Stories about: radiology

Real-time contextual information could help doctors interpret children’s brain scans

Radiologists who can tune in to the nuances of brain scans in children are a pretty rarified group. Only about 3 percent of U.S. radiologists, some 800 to 900 physicians, practice in pediatrics. Those specifically trained in pediatric neuroradiology are even scarcer.

To a less trained eye, normal developmental changes in a child’s brain may be misinterpreted as abnormal on MRI. Conversely, a complex brain disorder can sometimes appear normal. That’s especially true when the abnormality affects both sides of the brain equally (see sidebar).

It can be hard to find the cause of a child’s developmental delay without a proper read. “Pediatric brain scans of children under age 4 can be particularly tricky to read because the brain is rapidly developing during this period,” says Sanjay Prabhu, MBBS, a pediatric neuroradiologist at Boston Children’s Hospital. “If you’re looking at adult scans all the time, it’s incredibly difficult to transition to pediatric scans and understand what is considered ‘normal’ and ‘abnormal.’ Clinicians often wonder, ‘Should I repeat the scan? Should I send the patient to a specialist?’”

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Five cool medical innovations we saw last week

Last week, Boston Children’s Hospital’s Innovation Acceleration Program hosted a jam-packed Innovators’ Showcase where teams from around the hospital networked, traded ideas and showed off their projects. Here are a few Vector thinks are worth watching.

isotropic diffusion reveals information on axons on DTI1. An imaging ‘biomarker’ after concussion

Thirty percent of people who suffer a mild traumatic brain injury—a.k.a. concussion—have ongoing symptoms that can last months or years. If patients at risk could be identified, they could receive early interventions such as brain cooling and anti-seizure medications. New MRI protocols that can measure free, non-directional diffusion of water, coupled with sophisticated analytics, are achieving unprecedented pictures of what happens inside the brain after injury.

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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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Less is more: Do Hodgkin’s survivors really need CT scans after treatment?

shutterstock_101761009It’s music to the ear of any cancer patient: “Your scans are clear.” It means you’ve won, and the treatments you’ve endured have driven cancer from your body.

But once you hear those four magic words, are you also free of the need for future scans? There’s an argument to be made that continued scanning or surveillance imaging is a good thing. After all, if you have a relapse, you want to detect it as early as possible.

But that argument may not hold up in the face of data. Continued imaging can be expensive, can expose survivors to additional radiation, can have false positive results leading to additional worry and unnecessary medical care, and may not be any better at detecting tumor relapses than a physical exam or simply a survivor’s feeling that something is “wrong.”

Stephan Voss, MD, PhD, the director of Nuclear Medicine and Molecular Imaging and chief of Oncologic Imaging at Boston Children’s Hospital, decided to crunch the numbers, using Hodgkin lymphoma (HL) as a model for testing whether post-treatment surveillance with computed tomography (CT) scans makes clinical sense. His conclusion: not really.

“The conventional wisdom is that early detection of relapse means that we spare the patient side effects and poorer outcomes,” Voss says, referring to the belief that HL survivors should have a follow-up CT scan every year for up to five years after treatment. “But with Hodgkin disease, that’s not the case.”

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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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Glimpsing a baby’s brain: Advanced neuroimaging

Surprisingly little is known about the brains of babies under age 2 — because of the challenges of safely imaging children so young. Head-circumference measures at the pediatrician’s office tell very little about what’s going on inside. But there’s much to know, because rapidly developing brains are vulnerable to injury.

Here, Ellen Grant, a neuroradiologist trained in theoretical physics, describes how advanced imaging techniques and computational science are providing a better understanding of the newborn and even fetal brain. With these tools, neurologists can watch the brain as it forms and folds, track the growth of individual brain structures, and detect problems in brain organization before anything can be noticed by parents or physicians — then correlate these measurements with child developmental measures.

Children’s Hospital Boston is building a neuroimaging facility with specially designed, baby-sized equipment — the only one in the world to be situated near a neonatal and pediatric intensive care unit. It will help answer questions like: What prenatal brain development is missed when a baby is born even two weeks shy of its due date? What does a brain structure growing out of synch at 6 months mean for language development in preschool? Are interventions for brain injury, such as hypothermia, effective? Grant’s ultimate goal is to get advanced neuroimaging into routine clinical care, to monitor infants and newborns with brain injury, predict their future course, and evaluate new treatments.

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