New artificial organs and human anatomy mimic the real thing, even up to the point of bleeding when cut. The models offer highly realistic simulations for training and could even lead to surgery “rehearsals.”
Creating the models entails converting images from medical scans into computer-generated designs, and, with 3D printing, fabricating lifelike organs that can be poked, prodded, and dissected.
The program’s creators have dubbed it the Simulated Inanimate Model for a Physical Learning Experience, or SIMPLE. It is the brainchild of Ahmed Ghazi, an assistant professor in the urology department at the University of Rochester Medical Center, and Jonathan Stone, a neurosurgery resident with a degree in biomedical engineering.
“Very few surgical simulations are successful at recreating the live event from the beginning to the end,” says 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.”
Surgery meets ‘arts and crafts’
The 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, which was already being done in many other places, Ghazi and Stone instead 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 that, after freezing, assumes a solid state.
The water consistency of the hydrogel is identical to that found in our bodies. This gives the artificial organs the same feeling as the real thing. A great deal of research and experimentation went into the process of formulating the hydrogel so the final product had not only the right consistency but also the correct color.
“We think of it as a science and engineering, although at its heart it is really arts and crafts because at the end day we are creating sculptures that just happen to be anatomical,” says Stone.
In collaboration with the department of biomedical engineering, the team also subjected the models to a battery of scientific tests to ensure that the end product had the same mechanical properties as real tissue. They also compared the performance of surgeons on the models and in real patients and found that there was a correlation between the two.
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.
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.
Ghazi and Stone wanted students, trainees, and surgeons to be able to replicate the complete surgical experience, which required not only building the organs of interest, but also the rest of the surrounding human 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.
To accomplish this feat, the team assembles 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. Artificial blood vessels are connected to bags of red dye that will “bleed” if cut. This was also done with other bodily fluids such as urine or bile.
The assembled unit could then be brought into the operating room where it is hooked up to a robotic surgical system, and the entire procedure simulated from the first insertion of instruments to completion.
Double-takes in the OR
The lifelike nature of the simulation has occasionally caused even trained professionals to do a double-take.
“We have had times when we are doing these simulations in the OR when nurses or other physicians have looked in the window and thought we were doing the real thing, and have even gone so far as to scrub and put their masks on before coming in thinking there was a patient on the table,” says Ghazi.
“As an experienced surgeon, when I am working with these simulations it is often hard to tell that it is not a real patient,” says Jean Joseph, head of urologic laparoscopic and robotic surgery in the department of urology who has worked closely with the pair to develop the simulations.
Better training for surgeons
“Surgeons are just like pilots,” says Ghazi. “There will always be the first time a pilot takes a 747 up into the air and there will always be a first time a surgeon does a procedure from beginning to end on their own. While pilots have simulators that allow them to spend hours of training in a realistic environment, there really is no lifelike equivalent for surgeons.”
Medical students are also using the models. To learn to perform a cholecystectomy—the laparoscopic removal of the gallbladder—for example, medical students have previously been limited to observing real surgeries or practicing certain surgical techniques on cadavers.
Ghazi and Stone have 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,” says Stone. “Virtual reality hasn’t gotten far enough to feel like they are operating and, as a result, medical surgical education is lacking.”
Rehearsing for the unexpected
While the simulations can be used to train on a generic model of anatomy, the ultimate vision is to harness this technology so that it can enable surgeons to rehearse complex cases before the patient is brought into the operating room. In these instances, the team can build organs using the actual patient scans, accurately replicating the unique conditions that will be found during the live operation.
“Surgery is often like a Pandora’s Box. You don’t know what is inside until you open it up.”
An example of how this model could improve patient care and outcomes is in a partial nephrectomy, during which surgeons remove a tumor while attempting to preserve as much of the healthy kidney as possible. This procedure necessitates not only that the surgeon successfully remove the tumor and a very small “margin” of adjacent healthy tissue, but also that they complete the operation as quickly as possible. The procedure requires interrupting blood flow to the kidney, however, and after 20 minutes kidney function will begin to be lost if circulation is not restored, so the surgeon is essentially racing against the clock.
One of the keys, therefore, is to avoid surprises and anticipate potential complications that could slow the procedure down. While these events are very rare, surgeons will sometimes confront more complex cases due to the size and position of the tumor. In these instances, conducting a dry run of the surgery in advance can help guide the surgeons once the operation is conducted on the real patient.
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,” says 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. ”
Source: University of Rochester