New technique improves breast cancer screening

Innovative X-ray technology delivers higher-resolution 3D images with lower radiation dose

Comparison between a conventional computed tomography image of a breast tissue sample (top) and a photograph with the new low-dose phase-contrast CT; The tumor is highlighted in red, indicating the required radiation dose below the image. © ESRF-LMU / Brun
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A new technique can detect breast cancer in the future better and less radiation than before. Instead of only two-dimensional images of the breast in mammography, it enables high-contrast 3D images - without increasing the radiation exposure of the tissue. The so-called low-dose phase-contrast computed tomography was developed by an international research team in which researchers from the Ludwig-Maximilians-Universität München (LMU) played a leading role. Compared to conventional mammography examinations, the new procedure reduces radiation exposure fourfold, compared to conventional computed tomography (CT) even 25-fold. This is achieved by combining a special admission procedure with a new, more effective evaluation method, as the researchers report in the journal "Proceedings of the National Academy of Sciences".

"This new technology opens the door to a clinical use of computed tomography in the early detection of breast cancer, " explains Maximilian Reiser, co-author of the study and head of the radiology department at the LMU Munich. So far, the computer tomography had been unsuitable because it exposes the sensitive breast tissue too high a radiation dose.

For a three-dimensional CT scan, the tissue must be repeatedly illuminated by X-rays from different angles and at different levels. In normal, so-called "dual-view" mammography, the breast is only displayed in two views - from the side and from the top. This reduces the X-ray exposure, but provides less precise, but high-contrast images. "Ten to 20 percent of the tumors are not recognizable on the mammograms, " the researchers write. The CT provides a better resolution, but it could be due to the lower contrast certain tumor forms worse identify. The new method now combines the advantages of both methods, but avoids their disadvantages.

More energetic radiation and more effective evaluation

The new method differs from normal tomography in three main points: It uses particularly high-energy X-rays, so-called synchrotron beams. They penetrate tissue even at a lower dose than normal X-rays. In normal CT, the brighter and darker areas appear in the image, because the tissues absorb different amounts of radiation. On the other hand, the phase-contrast CT detects fine oscillations in the X-ray reflected from the tissue. "Because these shifts are two to three times stronger than absorption, you get a higher contrast, " the researchers explain. Finally, a new evaluation process requires fewer images compared to the previous ones in order to reconstruct a high-resolution 3D image from it. This also reduces radiation exposure.

However, the X-ray equipment needed for the new technology is still too large to be used in medical practices and clinics, the researchers say. It will therefore take some time before the new low-dose phase-contrast CT is available for patients. "However, many research groups are already working hard to develop a smaller device, " says Emmanuel Brun from LMU Munich, one of the first authors of the study. (doi: 10.1073 / pnas.1204460109) Display

(Proceedings of the National Academy of Sciences (PNAS), 23.10.2012 - NPO)