MICROSCOPY & IMAGING
Photoacoustic imaging is providing images of biological structures for increased visibility and facilitating the analysis of plaque composition to better diagnose and treat CAD
Tese lasers, which are available in a wide range of wavelengths, pulse energies, and repetition rates, generate high peak powers and short pulse widths, making them ideal for many photoacoustic applications. However, fixed nanosecond wavelength lasers such as the Nd:YAG often operate outside the ideal wavelengths required to reach a usable depth in biological tissue. Tese wavelengths are usually within the water absorption transparency window of 650 to 900nm, given animals and humans are mostly made of water. For this reason, pulsed mode Nd:YAGs that emit light at a fixed wavelength of 1064nm require optical parametric oscillators (OPO) to convert the Nd:YAG fundamental wavelength to the optimal frequency for photoacoustic diagnostic analysis. Tese OPO lasers are generally referred to as tunable lasers. To enable required laser tunability, leading manufacturers such as Opotek have developed fast-tuning technology that ensures that many wavelengths can easily be produced to image a variety of biological materials. Fast-tuning also helps to mitigate variations in the field of view due to motion between consecutive images, which allows for more detailed imaging of moving biological processes like blood flow. Opotek offers solutions for specialised applications including photoacoustic,
spectroscopy, diagnostics, hyperspectral imaging and medical research. Te company’s photoacoustic technology is now being used in a wide range of medical research projects.
LASERS IN THE LAB “We have two Opotek lasers – one located in my lab on the primary engineering campus of Johns Hopkins University, and one located in my lab space at the Johns Hopkins Hospital,” says Dr Muyinatu Bell, an assistant professor and director of the Photoacoustic & Ultrasonic Systems Engineering (PULSE) Lab at Johns Hopkins University. Te PULSE lab is developing the next generation of photoacoustic imaging systems using a combination of optics, acoustics, and robotics. “In the lab, we aim to understand fundamental design requirements for photoacoustic imaging systems that can be used to guide surgeries, as well as augment the vision capabilities of robotic surgical systems,” says Bell. Te structures of interest in her
research include major blood vessels that are hidden by tissue and need to be avoided during surgery, as well as the metal tips of surgical tools. Major blood vessels and tool tips both generate strong photoacoustic signals in comparison to surrounding tissue and can be used to
LEFT: Opotek has introduced additional innovations to its mobile platform including fibre bundle delivery, complete automation of all system functions and fast tuning over the entire wavelength range
transported to patient bedsides or to surgical suites to render extremely detailed diagnostic imaging tests for cardiovascular diseases, cancer, chronic respiratory diseases, and diabetes.
PHOTOACOUSTIC SYSTEMS FOR BIOMEDICAL IMAGING Although photoacoustic imaging equipment has been available for a few decades, the primary limiter has been the largest component in the system, the nanosecond laser used to transmit a pulse of laser light to the area of interest.
Mobile photoacoustic systems can be transported to patient bedsides or to surgical suites to render extremely detailed diagnostic imaging tests for cardiovascular and other diseases
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