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Researcher's view Scattered radiation Robert Speller What is scattered radiation? "X-ray mammography is the gold-standard in the detection of breast disease. When mammograms are taken using X-rays the beam of X-rays passes through the breast and the individual packets of energy that make up the beam either interact with the tissue or pass straight through and are detected by the film below the breast. The image is formed from those X-rays that pass straight through the tissue and these are called the ‘primary beam’ or ‘primary photons’." "Although this image is found to contain useful diagnostic information there are two points to consider: Firstly, the contrast between normal and diseased tissue as demonstrated by the primary beam is very small and this makes it very difficult to see small tumours directly. And secondly, primary photons have not interacted with the tissue and therefore cannot carry information about any changes in the ‘structure’ of the tissue that diseases will cause." "Both of these problems can be overcome by studying the X-rays that have interacted with the tissue. These are usually called the ‘secondary beam’ or ‘scattered photons’. Scattered photons will have interacted with the electrons of the atoms that make up the tissue and in doing so they may have lost some energy but they will certainly have their direction of travel altered." What advances have been made as a result of research? "Extensive research has been carried out to demonstrate that different types of breast tissue scatter X-rays differently. In fact the differences in the scattering properties are so large that the ‘contrast’ between normal and diseased tissue is several times greater if scattered radiation rather than primary radiation is used. This means that potentially much smaller tumours can be seen and hence disease detected at an earlier stage. The earlier disease is detected the more successful the treatment. Experiments have been carried out with both conventional sources of radiation and with highly specialised synchrotron sources to demonstrate this potential and a new imaging technique called Spectral Selective Momentum Transfer Imaging (SSMTI) has been developed. When applied to imaging for breast disease this technique is called DEBI (Diffraction Enhanced Breast Imaging)." What might we expect in the future? "An important aspect of the DEBI technique is that this new information is created during a conventional X-ray mammogram with little or no additional X-radiation required. It will be possible to combine or fuse these two sources of information to provide a more accurate diagnosis and characterisation of the disease. Thus in a single examination all the information could be collected that potentially might help to avoid exploratory biopsies, reduce the anxiety experienced by the patient and allow treatment to start more quickly. DEBI is a technique that leads to spatial localisation (or 3-D information) about the diseased state of the tissue that has been imaged. To take full advantage of this, stereoscopic mammography is also being developed and when combined with DEBI should allow the full potential of both techniques to be realized." Woman's view | Radiologist's view | Researcher's view | Research process |