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A Simple Invention Could Change How Fast Disease Is Detected

TheAtlantic 2019-08-22 16:30:00

So Prakash and his colleague Hongquan Li built a fancier microscope—a high-speed, malaria-detecting device that they’ve called Octopi. It can automatically scan entire blood-smeared slides for malaria parasites, using a neural network trained on more than 20,000 existing images. Octopi works off a phone charger. It analyzes slides at speeds that are 120 times faster than traditional microscopy. Weighing fewer than seven pounds, it’s portable. And at a do-it-yourself cost of $250 to $500, it’s cheaper than many basic microscopes or other automated slide-analyzing devices.


Prakash has spent his career building extremely cheap medical devices that can be used in some of the poorest parts of the world. Besides the Foldscope, he developed a $10 skin patch that can detect parasitic worms. And he developed a 20-cent, hand-powered centrifuge that can spin medical samples at up to 125,000 revolutions per minute, achieving what costly, bulky, and expensive machines can do using little more than paper, string, and tape. But diagnostic speed was a new challenge.


At first, Li disassembled and reverse-engineered hundreds of DVD drives to try to build something that could scan slides quickly and efficiently. Eventually, he decided to fashion something from scratch. What he built was a fully modular microscope, with separate illuminating, scanning, and processing units that snap together magnetically. It looks quite unlike a standard microscope: There’s no eyepiece, for a start, nor a need for one. To use it, a technician prepares a slide in the usual way. “And then, you load the slide in the microscope and hit the scan button,” Li says.

The modular design makes the microscope very flexible. Technicians can switch between a low-magnification module that can efficiently find the parasites on a slide, and a high-magnification one that can more sensitively count them within those hot spots. They can also swap between different types of imaging, from the basic kind, in which white light shines through a slide from below, to more advanced techniques that look at the colors of samples treated with fluorescent dyes.


For malaria, the latter is crucial, because Li found that malaria parasites fluoresce in a slightly different color than surrounding blood cells. The distinction—roughly, teal versus blue—is hard to discern with the naked eye, but to Octopi, it’s clear. At first “we thought, That can’t be right,” Prakash says. “But the parasites do light up differently!”

The Octopi name has many origins. It’s a very loose acronym, which stands for “open configurable high-throughput platform for infectious diseases.” The microscope is very versatile, in the way that octopuses are. The “pi” ending, though the wrong plural form for octopus, is a nod to Raspberry Pi, a simple computer designed for use in developing countries. And, “my kids are of the age where they love octopuses,” Prakash says.