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SPIE Professional January 2012

From Olympics to Optics

Photonics for a Better World: Finding answers with NIRS

By Babak Shadgan

SPIE Photonics for a Better World logo

In 2004, one of my patients was a gold medalist free-style wrestler. This athlete had to drop out of the competition at the 2004 Athens Olympic Games because of progressive leg pain, a condition called "chronic exertional compartment syndrome" (CECS). This condition causes a gradual increase in tissue pressure within a limited fibro-osseous compartment of the leg, interrupting intracompartmental blood flow. The resulting tissue ischemia is painful and at times disabling.

In contrast to the majority of medical conditions, which are challenging to manage, treatment of this syndrome is straightforward when an early diagnosis is made. The current standard diagnosis is based on clinical assessment confirmed by measurement of the leg's intracompartmental pressures. The technique requires inserting multiple needles into the leg compartments and recording intracompartmental pressure changes while the subject is running over a treadmill.

Difficult and subjective, this method often has limited diagnostic values. Many people, especially elite athletes, refuse to undergo this kind of investigation, simply because of its invasive nature.

That Olympics experience inspired me to start investigating an alternative, noninvasive, and sensitive technique for early and accurate diagnosis of CECS. I found the solution in the field of optics and photonics.

Finding answers with NIRS

In 2006, after 12 years of musculoskeletal and sports medicine practice, I turned to the clinical research field by starting a PhD study on using near infrared spectroscopy (NIRS) for early diagnosis of compartment syndrome at the University of British Columbia (UBC) (Canada).

NIRS is a non-invasive optical technology that uses energy from light in the near infrared spectrum to monitor changes in local tissue oxygenation and hemodynamics in real time (Figure 1). The science of NIRS is hinged on some of the fundamental principles of optics and photonics as they relate to the transmission of light through living tissues and the absorption of light by tissue chromophores.

  Figure 1: This NIRS instrumentation setup is configured for transcutaneous monitoring of muscle.

NIRS units use lasers or diodes that transmit pulses of multiple wavelengths of light into tissues, and optical sensors that detect returning photons. The changes in absorption of light at discrete wavelengths generate raw optical data that can be converted by mathematical software algorithms into real-time concentration changes for each chromophore using a modification of the Beer-Lambert law.

By placing a set of NIRS devices over the leg compartments in high-risk individuals and monitoring changes in the leg muscle oxygenation and hemodynamics during exercise, CECS can be diagnosed noninvasively and accurately. Applying the same NIRS technology on people who are at risk for an acute type of compartment syndrome, we showed that an early diagnosis of this critical condition is also possible.

  By applying NIRS technology to people who are at risk of acute type of compartment syndrome, an early diagnosis is possible.

My studies on different skeletal muscles have shown that by measuring changes in muscle oxygenation and hemodynamics during exercise, NIRS will enable exercise scientists to monitor skeletal muscle function and fitness and measure the exercise capacity noninvasively in real time.

New diagnostic concept for bladders

Millions of people worldwide are affected by voiding problems, especially urinary incontinence (UI), obstruction and retention, which negatively impact their quality of life and add to mounting health care costs. Almost 42 million people in North America suffer from UI and the numbers are expected to double within 20 years as the population ages. It is also estimated that 1% of young children exhibit lower urinary tract dysfunctions (LUTD) such as incontinence and nocturnal enuresis. The proper treatment and management of LUTD requires an accurate evaluation and diagnosis. The current diagnostic method relies on an invasive test that requires urethral and rectal catheter insertion to measure changes in bladder pressure and urine output during bladder filling and emptying. Urethral catheterization is an inconvenient and uncomfortable procedure especially in children and can lead to potential complications such as urethral trauma or urinary tract infection. It is estimated about 40% of patients with clinical symptoms aren't properly diagnosed because they refuse to take this difficult test.

  A NIRS setup for noninvasive evaluation of bladder function.

In 2007, I joined a group of clinical researchers at the UBC Department of Urology, lead by Dr. Andrew Macnab and Dr. Lynn Stothers. For the first time, our research group showed that NIRS can provide useful information about the bladder muscle oxygenation and hemodynamics during voiding that can facilitate diagnosis of bladder dysfunctions, non-invasively.

As a muscle expert who has been focusing on noninvasive optical monitoring of muscle function, my collaboration on the study of bladder function in adults and children helped the group find evidence of detrusor muscle fatigue as a possible mechanism behind bladder dysfunction. This new and important finding created a better understanding of the pathophysiology and therefore treatment of this most common urologic condition. Through our research, we developed a new diagnostic concept in urology.

Babak Shadgan

Babak ShadganBabak Shadgan received his MD from the Tehran Azad University Medical School (Iran), an MSc in Sports Medicine from the University of London (UK), and a PhD from the University of British Columbia (Canada).

Specializing in sports and exercise medicine, Shadgan received an AO-International Osteosynthesis Fellowship in 1998. In September 2006, he joined the UBC Faculty of Medicine.

In 2009, he completed a visiting fellowship on NIRS-Diffused Optical Tomography at Martinos Center for Biomedical Imaging of Harvard University.

Shadgan is currently working on remote monitoring of detrusor muscle function in people with spinal cord injury at his postdoctoral fellowship at the University of British Columbia. This project is supported by a Rick Hansen Foundation research grant, and a Michael Smith Foundation for Health Research postdoctoral fellowship.

A member of SPIE, Shadgan was awarded the 2010 D.J. Lovell Scholarship, SPIE's largest and most prestigious academic award.

Photonics for a Better World

Join the discussion celebrating the many ways that photonics are applied in creating a better world at PhotonicsforaBetterWorld.org.

Read more articles in the SPIE Professional series at spie.org/betterworld.

Do you have a story to tell about the work that you or colleagues do to make the world a better place? Write to us at spieprofessional@spie.org.

Have a question or comment about this article? Write to us at spieprofessional@spie.org.

DOI: 10.1117/2.4201201.13

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