def ps_ball(radius):
    r"""
    Creates spherical ball structuring element for morphological operations

    Parameters
    ----------
    radius : float or int
        The desired radius of the structuring element

    Returns
    -------
    strel : 3D-array
        A 3D numpy array of the structuring element
    """
    rad = int(sp.ceil(radius))
    other = sp.ones((2 * rad + 1, 2 * rad + 1, 2 * rad + 1), dtype=bool)
    other[rad, rad, rad] = False
    ball = spim.distance_transform_edt(other) < radius
    return ball