Computer-aided 3-D simulation and prediction of craniofacial surgery: a new approach

Quantitative Assessment of the Restoration of Original Anatomy after 3D Virtual Reduction of Long Bone Fractures

Background: The purpose of this study was to demonstrate the usefulness of 3D image-based virtual reduction by validating the evaluation criteria according to guidelines suggested by the AO Surgery Reference. Methods: For this experiment, 19 intact radial ORTHObones (ORTHObones radius, 3B Scientific, Germany, Hamburg) without any fractures were prepared. All ORTHObones with six cortical marking holes (three points on the distal part and three points on the proximal part) were scanned using a CT scanner twice (before/after intentional fracture of the ORTHObone). After the virtual reduction of all 19 ORTHObones, accuracy evaluations using the four criteria (length variation, apposition variation, alignment variation, Rotation Variation) suggested in the AO Surgery Reference were performed. Results: The mean (M) length variation was 0.42 mm, with 0.01 mm standard deviation (SD). The M apposition variation was 0.48 mm, with 0.40 mm SD. The M AP angulation variation (for alignment variation) was 3.24°, with 2.95° SD. The M lateral angulation variation (for alignment variation) was 0.09°, with 0.13° SD. The M angle of axial rotation was 1.27° with SD: 1.19°. Conclusions: The method of accuracy evaluation used in this study can be helpful in establishing a reliable plan.

Preoperative imaging patterns and intracranial findings in single-suture craniosynostosis: a study from the Synostosis Research Group

OBJECTIVE

The diagnosis of single-suture craniosynostosis can be made by physical examination, but the use of confirmatory imaging is common practice. The authors sought to investigate preoperative imaging use and to describe intracranial findings in children with single-suture synostosis from a large, prospective multicenter cohort.

METHODS

In this study from the Synostosis Research Group, the study population included children with clinically diagnosed single-suture synostosis between March 1, 2017, and October 31, 2020, at 5 institutions. The primary analysis correlated the clinical diagnosis and imaging diagnosis; secondary outcomes included intracranial findings by pathological suture type.

RESULTS

A total of 403 children (67% male) were identified with single-suture synostosis. Sagittal (n = 267), metopic (n = 77), coronal (n = 52), and lambdoid (n = 7) synostoses were reported; the most common presentation was abnormal head shape (97%), followed by a palpable or visible ridge (37%). Preoperative cranial imaging was performed in 90% of children; findings on 97% of these imaging studies matched the initial clinical diagnosis. Thirty-one additional fused sutures were identified in 18 children (5%) that differed from the clinical diagnosis. The most commonly used imaging modality by far was CT (n = 360), followed by radiography (n = 9) and MRI (n = 7). Most preoperative imaging was ordered as part of a protocolized pathway (67%); some images were obtained as a result of a nondiagnostic clinical examination (5.2%). Of the 360 patients who had CT imaging, 150 underwent total cranial vault surgery and 210 underwent strip craniectomy. The imaging findings influenced the surgical treatment 0.95% of the time. Among the 24% of children with additional (nonsynostosis) abnormal findings on CT, only 3.5% required further monitoring.

CONCLUSIONS

The authors found that a clinical diagnosis of single-suture craniosynostosis and the findings on CT were the same with rare exceptions. CT imaging very rarely altered the surgical treatment of children with single-suture synostosis.

A Novel Precise Optical Navigation System for Craniomaxillofacial Surgery Registered With an Occlusal Splint

BACKGROUND

An augmented reality tool allows visual tracking of real anatomical structures and superimposing virtual images, so it can be used for navigation of important structures during surgery.

OBJECTIVES

The authors have developed a new occlusal splint-based optical navigation system for craniomaxillofacial surgery. In this study, the authors aim to measure the accuracy of the system and further analyze the main factors influencing precision.

METHODS

Ten beagle dogs were selected and a three-dimensional model was established through computed tomography scanning, dental model making, and laser scanning, and then registration was performed according to the tooth marking points. The bilateral mandibular osteotomy was performed on Beagle dogs under navigation system based on the occlusal splint. The left side was taken to compare the deviation between the preoperative plan and the surgical results, and the accuracy of distance and angle and the stability of the system were analyzed.

RESULTS

The average position deviation between the preoperative design and intraoperative navigation was: 0.01 ± 0.73 mm on the lateral height of the mandibular ramus, 0.26 ± 0.57 mm on the inner height of the mandibular ramus, and 0.20 ± 0.51 mm on the osteotomy length. The average angle deviation is 0.94° ± 1.38° on the angle between the mandibular osteotomy plane and ramus plane and 0.66° ± 0.97° on the angle of the retained mandibular angle. And most of the data showed good consistency.

CONCLUSIONS

In summary, the accuracy of the system can meet clinical requirements and can be used as a useful tool to improve the accuracy of craniomaxillofacial surgery.

Watertight 2-manifold 3D bone surface model reconstruction from CT images based on visual hyper-spherical mapping

This paper proposes a general algorithm to reconstruct watertight 2-manifold 3D bone surface model from CT images based on visual hyper-spherical mapping. The reconstruction algorithm includes three main steps: two-step thresholding, initial watertight surface reconstruction and shape optimization. Firstly, volume sampling points of the target bone with given narrower threshold range are extracted by thresholding with combination of 3D morphology operation. Secondly, visible points near the bone's outer surface are extracted from its corresponding volume sampling points by hyper-spherical projection mapping method. Thirdly, implicit surface reconstruction algorithm is employed on the extracted visible surface points to obtain an initial watertight 3D bone surface model which is used as the deformation model in the following accurate bone surface model generation stage. Finally, the initial surface model is deformed according to the segmentation data with wider threshold range under given constraints in order to achieve an accurate watertight 3D bone surface model. Experiment and comparison results show that the proposed algorithm can reconstruct watertight 3D bone surface model from CT images, and local details of the bone surface can be restored accurately for the cases used in this paper.

The Use of Finite Element Method Analysis for Modeling Different Osteotomy Patterns and Biomechanical Analysis of Craniosynostosis Correction

PURPOSE

Several post-processing algorithms for 3D visualization of the skull in craniosynostosis with their specific advantages and disadvantages have been already described. The Finite Element Method (FEM) described herein can also be used to evaluate the efficacy of the cutting patterns with respect to an increase in the projected surface area under assumed uniform loading of the manipulated and cut bone segments.

METHODS

The FEM analysis was performed. Starting with the classic cranial osteotomies for bifrontal craniotomy and orbital bandeau a virtually mirroring of the unaffected triangular shaped frontal bone was performed to achieve a cup-shaped sphere of constant thickness of 2.5 mm with a radius of 65 mm. Mechanical properties required for the analysis were Young's modulus of 340 MPa and Poisson's ratio of 0.22. Four different cutting patterns from straight to curved geometries have been projected onto the inner surface of the sphere with a cutting depth set to 2/3rds of the shell thickness. The necessary force for the deformation, the resulting tensions and the volume loss due to the osteotomy pattern were measured.

RESULTS

Better outcomes were realized with pattern D. The necessary force was 73.6% smaller than the control group with 66N. Best stress distribution was achieved. Curved cutting patterns led to the highest peak of stress and thus to a higher risk of fracture. Straight bone cuts parallel to the corners or to the thighs of the sphere provided a better distribution of stresses with a small area with high stress. Additionally, also with pattern D a surface increase of 20.7% higher than reference was registered.

CONCLUSION

As a proof of concept for different cutting geometries for skull molding in the correction of craniosynostosis, this computational model shows that depending of the cutting pattern different biomechanical behavior is achieved.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

Reconstruction of the maxilla using a fibula graft and virtual planning techniques

Use of a vascularised free fibula flap has been a popular method of osseous reconstruction because of its adequate length and acceptance of dental implants. In this article we describe a case of maxillary reconstruction in which virtual planning techniques and rapid prototyping were used to insert a microvascular osteomyocutaneous fibula graft, Medpor implant, and immediate dental implants.

3D stereophotogrammetric analysis of operative effects after broad median craniectomy in premature sagittal craniosynostosis

INTRODUCTION

There is ongoing discussion on the diagnostic methods, the need of surgical treatment, and the surgical strategies for premature craniosynostosis.

MATERIALS AND METHODS

This study examined the operative procedure of a standardized broad median craniectomy, active tilting of the forehead, and bitemporal greenstick fracturing in children with premature sagittal craniosynostosis. To objectively analyze the direct surgical results, we used a 3D stereophotogrammetry scanner, as previously described.

RESULTS

A 3D analysis showed a significant increase in the width, cranial index (CI), head and coronal circumferences, intracranial volume, and cranial base width after surgery. Head length was the only parameter that demonstrated a significant decrease postoperatively. Asymmetry and the 30° diagonal difference showed no significant changes.

CONCLUSION

3D stereophotogrammetry is a reliable and valuable tool with no side effects. It demonstrated that the extended surgical procedure achieves good postoperative results with a reduced length and increased width and, therefore, an improved CI. Additionally, the total intracranial volume was significantly increased after surgery.

Virtual planning for craniomaxillofacial surgery--7 years of experience

Contemporary computer-assisted surgery systems more and more allow for virtual simulation of even complex surgical procedures with increasingly realistic predictions. Preoperative workflows are established and different commercially software solutions are available. Potential and feasibility of virtual craniomaxillofacial surgery as an additional planning tool was assessed retrospectively by comparing predictions and surgical results. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacial disorders (n = 8) in addition to standard surgical planning based on patient specific 3d-models. Virtual planning could be performed for all levels of the craniomaxillofacial framework within a reasonable preoperative workflow. Simulation of even complex skeletal displacements corresponded well with the real surgical result and soft tissue simulation proved to be helpful. In combination with classic 3d-models showing the underlying skeletal pathology virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional work and expenses may be justified by increased possibilities of visualisation, information, instruction and documentation in selected craniomaxillofacial procedures.

Pediatric Craniofacial Surgery: A Review for the Multidisciplinary Team

Pediatric craniofacial surgery is a specialty that grew dramatically in the 20th century and continues to evolve today. Out of the efforts to correct facial deformities encountered during World War II, the techniques of modern craniofacial surgery developed. An analysis of the relevant literature allowed the authors to explore this historical progression.

Current advances in technology, tissue engineering, and molecular biology have further refined pediatric craniofacial surgery. The development of distraction osteogenesis and the progressive study of craniosynostosis provide remarkable examples of this momentum. The growing study of genetics, biotechnology, the influence of growth factors, and stem cell research provide additional avenues of innovation for the future. The following article is intended to reveal a greater understanding of pediatric craniofacial surgery by examining the past, present, and possible future direction. It is intended both for the surgeon, as well as for the nonsurgical individual specialists vital to the multidisciplinary craniofacial team.

Craniofacial distractor applicator

Craniofacial distraction can be planned using cephalograms, computed tomography, medical models, and other forms of anatomic data. However, it is often difficult to translate this plan to the patient. Specifically, it is difficult to obtain true parallel placement of bilateral midface and mandibular distractors. Intraoperative translation of preoperatively determined vectors is also troublesome. One method of application uses computed tomography data with radiofrequency triangulation technology in a specially equipped room. This helps with the issue of placement on the patient but does not establish parallelism. We have developed a simple-to-use craniofacial application stabilization device that allows equal placement of bilateral distractors and measurement of distraction vectors. The applicator measures 20 cm in length in its open configuration. The terminal portion of the device has a coupler that holds the distractor during placement. The device is hinged in 3 points so that it can be easily folded into a compact and autoclavable device (7 x 3 cm). The hinges allow equal placement of bilateral distractors. Each hinge can be calibrated to determine the vector of distraction and confirm equal application. Lastly, the stabilizer can be fixed to nasion with a Steinmann pin for reference, allowing intraoperative translation of distraction vectors. We demonstrated on skull models that the craniofacial distractor applicator can accurately allow parallel intraoperative placement of craniofacial distractors. We demonstrated simultaneous placement of the distractors allowing a more precise determination of end points.

Reverse engineering techniques for cranioplasty: a case study

This paper presents rapid prototyping and reverse engineering techniques applied to create an implant for the surgical reconstruction of a large cranial defect. A series of computed tomography (CT) images was obtained and purpose built software was used to extract the cranial geometry in a point cloud. The point cloud produced was used for: (a) the creation of a stereolithographic (STL) physical model for direct assessment of the cranial defect; and (b) the creation of a 3D mould model for the fabrication of the patient-specific implant.

Computer-aided design for three-dimensional titanium mesh used for repairing skull base bone defect in pediatric neurofibromatosis type 1. A novel approach combining biomodeling and neuronavigation

BACKGROUND

Sphenoid dysplasia is a distinctive but uncommon manifestation of neurofibromatosis type 1. The absence of the sphenoid greater wing allows the temporal lobe to prolapse into the orbit resulting in temporal base encephalocele and pulsating exophthalmos. Surgical procedures are aimed at preserving vision and improving ocular movement and cosmesis. This defect can be closed using bone grafts or titanium mesh. However, the results of this procedure are often unsustainable due to bone graft resorption and graft displacement.

METHODS

In this report, we describe a novel surgical technique, combining computer-aided design, stereolithography and neuronavigation to repair a temporal base skull defect in a 16-year-old female patient with neurofibromatosis type 1. A three-dimensional model of the skull base defect and a template for graft were first constructed according to the image data, then transferred to a real-size stereolithographic biomodel using a rapid prototyping technique.

RESULTS

The final graft of titanium mesh, which was intraoperatively fabricated based on the biomodel, was precisely orientated and securely fixed to the surrounding bone under frameless navigation. Long-term follow-up result proved this repair to be effective and durable.

CONCLUSION

The approach combining computer-aided design, stereolithography and surgical navigation could help managing the complex lesions in the skull base and craniofacial area requiring rigid reconstruction.

3D visualization and simulation of frontoorbital advancement in metopic synostosis

OBJECTIVES

Current multislice computed tomography (CT) technology can be used for diagnosis and surgical planning applying computer-assisted three-dimensional (3D) visualization and surgical simulation. The usefulness of a technique for surgical simulation of frontoorbital advancement is demonstrated here in a child with metopic synostosis.

MATERIALS AND METHODS

Postprocessing of multi-slice CT data was performed using the software 3D slicer. 3D models were created for the purpose of surgical simulation. These allow planning the course of the osteotomies and individually placing the different bony fragments by an assigned matrix to simulate the surgical result. Photo documentation was obtained before and after surgery. Surgical simulation of the procedure allowed determination of the osteotomy course and assessment of the positioning of the individual bony fragments.

CONCLUSIONS

Computer-assisted postprocessing and simulation is a useful tool for surgical planning in craniosynostosis surgery. The time-effort for segmentation currently limits the routine clinical use of this technique.

A new system for computer-aided preoperative planning and intraoperative navigation during corrective jaw surgery

A new system for computer-aided corrective surgery of the jaws has been developed and introduced clinically. It combines three-dimensional (3-D) surgical planning with conventional dental occlusion planning. The developed software allows simulating the surgical correction on virtual 3-D models of the facial skeleton generated from computed tomography (CT) scans. Surgery planning and simulation include dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and segment repositioning. By coupling the software with a tracking system and with the help of a special registration procedure, we are able to acquire dental occlusion plans from plaster model mounts. Upon completion of the surgical plan, the setup is used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with the help of a display showing jaw positions and 3-D positioning guides updated in real time during the surgical procedure. The proposed approach offers the advantages of 3-D visualization and tracking technology without sacrificing long-proven cast-based techniques for dental occlusion evaluation. The system has been applied on one patient. Throughout this procedure, we have experienced improved assessment of pathology, increased precision, and augmented control.

Computer-Assisted Surgical Treatment of Orbitozygomatic Fractures

Orbitozygomatic fractures pertain to the most common injuries in craniofacial trauma patients. Accurate fracture reduction is of high importance for a successful outcome. This pilot study was performed to assess the potential benefit of surgical navigation to aid in orbitozygomatic fracture reduction. A non-comparative series of five consecutive patients with severely displaced orbitozygomatic fractures was treated using the guidance of computed tomography (CT)-based surgical navigation. Using a previously developed software platform, the fracture was reduced virtually by a three-dimensional shifting of the orbitozygomatic complex within the patient's preoperative multimodal CT data set. This treatment plan was transferred to a navigation system. Fracture reduction was performed according to the treatment plan using surgical navigation. Intraoperative control of fracture reduction by comparing the real with the virtual bone position using surgical navigation showed up as a helpful tool. Accurate treatment planning and immediate evaluation of craniofacial surgery outcome are the benefits of the new approach demonstrated. A major drawback of the presented approach is a high consumption of human and financial resources. A larger clinical series with long-term follow-up will be needed to determine reproducibility and cost-effectiveness. In addition to bone repositioning, a future application may include simulation of craniofacial osteotomies.

Rapid prototyping as a tool for diagnosis and treatment planning for maxillary canine impaction

Treating an impacted maxillary canine requires identifying its exact position; this can pose a challenge to both orthodontists and oral surgeons. The purpose of this article is to present a new method for diagnosis and treatment planning of maxillary canine impaction by using computed tomography combined with rapid prototyping. Computed tomography image files of a patient with tooth 13 impaction were edited to produce, by means of rapid prototyping, an anatomic model of the maxillary teeth and a single attachment model that was later used to fabricate a metal attachment to be bonded to the impacted tooth. The dental model was used in the diagnosis and orthodontic treatment planning, and to communicate with the patient and his parents. The model showed the exact anatomical relationship between the impacted tooth and the other teeth; it was the main aid in intraoperative navigation during surgery to expose the tooth. The metal attachment built from the prototype was bonded to tooth 13 during surgery. Prototyping could become a new tool for fabricating brackets and other precision accessories for specific needs. Dental models made with rapid prototyping could become the diagnostic procedure of choice for evaluating impacted maxillary canines.

Piezoelectric osteotomies in craniofacial procedures: a series of 15 pediatric patients. Technical note

Frontoorbital advancement has become a standard method both to increase intracranial volume and to improve facial appearance in patients with syndromal or nonsyndromal craniosynostosis. Relevant complications of this procedure include severe hemorrhage and trauma to intracranial, orbital, or facial soft tissues, which mostly arise during the process of bone exposure or osteotomy. To minimize the risk of soft tissue injury and to increase the precision of the osteotomy, the authors applied a piezoelectric osteotome for frontoorbital advancement in 15 patients with craniosynostosis seen consecutively (mean age 11.3 months). They demonstrated that this new device can cut cranial bones using ultrasonic microvibrations created by piezoelectric effects. In all patients, this instrument allowed an easy and precise handling during osteotomy with a reduced amount of trauma to adjacent soft tissues and with no complications. Although the time required for piezoelectric osteotomy was longer compared with conventional techniques, the total operation time remained approximately the same because the preparation requirements are less extensive. Postoperatively, bone regeneration was uneventful. The authors conclude that this new technique of piezoelectric osteotomy is a valuable tool for craniofacial reconstructive surgery in pediatric patients.

Finite-element-method (FEM) model generation of time-resolved 3D echocardiographic geometry data for mitral-valve volumetry

Introduction

Mitral Valve (MV) 3D structural data can be easily obtained using standard transesophageal echocardiography (TEE) devices but quantitative pre- and intraoperative volume analysis of the MV is presently not feasible in the cardiac operation room (OR). Finite element method (FEM) modelling is necessary to carry out precise and individual volume analysis and in the future will form the basis for simulation of cardiac interventions.

Method

With the present retrospective pilot study we describe a method to transfer MV geometric data to 3D Slicer 2 software, an open-source medical visualization and analysis software package. A newly developed software program (ROIExtract) allowed selection of a region-of-interest (ROI) from the TEE data and data transformation for use in 3D Slicer. FEM models for quantitative volumetric studies were generated.

Results

ROI selection permitted the visualization and calculations required to create a sequence of volume rendered models of the MV allowing time-based visualization of regional deformation. Quantitation of tissue volume, especially important in myxomatous degeneration can be carried out. Rendered volumes are shown in 3D as well as in time-resolved 4D animations.

Conclusion

The visualization of the segmented MV may significantly enhance clinical interpretation. This method provides an infrastructure for the study of image guided assessment of clinical findings and surgical planning. For complete pre- and intraoperative 3D MV FEM analysis, three input elements are necessary: 1. time-gated, reality-based structural information, 2. continuous MV pressure and 3. instantaneous tissue elastance. The present process makes the first of these elements available.

Volume defect analysis is essential to fully understand functional and geometrical dysfunction of but not limited to the valve. 3D Slicer was used for semi-automatic valve border detection and volume-rendering of clinical 3D echocardiographic data. FEM based models were also calculated.

Method

A Philips/HP Sonos 5500 ultrasound device stores volume data as time-resolved 4D volume data sets. Data sets for three subjects were used. Since 3D Slicer does not process time-resolved data sets, we employed a standard movie maker to animate the individual time-based models and visualizations.

Calculation time and model size were minimized.

Pressures were also easily available. We speculate that calculation of instantaneous elastance may be possible using instantaneous pressure values and tissue deformation data derived from the animated FEM.

[Craniotomy guided by computed tomography with three dimensional reconstruction: technical note]

OBJECTIVE

Searching usefulness of computed tomography with three dimensional reconstruction in planning accurate cranial approaches to treat subcortical lesions.

METHOD

Eight patients with neoplastic subcortical convexity-based lesions were surgically treated following spatial coordination obtained with three dimensional computed tomography reconstruction (CT 3D).

RESULTS

Accurate approaches were accomplished, allowing a safe and optimized removal of neoplasms in all cases.

CONCLUSION

The study manifests the benefits of CT 3D in planning suitable craniotomies, avoiding incongruous approaches.

Application of computer-assisted design in craniofacial reconstructive surgery using a commercial image guidance system

The technology of digital image guidance systems has transformed many aspects of neurosurgery, including intracranial tumor surgery, functional neurosurgery, and spinal surgery. Despite the central role of imaging studies in diagnosis and treatment planning, intraoperative image guidance has so far had very limited application to the surgical correction of craniofacial deformities, particularly those associated with craniosynostosis. The authors report an example of the marriage of computer-assisted design methods to a commercially available neurosurgical image-guidance system in the treatment of a case of anterior plagiocephaly due to unilateral coronal synostosis. They discuss the steps that must yet be taken to make this technology applicable to the management of craniosynostosis in infants.

Biomodels of Bone: A Review

In this paper, a definition of a biomodel is presented, based on which different specific types of biomodels are identified, viz., virtual biomodels, computational biomodels, and physical biomodels. The paper then focuses on both physical and virtual biomodels of bone, and presents a review of model generation methodologies, giving examples of typical biomodel applications. The use of macroscale biomodels for such issues as the design and preclinical testing of surgical implants and preoperative planning is discussed. At the microscale, biomodels of trabecular bone are examined and the link with scaffolds for tissue engineering is established. Conclusions are drawn on the state of the art, and the major developments necessary for the continued expansion of the field are identified. Finally, arguments are given on the benefits of integrating the use of the different types of biomodels reviewed in this paper, for the benefit of future research in biomechanics and biomaterials.

Comparison of the predicted surgical results following virtual planning with those actually achieved following bimaxillary operation of dysgnathia

AIM

To simulate the surgery of dysgnathia, several forms of computer software allowing two-dimensional 'virtual' planning are frequently used. However, in many cases it is not possible to transfer the virtual plan accurately to the surgical site. It is the purpose of this study to find the errors likely to occur when transferring the data.

METHODS

In 22 bimaxillary osteotomies for dysgnathia, the results of preoperative planning were compared with the surgical outcomes. The programme WinCeph 4.19 (Compudent) was used for cephalometric analyses and simulation of the operations.

RESULTS

Six major skeletal parameters were evaluated when comparing both the planned and the actual outcome, and the following results were recorded: Delta-SNA 1.53 degrees (+/-1.20), Delta-SNB 1.67 degrees (+/-1.29), Delta-ANB 1.62 degrees (+/-1.47), Delta-NL-NSL 3.9 degrees (+/-2.30), Delta-ML-NSL 3.6 degrees (+/-3.7) and Delta-ArGoMe 6.1 degrees (+/-4.6).

CONCLUSION

It was anticipated that the most important differences between planned and surgical outcomes were found to be in the vertical changes. Planning and data transfer was comparatively accurate with regard to sagittal data. Apart from several mechanical methods for data transfer, systems using navigation are therefore being discussed and used increasingly. They ensure accurate data transfer to the surgical site.

Rapid prototyping to create vascular replicas from CT scan data: Making tools to teach, rehearse, and choose treatment strategies

Our goal was to develop and prove the accuracy of a system that would allow us to re-create live patient arterial pathology. Anatomically accurate replicas of blood vessels could allow physicians to teach and practice dangerous interventional techniques and might also be used to gather basic physiologic information. The preparation of replicas has, until now, depended on acquisition of fresh cadaver material. Using rapid prototyping, it should be able to replicate vascular pathology in a live patient. We obtained CT angiographic scan data from two patients with known arterial abnormalities. We took such data and, using proprietary software, created a 3D replica using a commercially available rapid prototyping machine. From the prototypes, using a lost wax technique, we created vessel replicas, placed those replicas in the CT scanner, then compared those images with the original scans. Comparison of the images made directly from the patient and from the replica showed that with each step, the relationships were maintained, remaining within 3% of the original, but some smoothing occurred in the final computer manipulation. From routinely obtainable CT angiographic data, it is possible to create accurate replicas of human vascular pathology with the aid of commercially available stereolithography equipment. Visual analysis of the images appeared to be as important as the measurements. With 64 and 128 slice detector scanners becoming available, acquisition times fall enough that we should be able to model rapidly moving structures such as the aortic root.

Feasibility of rapid and automated importation of 3D echocardiographic left ventricular (LV) geometry into a finite element (FEM) analysis model

BACKGROUND

Finite element method (FEM) analysis for intraoperative modeling of the left ventricle (LV) is presently not possible. Since 3D structural data of the LV is now obtainable using standard transesophageal echocardiography (TEE) devices intraoperatively, the present study describes a method to transfer this data into a commercially available FEM analysis system: ABAQUS.

METHODS

In this prospective study TomTec LV Analysis TEE Software was used for semi-automatic endocardial border detection, reconstruction, and volume-rendering of the clinical 3D echocardiographic data. A newly developed software program MVCP FemCoGen, written in Delphi, reformats the TomTec file structures in five patients for use in ABAQUS and allows visualization of regional deformation of the LV.

RESULTS

This study demonstrates that a fully automated importation of 3D TEE data into FEM modeling is feasible and can be efficiently accomplished in the operating room.

CONCLUSION

For complete intraoperative 3D LV finite element analysis, three input elements are necessary: 1. time-gaited, reality-based structural information, 2. continuous LV pressure and 3. instantaneous tissue elastance. The first of these elements is now available using the methods presented herein.

Congenital abnormalities of the musculoskeletal system: Perinatal evaluation and long-term outcome

Many musculoskeletal malformations can be detected by prenatal US. Whether isolated or part of a syndrome, these anomalies can have a significant impact on the entire life of the individual. Nonfatal conditions may be subtle and become more recognizable in the second and third trimester. After delivery, radiography helps confirm the diagnosis. US, CT, and MRI all have a role in imaging the primary abnormality, the follow-up effects of treatment, and in monitoring for potential complications that may develop over time. Three-dimensional imaging has an increasing role, in US, CT, and MRI, both in the prenatal and postnatal periods.

[Rapid prototyping in planning reconstructive surgery of the head and neck. Review and evaluation of indications in clinical use]

PURPOSE

The aim was to define the indications for use of rapid prototyping models based on data of patients treated with this technique.

PATIENTS AND METHODS

Since 1987 our department has been developing methods of rapid prototyping in surgery planning. During the study, first the statistical and reproducible anatomical precision of rapid prototyping models was determined on pig skull measurements depending on CT parameters and method of rapid prototyping.

RESULTS

Measurements on stereolithography models and on selective laser sintered models confirmed an accuracy of +/-0.88 mm or 2.7% (maximum deviation: -3.0 mm to +3.2 mm) independently from CT parameters or method of rapid prototyping, respectively. With the same precision of models multilayer helical CT with a higher rate is the preferable method of data acquisition compared to conventional helical CT. From 1990 to 2002 in atotal of 122 patients, 127 rapid prototyping models were manufactured: in 112 patients stereolithography models, in 2 patients an additional stereolithography model, in 2 patients an additional selective laser sinter model, in 1 patient an additional milled model, and in 10 patients just a selective laser sinter model.

CONCLUSION

Reconstructive surgery, distraction osteogenesis including midface distraction, and dental implantology are proven to be the major indications for rapid prototyping as confirmed in a review of the literature. Surgery planning on rapid prototyping models should only be used in individual cases due to radiation dose and high costs. Routine use of this technique only seems to be indicated in skull reconstruction and distraction osteogenesis.

CT imaging of craniofacial malformations

Because of its superior depiction of bone detail, CT is a useful tool in the characterization of CF deformities and presurgical planning. Modern CT scanners and workstations provide 2D techniques such as multiplanar reformats and 3D techniques, such as MIP and volume renderings, which may be used effectively in the diagnosis and management of patients with CF malformations.