## 4 Conclusions  
The IMBL at the ANSTO Australian Synchrotron is well suited to propagation-based phase-contrast computed tomography imaging of biological samples such as excised mastectomies at low radiation doses, such as 2 mGy. With the help of the phase-retrieval TIE-Hom algorithm, the SNR is found to be enhanced, allowing the low-dose imaging of soft tissues while still producing high-quality, clinically-relevant results. Therefore, it is expected that propagation-based PCT will be incorporated into medical breast imaging at the IMBL in the near future providing higher tissue contrast and a better signal-to-noise ratio than is currently possible with conventional absorption-based imaging. Crucially, PCT also potentially reduces the radiation dose delivered to the patient and avoids the need for painful breast compression that is required as part of the current approaches to 2D mammography. With the combination of a highly efficient, high frame rate detector, a full PCT data set with 150 \(\upmu\)m spatial resolution and sufficiently high SNR can be collected in less than 1 min, e.g., 30 s for 1200 projections using the Xineos detector, or 71 s using 1200 projections for the Hamamatsu detector. The comparison between the Hamamatsu and the Xineos detectors shows that images of comparable quality can be obtained using either detector. Slightly better spatial resolution was obtained with the Hamamatsu, while better SNR/resolution was achieved with the Xineos. The user can quickly process the collected data during the beam time or access the data after the beam time using the ASCI desktop high-performance computing facility. In the future, higher-resolution PCT will be possible, albeit for smaller samples, using the new Micro-Computed Tomography (MCT) beamline, which is currently being constructed as part of the BRIGHT program at the Australian Synchrotron. The new MCT beamline will be used for high-resolution computed tomography and provide complementary information to the IMBL beamline.  
All authors contributed significantly to this work. [PERSON], [PERSON], [PERSON], [PERSON], S.J.L., P.C.B., M.D., D.H., T.E.G. wrote the manuscript, [PERSON], A.M., C.J.H., H.M.Q., S.T.T., S.J.L., P.C.B., D.H., T.E.G. designed experiments, [PERSON], Y.I.N., A.M., C.J.H., D.T., S.C.M., T.F., M.D., T.E.G. performed experiments, B.D.A., Y.I.N., D.T., T.E.G., S.T.T. analysed data. All authors have read and agreed to the published version of the manuscript.  
This research was funded by NHMRC Australia, Project Grant 1138283 \"Towards the clinical application of phase-contrast computed tomography in breast cancer imaging\" and ANSTO project funding.  
The imaging experiment was conducted under a Human Ethics Certificate of Approval from Monash University (project ID 26399) and with written consent from the patients.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data presented in this study are available on request from the corresponding author.  
We acknowledge the support of [PERSON], [PERSON], and [PERSON] from Monash University, Australia, in providing the mastectomy samples for this study. Special thanks to the individuals who consented to having their mastectomies used for research purposes in this study.  
The authors declare no conflict of interest.