Optics 101

Optical Communication in Non-invasive Surgery

Optical fibers have been used in the medical field for many decades and are one of the reasons for the realization of some invasive treatments, such as endoscopies. However, optical fibers have taken on a new role in the medical industry and are now used within many different optical sensors for a range of non-invasive and minimally-invasive surgical procedures. In this article, we look at how optical fibers have been at the forefront of the sensors and their subsequent use in less invasive surgeries.

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Fiber optics have become more widely used because of the benefits that they offer over other equipment in the surgical room. Aside from the ability to be non-invasive (or minimally-invasive in some cases), they are often smaller in size, do not possess any electrical parts, are not affected by any electromagnetic interference and have a higher robustness and sensitivity.

The optical-based sensors in use today are often based around Fabry-Perot interferometers or fiber Bragg gratings, both of which are widely used optical communication components across many applications. In addition to the many advantages over other monitoring methods, they can also be sterilized using an autoclave, which is a must for medical procedures of any kind.

Optical Biopsies

Biopsies are minimally invasive and are used to determine whether a tissue within a patient is diseased or cancerous. To perform an optical biopsy, it requires the use of spectroscopic (and microscopic) analyses using the fiber optic cable as a signal carrier. Work is also ongoing to try and make optical biopsies a fully non-invasive process where the surgeon would be able to analyze the tissue without having invade the patient at all. Current optical biopsies are very minimally invasive where an endoscopic probe is still required to go into the patient, but the analysis of the tissue can be performed by a sensor attached to the probe at the site of the tissue, thus negating the need to remove the tissue for a physical analysis. So, whilst it is not fully non-invasive, it is a much less invasive approach than other biopsy methods.

In addition to performing an analysis on the tissue, optical probes can also be used to simply illuminate the tissue. There are more complex optical systems that can also perform physical surgery after analysis, and again, whilst it is only minimally invasive, laser resection, ablation and coagulation approaches using light can be used to treat the tissue in a much less invasive and less complex manner than other methods. From a design point of view, the optical fiber devices that illuminate, treat or analyze tissues are almost identical in nature.

Bio-tactile Sensors

Bio-tactile sensors using optical fibers have been developed for a range of surgeries, including biopsies, laparoscopic and endoscopic surgeries, as an alternative to electrical tactile sensors which are traditionally more invasive (and bulkier) devices. Whilst some of the surgeries are more minimally invasive rather than completely non-invasive, the invasiveness of these optical sensors is greatly reduced and provides the surgeon with the option of remote surgery. These types of sensors provide tactile force information, which enables the surgeon to control the surgical tools more efficiently and helps to prevent any damage to healthy tissue, prevent any unwanted complications, as well as making it easier for the surgeon to characterise, distinguish and investigate any local tissues. Because remote surgery is significantly less invasive than when the surgeon is physically performing the task, the greater degree of control also helps to prevent the need for further invasive surgery from manifesting due to less issues arising during the initial surgery.

Non-Invasive Vital Sign Monitoring

Whilst it is not an active part of the surgery, measuring a patient’s vital signs throughout the procedure is still of high importance. Many methods to measure vital signs require the invasion of the patient, but optical sensor probes have been created that can measure the body temperature, respiratory rate and heart rate of a patient non-invasively.

These probes employ multifunctional sensors that can monitor the mechanical vibrations of the body to measure the breathing rate and heart rate of a patient, and the heart rate is compared against an ECG reference obtained by using electrodes fixed externally to a patient’s chest. Additionally, a patient’s body temperature can be determined and monitored by using two fiber Bragg gratings that possess different thermal and deformation sensitivities, where any changes in a patient’s temperature are picked up by the optical sensor.

Sources:

  • Photonics Media: https://www.photonics.com/Articles/Specialty_Optical_Fibers_Make_Surgery_Less/a48684
  • “A Non-Invasive Multichannel Hybrid Fiber-Optic Sensor System for Vital Sign Monitoring”- Fakjus M. et al, Sensors, 2017, DOI: 10.3390/s17010111
  • “Minimally invasive surgical instruments with an accessory channel capable of integrating fibre-optic cable for optical biopsy: A review of the state of the art”- Jelinek F. et al, Journal of Engineering in Medicine¸ 2014, DOI: 10.1177/0954411914546891
  • “Advances in Bio-Tactile Sensors for Minimally Invasive Surgery Using the Fibre Bragg Grating Force Sensor Technique:A Survey”- Abushagur A. A. G. et al, Sensors¸ 2014, DOI: 10.3390/s140406633

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