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MRI Magnet Madness

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One of the cooler medical devices invented in the last 30 years has to be the MRI machine. Introduced in 1977, it represented a huge leap forward in body imaging, allowing doctors to create greatly detailed maps -- in two or three dimensions -- of an injured knee, a shattered wrist, even a patient's brain. And while MRI scans are nearly free of side-effects, they're not completely free of dangers -- mostly because the main component of an MRI scanner is an insanely powerful magnet.

How powerful? Some estimates put the strength of MRI magnets at tens of thousands of times the strength of the Earth's magnetic field. That's why hospital staff (try to) make sure you remove all jewelry and metallic objects from your person before patients get scanned. Usually metal plates in people's heads and so on are made from surgical steel that won't respond to the MRI's magnet, but there have been cases where metal staples in people's brains have come loose, triggering aneurysms, and tiny slivers of metal in people's eyes (from a previous accident, long settled) have moved, blinding them. Pacemakers and MRI machines generally don't mix, and several deaths have resulted from their unwitting combination.

To really get a sense for how crazy strong MRI magnets are, though, we must turn to YouTube. Here's a video of what I can only imagine are some unauthorized band of yahoos fooling around after hours:

As MRI magnets have gotten more powerful over the years, magnet-related accidents have spiked. The irresponsible dodos in the video above unknowingly mimicked one of the most notorious MRI fatalities, described this way by the New York Times:

The most notorious accident was the death of 6-year-old Michael Colombini in 2001 at the Westchester Medical Center in Valhalla, N.Y. He was sedated in a scanner after a brain operation when his oxygen supply failed. An anesthesiologist ran for an oxygen tank and failed to notice that the one he found in the hall outside was made of steel. As he returned, the tank shot out of his hands, hitting Michael in the head.

There are other jaw-dropping accidents on the books, too: a police officer who's gun was sucked from his holster, slammed against the MRI machine's bore and went off, firing a round into the wall. The "sprinkler repairman whose acetylene tank was yanked inside, breaking its valve and starting a fire that razed the building." Everything from floor buffers to office chairs have gotten wedged in MRI bores, usually requiring four or more people to pry them out, as in this video:

A lot of people ask, "can't you just turn the magnet off?" The simple answer is, it's not that simple. MRI magnets are cooled by liquid helium to eliminate electrical resistance so that their magnetic fields persist indefinitely, so emergency shut-offs involve very rapid venting of the helium in gas form, which can displace oxygen rapidly and be more dangerous than simply leaving the magnet on all the time. How dangerous? Here's a clip of what happens when an MRI is improperly vented, caught by a local news crew:

Of course, as long as the technicians operating them are being safe, MRIs are safe -- all this is meant to illustrate the extreme power they harness. That said, here's a little "MRI magic" to close:

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Opening Ceremony
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These $425 Jeans Can Turn Into Jorts
May 19, 2017
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Opening Ceremony

Modular clothing used to consist of something simple, like a reversible jacket. Today, it’s a $425 pair of detachable jeans.

Apparel retailer Opening Ceremony recently debuted a pair of “2 in 1 Y/Project” trousers that look fairly peculiar. The legs are held to the crotch by a pair of loops, creating a disjointed C-3PO effect. Undo the loops and you can now remove the legs entirely, leaving a pair of jean shorts in their wake. The result goes from this:

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Opening Ceremony

To this:

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Opening Ceremony

The company also offers a slightly different cut with button tabs in black for $460. If these aren’t audacious enough for you, the Y/Project line includes jumpsuits with removable legs and garter-equipped jeans.

[h/t Mashable]

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