Optical Coherence Tomography of Pulmonary System (OCToPuS)

A bronchoscopy performed to reveal a normal broncial anatomy using a flexible fiberoptic bronchoscope from the larynx to the segmental bronchi.

Principal Investigator: Ashim Dhakal, BTech, MSc, PhD, Biophotonics Instrumentaiton Engg.

Associated Investigator: Gopal Lama,MBBS, MD, Pathology.

This research project aims to develop an Optical Coherence Tomography (OCT) imaging system operating at near-infrared wavelengths to image inner part of the lungs (the terminal bronchus) using a set of single-mode optical fibers. The system aims to use the camera integrated with the Android systems such as a smartphone or a tablet, and use the system processor to process the image. The idea is to develop a low-cost, point-of-care system to allow a minimally trained health officer to diagnose different stages of chronic obstructive pulmonary disease (COPD), using a bronchoscopy procedure that can be performed across all of the 1,559 health-posts in rural areas of Nepal. Below we outline the context and technology to be used in this project.

According to WHO data, COPD is the number-one cause of deaths in Nepal, and is accountable for more than 9.2 % of the total population mortality and hence similar number of population morbidity [1]. An estimated 23% of population, 43% of the non-communicable disease burden and 2.56% of hospitalizations in Nepal are attributed to COPD [1-3]. This condition is even more serious in our rural regions, due to exposure to smoke from biomass fuel [4]. The problem is exacerbated by low oxygen level, cold climate, stark poverty, and lack of access to basic diagnostic facilities.

Early diagnosis and management of COPD is crucial to prevent a major loss of the lung function. Unfortunately, a large population in Nepal face severe lack of basic diagnostic facilities. A detail anatomic and pathologic status of the respiratory tract at micro level is required to confirm early COPD, necessitating a high-resolution Computer Tomography imaging, which is only available in few tertiary hospitals in large cities such as Kathmandu, Pokhara and Biratnagar. OCT can provide a high-resolution image of the inner parts of the lungs at the micrometer level, thus showing even early symptoms of COPD, such as narrowed terminal bronchus due to growth (hypertrophy and hyperplasia) of bronchial mucinous glands.

One of the inventors of OCT explains OCT.

OCT is has now been fairly well established as a diagnostic system in Ophthalmology, and used routinely to image retina of the eye. With optical fibers, it has also been used to image blood vessels to image obstructions (plaques) [5-6]. Some groups have also applied this technique for imaging higher structure of the bronchus, for example, to image cancer tissues [7-8]. However, there are two major limitations of the current OCT system for the application we are seeking. First limitation has clinical aspect: bronchial structure is highly branched system. Hence, navigating through the branches to the affected bronchial region is a huge challenge that needs to be addressed. In this project we will adapt the existing commercial bronchoscopy system and develop a technology to navigate the optical fiber through the bronchial structure in order to acquire OCT images. The second limitation is the sheer cost,complexity and bulkiness of the current OCT systems, which is prohibitive for the application we are seeking in context of Nepal. There are number of ways we are seeking to reduce the cost and complexity of the system. Three examples of these are:

  1. Going towards near infrared wavelengths, therebyutilizing low-cost system available for shorter wavelengths
  2. Design of all-fiber based interferometer
  3. Integration with the image acquisition system built-in an Android system

A technique similar to that we have envisioned has been recently reported by ITRI Taiwan. This technique uses absorption spectroscopy and can detect residues as low as 0.75 ppm. However, this technique is applicable only to certain types of pesticides, soluble to water. The techique needs sample preparation and is not applicable to vegetables and fruits "on the go" as we are investigating.
Read more on their webpage.

In this project, we are also working closely with our advisors and partners directly linked with community medicine and public health in B.P. Koirala Institute of Health Sciences, Manmohan Cardiothoracic, Vascular and Transplant Centre and B.P. Koirala Lions Centre for Ophthalmic Studies. In addition, with our partners in Manchester University, Glasgow University, Harvard Medical School and University of Ghent, we are currently defining a very similar project to develop a microscopic nanophotonic OCT chip, where lasers and detectors are all integrated on the same chip. More information about this project will follow.

  1. WHO: Nepal profile
  2. Gautam, R., et. Al., Community-based management of COPD in Nepal. Int J Chron Obstruct Pulmon Dis, 7, pp.253-57. (2012)
  3. Bhandari, R. and Sharma, R., Epidemiology of chronic obstructive pulmonary disease: a descriptive study in the mid-western region of Nepal. Int J Chron Obstruct Pulmon Dis, 7, pp.253-7. (2012)
  4. Kurmi, O.P., et al. Reduced lung function due to biomass smoke exposure in young adults in rural Nepal. European Respiratory Journal, 41(1), pp.25-30. (2013)
  5. Tearney, GJ; et al. In vivo endoscopic optical biopsy with optical coherence tomography, Science. 276 (5321): 2037–2039. (1997)
  6. Tearney, GJ; et al, "Three-Dimensional Coronary Artery Microscopy by Intracoronary Optical Frequency Domain Imaging". JACC Cardiovascular Imaging. 1 (6): 752–761 (2008)
  7. S. Schlachter and P. MacCarthy, "Next-gen OCT for the esophagus". BioOptics World. (1 May 2013)
  8. Coxson, H.O., et al., New and current clinical imaging techniques to study chronic obstructive pulmonary disease. American journal of respiratory and critical care medicine, 180(7), pp.588-597. (2009)