Visualization of dementia
Biomedical engineers at Duke University have developed a new imaging device capable of measuring both the thickness and texture of various layers of the retina. It can be used for early detection of Alzheimer's disease, allowing timely measures to be taken to prevent the progression of the disease.
Previously, studies had shown retinal thinning in patients with Alzheimer's disease, but by adding a light scattering method to the thickness measurement, the group found that the layer of retinal nerve fibers becomes coarser and more chaotic. If you use this information, you can create a simple and cheap screening method that will be available not only in any doctor's office, but also in places such as a local pharmacy.
The diagnosis of Alzheimer's disease is currently made only after the patient begins to show symptoms of cognitive impairment. Even then, the only way to definitively determine the cause of the disease is an expensive MRI and PET scan or a post–mortem. But if the progress of the disease can be stopped with early interventions, such as drug therapy and mental exercises, that can significantly improve the quality of life of patients. That's why researchers are looking for biomarkers that could be used as early signs of the disease.
One of these potential biomarkers is the retina, which is considered part of the central nervous system. Previous studies have shown that Alzheimer's disease can cause structural changes in the retina, in particular, thinning of the inner layers.
A fluorescent image of retinal layers obtained using a confocal microscope in healthy wild-type mice (right) and mice genetically bred to detect symptoms of Alzheimer's disease (left). The green color indicates amyloid conglomerates, which are believed to correlate with Alzheimer's disease.
Some other diseases (glaucoma, Parkinson's disease) can also cause thinning of the retina. Inconsistent test results may come from differences between the devices most commonly used for these types of measurements, optical coherence tomography (OCT) devices, and how researchers use them.
Comparison of the thickness of retinal layers in healthy wild-type mice (top) and mice that have been genetically bred to detect symptoms of Alzheimer's disease (bottom). The upper layer of the retina in mice with Alzheimer's disease is noticeably thinner.
In a new paper, researchers show that the upper layer of retinal neurons in a mouse model of Alzheimer's disease has an altered structure. In combination with data on changes in the thickness of this layer, the new measurement may be a more accessible biomarker of Alzheimer's disease.
The new approach makes it possible to measure the structure and texture of the retinal nerve fiber layer and has great potential as an early diagnosis of the disease.
OCT is an optical analogue of ultrasound. It works by sending light waves into tissues and measuring how long it will take them to return. This is a very useful imaging technique commonly used to detect a wide range of diseases, but it has limitations.
To collect more data about the retina, the authors performed low-coherence interferometry with angle resolution, which uses the angles of scattered light to collect additional information about the structure of the tissue. By combining the two measurements, researchers can determine both thickness and structural information about each layer of the retina.
Currently, researchers are working on incorporating low-coherence interferometry into an inexpensive OCT system. While traditional OCT machines weigh about 30 kg, occupy the entire table and cost from 50 to 120 thousand dollars, the new device weighs a little more than one and a half kilograms, its size is like a lunch box and, as the authors expect, will be sold for less than 15 thousand dollars.
The key element is a detail created using three-dimensional printing that uses symmetry to compensate for mechanical inconsistencies that can occur in traditional OCT devices due to such minor factors as temperature changes. The group is also working on a 3D-printed rotating prism that allows a low-coherence interferometry device to scan the entire retina.
This study demonstrates a new way to use low-cost OCT technologies, in addition to simple screening for traditional retinal diseases. If in the future it is possible to use these devices to detect early signs of neurodegenerative diseases, perhaps this will allow people to be helped before it is too late.
Article G.Song et al. Multimodal Coherent Imaging of Retinal Biomarkers of Alzheimer’s Disease in a Mouse Model published in the journal Scientific Reports.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on materials from Duke University: Retinal Texture Could Provide Early Biomarker Of Alzheimer's Disease.