Update README.md

Updated description to include both lesion and prostate masks.

README.md

@@ -9,7 +9,9 @@ We encourage the use of this data for radiomics and machine learning investigati
 
 ## Files
 
-The files are in compressed NIFTI (.nii.gz) format and collected in separate folders for T2 and ADC images. Each filename contains the following information (separated by underscores):
+### Lesion masks
+
+The files are in compressed NIFTI (.nii.gz) format and collected in separate folders for T2 and ADC images (n = 299 lesions). Each filename contains the following information (separated by underscores):
 
 - "PROSTATEx Patient ID" + "Finding ID" + "Sequence name" + "ROI"
 
@@ -21,6 +23,22 @@ The sequence number corresponds to the number at the beginning of the PROSTATEx
 
 Full exam DICOM files are retrievable through the Cancer Imaging Archive at: [https://wiki.cancerimagingarchive.net/display/Public/SPIE-AAPM-NCI+PROSTATEx+Challenges](https://wiki.cancerimagingarchive.net/display/Public/SPIE-AAPM-NCI+PROSTATEx+Challenges)
 
+### Prostate and zonal anatomy masks
+
+The files are in compressed NIFTI (.nii.gz) format, and all segmentations have been performed on axial T2 images (n = 204 exams). Each filename contains the following information (separated by underscores):
+
+- "PROSTATEx Patient ID"
+
+The masks included in the "mask_prostate" directory represent whole-gland masks (binarized). Those included in "mask_pz" and "mask_tz" are limited respectively to the peripheral and rest (transition zone, central zone, anterior stroma) of the gland, also binarized. The last directory "mas_pz_tz" contains both annotations, with peripheral zone voxels having a value of 2 and the remaining (transition zone, central zone, anterior stroma) a value of 1. The backgorund always has a value of 0.
+ 
+As sometimes multiple axial T2 image sequences are available for a patient, the repository also includes a list in CSV format containing the correct images for each mask. The list is structured as follows (separated by underscores):
+
+- "PROSTATEx Patient ID" + "Sequence name" + "Sequence number"
+
+The sequence number corresponds to the number at the beginning of the PROSTATEx dataset DICOM image folders for each patient.
+
+Full exam DICOM files are retrievable through the Cancer Imaging Archive at: [https://wiki.cancerimagingarchive.net/display/Public/SPIE-AAPM-NCI+PROSTATEx+Challenges](https://wiki.cancerimagingarchive.net/display/Public/SPIE-AAPM-NCI+PROSTATEx+Challenges)
+
 ## License
 
 Creative Commons Attribution 4.0 International (CC-BY-4.0). See "LICENSE" file for full details.