An Assembled Prototype Multimaterial Three-Dimensional-Printed Model of the Neck for Computed Tomography- and Ultrasound-Guided Interventional Procedures

Creation and Validation of a Novel 3-Dimensional Pediatric Hip Ultrasound Model

OBJECTIVES

The aim of this study was to create and validate a 3-dimensional (3D) ultrasound model with normal and abnormal pediatric hip joint anatomy that is comparable to a pediatric hip joint in appearance and anatomy and replicates sonographic characteristics of a pediatric hip joint.

METHODS

A 3D rendering of the bone and soft tissue was created from a computed tomography pelvic scan of a pediatric patient. This rendering was modified to include a unilateral joint effusion. The bone was 3D printed with a photopolymer plastic, whereas the soft tissue was cast with a silicone mixture in a 3D-printed mold. The effusion was simulated by injecting saline into the soft tissue cavity surrounding the bone. The ultrasound model was validated by pediatric point-of-care ultrasonographers at an international pediatric ultrasound conference.

RESULTS

A pediatric hip ultrasound model was developed that simulates both normal and abnormal pediatric hip joint anatomy, each with an appropriately sized, measurable joint effusion. Validation by pediatric point-of-care ultrasonographers showed that the key aspects of a normal pediatric hip joint (femoral physis, sloped femoral neck, and adequate soft tissue) with an identifiable and measurable effusion were included in the ultrasound model.

CONCLUSIONS

In this study, we successfully created a cost-effective, reusable, and reproducible 3D pediatric hip ultrasound model. The majority of pediatric point-of-care ultrasonographers who evaluated the model agreed that this model is comparable to a pediatric patient for the purpose of teaching ultrasound skills and joint space measurement.

Imaging Properties of Additive Manufactured (3D Printed) Materials for Potential Use for Phantom Models

Over the last few decades, there has been growing interest in the application of additive manufacturing (AM) or 3D printing for medical research and clinical application. Imaging phantoms offer clear benefits in the way of training, planning, and quality assurance, but the model's availability per catalog tend to be suited for general testing purposes only. AM, on the contrary, offers flexibility to clinicians by enabling custom-built phantoms based on specific interests or even individual patient needs. This study aims to quantify the radiographic properties (ultrasound, magnetic resonance imaging, and computed tomography) of common additive manufacturing technologies and to discuss potential opportunities to fabricate imaging phantoms. Test phantoms were composed of samples from the three most common AM styles, namely PolyJet, fused deposition modeling (FDM), and stereolithography (SLA). Test imaging of the phantoms was performed on ultrasound, MRI, and CT and reviewed and evaluated with radiology software. The ultrasound images showed clearly defined upper and lower edges of the material but did not demonstrate distinct differences in internal echogenicity between materials. The MR scans revealed a distinct signal intensity difference between the model (17 grayscale value) and the printer support (778 grayscale value). Finally, the CT images showed a slight variation between the plastic (82 HU) and rubber (145 HU) materials. The radiographic properties of AM offer a clear opportunity to create basic two- or three-material phantoms. These would be high-accuracy and cost-effective models. Although the materials currently available are not suitable for complex multi-material applications as realistic as true human anatomy, one can easily foresee the development of new materials with broader density in the near future.

3D printing in critical care: a narrative review

BACKGROUND

3D printing (3DP) has gained interest in many fields of medicine including cardiology, plastic surgery, and urology due to its versatility, convenience, and low cost. However, critical care medicine, which is abundant with high acuity yet infrequent procedures, has not embraced 3DP as much as others. The discrepancy between the possible training or therapeutic uses of 3DP in critical care and what is currently utilized in other fields needs to be addressed.

OBJECTIVE

This narrative literature review describes the uses of 3DP in critical care that have been documented. It also discusses possible future directions based on recent technological advances.

METHODS

A literature search on PubMed was performed using keywords and Mesh terms for 3DP, critical care, and critical care skills.

RESULTS

Our search found that 3DP use in critical care fell under the major categories of medical education (23 papers), patient care (4 papers) and clinical equipment modification (4 papers). Medical education showed the use of 3DP in bronchoscopy, congenital heart disease, cricothyroidotomy, and medical imaging. On the other hand, patient care papers discussed 3DP use in wound care, personalized splints, and patient monitoring. Clinical equipment modification papers reported the use of 3DP to modify stethoscopes and laryngoscopes to improve their performance. Notably, we found that only 13 of the 31 papers were directly produced or studied by critical care physicians.

CONCLUSION

The papers discussed provide examples of the possible utilities of 3DP in critical care. The relative scarcity of papers produced by critical care physicians may indicate barriers to 3DP implementation. However, technological advances such as point-of-care 3DP tools and the increased demand for 3DP during the recent COVID-19 pandemic may change 3DP implementation across the critical care field.

Simulating Tissues with 3D-Printed and Castable Materials

Manufacturing technologies continue to be developed and utilized in medical prototyping, simulations, and imaging phantom production. For radiologic image-guided simulation and instruction, models should ideally have similar imaging characteristics and physical properties to the tissues they replicate. Due to the proliferation of different printing technologies and materials, there is a diverse and broad range of approaches and materials to consider before embarking on a project. Although many printed materials' biomechanical parameters have been reported, no manufacturer includes medical imaging properties that are essential for realistic phantom production. We hypothesize that there are now ample materials available to create high-fidelity imaging anthropomorphic phantoms using 3D printing and casting of common commercially available materials. A material database of radiological, physical, manufacturing, and economic properties for 29 castable and 68 printable materials was generated from samples fabricated by the authors or obtained from the manufacturer and scanned with CT at multiple tube voltages. This is the largest study assessing multiple different parameters associated with 3D printing to date. These data are being made freely available on GitHub, thus affording medical simulation experts access to a database of relevant imaging characteristics of common printable and castable materials. Full data available at: https://github.com/nmcross/Material-Imaging-Characteristics .

A prototype assembled 3D-printed phantom of the glenohumeral joint for fluoroscopic-guided shoulder arthrography

PURPOSE

To describe the methodology of constructing a three-dimensional (3D) printed model of the glenohumeral joint, to serve as an interventional phantom for fluoroscopy-guided shoulder arthrography training.

MATERIALS AND METHODS

The osseous structures, intra-articular space and skin surface of the shoulder were digitally extracted as separate 3D meshes from a normal CT arthrogram of the shoulder, using commercially available software. The osseous structures were 3D-printed in gypsum, a fluoroscopically radiopaque mineral, using binder jet technology. The joint capsule was 3D printed with rubber-like TangoPlus material, using PolyJet technology. The capsule was secured to the humeral head and glenoid to create a sealed intra-articular space. A polyamide mold of the skin was printed using selective laser sintering. The joint was stabilized inside the mold, and the surrounding soft tissues were cast in silicone of varying densities. Fluoroscopically-guided shoulder arthrography was performed using anterior, posterior, and rotator interval approaches. CT arthrographic imaging of the phantom was also performed.

RESULTS

A life-size phantom of the glenohumeral joint was constructed. The radiopaque osseous structures replicated in-vivo osseous corticomedullary differentiation, with dense cortical bone and less dense medullary cancellous bone. The glenoid labrum was successfully integrated into the printed capsule, and visualized on CT arthrography. The phantom was repeatedly used to perform shoulder arthrography using all three conventional approaches, and simulated the in vivo challenges of needle guidance.

CONCLUSIONS

3D printing of a complex capsule, such as the glenohumeral joint, is possible with this technique. Such a model can serve as a valuable training tool.