3D X-ray could improve mammograms
Scientists have developed a 3D X-ray technique with a radiation dose that is 25 times lower than conventional systems.
The new method enables the production of 3D diagnostic computed tomography (CT) images with a spatial resolution 2-3 times higher than present hospital scanners, but with a radiation dose that is about 25 times lower.
This advance has the potential to overcome the main obstacle limiting conventional CT imaging of the breast: the high radiosensitivity of the breast glandular tissue.
Synchrotron X-rays at the Medical station of the ESRF have been used for testing the technique which, once deployed in hospitals, will make CT scans a diagnostic tool to complement dual view mammography.
Limitation of dual-view digital mammography
The breast cancer screening method typically used today is “dual-view digital mammography”.
The limitation is that it only provides two images of the breast tissue, which can explain why 10 percent to 20 percent of breast tumours are not detectable on mammograms.
Mammograms can also sometimes appear abnormal, when no breast cancers are actually present.
Computed tomography (CT), an X-ray technique that allows a precise 3D visualisation of the human body organs, cannot be routinely applied in breast cancer diagnosis because the risk of long-term effects in radiosensitive organs like the breast is considered too high.
A new direction using high energy X-rays, phase contrast imaging and EST
Recognising these limitations, scientists went in a new direction.
CT scans for early detection of breast cancer may now become possible thanks to the combination of three ingredients: high energy X-rays, a special detection method called “phase contrast imaging” and the use of a sophisticated novel 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 dose is deposited (a factor of 6 in radiation dose reduction).
Phase contrast imaging, mastered by the ESRF and the LMU-MAP teams, allows producing images with much less X-rays to obtain the same image contrast. Finally the EST method, originally developed by researchers at UCLA, needs 4 times less radiation to obtain the same image quality.
The team X-rayed a human breast at multiple different angles using phase contrast tomography and applied the EST algorithm to 512 images to produce higher resolution 3-D images of the organ than ever before and at a lower dose than a mammogram.
In a blind evaluation, five independent radiologists from the LMU ranked the generated images as having the highest sharpness, contrast, and overall image quality compared to 3-D images of breast tissue created through other standard methods.
“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”, says Prof. Maximilian Reiser, Director of the Radiology Department of the LMU, which provided the medical expertise for this research. “
The new technology is in the research phase and will not be available to patients for some time. To be implemented in clinics, it needs an X-ray source small enough to become commonly used for breast cancer screening.