def normalize_hu(image, min_window=-1200.0, max_window=600.0):
    """
    Normalize image HU value to [-1, 1] using window of
    [min_window, max_window].
    """
    image = (image - min_window) / (max_window - min_window)
    image = image * 2 - 1.0
    image = image.clip(-1, 1)

    return image