code: def _modified_shepp_logan_ellipsoids(ellipsoids):
      
      intensities = [1.0, -0.8, -0.2, -0.2, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1]
  
      # Add minimal numbers to ensure that the result is nowhere negative.
      # This is needed due to numerical issues.
      intensities[2] += 5e-17
      intensities[3] += 5e-17
  
      assert len(ellipsoids) == len(intensities)
  
      for ellipsoid, intensity in zip(ellipsoids, intensities):
          ellipsoid[0] = intensity
docs: Modify ellipsoids to give the modified Shepp-Logan phantom.
  
      Works for both 2d and 3d.