Photonics technologies are one of the hidden workhorses in healthcare. In the UK, the NHS spends ~ 4% of its budget (£2.5 billion annually) on photonics-based diagnostic tests.1 This includes the use of lasers to record and sort incoming test results, a crucial task in busy hospital laboratories, through to rapid cancer diagnostics.
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The importance of photonics technologies, including lasers, in healthcare, has been recognized with the £8.3 million investment in the construction of the National Healthcare Photonics Centre.2 The center is dedicated to the development of new light-based diagnostic and treatment approaches by bringing together academic partners, small and medium enterprises, and larger industries to help accelerate these developments.
The reason photonics technologies, and in particular laser-based methods, have become so popular as part of diagnostic testing is that they can provide non-invasive alternatives to biopsies whilst still recovering molecular-level information that can be used for an accurate diagnosis. Developments in fiber-optic technologies and point-of-care devices are also helping change the way medical diagnostics are performed.
For a patient requiring analysis of a biopsy sample, the full diagnostic workflow will firstly involve surgical removal of tissue and the sample being sent to the hospital laboratory to be analyzed by a pathologist or trained technician. This is all before a full diagnosis can be given to the patient.
For diseases such as cancer, early diagnosis is one of the biggest indicators for improved patient outcomes.3 Hospital laboratories can be fraught with delays that may even lead to sample degradation and impair the accuracy of the diagnosis.4
Point-of-Care Devices
Point-of-care devices overcome many of these issues by not requiring surgical intervention to collect samples and allowing more rapid diagnoses. This is because laser-based imaging and spectroscopy methods can be interfaced with artificial intelligence methods to aid clinical decision-making.5
A point-of-care device can return information in minutes making them invaluable for providing real-time clinical information that would be inaccessible with traditional histopathology methods.
Several different spectroscopy and imaging methods have been used as part of diagnostic tests in medicine, including Raman, fluorescence, and two-photon absorption. All these methods have different advantages and disadvantages for looking at tissue types and are reliant on the availability of high-quality, compact laser sources.
Laser Wavelengths
Laser sources used for diagnostic tests often need to operate in specific wavelength ranges. One of the biggest challenges with deep tissue imaging as well as looking at soft tissue structures is choosing a laser wavelength that will not be absorbed completely by the tissue and fluids in the body. This means many laser-based diagnostic approaches try to exploit the ‘biological window’. While there is no clearly agreed definition of this window, the first of these windows is typically considered to be from ~ 750-900 nm.6
By exploiting this window with the development of fluorophores that emit towards the near-infrared region or light sources that operate in this range, it is possible to create diagnostic devices that can be used for both deep and shallow tissue imaging. This can also help improve the contrast and image quality to help clinicians in the diagnostic process.
For power-hungry techniques such as Raman and multi-photon imaging, lasers make an ideal light source for these types of diagnostic tests. Laser sources can achieve much higher peak brightness, and with developments in pulse femtosecond sources, it is possible to achieve peak powers that can stimulate several multiphoton processes for non-linear imaging techniques.
Laser sources can also be integrated with fiber optics for more flexibility in diagnostics and treatment. Being able to carry light pulses through optical fibers that can be inserted into a patient using minimally invasive keyhole methods rather than open surgical techniques for imaging has also opened up new possibilities for treatment and diagnosis. Highly localized irradiation delivered in this manner is particularly effective for light-activated cancer treatments such as photodynamic therapy.
The Future of Lasers in Miniaturization
Perhaps one of the biggest future areas for the use of lasers in diagnostics testing will be in miniaturization. Using high-precision lasers for the manufacturing of small medical devices is already a routine task as lasers can be used for welding and cutting even complex three-dimensional structures.
Many rapid ‘on-chip’ diagnostic tests have been developed as a response to the need for SARS-CoV-2 testing that makes use of either electrochemical signaling or optical responses.7
Many such tests offer competitive results to more traditional methods such as PCR analysis that require extensive and expensive infrastructure and equipment. Magnetic resonance imaging (MRI) is another diagnostic method that also has an extensive footprint, though is often considered to be one of the most detailed diagnostic approaches.
Lasers and associated photonics technologies are beginning to offer a wealth of new options for diagnosis. As new biomarkers are identified as signs of disease, photonics may offer a bright future for rapid, noninvasive testing with results delivered almost in real-time.
References and Further Reading
- Photonics Leadership Group (2022) Photonics by 2035, https://photonicsuk.org/wp-content/uploads/2021/10/Photonics_2035_Vision_Web_1.0.pdf, accessed February 2022
- National Healthcare Photonics Centre (2022) National Healthcare Photonics Centre, https://www.uk-cpi.com/about/national-centres/national-healthcare-photonics-centre accessed February 2022
- Neal, R. D. (2009). Do diagnostic delays in cancer matter? British Journal of Cancer, 101, 9-1S2. https://doi.org/10.1038/sj.bjc.6605384
- Pritzker, K. P. H., & Nieminen, H. J. (2019). Needle Biopsy Adequacy in the Era of Precision Medicine and Value-Based Health Care. Arch Pathol Lab Med, 143, 1399–1415. https://doi.org/10.5858/arpa.2018-0463-RA
- Hollon, T. C., Pandian, B., Adapa, A. R., Urias, E., Save, A. V, Khalsa, S. S. S., Eichberg, D. G., Amico, R. S. D., Farooq, Z. U., Lewis, S., Petridis, P. D., Marie, T., Shah, A. H., Garton, H. J. L., Maher, C. O., Heth, J. A., Mckean, E. L., Sullivan, S. E., Hervey-jumper, S. L., … Orringer, D. A. (2020). Near real-time intraoperative brain tumor diagnosis using stimulated Raman histology and deep neural networks. Nature Medicine, 26(January). https://doi.org/10.1038/s41591-019-0715-9
- Hemmer, E., Benayas, A., Legare, F., & Vetrone, F. (2016). Exploiting the biological windows: current perspectives on fluorescent bioprobes emitting above 1000 nm. Nanoscale Horizons, 1, 168. https://doi.org/10.1039/c5nh00073d
- T. Beduk, D. Beduk, J. I. de Oliveira Filho, F. Zihnioglu, C. Cicek, R. Sertoz, B. Arda, T. Goksel, K. Turhan, K. N. Salama and S. Timur, Anal. Chem., 2021, 93, 8585–8594. https://doi.org/10.1021/acs.analchem.1c01444
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