A system that analyses urine using holograms could lead to faster diagnoses for urinary tract infections (UTIs) and monitor urine content in real time.
The most common urine tests have been in use for decades. They typically involve dipstick tests for red and white blood cells, or require the urine to be sent to a lab to be tested for bacteria. While these methods are relatively cheap and straightforward, they aren鈥檛 always very sensitive, which can be a problem given that people with UTIs may drink water to ease their symptoms and so produce highly diluted urine.
at Johns Hopkins University in Maryland and his colleagues designed a tool that takes a urine sample and produces a hologram 鈥� a 3D representation of an object based on detailed information from light it interacts with.
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Durr and his team used a laser to pass light through a sample of urine that had been embedded in a jelly-like substance to immobilise the floating particles it contained, then recorded the resulting pattern of light with a camera.
鈥淲e record more information than you do with a normal camera,鈥� says Durr. 鈥淭hat extra information allows us to know about the three-dimensional object.鈥�
Once the light has been captured by the camera, it can then be reconstructed into a 3D image for Durr and his team to analyse, which helps them identify microscopic objects, such as cells, within the urine sample.
The system performed differently depending on the size of the objects it was measuring. For relatively large objects, such as red blood cells, it performed well enough to suggest it could have applications monitoring blood in urine. Bacteria, however, are similar in size to the camera鈥檚 pixels, so it is harder to resolve individual bacterial cells.
But the system still appears to be effective at measuring overall bacterial concentrations in urine, because holography works well with objects that contain large amounts of empty space, such as diluted urine.
鈥淓ven if [someone] has been drinking 2 litres of water before a test, [Durr鈥檚 team] can crank through very large volumes and still get meaningful results,鈥� says at University College London.
The poor resolution for single bacteria could be a drawback for the holographic system though, says Rohn. If it can鈥檛 specify which particular type of bacteria is present, it makes prescribing the correct antibiotic more difficult.
Durr and his team say future work will involve expanding the system so it isn鈥檛 just suitable for analysing static urine samples held in containers, but can also analyse urine flowing through catheters. This would make it more useful in clinical settings given that catheters are a common source of infections. 鈥淲e know it鈥檚 possible with the kind of system that we have to image physiological flow rates you鈥檇 expect from typical urine outputs,鈥� says Durr.
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