Using 3D Printing For Solid Tumor Modeling

Medical 3D printing applications are transforming the way patients receive care, and the way doctors practice and teach medicine. There are a few companies who are making headway in creating an existence where 3D printed human organs could be a reality. And though that possibility is far off on the horizon of time, current applications are already making a big impact.

Cross-sectional imaging, where multiple pictures are take on different anatomic levels, produces information which is well suited for 3D printing as each digital slice of data equals a layer of 3D printed physical data. The finer the digital data slices of CT or MRI images, the more precise the physical model will be to the endogenous structure.

3D printers are routinely used by medical professionals to transform cross-sectional imaging of damaged bone structures into 3D printed models, which allow maxillofacial surgeons to plan realignment and reconstruction procedures using an unparalleled visual approach.

How Tulane Creates and Uses Models

In the Department of Urology at Tulane University School of Medicine, researchers have been working on using 3D printing technology to create models of solid organ soft tissue tumors. The models will be used to help patients understand and visualize diagnoses, and will aid in a variety of areas: surgery selection, medical student and resident education, surgical simulation, and planning and improving surgical outcomes.

Since researchers have printed models in different materials with different physical properties, they've realized a number of specific utilities associated with each one.

Figure 1 depicts one of the first renal models, which was created using a single material and a single color; this is the methodology used by many orthopedic and maxillofacial surgeons to construct boney structures, but it is relatively useless for soft tissue solid organ malignancies. Other than the abnormal contour, there is no way to discern the size, location, or depth of the renal tumor.

Patient Care:

Most patients are candidates for organ-sparing surgery. This type of surgery would preserve a lot of their normal renal function, and yet, the majority of patients have their entire kidney removed, which dramatically increase the likelihood for chronic kidney disease. By showing a patient their own kidney in the form of a 3D physical model of his or her specific mass, the patient could visualize and understand the surgery in a better way and end up way more comfortable with the idea of organ-preserving surgery.

Figure 2a-d shows some preliminary work in which researchers used a CT scan to demonstrate an enhancing renal mass in order to: (1) create a high-fidelity physical 3D model (Figure 2a); (2) demonstrate the normal renal parenchyma in a clear resin and the tumor and blood vessels in a red hue (Figure 2b); and (3) allow resection of the tumor and preservation of the normal renal parenchyma (Figure 2c, 2d).

Medical Student Education:

Another critical use of patient-specific 3D models is for educational purposes. At Tulane University School of Medicine, a large series of medical students with training in radiographic imaging were asked to evaluate various renal masses using traditional cross-sectional imaging and then using high-fidelity 3D models.

Using the nephrometry score which is a well-established quantitative scoring system for renal masses, students were asked to assign values to renal masses based on their maximum diameter, exophytic/endophytic properties, nearness to the collecting system, and location of mass relative to polar lines. The participating students scored much closer to experts, dramatically reducing the variation between individual assessments when using 3D models as compared to standard imaging. This clearly demonstrated the value of 3D models in the training students who are learning how to read and interpret imaging modalities.

This type of model allowed researchers to highlight both the tumor and the normal renal parenchyma in different colors but with a translucent hue, thus enabling them to determine and demonstrate the depth of invasion (Figure 3a). To test the utility of 3D tumor modeling, they constructed physical models of renal units with suspected malignancies for five patients who then underwent partial nephrectomy (4 robotic and 1 open). Average ischemia time was 21 minutes, nephrectomy score was 6.8, and all margins were negative. Researchers found that analyzing these types of models prior to performing surgery enhance the ability to conduct organ-sparing surgery. This process works particularly well with respect to robotic surgery since the physical manipulation of the model helps restore the surgeon’s lost sense of tactile sensation of the organ of interest (Figure 3b).

Surgical Simulation:

Researchers at Tulane University's School of Medicine made progress in approximating the softer spongey texture of renal tissue.The more realistic the characteristics of the model are to the actual organ, the more valuable the model becomes to the surgical simulation. The high-fidelity 3D printed patient-specific model allows a surgeon to perform a“dry run” without ever touching the patient. The ability to perform this kind of simulation before performing a partial nephrectomy (a surgery known for its high learning curve and potential for significant complications) could have a huge impact on surgical outcomes and patient safety.

SOURCE: Dr. Josh Silberstein, Oncology Live