In stnava/surgeRy: Processing, Filtering and Data Organization for Deep Learning Training

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
set.seed( 000 )
myeval=FALSE

Overview of surgeRy

We overview landmark-specific training although the approach is very similar for segmentations or segmentations and landmarks.

the augmentation strategy will use:

• geometric transformation of images (rigid, affine, etc)

• gaussian noise

• simulated bias field

• histogram warping

to create new versions of images and points from an input image list. Points are in physical space.

Setting up the data

This will be run on a separate thread (or R session) from the surgeRyLMtrain.Rmd code. Environment variables control multi-threading for CPU in ANTs and tensorflow. See below for how to set these at the beginning on an experiment. We set the number of threads to 12 below.

Sys.setenv("TF_NUM_INTEROP_THREADS"=12)
Sys.setenv("TF_NUM_INTRAOP_THREADS"=12)
Sys.setenv("ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS"=12)

See the code below for how to assemble the images and points for augmentation.

# record the GPU
gpuid = Sys.getenv(x = "CUDA_VISIBLE_DEVICES")
library( ANTsR )
library( ANTsRNet )
library( tensorflow )
library( keras )
library( tfdatasets )
library( reticulate )
library( patchMatchR )
library( surgeRy )
np <- import("numpy")
mytype = "float32"
downsam = 4   # downsamples images
# collect your images - a list of lists - multiple entries in each list are fine
rids <- function( x, downsammer=4 ) {
  img = ri( x )
  resampleImage( img, dim(img)/downsammer, useVoxels=TRUE )
}
upperhalf = rids( 1 ) * 0 + 1 # this just gives us more segmentation labels
upperhalf[33:64,1:32] = 2
upperhalf[1:32,33:64] = 3
upperhalf[33:64,33:64] = 4
ilist = list(
  list( rids( 1 ), getMask( rids( 1 ) ) ),
  list( rids( 2 ), getMask( rids( 2 ) ) ),
  list( rids( 3 ), getMask( rids( 3 ) ) ),
  list( rids( 4 ), getMask( rids( 4 ) ) ),
  list( rids( 6 ), getMask( rids( 6 ) ) ) )

slist = list()
plist = list()
for ( k in 1:length( ilist ) ) {
  temp = thresholdImage( ilist[[k]][[1]], "Otsu", 3 )
  temp = temp * ( ilist[[k]][[2]] - iMath( ilist[[k]][[2]], "ME", 6 ) )
  slist[[k]] = thresholdImage( temp, 2, 2 ) * upperhalf
  plist[[k]] = getCentroids( slist[[k]] )[,1:2]
  plot( ilist[[k]][[1]], slist[[k]] )
}

Here are definitions for some variables important for training: which images are for training and testing.

# identify the number of segmentation classes
isTrain = c( rep(TRUE,length(slist)-1), FALSE )

This example will do landmark learning.

Preparing to write the data to disk

We will generate (in this case) 5 files. For each, we generate a random file unique ID and then create file extensions that map to the type of augmented data we will be generating. In this case, we will generate augmented images, the associated masks, the points, coord conv output and a heatmap. These all derive from the image lists we defined above. This stuff will be run on CPU separately from the training loop.

nFiles = 5
dir.create( "numpy", showWarnings=FALSE )
if ( ! exists( "uid" ) )
  uid = paste0("LM",sample(1:1000000,nFiles),"Z")
types = c("Images.npy", "pointset.npy", "mask.npy", "coordconv.npy", "heatmap.npy" )
nmats = length(types) # 5 arrays out
trainTestFileNames = data.frame( matrix("",nrow=nFiles,ncol=nmats*2))
colnamesTT = c(
  paste0("train",gsub(".npy","",types)),
  paste0("test",gsub(".npy","",types)) )
colnames( trainTestFileNames ) = colnamesTT
for ( k in 1:nFiles ) {
  twogroups = paste0("numpy/",uid[k],c("train","test"))
  npextsTr = paste0( twogroups[1], types )
  npextsTe = paste0( twogroups[2], types )
  trainTestFileNames[k,]=as.character( c(npextsTr,npextsTe) )
}
write.csv( trainTestFileNames, "numpy/LMtrainttestfiles.csv", row.names=FALSE)

Augmenting the data

We generate the data based on default parameters. If you want to learn more about the possibilities here, then please change the parameters and take a look at the results. We will show an example that looks at some parameter variations below.

The call below will write a test file to numpy. We just write one in this case as we keep it constant during training. Write as many as you want for your application

testfilename = as.character(trainTestFileNames[1,grep("test",colnames(trainTestFileNames))])
gg = generateDiskPointAndSegmentationData(
    inputImageList = ilist,
    pointsetList = plist,
    selector = !isTrain,
    smoothHeatMaps = 3.0,
    maskIndex = 2,
    transformType = "scaleShear",
    noiseParameters = c(0, 0.05),
    sdSimulatedBiasField = 0.01,
    sdHistogramWarping = 0.01,
    sdAffine = 0.1, # limited
    numpynames = testfilename,
    numberOfSimulations = 8
    )
# visualize example augmented images
layout( matrix(1:8,nrow=2))
for ( k in 1:8 ) {
  temp = as.antsImage( gg[[1]][k,,,1] )
  plot( temp )
  }

We would typically run something like the code below in a continuous loop on a CPU thread separate from the GPU training loop. In practice, you may keep the parameters the same across train and test or set minimal augmentation parameters for test data.

while( TRUE ) {
  for ( k in 1:nFiles ) {
    trnfilename = as.character(trainTestFileNames[k,grep("train",colnames(trainTestFileNames))])
    print( paste(k, trnfilename[1] ) )
    gg = generateDiskPointAndSegmentationData(
        inputImageList = ilist,
        pointsetList = plist,
        selector = isTrain,
        smoothHeatMaps = 3.0,
        maskIndex = 2,
        transformType = "scaleShear",
        noiseParameters = c(0, 0.05),
        sdSimulatedBiasField = 0.01,
        sdHistogramWarping = 0.01,
        sdAffine = 0.1,
        numpynames = trnfilename,
        numberOfSimulations = 64
        )
    }
  }

Getting the above steps correct is very critical to successful training. This package currently hides some of that complexity for basic segmentation and landmark prediction. However, it is always possible to make mistakes if the training decisions are inconsistent with the underlying theory. A forthcoming publication will explain the theory associated with this package.

stnava/surgeRy documentation built on Dec. 23, 2021, 6:37 a.m.