Extension of RandCropByPosNegLabeld to extract patches with positive voxels anywhere in the patch

Is your feature request related to a problem? Please describe. I would like to make sure I compose my batch with both positive and negative examples. However, I do have a patch size corresponding to the whole 2D slice from a 3D volume, and the labelled object might not necessarily be at the centre of it. I understand that the RandCropByPosNegLabeld transform goes towards the direction of balancing samples, but selects the patch as positive/negative based on the patch centre voxel only.

Describe the solution you’d like Would it be possible to extend the RandCropByPosNegLabeld transform so as to consider a patch positive based on the presence of foreground label anywhere in the patch?

Additional context I have noticed there is only a dict implementation of this transform and not an array one. Is there a particular reason for it?

[Nic-Ma]

Hi @martaranzini ,

I think you mean to do 3 steps: (1) randomly select a point(based on pos/neg ratio), (2) select a random distance(0, crop_size/2), (3) use point + distance as the patch center to crop patch. Is it right?

BTW, I will add Array level PosNegCrop soon in https://github.com/Project-MONAI/MONAI/issues/583.

Thanks.

[Nic-Ma]

Hi @martaranzini ,

Mark: I added Array version PosNeg crop in PR: https://github.com/Project-MONAI/MONAI/pull/628. Thanks.