Microscopically small bubbles of a substance which attaches itself to tumour cells in the bloodstream can be captured on film. It then becomes possible to detect the presence of cancer at the level of the individual cell. To monitor the behaviour of a single ‘micro-bubble’, researchers from the Physics of Fluids department have developed the world’s fastest camera. This unique device produces images at the rate of 25 million frames a second.
The Physics of Fluids department develops technologies which reveal the bloodflow within the very smallest blood vessels of the body. One very promising method involves the use of contrast echography to monitor the behaviour of microscopic air bubbles within a fluid. The bubbles carry a substance which can identify certain types of cancer such as leukaemia.
There are already several applications of contrast echography. For example, doctors use the technology to determine whether the bloodflow in a patient's kidneys or liver is sufficient. Cardiologists can measure the rate of bloodflow in the very smallest vessels (the capillaries) of the heart muscle in order to assess the effects of a cardiac incident. It is now possible to detect a single cancer cell in the bloodstream by introducing a microscopically small air bubble carrying a substance which is attracted to such cells.
A new form of echography
Echography has been used for many years to monitor the development of a baby in the womb. Even in its simplest form, it enables the foetus to be clearly distinguished from the surrounding amniotic fluid: tissue shows white, while the fluid itself appears dark. More recently, a special form of echography has been developed which can show the movement of fluids. It is known as 'contrast echography' and will reveal fluids in even the most inaccessible parts of the body, such as the blood within capillary blood vessels. A contrast fluid containing microscopic air bubbles is injected. Those bubbles reflect ultrasound differently than the surrounding tissue. The movement of the fluids can then be monitored 'live' on the echograph.
The Brandaris 128, developed by the Physics of Fluids department, is the world's fastest camera. It can take 25 million frames a second.
All sound is caused by vibrations; they set up waves which travel through a medium. That medium can be air, but sound actually travels even better through fluids and solids. The human ear can detect sound at frequencies of between 20 and 20,000 Hertz, this being the number of vibrations per second.
Echography and contrast echography rely on 'ultrasound' at the far higher frequency of over a million vibrations a second, or 1 MegaHertz. When the ultrasound strikes a surface of a different density, it is reflected at a slightly different frequency.
Other areas of research
The Physics of Fluids department is working on several other projects to optimize treatment methods which rely on ultrasound. For example, ultrasound can be used to eradicate bacteria and is a valuable aid in targeted drug delivery techniques.