Big versus small: Image of colon cancer (left) and a supernova captured by similar cameras

Astronomer George Fraser projected two spectacular images from his powerpoint projector. Both of them looked identical with bright rings, colourful cloudbursts and brilliant blue protrusions. ?The right-hand image shows the supernova remnant RCW 103 captured from a UK-German satellite,? said the professor at the University of Leicester. ?Now guess what we?ve got on the left hand side?? quizzed Fraser rather dramatically. Before any one of us among the group of six visiting Indian journalists could shoot any wild guesses, Fraser hastened his reply: ?It?s a mouse tumour labelled with a radioactive substance ? photographed with a similar camera.?

Leicester astronomers are well-known for their work in x-ray astronomy, and for developing novel instruments for space satellites that can both detect image x-rays from space objects such as an active galactic nuclei or supernovae. The team led by Fraser and John Lees has supplied high-resolution cameras to several space projects which include NASA?s spacecraft Chandra observatory and the forthcoming Advanced X-ray Astrophysics Facility (AXAF).

The camera is a large, square detector, 10 centimetres across with a resolution down to 25 micrometre. ?Its key elements are microchannel plates (MCP) meant for collecting photons of light and convert them into an amplified electrical signal,? explained Fraser. The device looked like an array of thin glass tubes originally developed for capturing gamma-, x- or ultraviolet rays emitted from distant bodies most accurately.

?MCPs can detect fast electrons quite efficiently,? said Fraser. ?So in a moment of epiphany we?d decided to try out the device to monitor a new type of radiotherapy treatment in cancer.? It was an idea of imaging structures on a dramatically different scale ? millimetres rather than light-years.

The therapy, called radioimmunotherapy, involves designing antibodies that can carry therapeutic radiation to cancer cells. The drug ?tagged? or labelled with a radioactive isotope emitts high-energy electrons which kills cancer cells, protecting the healthy ones from its toxic effects. This approach is being used to treat cancer in bladder, breast or ovary. ?The current imaging techniques are not sensitive enough to detect small tumours accurately ? so as to tell whether the radiotherapy technique is working properly,? said Fraser. Besides, making a print of the tumour with an x-ray film and the resulting exposures are very long ? sometimes it can take more than a couple of months. In their first experiment the Leicester team used the MCP detector to image a thin tissue section of a mouse, labelled with a radioactive carbon. The tissue had already been injected with a drug. In just two hours the MCP snapped an image showing clearly how the drug had recahed the oesophagus, liver or gut.

To assess the performance of the technique in human cancer patients Leicester scientists collaborated with the Queen?s Medical Centre in Nottingham. The detector, called the Beta 2000 digital autoradiography system, has been offering a considerable improvement in making cancer therapy more effective.

?Basically we are trying to bridge the chasm between physics and bilogy,? said Fraser. ?Fundamental physics has already spawned revolutionary diagnostic techniques like MRI and PET scanners. Our bioimaging efforts simply continues this trend.?

Leicester space researchers are currently trying to use another astronomical device called charge-coupled detectors (CCD)s ? a standard component for space telescopes ? to see if their technology can improvethe process of identifying DNA samples. A standard way of DNA identification ?tags? a particular sample with a chemical that fluoresces in ultraviolet light. ?Our technique helps detect fluoroscent labels more efficiently enabling better identification of defective genes,? said Fraser.