Two groups of researchers, one in the United States and one in Australia, are announcing the development of new optical techniques for visualizing the invisible processes at work in several human diseases. The published results are the first to showcase the Optical Society's (OSA) Interactive Science Publishing (ISP) initiative, which allows authors to submit a manuscript that includes large three-dimensional data and gives researchers, scientists and engineers a way to evaluate new research results more thoroughly.
One of these techniques may help clinicians diagnose and treat people with breathing disorders. The other can show three-dimensional structure and the blood flow mechanism at the earliest stages of heart development.
Imaging the airways in people with breathing problems
When the small airways inside a person's lungs narrow, a problem referred to as "stenosis," severe breathing difficulties can result. Doctors often treat this condition by inserting a small medical stent into the airway to open it up and ease breathing. Critical to this procedure is the ability of doctors to measure the extent of stenosis -- the diameter and length of the narrowed section of airway. Making this measurement accurately helps doctors choose the most appropriately sized stent for each person.
The current clinical practice for imaging the airway combines CT scans with "video endoscopy" images, which involves inserting a tiny video camera into the airways inside the lungs. Now a group of engineers, clinicians and medical researchers at the University of Western Australia and Sir Charles Gairdner Hospital have developed a new optical technique to help better guide treatment decisions. Their technique, called anatomical optical coherence tomography (aOCT), can accurately measure the shape, diameter and length of the airways inside the lungs, even as they expand and contract during breathing.
This new technique is an improvement over video endoscopy, says Robert McLaughlin, who was part of the research team. Video images captured with endoscopy are two-dimensional, which makes it difficult for doctors to accurately estimate the true three-dimensional size and shape of the narrowing airways. Imaging the airway with aOCT, on the other hand, relies on inserting a probe into the airway that emits a very safe, low-power light. The size of the airway can then be measured by detecting the reflected light.
The technology is being tested to see if it can help doctors diagnose and treat people with breathing disorders, says McLaughlin. Other current clinical studies are testing whether aOCT can detect airway changes in people with asthma and chronic obstructive pulmonary disease. According to McLaughlin, this technology can also be used during sleep in patients with sleep apnea, to better understand why the upper airway (throat) collapses and narrows in these individuals.
The new ISP technology enables those reading the paper to see first-hand how aOCT works in airway imaging.
The research was funded by the National Health and Medical Research Council in Australia and The Raine Medical Research Foundation.
Looking for the first beats of a developing heart
Congenital heart defects are responsible for more deaths in the first year of life than any other congenital problem. Some are caused by genetic defects, but the forces that lead to the formation of abnormal hearts in many people are poorly understood.
Part of the problem is that there are no good ways of directly observing a young embryo's heart, where blood begins flowing early in development. Scientists can potentially study this process using fertilized chicken eggs, observing as the chicken embryo forms. In the earliest days of the heart's development, however, the organ is so small that there is no way to image it without harming the embryo.
Now Anjul Davis and colleagues at Duke University and the University of Cincinnati have come up with a new way of measuring blood flow and imaging the structure of the heart in a developing chicken embryo. They have combined two optical techniques called "spectral-domain optical coherence tomography" and "spectral Doppler velocimetry" and their work provides some of the first insights into the mechanism of blood flow at the earliest stages of heart development.
A chicken's heart is very similar to a human's; by studying embryonic heart development in chickens we can better understand and develop treatments for congenital heart disease in humans, says Davis. Understanding how congenital heart defects arise would be a boon for humanity, Davis says, because evidence suggests that earlier interventions for people born with heart defects saves lives and improves the quality of life.
The technology can also be applied to studying blood flow in cancer tumors or in the tiny blood vessels in the brain, says Davis, whose research was funded by National Institutes of Health.
The research takes advantage of ISP, an initiative undertaken by OSA in partnership with the National Library of Medicine, part of the National Institutes of Health, and with the support of the United States Air Force Office of Scientific Research. This initiative allows scientists to expand upon traditional research results by providing software for interactively viewing underlying source data and to objectively compare the performance of different technologies. This data may be related to medical images, such as those taken with X-rays, MRIs, CT scans and ultrasounds, or it may be created in research involving oil and gas exploration, climatology, pollution monitoring and many other fields.
- McLaughlin et al. Applying anatomical optical coherence tomography to quantitative 3D imaging of the lower airway. Optics Express, 2008; 16 (22): 17521 DOI: 10.1364/OE.16.017521
- A. M. Davis, F. G. Rothenberg, N. Shepherd, and J. A. Izatt. In vivo spectral domain optical coherence tomography volumetric imaging and spectral Doppler velocimetry of early stage embryonic chicken heart development. J. Opt. Soc. Am. A, Posted 20 October 2008, in press [link]
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