Medical folks will know best (like Stephen and friends)
but…could you try generating a better image from the current gpu shader? What you posted looks really specular and I think the gpu mapper can do better than that with the right parameters. Just odd to compare the two when the existing approach looks so off.
The hybrid row looks like it is missing lighting or something, is something off on that row? More contrast, lighting? It looks dark and flat compared to the other rows like it needs more lighting or something.