[Calculate volume diameter]

calc_diameter.py

import numpy as np
from scipy.ndimage import morphology

def calc_diameter(labels, target):
    # Find slice with maximum area
    i = np.argmax(np.where(labels == target, 1, 0).sum(axis=(0, 1)))
    s = np.where(labels[:, :, i] == target, 1, 0)
    # Extract contour points of target area
    c = s - morphology.binary_erosion(s)
    p = np.argwhere(c == 1)
    # Calculate pairwise distance of points on the contour
    n = p.shape[0]
    # Use (x - y)^2 = x^2 + y^2 - 2xy
    d = np.broadcast_to(np.sum(np.square(p), axis=1), (n, n))
    d = d + d.T - 2 * np.matmul(p, p.T)
    d = np.sqrt(np.max(d))
    return d
#end