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Threshold Isocontouring on High b-Value Diffusion-Weighted Images in Magnetic Resonance Mammography

Zong, Fangrong, PhD*; Bickelhaupt, Sebastian, MD; Kuder, Tristan Anselm, PhD; Lederer, Wolfgang, MD§; Daniel, Heidi, MD; Stieber, Anne, MD; Schlemmer, Heinz-Peter, PhD; Galvosas, Petrik, Dr. rer. nat.#; Laun, Frederik Bernd, PhD**

Journal of Computer Assisted Tomography: May/June 2019 - Volume 43 - Issue 3 - p 434–442
doi: 10.1097/RCT.0000000000000868
Cardiothoracic and Breast Imaging
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Objectives Motivated by the similar appearance of malignant breast lesions in high b-value diffusion-weighted imaging (DWI) and positron emission tomography, the purpose of this work was to evaluate the applicability of a threshold isocontouring approach commonly used in positron emission tomography to analyze DWI data acquired from female human breasts with minimal interobserver variability.

Methods Twenty-three female participants (59.4 ± 10.0 years) with 23 lesions initially classified as suggestive of cancers in x-ray mammography screening were subsequently imaged on a 1.5-T magnetic resonance imaging scanner. Diffusion-weighted imaging was performed prior to biopsy with b values of 0, 100, 750, and 1500 s/mm2. Isocontouring with different threshold levels was performed on the highest b-value image to determine the voxels used for subsequent evaluation of diffusion metrics. The coefficient of variation was computed by specifying 4 different regions of interest drawn around the lesion. Additionally, a receiver operating statistical analysis was performed.

Results Using a relative threshold level greater than or equal to 0.85 almost completely suppresses the intra-individual and inter-individual variability. Among 4 studied diffusion metrics, the diffusion coefficients from the intravoxel incoherent motion model returned the highest area under curve value of 0.9. The optimal cut-off diffusivity was found to be 0.85 μm2/ms with a sensitivity of 87.5% and specificity of 90.9%.

Conclusion Threshold isocontouring on high b-value maps is a viable approach to reliably evaluate DWI data of suspicious focal lesions in magnetic resonance mammography.

From the *The Key Laboratory for Interdisciplinary Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing China;

Department of Radiology and

Medical Physics in Radiology, German Cancer Research Centre (DKFZ); and

§Radiological Practice at the ATOS Clinic Heidelberg, Heidelberg;

Radiology Centre Mannheim (RZM), Mannheim; and

Department of Clinical and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany;

#MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Physical and Chemical Sciences, Victoria University of Wellington, Wellington, New Zealand; and

**Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany.

Received for publication August 22, 2018; accepted January 7, 2019.

Correspondence to: Fangrong Zong, PhD, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Rd, Beijing 100101, China (e-mail: fangrong.zong@ibp.ac.cn); Sebastian Bickelhaupt, MD, Department of Radiology, German Cancer Research Centre (DKFZ), Heidelberg, Germany (e-mail: s.bickelhaupt@dkfz-Heidelberg.de).

F.Z. and S.B. contributed equally to this work.

This manuscript has not been previously published and is not under consideration in the same or substantially similar form in any other peer-reviewed media. All experiments included in the article had been approved by an institutional ethical review board. Written informed consents of all subjects were obtained prior to the magnetic resonance imaging scans and biopsies.

All data acquisition and analysis were completed at the German Cancer Research Centre (DKFZ). Visiting scientists F.Z. and P.G. were funded by the Ministry of Business, Innovation and Employment, New Zealand, via the grant “New NMR Technologies” and Chinese Academy of Sciences via the grant Hundred Talents Program Class-A Award. Financial support by the Dietmar-Hopp-Foundation, the Deutsche Forschungsgemeinschaft (DFG LA 2804/6-1), is gratefully acknowledged.

The authors declare no conflict of interest.

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