From The Editor | October 5, 2023

My Flex Sig, Fiber Optics, And OCT

John Oncea

By John Oncea, Editor

GettyImages-1454008881 Gentec E-O optical fiber

Fiber optics are omnipresent in medicine, helping improve procedures and outcomes. Here we dig into one specific technology making use of fiber optics: optical coherence tomography. As a bonus, you also get to read about my flexible sigmoidoscopy, performed nearly 30 years ago and burned into my mind forever.

Back when I turned 30, I was advised to get a flexible sigmoidoscopy (flex sig), a non-evasive procedure that examines a portion of the colon. A flex sig is often used to diagnose the cause of gastrointestinal problems, such as abdominal pain and rectal bleeding, but in my case, it was a screening for colon cancer, which runs in my family.

During a flex sig, a trained medical professional* uses a flexible, narrow tube with a light and tiny camera on one end, called a sigmoidoscope or scope, to look inside your rectum and lower colon, also called the sigmoid colon and descending colon, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

So, I scheduled my appointment, did my prep work, and on the day of the appointment met my family doctor at the hospital. There, I was asked to lie on my side and the doctor inserted a sigmoidoscope and began to do her thing. The camera at the tip of the sigmoidoscope sent a video image of my intestinal lining to a monitor, allowing the doctor to examine the tissues lining my sigmoid colon and rectum.

Easy peasy.

Oh, I forgot to mention I had the option of being sedated and I chose not to. Also, when I was lying on my side, I had a direct view of the monitor. So, yeah, I was fully alert the entire 20 minutes, looking at my insides. It was alternatively fascinating and, well, not disgusting but something close.**

Anyway, ask your doctor about this procedure if you’re 50 or older and have no colon cancer risk factors other than age — which puts you at average risk — or if you have abdominal pain, rectal bleeding, changes in bowel habits, chronic diarrhea, or other intestinal problems.

So, the point of this trip down memory lane is to explore some of the ways fiber optics, which can reduce the risk of complications during procedures, reduce procedure duration, and quicken recovery, are being put to use in medicine.

* Trust me, you don’t want an untrained person performing this procedure.

** I was told that, after the flex sig, I might have abdominal cramping and/or bloating during the first hour after the procedure, I could resume regular activity right away, and I could return to a normal diet. I wasn’t told not to walk two blocks to the parking garage my car was in. I have to imagine the drivers of the cars passing me as I took two steps, stopped, doubled over, took two more steps, doubled over again, etc. had quite a laugh. I know I did.

Enough About Me, On To OCT

There are many ways fiber optics are used in medicine, including optical coherence tomography (OCT), a technology used to perform high-resolution cross-sectional imaging. The medical community has embraced OCT in large part because it provides tissue morphology imagery at much higher resolution (less than 10 μm axially and less than 20 μm laterally [36]) than other imaging modalities such as MRI or ultrasound. Other benefits of the technology include live sub-surface images at near-microscopic resolution; instant, direct imaging of tissue morphology; no preparation of the sample or subject; and no ionizing radiation.

“OCT is analogous to ultrasound imaging, except that it uses light instead of sound,” writes the National Center for Biotechnology Information (NCBI). “OCT can provide cross-sectional images of tissue structure on the micron scale in situ and in real-time.” Used in combination with catheters and endoscopes, OCT can provide high-resolution intraluminal imaging of organ systems.

“OCT can function as a type of optical biopsy and is a powerful imaging technology for medical diagnostics because, unlike conventional histopathology which requires the removal of a tissue specimen and processing for microscopic examination, OCT can provide images of tissue in situ and in real-time,” NCBI continues. “OCT can be used where standard excisional biopsy is hazardous or impossible, to reduce sampling errors associated with excisional biopsy, and to guide interventional procedures.”

“So, what do fiber optics have to do with this,” you may be asking. Well, let me tell you.

  • Light Transmission: Fiber optic cables are used to deliver light from a source to the target tissue or organ in a minimally invasive manner. In OCT surgery, a low-power laser light source is transmitted through these optical fibers into the body, allowing for precise imaging without causing harm to the patient.
  • Image Acquisition: In OCT surgery, the reflected light from the tissue is collected by a probe or catheter with a fiber optic component. The reflected light carries information about the internal structure of the tissue, which is then analyzed to create real-time, high-resolution images.
  • Flexibility and Miniaturization: Fiber optics are highly flexible and can be integrated into thin and compact catheters or endoscopes. This flexibility is especially advantageous in minimally invasive surgeries where the instruments need to navigate through narrow and complex anatomical structures.
  • Real-Time Imaging: OCT provides real-time imaging capabilities, which are valuable during surgical procedures. Surgeons can visualize tissues and make immediate decisions based on the OCT images, improving precision and safety.
  • High Resolution: Fiber optic-based OCT systems offer high-resolution images, allowing for detailed examination of tissues. This is particularly beneficial in ophthalmology, where OCT is commonly used for retinal imaging.
  • Diagnostic and Monitoring: OCT is not limited to surgery; it's also used for diagnostic purposes, such as identifying tissue abnormalities and monitoring disease progression. For instance, in cardiology, intravascular OCT is employed to assess coronary arteries.
  • Guidance: Fiber optic-based OCT can serve as a guidance tool during various surgical procedures, assisting surgeons in targeting specific areas and ensuring accurate tissue removal or treatment.
  • Treatment Planning: In addition to imaging, fiber optics can be used to deliver therapeutic light or energy to treat tissues. For example, laser ablation procedures can be guided and monitored using OCT.
  • Research and Development: Fiber optics also play a significant role in the development of new medical devices and surgical techniques. Researchers use fiber optic technology to explore innovative ways to improve patient care and outcomes.

Fiber optics are a critical component in OCT surgery and a range of other medical applications. Their flexibility, high-resolution imaging capabilities, and minimally invasive nature make them invaluable tools for medical professionals, enhancing diagnostic and surgical precision while minimizing patient risk and discomfort.