Fabrication of Low-Cost Patient-Specific Vascular Models for Particle Image Velocimetry.

PURPOSE: Particle image velocimetry (PIV), an in vitro experimentation technique that optically measures velocity components to analyze fluid velocity fields, has become increasingly popular to study flow dynamics in various vascular territories. However, it can be difficult and expensive to create patient-specific clear models for PIV due to the importance of refractive index matching of the model and the fluid. We aim to implement and test the use of poly-vinyl alcohol (PVA) in a lost-core casting technique to create low-cost, patient-specific models for PIV. METHODS: Anonymized patient vascular anatomies were segmented and processed in Mimics/3Matic to create patient-specific cores from 3D digital subtraction angiographies. The cores were 3D-printed with PVA and post-processed with a 80:20 water:glue mixture to smooth the surface. Two silicones, Sylgard 184 and Solaris, were used to encapsulate the model and the PVA core was dissolved using warm water. Computed tomography scans were used to evaluate geometric accuracy using circumferences and surface differences in the model. RESULTS: Mean geometric differences in circumference along the inlet centerline and the mean surface difference in the aneurysm between the final Silicone Model and the desired STL Print geometry were statistically insignificant (0.6 mm, 95% CI [- 1.4, 2.8] and 0.3 mm 95% CI [- 0.1, 0.7], respectively). Particle illumination within each model was successful. The cost of one 10 cm × 10 cm × 5 cm model was $69. CONCLUSION: This technique was successful to implement and test the use of PVA in a lost-core casting technique to create low-cost, patient-specific in vitro models for PIV experimentation.

A 3-Dimensional-Printed Short-Segment Template Prototype for Mandibular Fracture Repair.

IMPORTANCE: After reduction of complex mandibular fractures, contouring of the fracture plates to fixate the reduced mandibular segments can be time-consuming. OBJECTIVE: To explore the potential application of a 3-dimensional (3-D)-printed short-segment mandibular template in the management of complex mandibular fractures. DESIGN, SETTING, AND PARTICIPANTS: A feasibility study was performed at a tertiary academic center using maxillofacial computed tomography data of 3 patients with comminuted mandibular fractures who required preoperative planning with a perfected complete mandible model. INTERVENTIONS: Thresholding, segmentation, and realignment of the fractured mandible were performed based on computed tomography data. Each reduced mandible design was divided to create 3-D templates for 6 fracture sites: right and left angle, body, and symphyseal/parasymphyseal. Sessions were conducted with junior otolaryngology and plastic surgery residents, during which mandibular fracture plates were contoured in a "preoperative" setting against the 3-D-printed short-segment templates, and an "intraoperative" setting against the previously manufactured, complete mandible model. The previously manufactured, complete model served as a surrogate for the intraoperative mandible with the fracture site reduced. MAIN OUTCOMES AND MEASURES: The time for 3-D template printing, the "preoperative" (measure of the time consumed preoperatively), and "intraoperative" (measure of the time saved intraoperatively) times were recorded. Comparisons were made for cost estimates between a complete model and the 3-D-printed short-segment template. The operating room charge equivalent of the intraoperative time was also calculated. RESULTS: Of the 3 patients whose data were used, 1 was a teenager and 2 were young adults. The total time for 3-D modeling and printing per short-segment template was less than 3 hours. The median (range) intraoperative time saved by precontouring the fracture plates was 7 (1-14), 5 (1-30), and 7 (2-15) minutes, and the operating room charge equivalents were $350.35 ($50.05-$700.70), $250 ($50.05-$1501.50), and $350.35 ($100.10-$750.75) for the angle, body, and symphyseal/parasymphyseal segments, respectively. The total cost for a single 3-D-printed template was less than $20, while that for a perfected complete model was approximately $2200. CONCLUSIONS AND RELEVANCE: We demonstrate that patient- and site-specific 3-D-printed short-segment templates can be created within the timeframe required for mandibular fracture repair. These novel 3-D-printed templates also demonstrate cost efficiency in the preoperative planning for complex mandibular fracture management compared with perfected models and facilitate plate contouring in a similar fashion. Estimation of reduced operative room cost and time with the application of these short-segment templates warrants studies in actual patient care. LEVEL OF EVIDENCE: NA.

Three-dimensional printing in cardiology: Current applications and future challenges.

Three-dimensional (3D) printing has attracted a huge interest in recent years. Broadly speaking, it refers to the technology which converts a predesigned virtual model to a touchable object. In clinical medicine, it usually converts a series of two-dimensional medical images acquired through computed tomography, magnetic resonance imaging or 3D echocardiography into a physical model. Medical 3D printing consists of three main steps: image acquisition, virtual reconstruction and 3D manufacturing. It is a promising tool for preoperative evaluation, medical device design, hemodynamic simulation and medical education, it is also likely to reduce operative risk and increase operative success. However, the most relevant studies are case reports or series which are underpowered in testing its actual effect on patient outcomes. The decision of making a 3D cardiac model may seem arbitrary since it is mostly based on a cardiologist's perceived difficulty in performing an interventional procedure. A uniform consensus is urgently necessary to standardize the key steps of 3D printing from imaging acquisition to final production. In the future, more clinical trials of rigorous design are possible to further validate the effect of 3D printing on the treatment of cardiovascular diseases. (Cardiol J 2017; 24, 4: 436-444).

The indirect cost of Patient-Specific Instruments.

PURPOSE: To calculate the indirect costs of Patient Specific Instruments (PSI) based on an opportunity cost, cost of efforts and a supply chain cost model to compare PSI for value with conventional total knee arthroplasty (TKA). METHODS: In 81 patients the total (direct+indirect) cost of PSI-assisted TKA was compared with conventional TKA. Surgical times and coronal mechanical alignment were measured to evaluate the effectiveness of the PSI system. RESULTS: Indirect costs (459 euro) make up 40% of the total cost that can run up to 1142 euro for a patient operated with PSI guides. No difference in surgical times or coronal alignment was observed in between both groups. CONCLUSION: Considering the total cost of PSI no value was found for the use of PSI in primary TKA as measured by surgical times or for obtaining a neutral mechanical axis in the coronal plane.