June 20, 2022

Phototherapy Lighting: Therapeutic and Diagnostic Technology

One could consider the science of medicine to consist of two categories: diagnostics (the science of finding out what is wrong with the body) and therapeutics (the science of fixing what is wrong).

Interestingly enough, light has proven itself worth in both the diagnostic and therapeutic areas of the medical world. 

Phototherapy has evolved impressively over the years as an emerging treatment modality to satisfy therapeutic needs. However, even more impressive is the progress made on the complementary side, where biophotonics, the interdisciplinary field at the intersection of biology and photonics, shows promise to satisfy a variety of diagnostic needs.

At Lumitex, we strive to be a world-class medical lighting system provider, and with that role comes the responsibility to be intimately familiar with technological advancements in the phototherapy market. This article covers phototherapy (therapeutic) applications today and biophotonics (diagnostic) opportunities of the future.

History of Phototherapy 

Phototherapy has been used in various configurations dating back into the BCE era. In ancient times, the sun served as the sole source of phototherapeutic light for treating multiple skin conditions.

Over time, knowledge of phototherapy and wavelengths grew, and blue light was discovered to help treat neonatal jaundice and ultraviolet light for treating various skin diseases. Eventually, phototherapy practitioners began targeting the eyes to directly treat retinopathies and using the eyes as an input to stimulate the brain to treat depression and circadian disruptions.

In recent times, phototherapy has continued towards more and more targeted applications.

Solid-state Lighting in Phototherapy

The most recent success of phototherapy as a legitimate treatment modality started with the invention of electric light. It accelerated with the invention of solid-state lighting, including light-emitting diodes and semiconductor lasers. 

A key aspect of phototherapy is that different tissues in the body are more or less responsive to light treatment depending on the wavelength of the light being applied.

A complication is that phototherapy sometimes needs to be applied to tissue structures below the skin surface where light cannot easily penetrate. The strength of solid-state lighting is that emitters can be designed in a broad array of wavelengths from the infrared to the ultraviolet spectrum, with a high resolution of wavelengths in between.

This offers the phototherapy device designer the ability to fine-tune the light delivery for best penetration and tissue response.

Phototherapy Applications Today

The first phototherapy devices were simple skin surface treatment devices.

Today the new frontiers of phototherapy may deliver high power to internal tissues, dealing with obstacles like absorption and heat accumulation.

New applications aim for shallow tissue treatment (red and infrared light for sports injuries) and deep tissue treatments (direct irradiation of the brain to treat depression, cognitive impairments, and acute injuries such as TBI and stroke). 

The Future of Phototherapy

Phototherapy is showing promise in anti-cancer treatments in the form of an offshoot modality known as Photodynamic Therapy (PDT). The light doesn’t directly stimulate the biological tissue; instead, the light is used in conjunction with a photosensitive pharmaceutical which allows precise delivery of anti-cancer drugs to tumors and avoids damage to healthy, non-cancerous tissue. 

This new frontier in deep tissue phototherapy will require new techniques to overcome inherent obstacles. Implantable light sources and fiber optics, wavelength converting materials, low-level laser therapy, and the development of novel photosensitizer systems are all tools being explored to enhance phototherapy in the future. 

As technology evolves and the limits of phototherapy are pushed and expanded, medical device designers can continuously think about ‘what’s next?’ What other diseases can be treated with light? What existing treatments can be improved or replaced altogether by non-invasive phototherapy?

Resources: 

Royal Society of Chemistry, The Journey of PDT Throughout History: PDT from Pharos to Present 

ScienceDirect, A Brief Report on the History of Phototherapy  

Wikipedia, Light Therapy 

Biophotonics Opportunities: Interaction Between Light and Biological Matter   

The field of biophotonics is not exactly new.

Many attribute the first exploration of biophotonic phenomena to Alexander Gurwitsch, who reported the presence of weak bioluminescence in various living tissues. Perhaps the most well-known application of biophotonics, medical imaging, has been around in various manifestations since the mid-20th Century. 

However, what is new and exciting with the current state of the technology is the ability to translate functionality that used to require large and expensive lab equipment into an inexpensive, readily available, and wearable format. At the heart of this transition is the emerging field of silicon biophotonics. 

Medical diagnostics is all about information, specifically information related to the health state of a living body.

Biophotonics is the technology utilizing light to obtain that information, typically non-invasively, from the living body. At the heart of the process is a handful of phenomena that arise from light-matter interactions, for example, scattering or fluorescence.   

The central underlying premise that the phenomena share is that various tissues exhibit different responses to light exposure. This varying response results from biomechanical, biochemical, and bioelectrical properties. Different tissues respond to different wavelengths of light and can be identified by the measured light-matter interaction. This is a critical point in discussing the future of wearable biophotonics.
 

Bioinformatic: Science, Medicine, and Future 

When developing a wearable biophotonic device, you may be required to implement a variety of wavelengths depending on the interactions (in other words, the array of biomarkers) you’re interested in. Since bioinformatics is the name of the game, you may find it necessary to keep each of those different wavelengths as discrete from each other as possible to avoid mixing signals and generating noise.
 
This is where silicon biophotonics shows promise. Silicon technology, in general, has enjoyed many years of development which has led us progressively through the Computer Age. Silicon photonics can leverage much of the infrastructure and fabrication techniques that already exist due to constantly pushing Moore’s Law for decades.
 
The remaining challenges are translating photonics technology to smaller scales, specifically chip-scale, where wearable technology must live.
 
The promise of biophotonics to address critical healthcare needs has been receiving more attention in recent years with several publications such as “Harnessing Light: Optical Science and Engineering for the 21st Century” in 1998 and its successor “Optics and Photonics: Essential Technologies for Our Nation” in 2013.
 
With unprecedented progress in photonics manufacturing, machine learning, and miniaturization, we now see companies positioning themselves to fill the emerging space of wearable biophotonics. Most notable are Rockley Photonics, which advertises a full-stack platform of photonics technology specifically targeting biomarker sensing, and imec, which promotes biophotonic hardware across the full spectrum from PCR chips, neural probes, and spectroscopy chips.  As this technology matures, it will offer medical device designers a whole new toolbox for adding valuable diagnostic functionality to their products.
View the State of Medical Lighting Report 
Resources:
 
Wikipedia, Biophoton
 
News Medical Life Sciences, Biomedical Applications of Biophotonics
 
International Journal of Pharmaceutical Sciences Review and Research, Biophotonics: A Novel Approach Biomedical Diagnosis  
Author
Mike Kerns

Mike Kerns

Mike Kerns is a Senior Design Engineer at Lumitex, where his first role was focused on the company’s line of phototherapy products. Today, Mike serves as the team lead for Lumitex’s R&D engineering group, striving to apply Lumitex’s light delivery expertise to new medical device applications.  

Authors