For centuries, medicine has relied on physical representations of human anatomy, from clay figures to carved stone, to aid in understanding disease. Modern imaging technologies such as CT and MRI have vastly improved anatomical visualization, yet their two-dimensional nature limits comprehension of complex spatial relationships. Virtual 3D models offer better visualization but lack tactile realism. The advent of additive manufacturing—3D printing—has transformed this landscape, enabling creation of patient-specific physical organ models with unprecedented detail.
Unlike subtractive manufacturing, which removes material through cutting or milling, 3D printing builds structures layer-by-layer directly from CAD data. This approach minimizes waste and accommodates intricate geometries such as vascular networks. As costs for printers and materials decline, accessibility has increased, fostering collaborations between engineers, clinicians, and researchers to produce organ models for surgical planning, training, and education.
Several printing technologies dominate organ model fabrication. Vat photopolymerization, including stereolithography (SLA) and digital light processing (DLP), cures liquid photopolymers with light, achieving resolutions as fine as 5 µm. Material jetting, exemplified by Polyjet systems, deposits droplets of resin and cures them with UV light, enabling multi-material, multi-color models. Material extrusion, such as fused deposition modeling (FDM), melts thermoplastic filaments for deposition; while less precise, it is low-cost and versatile. Powder bed fusion uses lasers to sinter powdered materials, and binder jetting employs liquid binders to cement powders—both more common for molds than direct organ models.
Creating an organ model begins with medical image acquisition, often via CT or MRI, followed by segmentation and CAD processing to isolate relevant anatomy. The digital model is converted to printer-compatible formats such as STL or AMF. Depending on material properties and structural complexity, fabrication proceeds via direct printing—producing the model itself—or indirect printing, in which molds or sacrificial structures are printed and then cast with soft materials like silicone or hydrogels.
Direct printing excels at producing complex hollow structures, especially with Polyjet’s multi-material capability. However, flexible materials that truly mimic soft tissue remain limited. Indirect methods, though more labor-intensive, allow use of materials with tailored mechanical properties, making them ideal for simulating tissue feel. Hybrid approaches combine direct printing of rigid components with indirect casting of soft parenchyma, optimizing cost and performance.
Post-processing may involve surface smoothing, coloring, assembly of multi-part models, and sterilization for intraoperative use. Method selection depends on application: visual interaction models prioritize anatomical accuracy over tactile realism and can be produced with low-cost methods; simulation models require both anatomical and biomechanical fidelity; experimental models may simplify geometry but must replicate functional properties for device testing or physiological studies.
Applications span multiple medical domains. In neurosurgery, models of brain vasculature and parenchyma aid in planning delicate interventions, with materials ranging from plaster for skulls to composite hydrogels mimicking brain tissue. Cardiovascular models support congenital heart disease treatment, valve repair simulation, and hemodynamic testing. Thoracic and tracheal models serve in imaging quality evaluation, dosimetry, and surgical rehearsal, with materials tuned for radiodensity or mechanical properties. Abdominal models, notably of kidneys and livers, assist in transplantation planning, robotic surgery training, and vascular reconstruction. Craniomaxillofacial and musculoskeletal models often replicate bone structures for reconstructive surgery planning, prosthesis fitting, and orthopedic procedure rehearsal.
Challenges remain. High costs for equipment, materials, and labor limit widespread adoption. Material limitations hinder perfect simulation of soft tissue mechanics. Accuracy depends on imaging resolution, CAD processing, and printer capability, with errors potentially impacting surgical outcomes. Lack of standardized protocols and large-scale validation studies constrains clinical integration.
Future directions include dynamic models incorporating flexible electronics or soft robotics, enabling simulation of physiological processes. Advances in 4D printing and self-assembly could produce structures that change over time or integrate living cells, bridging toward functional bioartificial organs. Embedding production capabilities within hospitals could reduce transport risks and enable rapid turnaround for urgent cases. Cross-pollination with fields like bioprinting, tissue engineering, and organ-on-chip research promises mutual enhancement, pushing organ models from mere anatomical replicas toward functional surrogates with “spiritual resemblance” to living organs.