This new method should be able to reveal structures that cannot be seen using conventional mammography. Standard procedures only determine the extent to which X-rays are attenuated by various tissue structures. In contrast to this, the new method also makes use of the fact that X-rays actually consist of waves, and that their properties change slightly as they travel through tissue. These changes are now measurable and can contribute to the creation of a more meaningful image of the object under investigation.
The aim of any mammography investigation is to detect tumours in the female breast as early as possible, so that treatment can start in good time. A good mammography procedure is therefore expected to recognise as many tissue changes as possible and to distinguish tumour tissue clearly from any other tissue. At the same time, the radiation dose administered during the investigation must be kept as low as possible.
The researchers have now succeeded for the first time in generating images of tissue that originated from breast surgery but had not been preserved. This approach produces an extremely close approximation to the situation in which an actual investigation is carried out on human beings. “For example, we could use this new process to distinguish scars from tumour tissue and identify extremely small cancer nodules, of a size never yet identified by current investigation techniques”, said Doctor Nik Hauser, who led the project.
In this new procedure, X-rays pass through the breast in exactly the same way as in conventional mammography. However, a normal X-ray image can only determine how much of the beam has been retained by the tissue – basically, an X-ray image just shows the shadow cast by the object under investigation. However, X-rays also undergo another subtle change as they travel through an object. Physically, X-rays are electromagnetic waves and, as they pass through various tissue structures, the direction of the waves undergoes slight changes – a similar effect to that shown by water waves hitting a pier in a harbour.
One particular feature of the phase-contrast method used in this process is the three extremely fine gratings through which the X-rays have to pass – one in front of the object under investigation and the other two located behind it. The various components of the light waves interact with each other here in such a way as to provide the required information. The X-rays are generated in a tube that is essentially the same as an X-ray tube used in normal, everyday clinical practice.
The long-term aim of this work is to develop a novel piece of equipment that can be used for regular routine breast examinations in clinical practice, and deliver improved images of breast tissue – at a significantly lower cost than techniques such as computer tomography or magnetic resonance imaging.
COMPAMED.de; Source: Paul Scherrer Institut (PSI)