Breast

European Radiology

, Volume 16, Issue 5, pp 1138-1146

Cluster analysis of signal-intensity time course in dynamic breast MRI: does unsupervised vector quantization help to evaluate small mammographic lesions?

  • Gerda LeinsingerAffiliated withInstitute for Clinical Radiology University of Munich
  • , Thomas SchlossbauerAffiliated withInstitute for Clinical Radiology University of Munich Email author 
  • , Michael ScherrAffiliated withInstitute for Clinical Radiology University of Munich
  • , Oliver LangeAffiliated withInstitute for Clinical Radiology University of Munich
  • , Maximilian ReiserAffiliated withInstitute for Clinical Radiology University of Munich
  • , Axel WismüllerAffiliated withInstitute for Clinical Radiology University of Munich

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Abstract

We examined whether neural network clustering could support the characterization of diagnostically challenging breast lesions in dynamic magnetic resonance imaging (MRI). We examined 88 patients with 92 breast lesions (51 malignant, 41 benign). Lesions were detected by mammography and classified Breast Imaging and Reporting Data System (BIRADS) III (median diameter 14 mm). MRI was performed with a dynamic T1-weighted gradient echo sequence (one precontrast and five postcontrast series). Lesions with an initial contrast enhancement ≥50% were selected with semiautomatic segmentation. For conventional analysis, we calculated the mean initial signal increase and postinitial course of all voxels included in a lesion. Secondly, all voxels within the lesions were divided into four clusters using minimal-free-energy vector quantization (VQ). With conventional analysis, maximum accuracy in detecting breast cancer was 71%. With VQ, a maximum accuracy of 75% was observed. The slight improvement using VQ was mainly achieved by an increase of sensitivity, especially in invasive lobular carcinoma and ductal carcinoma in situ (DCIS). For lesion size, a high correlation between different observers was found (R2 = 0.98). VQ slightly improved the discrimination between malignant and benign indeterminate lesions (BIRADS III) in comparison with a standard evaluation method.

Keywords

Breast cancer MR mammography Vector quantization