A research team at The University of Texas at Austin, led by Associate Professor Andrew Dunn, have developed a new biological imaging system fifty times less expensive than standard equipment, suitable for imaging applications outside of the lab. The researchers describe their development in the latest issue of the Optical Society’s (OSA) journal Biomedical Optics Express, an open-access journal and is available at no cost to readers online at:
An OSA release notes that tracking blood flow in the laboratory is an important tool for studying ailments like migraines or strokes and designing new ways to address them. Blood flow is also routinely measured in clinical settings, and laser speckle contrast imaging (LSCI) is one way of measuring these changes; however, this technique requires professional-grade imaging equipment, which limits its use. However, using just $90 worth of off-the-shelf commercial parts, including a webcam and a laser pointer, Dr, Dunn and his research team at UT-Austin have duplicated the performance of expensive, scientific-grade LSCI instruments at a fraction of the cost. The work is the first to show that it is possible to make a reliable blood flow imaging system solely with inexpensive parts, the authors say.
“We demonstrate that the high cost of standard systems is unnecessary, because a system that costs $90 can give equivalent results for both in vitro and in vivo imaging applications,” says biomedical engineer Andrew Dunn, Dr. Dunn is a UT Austin Associate Professor, Graduate Advisor, Co-Director of Center for Emerging Imaging Technologies, Werner W. Dornberger Centennial Teaching Fellow in Engineering, and corresponding co-author of a study describing the imaging research published in the latest edition of the OSA journal Biomedical Optics Express – Vol. 4, Issue 10, pp. 2269-2283 (2013).
The paper, entitled “Low-cost laser speckle contrast imaging of blood flow using a webcam,” is co-authored by Lisa M. Richards, S. M. Shams Kazmi, Janel L. Davis, Katherine E. Olin, and Andrew K. Dunn – all of UT Austin.
The paper’s abstract notes that laser speckle contrast imaging has become a widely used tool for dynamic imaging of blood flow, and typically, laser speckle contrast imaging is performed using scientific-grade instrumentation. However, the co-authors note that due to recent advances in camera technology, these expensive components may not be necessary to produce accurate images. In the paper, they demonstrate that a consumer-grade webcam can be used to visualize changes in flow, both in a microfluidic flow phantom and in vivo in a mouse model. A two-camera setup was used to simultaneously image with a high performance monochrome CCD camera and the webcam for direct comparison. The webcam was also tested with inexpensive aspheric lenses and a laser pointer for a complete low-cost, compact setup ($90, 5.6 cm length, 25 g). The CCD and webcam showed excellent agreement with the two-camera setup, and the inexpensive setup was used to image dynamic blood flow changes before and after a targeted cerebral occlusion.
Dr. Dunn’s research is focused on developing novel optical imaging techniques for imaging brain function. He and his research team seek to integrate innovative photonics and computational techniques and to apply them to research questions in areas such as stroke, migraine, functional mapping during neurosurgery, and Alzheimer’s disease.
Measuring blood flow changes using LSCI requires just a few parts – laser light to illuminate the tissue, a camera to record the image, and focusing optics to direct the scattered light to the camera – but at least one of them usually comes with a lofty price tag. The laser light reflects or scatters off the tissue and interferes with itself to create the speckle pattern collected by the camera. This speckle pattern provides a way to visualize the flow of blood within the tissue: areas with a high flow rate show up in the resulting image as blurrier speckles, which can be measured by their lower contrast. Together, all the parts can add up to as much as $5,000.
Unlike past attempts to create a cheaper speckle imager, the UT-Austin team’s new method uses only inexpensive pieces of equipment. A $5 laser pointer is used to illuminate the patch of tissue to be imaged. Light is reflected off the tissue and focused by a pair of generic 40-mm camera lenses onto the sensor of a $35 webcam. The team used their setup to image changes in blood flow in a mouse model and found that they were able to identify areas of high flow versus low flow.
At just 5.6 centimeters in length and weighing only 25 grams, the system is compact and lightweight, which would make it easier to transport for imaging applications outside of the lab, including clinics in areas with limited access to medical care, Dr. Dunn says.
Currently, the new system’s field of view, which is just a few square millimeters across, and resolution are limited by the size of the webcam sensor, but future versions could have a more flexible layout.
“The lens configuration could be easily adjusted to visualize even smaller structures by magnifying or to visualize larger structures by increasing the field of view, depending on what kind of flow the user is interested in visualizing,” Dr. Dunn says.