The new technique generates 3D diagnostic computed tomography (CT) images with a spatial resolution two to three- times higher than currently used scanners, but with a radiation dose that is around 25 times lower.
This advance has the potential to resolve the critical hurdle of limiting traditional CT imaging of the breast: the high radiosensitivity of the breast glandular tissue. Synchrotron X-rays at the ESRF European Synchrotron Radiation Facility (Grenoble, France) have been used for assessing the technique that, once deployed in hospitals, will make CT scans a diagnostic tool to be used as an adjunct to dual-view mammography.
A report of this novel imaging modality was published October 23, 2012, in the online early edition of the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS). The multidisciplinary group of scientists included radiologists, physicists, and mathematicians from the ESRF European Synchrotron Radiation Facility, Ludwig Maximilians University (LMU; Cluster of Excellence MAP; Munich, Germany), and the University of California at Los Angeles (UCLA; USA). The first authors were Dr. Yunzhe Zhao of UCLA and Dr. Emmanuel Brun of the LMU/ESRF.
Early detection in large part adds to an improved prognosis and findings in decreased breast cancer mortality. The breast cancer screening technology typically employed now is dual-view digital mammography. The limitation is that it only generates two images of the breast tissue, which may clarify why 10%-20% of breast tumors are not identifiable on mammograms. At times, mammograms can also appear abnormal, when no breast tumors are truly present.
Computed tomography (CT), an X-ray technique that allows a precise 3D visualization of body organs, cannot be routinely applied in breast cancer diagnosis because the risk of long-term effects in radiosensitive organs such as the breast is considered too high.
Acknowledging these limitations, scientists decided to try something new. CT scans for early detection of breast cancer may now become possible due to the combination of three components: a detection modality called phase contrast imaging, high energy X-rays, and the use of a sophisticated mathematical algorithm, known as equally sloped tomography (EST), to reconstruct the CT images from X-ray data. Tissues are more transparent to high energy X-rays and therefore less of a dose is administered (a factor of six in radiation dose reduction). Phase contrast imaging, conducted by the ESRF and the LMU-MAP teams, generates images with much less X-rays to acquire the same image contrast. Finally, the EST method, originally developed by researchers at UCLA, needs four times less radiation to obtain the same image quality.
The investigators X-rayed a human breast at multiple different angles using phase contrast tomography and applied the EST algorithm to 512 images to generate higher resolution 3D images of the organ than ever before and at a lower dose than a mammogram. In a blind assessment, five independent radiologists from the LMU categorized the resulting images as having the highest sharpness, contrast, and overall image quality compared to 3D images of breast tissue created through other conventional techniques.
“This new technique can open up the doors to the clinical use of computed tomography in the breast diagnosis, which would be a powerful tool to fight even better and earlier against breast cancer,” said Prof. Maximilian Reiser, director of the radiology department of the LMU, which provided the medical expertise for this research.
“This result has been obtained thanks to the synergy of the expertise by researchers from very different disciplines. These high-quality X-ray CT images at high energies are the result of a 10-year effort at the ESRF,” stated Alberto Bravin, head of the ESRF medical research laboratory who led the team in Grenoble. “After dramatically reducing the dose delivered during the examination of the breast, our next objective is to develop this technique in the early visualization of other human diseases and to work towards its clinical implementation,” added Paola Coan, professor of X-ray imaging at LMU and member of Munich-Center for Advanced Photonics (MAP) who led the group from Munich.
“Three-dimensional reconstructions, like the ones created in this research, are produced using sophisticated software and a powerful computer that can combine many images into one 3D image, much like slices of an orange. By rethinking the mathematic equations of the software in use today,” noted Jianwei Miao, UCLA professor of physics and astronomy and researcher with the California NanoSystems Institute at UCLA “we developed a more powerful algorithm that requires fewer slices to get a clearer 3D picture.”
The new technology is now in the research stage and will not be clinically available for a while. To be implemented in clinics, it needs an X-ray source small enough to become typically used for breast cancer screening. “Many research groups are actively working to develop this device and once this hurdle is cleared, the new X-ray technique is poised to make a big impact on society,” concluded Dr. Brun, a scientist from ESRF-LMU.
Source:
medimaging.net
