10.1117/2.1201304.004852 New imaging technology lowers radiation dose in breast scans Paola Coan, Susanne Grandl, Anik ´ o Sztr´ okay-Gaul, Alberto Bravin, Jianwei Miao, Yunzhe Zhao, and Emmanuel Brun Improved 3D computed tomography produces clearer images and im- proved clinical diagnoses of breast cancer while dramatically reducing patients’ exposure to radiation. Early detection of breast cancer largely contributes to an improved prognosis and results in reduced disease mortality. The breast cancer screening technique used today in clinics is known as dual-view digital mammography. Its limitation is that it only provides two images of the breast, which can explain why up to 20% of breast tumors are not detectable on mam- mograms. Mammograms can also appear abnormal although no breast cancers are actually present. Computed tomography (CT) allows a precise 3D visualization of the human body, but it cannot be routinely used for breast cancer diagnosis because of the breast’s high radiosensitivity. This vulnerability significantly reduces the benefit-risk ratio owing to the potential for tumor development resulting from the exam itself. Recognizing these limitations, we developed a way to pro- duce 3D x-ray images of the breast at a radiation dose that is lower than 2D radiographies. 1 We performed phase-contrast x-ray tomography at 60keV of a whole human breast at the biomedical beamline of the European Synchrotron Radiation Facility (ESRF) in France. We reconstructed images by applying the novel mathematical equally sloped tomography (EST) algo- rithm using 512 projections to produce 3D images of the tissue at a resolution higher than that used in clinical CT (pixel size of 92m versus more than 200m for clinical CT scanners) and at a dose lower than that of dual view mammography (which is typ- ically about 3mGy). The new method allowed a clear and precise identification of a malignant cancer. According to a blind evalua- tion by five experienced radiologists, this method can reduce the radiation dose and acquisition time by 74% relative to conven- tional phase-contrast x-ray tomography while maintaining high resolution and contrast. Despite the significant reduction in the number of projec- tions used (corresponding to important savings in dose and Figure 1. Comparison between a conventional computed tomography (CT) scan of the breast based on the filtered back projection algorithm and one based on the equally sloped tomography algorithm with phase- contrast imaging. In the second image, the tumor is highlighted in red. The radiation dose needed for the scans is shown at the bottom of each image. acquisition time), radiologists ranked the generated images as having the highest sharpness, contrast, and overall image qual- ity compared to 3D images of breast tissue created through other standard methods based on the filtered back projection (FBP) algorithm (see Figure 1). Improved detection of breast cancer using CT scans now seems possible thanks to the combination of three technologies: high energy x-rays, phase-contrast imaging, and the use of the sophisticated EST algorithm to reconstruct the CT images from x-ray data. High-energy x-rays render tissues more transparent, which reduces the radiation dose that is deposited by a factor of six. Phase-contrast imaging, which our teams at the ESRF and the Ludwig Maximilians University are working on, may allow contrast from the x-ray’s phase modulation (or refraction) even if amplitude (i.e., absorption) modulation is weak or absent. This is possible with a radiation dose similar to, or even smaller than, that used in conventional absorption radiography. The final element is EST, originally developed by researchers at the University of California-Los Angeles, is a computational Continued on next page