LEDs light a path to diagnosis

DOUGLAS FARMER, SENIOR EDITOR DOUG.FARMER@PHOTONICS.COM

Cardiovascular disease is the leading cause of death worldwide, causing nearly 18 million deaths in 2019 alone, according to the World Health Organization. The vast majority of these deaths occurred in low- and middle-income countries, indicating the need for a point-of-care diagnostic method capable of adapting to resource-limited clinical settings. Because of the ability of photoacoustic imaging to capture detail from deep within vasculature, the technique provides an ideal solution — especially given the availability of light-emitting diode (LED)-based illumination sources, which, thanks to recent advancements, are more portable, affordable, and energy efficient than ever before.

In photoacoustic imaging, short light pulses in the near- to far-infrared wavelength range are shined on tissue and absorbed by chromophores, resulting in thermoelastic expansion that produces ultrasound signals. These signals reveal details such as oxygen saturation levels, which can indicate cancer or its progression. Historically, the heavy, bulky laser systems used in photoacoustic imaging have hindered the technique’s usability in low-resource or cramped settings.

Now, LED arrays that provide pulsed light are being adapted for photoacoustic imaging, as Mithun Kuniyil Ajith Singh and Naoto Sato explain in our cover story. Additionally, the development of LED elements with double-stack structures has helped to overcome power limitations that, up to this point, have led to the continued choice of laser illumination over LEDs. Read more about what the future holds for this technology here.

LED arrays are also playing a prominent role in enhancing wearable optical technology. I write in another feature story that, by incorporating flexible sensors and other components, the capabilities of wearables are expected to move beyond capturing basic health data such as heart rate and into more advanced areas, including tracking levels of glucose and protein, monitoring neural activity, and helping to gauge the effectiveness of various therapies. Learn here about the advancements currently making their way into a clinical trial.

Elsewhere in this edition, here, Karina Weber and Jürgen Popp write that Raman spectroscopy is reaching its full potential when used in conjunction with artificial intelligence, enabling the noninvasive characterization of samples and the specific identification of diseased cells in real time.

Rob Morris writes in a feature that spectroscopy has a whole host of applications in environmental analysis, including the monitoring of spectral data in lakes and rivers to ascertain the existence or absence of various aquatic species and harmful agents. Find out here which technologies are being used to keep our waterways healthy.

Finally, in “Biopinion,” Steven Le offers the view that new methodologies are needed to track the safety of the increasing number of biopharmaceuticals being produced. Although light obscuration — in which light particles are passed between a light source and a detector — has been used by the industry for many years, its requirement for a large volume of samples negates its usefulness at the early stages of treatment. Le believes that the FDA needs to consider the use of new technologies, such as fluorescence membrane microscopy — in which drug particles are filtered through a membrane — to ensure the safety of patients. Read about what he has to say here.

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