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Keywords:
Breast, MR-Diffusion/Perfusion, MR, Comparative studies, Cancer
Authors:
M. Wielema, M. D. Dorrius, H. Dijkstra, E. Langius, M. Oudkerk, P. E. Sijens; Groningen/NL
DOI:
10.1594/ecr2017/C-2765
Aims and objectives
Diffusion Weighted Imaging (DWI) is currently used in addition to the standard DCE-T1 and T2 series in breast MRI.
DWI acquires the diffusion or motion of hydrogen protons in a voxel due to Brownian motion and is most often quantified in the apparent diffusion coefficient (ADC).
Diffusion is affected by the tissue properties and obstacles (for example lipophilic cell membranes) and restricted in tissues with a high cellular density.
In malignant lesions,
the cells are more densely packed and the extracellular space is reduced,
in comparison to benign lesions and normal breast tissue.
Therefore,
diffusion is restricted in malignant lesions.
[1].
Apart from differences in the DWI acquisition protocols and postprocessing approaches [2-4],
the method of region of interest (ROI) delineation also has a decisive influence on the ADC.
This leads to different outcomes affecting the differentiation between malignant and benign breast lesions.
[5]
In most clinical DWI studies published up to now ROIs have been drawn circular or ellipsoidal,
or freeform to enclose as much of the lesion as possible while staying within the hyperintense lesion on DW images.
[6-10] Alternatively,
the brightest part of the lesion on the DW images is captured in the ROI [11-14],
the hypointense part at the ADC map [15] or inside the solid portion of the lesion.
[16-19] It was recently shown that the selection of subregions within lesions with high,
intermediate or low ADCs influences the differentiation between benign and malignant lesions.
[20] In that particular study the ROIs were not standardized in terms of either size or shape.
Therefore,
the purpose of this study was to compare the reproducibility and diagnostic use of three alternative methods comparing the ADC values in ROIs standardized by fixing both size and shape,
to cover the whole lesion.