Physicians at the University of Rochester Medical Center (URMC) developed a new way to fabricate artificial organs and human anatomy that mimics the real thing, even up to the point of bleeding when cut. These models can create highly realistic simulations for training and could soon be widely used to rehearse complex cases prior to surgery.

The program, called Simulated Inanimate Model for a Physical Learning Experience (SIMPLE), is the brainchild of Ahmed Ghazi, M.D., M.Sc., an assistant professor in the Department of Urology, and Jonathan Stone, M.D., a Neurosurgery resident who also holds a degree in biomedical engineering. The process entails converting images obtained from medical scans into computer generated designs and, through the assistance of 3D printing, fabricating lifelike organs that can be poked, prodded and dissected.

“Very few surgical simulations are successful at recreating the live event from the beginning to the end,” said Ghazi. “What we have created is a model that looks, feels, and reacts like a live organ and allows trainees and surgeons to replicate the same experience they would face in the operating room with a real patient.”

urmc-hydrogel-kidney
Injecting hydrogel into a 3D printed mold produced this artificial kidney.

The fabricating process begins with images obtained from MRI, CT, or ultrasound scans into computer-assisted designs (CAD). Instead of using these designs to create rigid plastic replicas of human anatomy, the pair converted the CADs of organs into molds, or negatives, which were built using a 3D printer. In a process akin to casting a bronze statue, the molds are then injected with a hydrogel which, after freezing, assumes a solid state. The water consistency of the hydrogel is identical to that found in human bodies, giving the artificial organs the same feeling as the real thing.

The team also worked with the University of Rochester Department of Biomedical Engineering to ensure the end product had the same mechanical properties as real tissue – and they compared the performance of surgeons on the models and in real patients and found there was a correlation between the two. These simulations were recognized during annual meetings of the American Urological Association, which awarded video presentations of the SIMPLE program with top honors in 2015 and 2016.

Once the basic models of human anatomy were created, the pair began to tweak the designs in order to change the pathology. For example, they would alter the concentration of the hydrogel to add a denser tumor mass to a liver, or a blockage in a kidney, or plaque in an artery. Using the 3D printer to create more rigid structures, the team can also create bone to simulate procedures involving the spine and skull. In fact, the potential medical scenarios that the technology could replicate are essentially endless.

Just being able to handle and examine a replica of a real organ can provide surgeons with a great deal of insight and information. They can observe where the blood vessels enter and leave the organ and, if it is a cancer model, the size and location of the tumor. They can even cut away at the organ to take a look at the interior.

Taking the process even further, Ghazi and Stone assembled entire segments of the body, complete with artificial muscle tissue, skin and fat, and, depending upon the area of interest, the liver, intestines, spleen, kidney, and other adjacent organs and structures because they wanted students, trainees and surgeons to be able to replicate the complete surgical experience. That also meant building the rest of the surrounding anatomy so the entire surgical process of guiding instruments to the right location, moving other organs out of the way, clamping blood vessels, and resecting and removing tumors could be replicated.

While the SIMPLE program represents an opportunity for surgical residents to practice full procedures and trained surgeons to keep their skills sharp and learn new surgical technologies, the models are also being used with medical students. The surgical procedure that third year medical students at the University of Rochester School of Medicine and Dentistry are required to learn during their surgical clerkship is a cholecystectomy, the laparoscopic removal of the gallbladder.

Ghazi and Stone built a simulation of a cholecystectomy which allows students to perform the surgery in teams from beginning to end, requiring them to do everything from making the initial incision, inserting and guiding instruments, and separating, clamping, and removing the gallbladder via minimally invasive surgery.

“There really isn’t another effective alternative for students,” said Stone. “Virtual reality hasn’t gotten far enough to feel like they are operating and, as a result, medical surgical education is lacking. This gives them a whole task training model and that not only benefits the students that want to go into surgery, but also those that aren’t interested in it as well because they are able to gain a perspective and appreciation of surgical methods and technologies that they may not otherwise be exposed to.”

While the simulations can be used to train on a generic model of anatomy, the ultimate vision is to harness this technology so surgeons can rehearse complex using the actual patient’s scans, accurately replicating the unique conditions that will be found during the live operation.

While widespread use of these patient-specific simulations is the long-term vision, Ghazi has already used these models to practice real partial nephrectomies case in several instances.

“Surgery is often like a Pandora’s Box,” said Ghazi. “You don’t know what is inside until you open it up. The fact that we could someday have surgeons practice procedures on these models before going to the operating room helps eliminate the unknown, increases safety, and improves the quality of care. Patients can, in turn, reassure themselves by asking their surgeons ‘how did the rehearsal go yesterday?’ That is going to be the future of surgery.”