An article published by Atmel (a microchip manufacturer popular in microcontrollers) explains the use of 3D printer to print a malformed and dysfunctional heart of a two week-old baby.
The article explains that doctors were able to print a replica of the baby’s heart which gave them an immediate and non-invasive view of the failing organ, allowing them closely examine holes and improper pathways with less risk to the baby. Until this point, they would have had to stop the heart, and in some cases remove it, in order to study the deformations.
There have been cases and studies in the medical field regarding 3D printing, but they tend to involve printing functional, “living” organs. In this scenario, it was a plastic replica taken from ultrasound images.