Better Patient Experience leads to Better MRI

On my way into work, I was reading a news article by Katharine Sanderson in Nature 457 947 (2009) about an interesting innovation to an MRI (Magnetic Resonance Imaging) machine made by Klaas Pruessmann and David Brunner of the University of Zurich and their colleagues.

As anyone who has ever been inside an MRI would know, it can be a tight squeeze. In creating a better "Patient Experience," Pruessmann, et al, modified the machine's RF apparatus so it could be relocated several meters away, and still focus its radio waves onto the subject by using a cylindrical screen that fits inside the MRI bore as a waveguide.

Thinking Outside the Bore

Normally an MRI involves an RF coil inside a large toroidal superconducting magnet, and this RF coil needs to be close to the subject's body leaving little room for comfort. "Open" MRI are more expensive, because they get their open space by using an even larger-radius superconducting magnet. Larger superconducting anything comes at a premium.

What's great about this innovation is it eliminates RF apparatus which had fit inside of the toroidal superconducting magnet and moves it upfield from the subject. But wouldn't you know, the spillover benefits from improving the user experience get even better!

Travelling Wave

The genius of the Zurich team's work is in toppling the conventional dogma of near field standing-waves, and instead trying a new approach in using far field travelling-waves. This let them solve an even bigger problem.

As MRIs use stronger magnetic fields to produce better images, there is a trade-off. The stronger the magnetic induction B, the higher the frequency of radio waves f  needed to "jostle the atoms" in your body to form a clear picture (I won't go into detail on hydrogen nuclei precession, just pretend to feel like your atoms have been jostled, and you will get the idea.)  As frequency rises, so must wavelength λ fall.  This follows from a relation you probably remember from high school physics class, where the speed of light in a vacuum is constant,

c = λ 

When the wavelength is less than the width of the body being scanned, "dark spots" appear in the MRI picture which prevent physicians from seeing what may be there. A simplified illustration of why short wavelengths lead to dark spots is shown by the following diagrams:

My Head in Todays 1.5 tesla MRI, low B, low f, longer lambda

In a typical 1.5 tesla MRI machine the frequency is low enough such that (even allowing for the index of refraction of my head, not shown) the wavelength is long enough so that a good imaging signal can be detected for everything in my noggin. See, at those points where the RF wave is at zero-strength, that is where there is no jostling of atoms going on for the MRI to make an image and so it would appear dark.

My Head in Experimental 7 tesla MRI, high B, high f, shorter lambda

One drawback of 1.5 tesla scans is they don't have as great a resolution, so for better resolution MRI manufacturers are experimenting with stronger magnets, some up to 7 tesla which can produce high resolution scans but necessitate short wavelengths, much shorter than the width of people's heads. This results in a pattern of dark spots into which physicians cannot see.

My Head in a Travelling-Wave MRI, high B, high f, shorter lambda, nodes homogenized

Enter the travelling-wave, no longer are the points at which the RF wave has zero strength standing stationary in one place, but they continuously move with the wave. With proper image processing, the signals detected by the MRI can be leveled out into one clear picture devoid of black spots!

Lessons for the Software Developer

Engineering for a superior user experience can have far-reaching benefits, and payback dividends in ways you may or may not have expected.  Look closely at the user experience you're offering and measure the benefits of any improvements.  For example, when you give customers a fun experience demoing your product online and make it easy for share that experience with their friends or colleagues, you might find quantifiable benefits in the word-of-mouth marketing and referral traffic driven to your site. "Refer a Friend" and "Send this to my Boss" buttons are appearing increasingly often because they're a UX pattern that works well.

Innovation comes to those who think outside of the box. It doesn't matter if it is an MRI bore cylinder or a rectangular region on your user's screen. If you think of something that can benefit your users, try it out, you just might have hit on something special.

This isn't going to be the last word from us on topics of interest to software developers working in the health services industry, either. We have the expertise to help you create user experiences that can really make a difference for healthcare. Keep your eye on our blogs in the next few months for more on healthcare.

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Sanderson, Katharine. "MRI modified for better images" Nature 457 947 <doi:10.1038/457947a> [A summary for the non-scientist.]
Brunner, David O., et al. "Travelling-wave nuclear magnetic resonance" Nature 457 994-998 <doi:10.1038/nature07752> [The scientific research paper.]


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