MEDICAL IMAGING Eyes on diagnosis
Jessica Rowbury takes a look at how imaging technologies are being used to test, diagnose and study disease
T
he most common reason people visit the optician is to have their eyesight tested. But, more than just myopia
can be evaluated by examining the eyes − a simple ophthalmic exam can reveal signs of systemic diseases such as hypertension and diabetes and, in the future, could even help to diagnose brain conditions such as dementia and Alzheimer’s. Te eye is a unique organ as it allows for a minimally invasive insight into a person’s health. ‘Te reason why a lot of vision is being used in eye applications is that it is the only transparent area of the body where you can look at a person’s blood flow without
opening up the body,’ said Joost van Kuijk, vice president of marketing and technology at Adimec. ‘So, you can actually look inside the body through this transparent organ, the eye, and do medical diagnostics.’ To diagnose diabetic-related diseases, a
typical examination is Fundus Fluorescein Angiography (FFA), which allows leakages, blockages or aneurisms to be detected using a specific contrast dye, fluorescein. Te procedure involves first taking images of both eyes in colour, and also in red to make blood vessels appear dark. A cobalt optical filter may also be used to make the translucent retinal nerve fibre layer visible. ‘Te fluorescein will
14 Imaging and Machine Vision Europe • February/March 2015
then be injected and a large number of images will be taken, initially in a very rapid sequence, to follow the flow of the dye,’ explained Chris van Wijk, product manager of the Eye Care Division at Canon’s Medical Imaging Group. ‘First the filling of the arteries can be observed and then the veins.’ Tis is then followed by a so-called ‘late phase’, where the effects of recirculation, dilution and elimination of dye can be observed. To provide a clear view of the vascular
structure and enable accurate conclusions to be drawn from the images, there are many features that a camera must have. ‘To take good quality retinal images, through a pupil, and on a curved surface, is far from easy. Tere can also be interference from reflections of the cornea and the crystalline lens,’ Van Wijik remarked. ‘A retinal camera therefore needs
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