. All parts exposed to the magnetic field are metal-free and MRI-compatible.

While MRI-compatible robots have been built before, this was the first demo of a motor powered by MRI, says Pierre Dupont, chief of Pediatric Cardiac Bioengineering at Children’s Hospital Boston. His engineering team was one of five finalists for Best Paper Award — out of 790 papers presented — at last week’s International Conference on Intelligent Robots and Systems (IROS 2011).

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