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Table 2 Features extracted for each voxel (x) within the breast (M)

From: Automatic segmentation and classification of breast lesions through identification of informative multiparametric PET/MRI features

Feature group Description Definition Number of features per voxel
f dce DCE-MRI intensity values for each frame of the DCE-MRI time series fdce(x)  {Idce(x, i), j ≤ i ≤ j + 25}, where j is the first frame with contrast-enhancement and i is the frame number in the DCE sequence 26
f δdce Difference of DCE-MRI intensity values between two frames with distance 2 \( {\mathbf{f}}_{\updelta \mathrm{dce}}\left(\mathbf{x}\right):= \left\{\frac{{\mathbf{I}}_{\mathrm{dce}}\left(\mathbf{x},i+2\right)-{\mathbf{I}}_{\mathrm{dce}}\left(\mathbf{x},i\right)}{t_{i+2}-{t}_i}|j\le i\le j+25\right\} \), where ti is the time point of acquisition of frame i 25
f nsumdce Normalised sum of DCE-MRI intensities \( {\mathbf{f}}_{\mathrm{nsumdce}}\left(\mathbf{x}\right):= \frac{{\mathbf{f}}_{\mathrm{sumdce}}\left(\mathbf{x}\right)}{\max_{y\in M}\left({\mathbf{f}}_{\mathrm{sumdce}}(y)\right)} \) where \( {\mathbf{f}}_{\mathrm{sumdce}}\left(\mathbf{x}\right):= {\sum}_{i=j}^{j+25}{\mathbf{I}}_{\mathrm{dce}}\left(\mathbf{x},i\right) \) 1
f mri Intensity values for high-resolution MRI: Idcepre, Idcepeak, and Idcepost fmri(x)  {Idcepre(x), Idcepeak(x), Idcepost(x)} 3
f δmri Difference in intensity values for high-resolution MR images fδmri(x)  {Idcepost(x) − Idcepre(x), Idcepeak(x) − Idcepre(x), Idcepost(x) − Idcepeak(x)} 3
f dwi DWI intensity value fdwi(x)  {Idwi b0(x), Idwi b850(x), Iadc(x)} 3
f pet PET intensity value fpet(x)  {Ipet(x)} 1
  1. DCE-MRI dynamic contrast-enhanced magnetic resonance imaging, DWI diffusion-weighted imaging, PET positron emission tomography