Development of Ventral Hernia Repair Curriculum Using the AWSSOM-a Synthetic Abdominal Wall Surgical Skills Operational Model.

INTRODUCTION: Ventral hernia repair cost the U.S. healthcare system nearly 3 billion dollars annually. Surgical repair is a critical competency for residents yet hernia recurrence rates following mesh-based repair range from 0.8% to 24%. Improving surgical techniques using cadavers is often cost-prohibited for many education programs and limited research exists using simulation models with a corresponding hernia repair curriculum in the graduate medical education setting. This pilot project aimed to develop a low cost, easily reproducible novel abdominal wall reconstruction model and pilot-test the ventral hernia repair curriculum to inform further refinement prior to formal evaluation. MATERIAL AND METHODS: This descriptive study pilot-tested the newly refined Abdominal Wall Surgical Skills Operative Model (AWSSOM) simulator for ventral hernia repair with mesh and its corresponding 2-h training curriculum for use at all levels of general surgery graduate medical education. The AWSSOM is a 3D printed synthetic anatomically realistic abdominal wall model consisting of silicone cured layers of skin, fat, rectus abdominis and a posterior rectus sheath fascia, and silicone tubules to simulate lateral neurovascular bundles. The curriculum incorporated didactic content reflecting surgical practice guidelines, hands-on practice, and faculty guidance promoting interactive critical thinking development during task performance. A pre-/post-assessment included a 10-item knowledge test, a 19-item psychomotor assessment, and 4-items confidence survey to examine changes in performance, knowledge, and confidence in competently completing the ventral hernia repair technique. Descriptive statistics were used to report the limited results of six military surgical resident participants and inform further model and curriculum refinement prior to formal evaluation. RESULTS: The five-layer AWSSOM model was manufactured in 65 h at a material cost of $87 per model frame, is reusable model, and secure base. Six surgical residents were recruited; only four completed both pre- and post-tests due to resident schedule conflicts. The average increase in knowledge was 25%, although variable changes in confidence were observed over the four program year participants. A larger sample size and a control group are needed to demonstrate curriculum effectiveness at improving knowledge, performance, and confidence in ventral hernia repair with mesh and better delineate if high scores translate to better operative skills. A key improvement requested by residents was a more secure model base for dissection and performance of the hernia repair. CONCLUSIONS: The novel abdominal wall surgical skills operative model fills an important proof of concept gap in simulation training. It is low cost with the potential to improve cognitive and psychomotor skills, as well as confidence to competently complete ventral hernia repair with mesh in the graduate medical education setting. Prior to formal effectiveness testing, our lessons learned should be addressed in both the model and curriculum. Future studies must include an adequately powered statistical evaluation with a larger sample across all levels of training.

Cranioplasty in the deployed environment: experience for host-country nationals.

OBJECTIVE: Decompressive craniectomy (DC) is the definitive neurosurgical treatment for managing refractory malignant cerebral edema and intracranial hypertension due to combat-related severe traumatic brain injury (TBI). To date, the long-term outcomes and sequelae of this procedure on host-country national (HCN) populations during Operation Iraqi Freedom (Iraq, 2003-2011), Operation Enduring Freedom (Afghanistan, 2001-2014), and Operation Freedom's Sentinel (Afghanistan, 2015-2021) have not been described, specifically the process and results of delayed custom synthetic cranioplasty. The Joint Trauma System's Clinical Practice Guidelines (JTS-CPG) for severe head injury counsels surgeons to discard the cranial osseous explant when treating coalition service members. Ongoing political and healthcare system instabilities often preclude opportunities for delayed cranioplasty by host-country assets. Various surgical options (such as hinge craniectomy) are inadequate in the setting of complicated cranial comminution from blast or missile injuries, severe cerebral edema, grossly contaminated wounds, complex polytrauma, and tissue devitalization. Delayed cranioplasty with a custom synthetic implant is a viable but logistically challenging alternative. In this retrospective review, the authors present the first patient series describing delayed custom synthetic cranioplasty in an HCN population performed during active military conflict. METHODS: Patients were identified through the Joint Trauma System/Theater Medical Data Store, and subgroup analyses were performed to include mechanisms of injury, surgical complications, and clinical outcomes. RESULTS: Twenty-five patients underwent DC between 2012 and 2020 to treat penetrating, blast, and high-energy closed head injuries per JTS-CPG criteria. The average time from injury to surgery was 1.4 days, although 6 patients received delayed care (3-6 days) due to protracted evacuation from local hospitals. Delayed care correlated with an increased rate of intracranial abscess and empyema. The average time to cranioplasty was 134 days due to a lack of robust mechanisms for patient follow-up, tracking, and access to NATO hospitals. HCN patients who recovered from DC demonstrated overall benefit from custom synthetic cranioplasty, although formal statistical analysis was impeded by a lack of long-term follow-up. CONCLUSIONS: This review demonstrates that cranioplasty with a custom synthetic implant is a safe and feasible treatment for vulnerable HCN patients who survive their index DC surgery. This unique paradigm of care highlights the capabilities of deployed neurosurgical healthcare teams working in partnership with the prosthetics laboratory at Walter Reed National Military Medical Center.

Volumetric changes in edentulous alveolar ridge sites utilizing guided bone regeneration and a custom titanium ridge augmentation matrix (CTRAM): a case series study.

BACKGROUND: The purpose of this study was to evaluate the volumetric changes in partially edentulous alveolar ridges augmented with customized titanium ridge augmentation matrices (CTRAM), freeze-dried bone allograft, and a resorbable collagen membrane. METHODS: A pre-surgical cone beam computed tomography (CBCT) scan was obtained for CTRAM design/fabrication and to evaluate pre-surgical ridge dimensions. Ridge augmentation surgery using CTRAM, freeze-dried bone allograft, and a resorbable collagen membrane was performed at each deficient site. Clinical measurements of the area of augmentation were made at the time of CTRAM placement and re-entry, and a 2nd CBCT scan 7 months after graft placement was used for volumetric analysis. Locations of each CTRAM in situ were also compared to their planned positions. Re-entry surgery and implant placement was performed 8 months after CTRAM placement. RESULTS: Nine subjects were treated with CTRAM and freeze-dried bone allograft. Four out of the nine patients enrolled (44.4%) experienced premature CTRAM exposure during healing, and in two of these cases, CTRAM were removed early. Early exposure did not result in total graft failure in any case. Mean volumetric bone gain was 85.5 ± 30.9% of planned augmentation volume (61.3 ± 33.6% in subjects with premature CTRAM exposure vs. 104.9% for subjects without premature exposure, p = 0.03). Mean horizontal augmentation (measured clinically) was 3.02 mm, and vertical augmentation 2.86 mm. Mean surgical positional deviation of CTRAM from the planned location was 1.09 mm. CONCLUSION: The use of CTRAM in conjunction with bone graft and a collagen membrane resulted in vertical and horizontal bone gain suitable for implant placement.

Clinical situations for which 3D printing is considered an appropriate representation or extension of data contained in a medical imaging examination: adult cardiac conditions.

BACKGROUND: Medical 3D printing as a component of care for adults with cardiovascular diseases has expanded dramatically. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (SIG) provides appropriateness criteria for adult cardiac 3D printing indications. METHODS: A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with a number of adult cardiac indications, physiologic, and pathologic processes. Each study was vetted by the authors and graded according to published guidelines. RESULTS: Evidence-based appropriateness guidelines are provided for the following areas in adult cardiac care; cardiac fundamentals, perioperative and intraoperative care, coronary disease and ischemic heart disease, complications of myocardial infarction, valve disease, cardiac arrhythmias, cardiac neoplasm, cardiac transplant and mechanical circulatory support, heart failure, preventative cardiology, cardiac and pericardial disease and cardiac trauma. CONCLUSIONS: Adoption of common clinical standards regarding appropriate use, information and material management, and quality control are needed to ensure the greatest possible clinical benefit from 3D printing. This consensus guideline document, created by the members of the RSNA 3D printing Special Interest Group, will provide a reference for clinical standards of 3D printing for adult cardiac indications.

Early-Onset Dementia in War Veterans: Brain Polypathology and Clinicopathologic Complexity.

The neuropathology associated with cognitive decline in military personnel exposed to traumatic brain injury (TBI) and chronic stress is incompletely understood. Few studies have examined clinicopathologic correlations between phosphorylated-tau neurofibrillary tangles, ß-amyloid neuritic plaques, neuroinflammation, or white matter (WM) lesions, and neuropsychiatric disorders in veterans. We describe clinicopathologic findings in 4 military veterans with early-onset dementia (EOD) who had varying histories of blunt- and blast-TBI, cognitive decline, behavioral abnormalities, post-traumatic stress disorder, suicidal ideation, and suicide. We found that pathologic lesions in these military-EOD cases could not be categorized as classic Alzheimer's disease (AD), chronic traumatic encephalopathy, traumatic axonal injury, or other well-characterized clinicopathologic entities. Rather, we observed a mixture of polypathology with unusual patterns compared with pathologies found in AD or other dementias. Also, ultrahigh resolution ex vivo MRI in 2 of these 4 brains revealed unusual patterns of periventricular WM injury. These findings suggest that military-EOD cases are associated with atypical combinations of brain lesions and distribution rarely seen in nonmilitary populations. Future prospective studies that acquire neuropsychiatric data before and after deployments, as well as genetic and environmental exposure data, are needed to further elucidate clinicopathologic correlations in military-EOD.

CT-Based 3D Printing of the Glenoid Prior to Shoulder Arthroplasty: Bony Morphology and Model Evaluation.

To demonstrate the 3D printed appearance of glenoid morphologies relevant to shoulder replacement surgery and to evaluate the benefits of printed models of the glenoid with regard to surgical planning. A retrospective review of patients referred for shoulder CT was performed, leading to a cohort of nine patients without arthroplasty hardware and exhibiting glenoid changes relevant to shoulder arthroplasty planning. Thin slice CT images were used to create both humerus-subtracted volume renderings of the glenoid, as well as 3D surface models of the glenoid, and 11 printed models were created. Volume renderings, surface models, and printed models were reviewed by a musculoskeletal radiologist for accuracy. Four fellowship-trained orthopaedic surgeons specializing in shoulder surgery reviewed each case individually as follows: First, the source CT images were reviewed, and a score for the clarity of the bony morphologies relevant to shoulder arthroplasty surgery was given. The volume rendering was reviewed, and the clarity was again scored. Finally, the printed model was reviewed, and the clarity again scored. Each printed model was also scored for morphologic complexity, expected usefulness of the printed model, and physical properties of the model. Mann-Whitney-Wilcoxon signed rank tests of the clarity scores were calculated, and the Spearman's ρ correlation coefficient between complexity and usefulness scores was computed. Printed models demonstrated a range of glenoid bony changes including osteophytes, glenoid bone loss, retroversion, and biconcavity. Surgeons rated the glenoid morphology as more clear after review of humerus-subtracted volume rendering, compared with review of the source CT images (p = 0.00903). Clarity was also better with 3D printed models compared to CT (p = 0.00903) and better with 3D printed models compared to humerus-subtracted volume rendering (p = 0. 00879). The expected usefulness of printed models demonstrated a positive correlation with morphologic complexity, with Spearman's ρ 0.73 (p = 0.0108). 3D printing of the glenoid based on pre-operative CT provides a physical representation of patient anatomy. Printed models enabled shoulder surgeons to appreciate glenoid bony morphology more clearly compared to review of CT images or humerus-subtracted volume renderings. These models were more useful as glenoid complexity increased.

Physical Simulation Models in Oral and Maxillofacial Surgery: A New Concept in 3-Dimensional Modeling for Removal of Impacted Third Molars.

A medical-grade computed tomography scan of a mandible was obtained. A DICOM (Digital Imaging and Communications in Medicine) series was exported in 1-mm slices and digitally 3-dimensionally reconstructed to create a stereolithography file. The mandible stereolithography file was digitally manipulated to create sites for simulated placement of third molar teeth and then 3-dimensionally printed in a plastic material. Third molar tooth models were coated in red box wax, simulating a ligament space, and then submerged into the mandible site using laboratory stone. A layer of GI-Mask (Coltene/Whaldent AG, Altstätten, Switzerland) was placed over the impacted third molar site for soft tissue simulation.

Creating patient-specific anatomical models for 3D printing and AR/VR: a supplement for the 2018 Radiological Society of North America (RSNA) hands-on course.

Advanced visualization of medical image data in the form of three-dimensional (3D) printing continues to expand in clinical settings and many hospitals have started to adapt 3D technologies to aid in patient care. It is imperative that radiologists and other medical professionals understand the multi-step process of converting medical imaging data to digital files. To educate health care professionals about the steps required to prepare DICOM data for 3D printing anatomical models, hands-on courses have been delivered at the Radiological Society of North America (RSNA) annual meeting since 2014. In this paper, a supplement to the RSNA 2018 hands-on 3D printing course, we review methods to create cranio-maxillofacial (CMF), orthopedic, and renal cancer models which can be 3D printed or visualized in augmented reality (AR) or virtual reality (VR).

Using 3D models in orthopedic oncology: presenting personalized advantages in surgical planning and intraoperative outcomes.

BACKGROUND: Three Dimensional (3D) printed models can aid in effective pre-operative planning by defining the geometry of tumor mass, bone loss, and nearby vessels to help determine the most accurate osteotomy site and the most appropriate prosthesis, especially in the case of complex acetabular deficiency, resulting in decreased operative time and decreased blood loss. METHODS: Four complicated cases were selected, reconstructed and printed. These 4 cases were divided in 3 groups of 3D printed models. Group 1 consisted of anatomical models with major vascular considerations during surgery. Group 2 consisted of an anatomical model showing a bone defect, which was intended to be used for substantial instrumentation, pre-operatively. Group 3 consisted of an extra-compartmental bone tumor which displayed a deteriorated cortical outline; thus, using CT and MRI fused images to reconstruct the model accurately. An orthopedic surgeon created the 3D models of groups 1 and 2 using standard segmentation techniques. Because group 3 required complex techniques, an engineer assisted during digital model construction. RESULTS: These models helped to guide the orthopedic surgeon in creating a personalized pre-operative plan and a physical simulation. The models proved to be beneficial and assisted with all 4 cases, by decreasing blood loss, operative time and surgical incision length, and helped to select the appropriate acetabular supporting ring in complex acetabular deficiency, pre-operatively. CONCLUSION: Qualitatively, using 3D printing in tumor cases, provides personalized advantages regarding the various characteristics of each skeletal tumor.

Preoperative planning and tracheal stent design in thoracic surgery: a primer for the 2017 Radiological Society of North America (RSNA) hands-on course in 3D printing.

In this work, we provide specific clinical examples to demonstrate basic practical techniques involved in image segmentation, computer-aided design, and 3D printing. A step-by-step approach using United States Food and Drug Administration cleared software is provided to enhance surgical intervention in a patient with a complex superior sulcus tumor. Furthermore, patient-specific device creation is demonstrated using dedicated computer-aided design software. Relevant anatomy for these tasks is obtained from CT Digital Imaging and Communications in Medicine images, leading to the generation of 3D printable files and delivery of these files to a 3D printer.

Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

PURPOSE: To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties. METHODS: A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom were measured and 1 H spectra were acquired to provide insight into the nature of the proton signal. Finally, T2 -weighted imaging was performed during cryoablation of the model. RESULTS: The printed model produced a CT signal of 102 ± 8 Hounsfield unit, and an MR signal roughly 1/3rd that of saline in short echo time/short repetition time GRE MRI (456 ± 36 versus 1526 ± 121 arbitrary signal units). Compared with the model designed from the in vivo CT scan, the printed model differed by 0.13 ± 0.11 mm in CT, and 0.62 ± 0.28 mm in MR. The printed material had T2 ∼32 ms, T2*∼7 ms, T1 ∼193 ms, and a very small diffusion coefficient less than olive oil. MRI monitoring of the cryoablation demonstrated iceball formation similar to an in vivo procedure. CONCLUSION: Current 3D printing technology can be used to print anatomically accurate phantoms that can be imaged by both CT and MRI. Such models can be used to simulate MRI-guided interventions such as cryosurgeries. Future development of the proposed technique can potentially lead to printed models that depict different tissues and anatomical structures with different MR signal characteristics. Magn Reson Med 77:613-622, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

A Craniomaxillofacial Surgical Assistance Workstation for Enhanced Single-Stage Reconstruction Using Patient-Specific Implants.

BACKGROUND: Craniomaxillofacial reconstruction with patient-specific, customized craniofacial implants (CCIs) is ideal for skeletal defects involving areas of aesthetic concern-the non-weight-bearing facial skeleton, temporal skull, and/or frontal-forehead region. Results to date are superior to a variety of "off-the-shelf" materials, but require a protocol computed tomography scan and preexisting defect for computer-assisted design/computer-assisted manufacturing of the CCI. The authors developed a craniomaxillofacial surgical assistance workstation to address these challenges and intraoperatively guide CCI modification for an unknown defect size/shape. METHODS: First, the surgeon designed an oversized CCI based on his/her surgical plan. Intraoperatively, the surgeon resected the bone and digitized the resection using a navigation pointer. Next, a projector displayed the limits of the craniofacial bone defect onto the prefabricated, oversized CCI for the size modification process; the surgeon followed the projected trace to modify the implant. A cadaveric study compared the standard technique (n = 1) to the experimental technique (n = 5) using surgical time and implant fit. RESULTS: The technology reduced the time and effort needed to resize the oversized CCI by an order of magnitude as compared with the standard manual resizing process. Implant fit was consistently better for the computer-assisted case compared with the control by at least 30%, requiring only 5.17 minutes in the computer-assisted cases compared with 35 minutes for the control. CONCLUSION: This approach demonstrated improvement in surgical time and accuracy of CCI-based craniomaxillofacial reconstruction compared with previously reported methods. The craniomaxillofacial surgical assistance workstation will provide craniofacial surgeons a computer-assisted technology for effective and efficient single-stage reconstruction when exact craniofacial bone defect sizes are unknown.

Custom Anatomical 3D Spacer for Temporomandibular Joint Resection and Reconstruction.

Two cases are presented using a two-stage approach and a custom antibiotic spacer placement. Temporomandibular reconstruction can be very demanding and accomplished with a variety of methods in preparation of a total joint and ramus reconstruction with total joint prostheses (TMJ Concepts, Ventura, CA). Three-dimensional reconstructions from diagnostic computed tomography were used to establish a virtually planned resection which included the entire condyle-ramus complex. From these data, digital designs were used to manufacture molds to facilitate intraoperative fabrication of precise custom anatomic spacers from rapidly setting antibiotic-impregnated polymethyl methacrylate. Molds were manufactured using vat polymerization (stereolithography) with a photopolymer in the first case and powder bed fusion (electron beam melting) with Ti6AL4V for the second. Surgical methodology and the use of molds for intraoperative spacer fabrication for each case are discussed.

Medical 3D Printing for the Radiologist.

While use of advanced visualization in radiology is instrumental in diagnosis and communication with referring clinicians, there is an unmet need to render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states. Three-dimensional printed models, already entrenched in the nonmedical sciences, are rapidly being embraced in medicine as well as in the lay community. Incorporating 3D printing from images generated and interpreted by radiologists presents particular challenges, including training, materials and equipment, and guidelines. The overall costs of a 3D printing laboratory must be balanced by the clinical benefits. It is expected that the number of 3D-printed models generated from DICOM images for planning interventions and fabricating implants will grow exponentially. Radiologists should at a minimum be familiar with 3D printing as it relates to their field, including types of 3D printing technologies and materials used to create 3D-printed anatomic models, published applications of models to date, and clinical benefits in radiology. Online supplemental material is available for this article.

3D printer generated thorax phantom with mobile tumor for radiation dosimetry.

This article describes the design, construction, and properties of an anthropomorphic thorax phantom with a moving surrogate tumor. This novel phantom permits detection of dose both inside and outside a moving tumor and within the substitute lung tissue material. A 3D printer generated the thorax shell composed of a chest wall, spinal column, and posterior regions of the phantom. Images of a computed tomography scan of the thorax from a patient with lung cancer provided the template for the 3D printing. The plastic phantom is segmented into two materials representing the muscle and bones, and its geometry closely matches a patient. A surrogate spherical plastic tumor controlled by a 3D linear stage simulates a lung tumor's trajectory during normal breathing. Sawdust emulates the lung tissue in terms of average and distribution in Hounsfield numbers. The sawdust also provides a forgiving medium that permits tumor motion and sandwiching of radiochromic film inside the mobile surrogate plastic tumor for dosimetry. A custom cork casing shields the film and tumor and eliminates film bending during extended scans. The phantom, lung tissue surrogate, and radiochromic film are exposed to a seven field plan based on an ECLIPSE plan for 6 MV photons from a Trilogy machine delivering 230 cGy to the isocenter. The dose collected in a sagittal plane is compared to the calculated plan. Gamma analysis finds 8.8% and 5.5% gamma failure rates for measurements of large amplitude trajectory and static measurements relative to the large amplitude plan, respectively. These particular gamma analysis results were achieved using parameters of 3% dose and 3 mm, for regions receiving doses >150 cGy. The plan assumes a stationary detection grid unlike the moving radiochromic film and tissues. This difference was experimentally observed and motivated calculated dose distributions that incorporated the phase of the tumor periodic motion. These calculations modestly improve agreement between the measured and intended doses.

Optimizing Hybrid Occlusion in Face-Jaw-Teeth Transplantation: A Preliminary Assessment of Real-Time Cephalometry as Part of the Computer-Assisted Planning and Execution Workstation for Craniomaxillofacial Surgery.

BACKGROUND: The aesthetic and functional outcomes surrounding Le Fort-based, face-jaw-teeth transplantation have been suboptimal, often leading to posttransplant class II/III skeletal profiles, palatal defects, and "hybrid malocclusion." Therefore, a novel technology-real-time cephalometry-was developed to provide the surgical team instantaneous, intraoperative knowledge of three-dimensional dentoskeletal parameters. METHODS: Mock face-jaw-teeth transplantation operations were performed on plastic and cadaveric human donor/recipient pairs (n = 2). Preoperatively, cephalometric landmarks were identified on donor/recipient skeletons using segmented computed tomographic scans. The computer-assisted planning and execution workstation tracked the position of the donor face-jaw-teeth segment in real time during the placement/inset onto recipient, reporting pertinent hybrid cephalometric parameters from any movement of donor tissue. The intraoperative data measured through real-time cephalometry were compared to posttransplant measurements for accuracy assessment. In addition, posttransplant cephalometric relationships were compared to planned outcomes to determine face-jaw-teeth transplantation success. RESULTS: Compared with postoperative data, the real-time cephalometry-calculated intraoperative measurement errors were 1.37 ± 1.11 mm and 0.45 ± 0.28 degrees for the plastic skull and 2.99 ± 2.24 mm and 2.63 ± 1.33 degrees for the human cadaver experiments. These results were comparable to the posttransplant relations to planned outcome (human cadaver experiment, 1.39 ± 1.81 mm and 2.18 ± 1.88 degrees; plastic skull experiment, 1.06 ± 0.63 mm and 0.53 ± 0.39 degrees). CONCLUSION: Based on this preliminary testing, real-time cephalometry may be a valuable adjunct for adjusting and measuring "hybrid occlusion" in face-jaw-teeth transplantation and other orthognathic surgical procedures.

Digital capture, design, and manufacturing of a facial prosthesis: Clinical report on a pediatric patient.

A digitally captured, designed, and fabricated facial prosthesis is presented as an alternative to customary maxillofacial prosthodontics fabrication techniques, where a facial moulage and patient cooperation may be difficult.

Computer-assisted single-stage cranioplasty.

Cranioplasty treats and repairs cranial defects with a custom craniofacial implant (CCI). Typically, surgeons know the defect size prior to surgery. Recent efforts consider single-stage cranioplasty-performing the bony resection and fixating the CCI in a single operation. This paper develops a computer-assisted technique to perform single-stage cranioplasty. Intraoperatively, the surgeon traces the bony resection. The outline of the bony cuts is projected on a preoperatively-designed CCI to guide the surgeon during the resizing. A cadaveric case study showed good fit with minimal gaps between the implant and remaining skull. Moreover, the procedure reduced the time to resize the implant by an order of magnitude compared to manual resizing without the use of the computer-assisted technique. This approach represents the next step in quickly, effectively, and robustly performing single-stage CCI to treat craniofacial defects.

The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images.

BACKGROUND: The effects of reduced radiation dose CT for the generation of maxillofacial bone STL models for 3D printing is currently unknown. Images of two full-face transplantation patients scanned with non-contrast 320-detector row CT were reconstructed at fractions of the acquisition radiation dose using noise simulation software and both filtered back-projection (FBP) and Adaptive Iterative Dose Reduction 3D (AIDR3D). The maxillofacial bone STL model segmented with thresholding from AIDR3D images at 100 % dose was considered the reference. For all other dose/reconstruction method combinations, a "residual STL volume" was calculated as the topologic subtraction of the STL model derived from that dataset from the reference and correlated to radiation dose. RESULTS: The residual volume decreased with increasing radiation dose and was lower for AIDR3D compared to FBP reconstructions at all doses. As a fraction of the reference STL volume, the residual volume decreased from 2.9 % (20 % dose) to 1.4 % (50 % dose) in patient 1, and from 4.1 % to 1.9 %, respectively in patient 2 for AIDR3D reconstructions. For FBP reconstructions it decreased from 3.3 % (20 % dose) to 1.0 % (100 % dose) in patient 1, and from 5.5 % to 1.6 %, respectively in patient 2. Its morphology resembled a thin shell on the osseous surface with average thickness <0.1 mm. CONCLUSION: The residual volume, a topological difference metric of STL models of tissue depicted in DICOM images supports that reduction of CT dose by up to 80 % of the clinical acquisition in conjunction with iterative reconstruction yields maxillofacial bone models accurate for 3D printing.