Introduction of a breast apparent diffusion coefficient category system (ADC-B) derived from a large multicenter MRI database.

"Declarations GuarantorThe scientific guarantor of this publication is Pascal Baltzer. Conflict of interestThe authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article. Paola Clauser and Katja Pinker are members of the European Radiology Scientific Editorial Board. They have not taken part in the review or selection process of this article. Statistics and biometryOne of the authors (Pascal Baltzer) has significant statistical expertise. Informed consentFor this retrospective study, data from multiple previous prospective studies were analyzed. In the course of these previous studies, written informed consent was obtained from all included subjects (patients). Ethical approvalInstitutional review board approval was obtained. Study subjects or cohorts overlapSince this is a retrospective analysis of multiple study populations, some of the original data analyzed in this study have, at least in part, already been analyzed and published with different research questions.The according most recent publications are referenced below:-Bickel, H. et al Quantitative apparent diffusion coefficient as a noninvasive imaging biomarker for the differentiation of invasive breast cancer and ductal carcinoma in situ. Investigative Radiology 50, 95–100, https://doi.org/10.1097/rli.0000000000000104 (2015).-Clauser, P. et al Is there a systematic bias of apparent diffusion coefficient (ADC) measurements of the breast if measured on different workstations? An inter- and intra-reader agreement study. Eur Radiol, https://doi.org/10.1007/s00330-015-4051-2 (2015).-Dietzel, M. et al A multicentric comparison of apparent diffusion coefficient mapping and the Kaiser score in the assessment of breast lesions. Investigative Radiology 56, 274-282, https://doi.org/10.1097/rli.0000000000000739 (2021).-Spick, C., Pinker-Domenig, K., Rudas, M., Helbich, T. H. & Baltzer, P. A. MRI-only lesions: application of diffusion-weighted imaging obviates unnecessary MR-guided breast biopsies. Eur Radiol 24, 1204-1210, https://doi.org/10.1007/s00330-014-3153-6 (2014).-Clauser, P. et al Diffusion-weighted imaging allows for downgrading MR BI-RADS 4 lesions in contrast-enhanced MRI of the breast to avoid unnecessary biopsy. Clinical Cancer Research, 1941-1948, https://doi.org/10.1158/1078-0432.Ccr-20-3037 (2021).-Marino, M. A. et al A simple scoring system for breast MRI interpretation: does it compensate for reader experience? Eur Radiol 26, 2529-2537, https://doi.org/10.1007/s00330-015-4075-7 (2016)-Molinari, C. et al MR mammography using diffusion-weighted imaging in evaluating breast cancer: a correlation with proliferation index. Radiol Med 120, 911-918, https://doi.org/10.1007/s11547-015-0527-z (2015).-Baltzer, A., Dietzel, M., Kaiser, C. G. & Baltzer, P. A. Combined reading of contrast enhanced and diffusion weighted magnetic resonance imaging by using a simple sum score. European Radiology 26, 884-891, https://doi.org/10.1007/s00330-015-3886-x (2016).-Baltzer, P. A. T. et al Diffusion-weighted imaging (DWI) in MR mammography (MRM): clinical comparison of echo planar imaging (EPI) and half-Fourier single-shot turbo spin echo (HASTE) diffusion techniques. Eur Radiol 19, 1612-1620 (2009).-Dietzel, M. et al Breast MRI in the era of diffusion weighted imaging: do we still need signal-intensity time curves? Eur Radiol 30, 47-56, https://doi.org/10.1007/s00330-019-06346-x (2020).-Moschetta, M., Telegrafo, M., Rella, L., Stabile Ianora, A. A. & Angelelli, G. Effect of gadolinium injection on diffusion-weighted imaging with background body signal suppression (DWIBS) imaging of breast lesions. Magn Reson Imaging 32, 1242-1246, https://doi.org/10.1016/j.mri.2014.07.014 (2014).As opposed to these previous publications, we conjugated the original data from the different imaging centers to develop an easily and generally applicable ADC categorization system (bADC). Methodology• retrospective• cross sectional• multicenter study Conflict of interest The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article. Paola Clauser and Katja Pinker are members of the European Radiology Scientific Editorial Board. They have not taken part in the review or selection process of this article."

"Funding Open access funding provided by Medical University of Vienna. The authors state that this work has not received any funding."