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step1.py
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import numpy as np # linear algebra
import pandas as pd # data processing, CSV file I/O (e.g. pd.read_csv)
import dicom
import os
import scipy.ndimage
import matplotlib.pyplot as plt
import SimpleITK as sitk
from skimage import measure, morphology
def binarize_per_slice(image, spacing, intensity_th=-600, sigma=1, area_th=30, eccen_th=0.99, bg_patch_size=10):
bw = np.zeros(image.shape, dtype=bool)
# prepare a mask, with all corner values set to nan
image_size = image.shape[1]
grid_axis = np.linspace(-image_size/2+0.5, image_size/2-0.5, image_size)
x, y = np.meshgrid(grid_axis, grid_axis)
d = (x**2+y**2)**0.5
nan_mask = (d<image_size/2).astype(float)
nan_mask[nan_mask == 0] = np.nan
for i in range(image.shape[0]):
# Check if corner pixels are identical, if so the slice before Gaussian filtering
if len(np.unique(image[i, 0:bg_patch_size, 0:bg_patch_size])) == 1:
current_bw = scipy.ndimage.filters.gaussian_filter(np.multiply(image[i].astype('float32'), nan_mask), sigma, truncate=2.0) < intensity_th
else:
current_bw = scipy.ndimage.filters.gaussian_filter(image[i].astype('float32'), sigma, truncate=2.0) < intensity_th
# select proper components
label = measure.label(current_bw)
properties = measure.regionprops(label)
valid_label = set()
for prop in properties:
if prop.area * spacing[1] * spacing[2] > area_th and prop.eccentricity < eccen_th:
valid_label.add(prop.label)
current_bw = np.in1d(label, list(valid_label)).reshape(label.shape)
bw[i] = current_bw
return bw
def all_slice_analysis(bw, spacing, cut_num=0, vol_limit=[0.68, 8.2], area_th=6e3, dist_th=62):
# in some cases, several top layers need to be removed first
if cut_num > 0:
bw0 = np.copy(bw)
bw[-cut_num:] = False
label = measure.label(bw, connectivity=1)
# remove components access to corners
mid = int(label.shape[2] / 2)
bg_label = set([label[0, 0, 0], label[0, 0, -1], label[0, -1, 0], label[0, -1, -1], \
label[-1-cut_num, 0, 0], label[-1-cut_num, 0, -1], label[-1-cut_num, -1, 0], label[-1-cut_num, -1, -1], \
label[0, 0, mid], label[0, -1, mid], label[-1-cut_num, 0, mid], label[-1-cut_num, -1, mid]])
for l in bg_label:
label[label == l] = 0
# select components based on volume
properties = measure.regionprops(label)
for prop in properties:
if prop.area * spacing.prod() < vol_limit[0] * 1e6 or prop.area * spacing.prod() > vol_limit[1] * 1e6:
label[label == prop.label] = 0
# prepare a distance map for further analysis
x_axis = np.linspace(-label.shape[1]/2+0.5, label.shape[1]/2-0.5, label.shape[1]) * spacing[1]
y_axis = np.linspace(-label.shape[2]/2+0.5, label.shape[2]/2-0.5, label.shape[2]) * spacing[2]
x, y = np.meshgrid(x_axis, y_axis)
d = (x**2+y**2)**0.5
vols = measure.regionprops(label)
valid_label = set()
# select components based on their area and distance to center axis on all slices
for vol in vols:
single_vol = label == vol.label
slice_area = np.zeros(label.shape[0])
min_distance = np.zeros(label.shape[0])
for i in range(label.shape[0]):
slice_area[i] = np.sum(single_vol[i]) * np.prod(spacing[1:3])
min_distance[i] = np.min(single_vol[i] * d + (1 - single_vol[i]) * np.max(d))
if np.average([min_distance[i] for i in range(label.shape[0]) if slice_area[i] > area_th]) < dist_th:
valid_label.add(vol.label)
bw = np.in1d(label, list(valid_label)).reshape(label.shape)
# fill back the parts removed earlier
if cut_num > 0:
# bw1 is bw with removed slices, bw2 is a dilated version of bw, part of their intersection is returned as final mask
bw1 = np.copy(bw)
bw1[-cut_num:] = bw0[-cut_num:]
bw2 = np.copy(bw)
bw2 = scipy.ndimage.binary_dilation(bw2, iterations=cut_num)
bw3 = bw1 & bw2
label = measure.label(bw, connectivity=1)
label3 = measure.label(bw3, connectivity=1)
l_list = list(set(np.unique(label)) - {0})
valid_l3 = set()
for l in l_list:
indices = np.nonzero(label==l)
l3 = label3[indices[0][0], indices[1][0], indices[2][0]]
if l3 > 0:
valid_l3.add(l3)
bw = np.in1d(label3, list(valid_l3)).reshape(label3.shape)
return bw, len(valid_label)
def fill_hole(bw):
# fill 3d holes
label = measure.label(~bw)
# idendify corner components
bg_label = set([label[0, 0, 0], label[0, 0, -1], label[0, -1, 0], label[0, -1, -1], \
label[-1, 0, 0], label[-1, 0, -1], label[-1, -1, 0], label[-1, -1, -1]])
bw = ~np.in1d(label, list(bg_label)).reshape(label.shape)
return bw
def two_lung_only(bw, spacing, max_iter=22, max_ratio=4.8):
def extract_main(bw, cover=0.95):
for i in range(bw.shape[0]):
current_slice = bw[i]
label = measure.label(current_slice)
properties = measure.regionprops(label)
properties.sort(key=lambda x: x.area, reverse=True)
area = [prop.area for prop in properties]
count = 0
sum = 0
while sum < np.sum(area)*cover:
sum = sum+area[count]
count = count+1
filter = np.zeros(current_slice.shape, dtype=bool)
for j in range(count):
bb = properties[j].bbox
filter[bb[0]:bb[2], bb[1]:bb[3]] = filter[bb[0]:bb[2], bb[1]:bb[3]] | properties[j].convex_image
bw[i] = bw[i] & filter
label = measure.label(bw)
properties = measure.regionprops(label)
properties.sort(key=lambda x: x.area, reverse=True)
bw = label==properties[0].label
return bw
def fill_2d_hole(bw):
for i in range(bw.shape[0]):
current_slice = bw[i]
label = measure.label(current_slice)
properties = measure.regionprops(label)
for prop in properties:
bb = prop.bbox
current_slice[bb[0]:bb[2], bb[1]:bb[3]] = current_slice[bb[0]:bb[2], bb[1]:bb[3]] | prop.filled_image
bw[i] = current_slice
return bw
found_flag = False
iter_count = 0
bw0 = np.copy(bw)
while not found_flag and iter_count < max_iter:
label = measure.label(bw, connectivity=2)
properties = measure.regionprops(label)
properties.sort(key=lambda x: x.area, reverse=True)
if len(properties) > 1 and properties[0].area/properties[1].area < max_ratio:
found_flag = True
bw1 = label == properties[0].label
bw2 = label == properties[1].label
else:
bw = scipy.ndimage.binary_erosion(bw)
iter_count = iter_count + 1
if found_flag:
d1 = scipy.ndimage.morphology.distance_transform_edt(bw1 == False, sampling=spacing)
d2 = scipy.ndimage.morphology.distance_transform_edt(bw2 == False, sampling=spacing)
bw1 = bw0 & (d1 < d2)
bw2 = bw0 & (d1 > d2)
bw1 = extract_main(bw1)
bw2 = extract_main(bw2)
else:
bw1 = bw0
bw2 = np.zeros(bw.shape).astype('bool')
bw1 = fill_2d_hole(bw1)
bw2 = fill_2d_hole(bw2)
bw = bw1 | bw2
return bw1, bw2, bw
def step1_python(case_path):
itkimage = sitk.ReadImage(case_path)
case_pixels = sitk.GetArrayFromImage(itkimage)
spacing = np.array(list(reversed(itkimage.GetSpacing())))
origin = np.array(list(reversed(itkimage.GetOrigin())))
bw = binarize_per_slice(case_pixels, spacing)
flag = 0
cut_num = 0
cut_step = 2
bw0 = np.copy(bw)
while flag == 0 and cut_num < bw.shape[0]:
bw = np.copy(bw0)
bw, flag = all_slice_analysis(bw, spacing, cut_num=cut_num, vol_limit=[0.68,7.5])
cut_num = cut_num + cut_step
bw = fill_hole(bw)
bw1, bw2, bw = two_lung_only(bw, spacing)
return case_pixels, bw1, bw2, spacing, origin