Due to mass production, smartphones are a relatively inexpensive way to combine processing power with a quality camera. Developers have found a wide range of qualitative uses for smartphone cameras in digital health applications.
In addition, the question of quantitative imaging has arisen. Researchers recently evaluated multiple smartphones to see if they could be used with a microscope to take pictures consistently enough for quantitative image analysis. To do so, they used a mobile phone microscope called CellScope out of the University of California – Berkeley.
Traditional cameras used with microscopy allow the user to control parameters that are automatically set in mobile phone cameras (e.g. focus, exposure time, etc.). Additionally, mobile phone cameras provide compressed images instead of raw data.
To evaluate the smartphone cameras, researchers looked at spatial resolution, image contrast, and color independently. They compared images from the smartphones with images taken by a scientific camera on the same microscope.
The first conclusion was not surprising: the default camera function failed to create images that were consistently reproducible. Therefore, a custom app would have to be created to have any hope of quantifying images.
Creating a custom app did actually produce usable images after following specific algorithms to calibrate the cameras. In the phones tested, there was no way to set exposure and color gain manually, but the apps could lock the settings chosen by the phones’ automation. The researchers developed a calibration algorithm that took advantage of this feature.
Although the images produced by the mobile phone microscope are consistent enough to be quantitatively analyzed, the automatic processing still leaves artifacts on images produced by the smartphones. These artifacts don’t affect parameters that would be used for analysis such as morphology or color, but they do distinguish these images from those taken by a traditional scientific camera.
Although smartphones are cheaper than regular clinical grade microscopes & cameras this study does not show enough of a benefit to replace the old with the new. On the other hand, it does show that mobile phones may be good enough to fill in where the traditional cameras aren’t available.
The results are interesting because they further support that smartphone microscopes could make microscopy available where funding prohibited it before. And that it can be quantifiable suggests that analysis could, in some settings, be automated; that could be important as resource-limited areas are also less likely to have qualified pathologists to interpret images.
