Human World

iPhone morphs into medical imaging device

A team of researchers from the University of California, Davis has transformed everyday iPhones into medical-quality imaging and chemical detection devices. With add-on materials that cost about as much as a typical app, the decked-out smartphones are able to use their heightened senses to perform detailed microscopy and spectroscopy.

The team will present their findings at the Optical Society’s (OSA) annual meeting in San Jose, California on October 16-20, 2011.

Images of a sugar crystal taken through polarized light filters. Left: traditional microscope. Right: cell phone microscope. Via OSA

The enhanced iPhones could help doctors and nurses diagnose blood diseases in developing nations where many hospitals and rural clinics have limited or no access to labs. The modified phones are also able transmit real-time data to colleagues around the globe for further analysis.

Sebastian Wachsmann-Hogiu, lead author of the research, said:

Field workers could put a blood sample on a slide, take a picture, and send it to specialists to analyze.

The group is not the first to build a smartphone microscope. Wachsmann-Hogiu said:

But we thought we could make something simpler and less expensive.

Stained samples of pollen (left images) and plant stems (right two images). Top row: commercial microscope. Bottom row: cell phone microscope. Via OSA

His first attempt took simplicity too far:

We started with a drop of water on the camera’s lens. The water formed a meniscus, and its curved surface acted like a magnifying lens. It worked fine, but the water evaporated too fast.

Then the team turned to ball lenses. These are finely ground glass spheres that act as low-powered magnifying glasses. The team used a 1-millimeter-diameter ball lens that costs $30-40 USD in their prototype, noting that mass-produced lenses could reduce the price.

To build the microscope’s lens, Kaiqin Chu, a post-doctoral researcher in optics, inserted a ball lens into a hole in a rubber sheet, then simply taped the sheet over the smartphone’s camera.

The iPhone microscope consists of a 1-millimeter-diameter ball lens embedded in a rubber sheet and taped over the smartphone’s camera. Via OSA

At 5x magnification, the ball lens is no more powerful than a child’s magnifying glass. Yet when paired with the camera of a smartphone, the microscope can resolve features on the order of 1.5 microns, small enough to identify different types of blood cells.

There are two reasons why such low magnification produces such high-resolution images. First, ball lenses excel at gathering light, which determines resolution. Second, the camera’s semiconductor sensor consists of millions of light-capturing cells. Each cell is only about 1.7 microns across. This is small enough to capture precisely the tiny high-resolution image that comes through the ball lens.

The researchers used digital image software to correct for the distorting nature of a ball lens and to bring tiny in-focus areas into a single image large enough for analysis.

The upper row shows images of blood samples taken with a traditional microscope. From left to right: normal, iron deficiency anemia, and sickle cell anemia. The bottom row shows the same samples imaged on a smartphone. Via OSA

Even though smartphone micrographs are not as sharp as those from laboratory microscopes, they are able to reveal important medical information, such as the reduced number and increased variation of cells in iron deficiency anemia, and the banana-shaped red blood cells characteristic of sickle cell anemia.

Wachsmann-Hogiu’s team is working with UC Davis Medical Center to validate the device and determine how to use it in the field. They may also add features such as larger lenses to diagnose skin diseases, and software to count and classify blood cells automatically in order to provide instant feedback and perhaps recognize a wider range of diseases.

When researchers need additional diagnostic tools, the microscope could be swapped for a simple spectrometer that also uses light collected by the iPhone’s camera.

Above, the spectrum of a fluorescent bulb taken by an iPhone spectrometer. Below, a comparison of spectra from an iPhone and a commercial spectrometer. While the iPhone is not as precise as the commercial unit, it accurately picks up the peaks in color intensity. Via OSA

Spectrometers smear out light from an object, separating it into its composite wavelengths in much the way a prism breaks up white light in the familiar colors of the rainbow. Since atoms and molecules absorb very specific wavelengths when exposed to light, it is possible to tease out the chemical signature of materials by studying their spectra.

Like the microscope, the iPhone’s spectrometer takes advantage of smartphone imaging capabilities. The spectrometer they added to the iPhone is easy to build. It starts with a short plastic tube covered at both ends with black electrical tape. Narrow slits cut into the tape allow only roughly parallel beams of light from the sample to enter and exit the tube. It is this grating that spreads the light into a spectrum of colors that scientists can use like a fingerprint to identify various molecules.

Though the spectrometer is still in its early stages, the researchers believe it could measure the amount of oxygen in the blood and help diagnose chemical markers of disease.

Because smartphone instruments are powerful and cheap, Wachsmann-Hogiu believes schools could use them to enrich science classes. Spectrometers could help illustrate lessons about light and energy. Microscopes could unveil an invisible world of sugar crystals, pollen grains, and microscopic organisms.

Bottom line: UC-Davis researchers have developed an add-on for the iPhone that transforms it into a medical imaging device. They will present their findings at the Optical Society’s (OSA) annual meeting in San Jose, California on October 16-20, 2011.

Read more at Optical Society of America

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October 4, 2011
Human World

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