Quantitative Imaging with a Mobile Phone Microscope

Abstract

Use of optical imaging for medical and scientific applications requires accurate quantification of features such as object size, color, and brightness. High pixel density cameras available on modern mobile phones have made photography simple and convenient for consumer applications; however, the camera hardware and software that enables this simplicity can present a barrier to accurate quantification of image data. This issue is exacerbated by automated settings, proprietary image processing algorithms, rapid phone evolution, and the diversity of manufacturers. If mobile phone cameras are to live up to their potential to increase access to healthcare in low-resource settings, limitations of mobile phone–based imaging must be fully understood and addressed with procedures that minimize their effects on image quantification. Here we focus on microscopic optical imaging using a custom mobile phone microscope that is compatible with phones from multiple manufacturers. We demonstrate that quantitative microscopy with micron-scale spatial resolution can be carried out with multiple phones and that image linearity, distortion, and color can be corrected as needed. Using all versions of the iPhone and a selection of Android phones released between 2007 and 2012, we show that phones with greater than 5 MP are capable of nearly diffraction-limited resolution over a broad range of magnifications, including those relevant for single cell imaging. We find that automatic focus, exposure, and color gain standard on mobile phones can degrade image resolution and reduce accuracy of color capture if uncorrected, and we devise procedures to avoid these barriers to quantitative imaging. By accommodating the differences between mobile phone cameras and the scientific cameras, mobile phone microscopes can be reliably used to increase access to quantitative imaging for a variety of medical and scientific applications.

Diagnosis of Schistosoma haematobium Infection with a Mobile Phone-Mounted Foldscope and a Reversed-Lens CellScope in Ghana

“…The CellScope is a mobile phone microscope that integrates imaging and illumination optics directly with an unmodified mobile phone. 13,14 The reversed-lens CellScope 12 ( Figure 1B) used in this study is a small three-dimensional-printed plastic attachment for the iPhone 5S with an embedded lens for microscopic imaging. It harnesses the mobile phone's light source to illuminate slides by reflecting light off of a white slide holder placed underneath the microscope slide.…”

Cellphone-based diagnostic devices

“…This system exploited the powerful computational capability of a cellphone for automatic cell counting. Since then, they have dedicated their efforts to the development of practical cellphone-based microscopy, something they call "CellScope" [30]. CellScope devices were designed for imaging granulocyte and red blood cells and performed high degrees of sensitivity and specificity in clinical Schistosoma haematobium infection diagnosis and blood-borne filarial parasites inspection (e.g., Loa loa) ( Figure 2) [24,30,31].…”

“…Since then, they have dedicated their efforts to the development of practical cellphone-based microscopy, something they call "CellScope" [30]. CellScope devices were designed for imaging granulocyte and red blood cells and performed high degrees of sensitivity and specificity in clinical Schistosoma haematobium infection diagnosis and blood-borne filarial parasites inspection (e.g., Loa loa) ( Figure 2) [24,30,31]. In other developments, Prof. Ozcan's group at UCLA presented the first cellphone-based lens-free holographic microscopy (without an additional lens-based attachment) in 2010 ( Figure 1B) [32].…”

Early warning smartphone diagnostics for water security and analysis using real-time pH mapping

“…Such a smartphone technology is increasingly reported recently as a field-portable platform for many applications specially in bio-diagnostic and environmental monitoring. Most of these approaches are based on simple colorimetry [8][9][10][11][12][13][14][15][16], imaging [17][18][19][20][21][22][23], and spectroscopy [24][25][26][27]. Paper microfluidic devices are sometimes integrated to the calorimetric approaches [28][29][30][31][32][33][34][35].…”