Detecting tiny tumours

A new approach to cancer detection is being developed at the US Department of Energy’s Argonne National Laboratory. Using a copper crystal lens, researchers expect to find tumours no larger than a grain of rice.

The technology, developed by scientists at Argonne’s Advanced Photon Source, uses gamma rays diffracted by a set of 828 copper crystal cubes arranged in 13 concentric rings in a disk slightly smaller than a dinner plate.

The lens focuses the gamma radiation emitted from a small radioactive source in the body of a patient into a small, well-shielded detector. This application is simulated by placing a small radioactive source in a ‘phantom’ – an acrylic plastic device designed to simulate areas of the human body – and scanning the phantom with the lens system.

‘The key is sensitivity and special resolution,’ said developer Bob Smither. In addition to picking up the smaller sized tumour, the technology can also pinpoint its location within a millimetre or two.

Most cancers are presently found with gamma cameras, which provide images of potential tumours in the body by detecting the radiation emitted by a radiopharmaceutical given to a patient undergoing a full-body scan.

Suspected tumour regions collect higher concentrations of the radiopharmaceutical, which produces a higher count rate and therefore a detectable contrast between the tumour region and its surroundings.

The Argonne-developed lens is designed to supplement full-body scans done with a gamma camera. The gamma lens could be used following the full-body scan to reveal additional detail about suspect areas found during the scan, which means no additional radiopharmaceutical would be needed.

The device, set up as a six-lens array, will detect tumours as small as two millimetres in diameter, Smither said. ‘Moreover, it can provide sufficient information to determine the location of a tumour accurately in three dimensions, and thereby eliminate the uncertainties in the full-body scan,’ he added.

Smither also sees great potential for the gamma lens in a two-lens array as a possible replacement for mammography, because of its ability to locate very small tumours without discomfort to the patient. A full-scale medical imaging lens was constructed and tested with a number of phantoms in Smither’s research laboratory.

The researchers say their step is to design and build a smaller lens to see if the resolution can be improved even more, continuing experiments with phantoms. They expect to test the array in clinical trials in two or three years.