Three-dimensional cephalometry: spiral multi-slice vs cone-beam computed tomography.

Item does not contain fulltextThree-dimensional (3D) craniofacial imaging techniques are becoming increasingly popular and have opened new possibilities for orthodontic assessment, treatment, and follow-up. Recently, a new 3D cephalometric method based on spiral multi-slice (MS) computed tomography (CT) was developed and validated by our research group. This innovative 3D virtual approach is a bridge between conventional cephalometry and modern craniofacial imaging techniques and provides high-quality, accurate, and reliable quantitative 3D data. The aim of this article was to describe the advantages and the disadvantages of spiral MS-CT 3D cephalometry and to discuss the potential of cone-beam CT 3D cephalometry

Three-dimensional treatment planning of orthognathic surgery in the era of virtual imaging.

Item does not contain fulltextPURPOSE: The aim of this report was to present an integrated 3-dimensional (3D) virtual approach toward cone-beam computed tomography-based treatment planning of orthognathic surgery in the clinical routine. MATERIALS AND METHODS: We have described the different stages of the workflow process for routine 3D virtual treatment planning of orthognathic surgery: 1) image acquisition for 3D virtual orthognathic surgery; 2) processing of acquired image data toward a 3D virtual augmented model of the patient's head; 3) 3D virtual diagnosis of the patient; 4) 3D virtual treatment planning of orthognathic surgery; 5) 3D virtual treatment planning communication; 6) 3D splint manufacturing; 7) 3D virtual treatment planning transfer to the operating room; and 8) 3D virtual treatment outcome evaluation. CONCLUSIONS: The potential benefits and actual limits of an integrated 3D virtual approach for the treatment of the patient with a maxillofacial deformity are discussed comprehensively from our experience using 3D virtual treatment planning clinically

Calibrated segmentation of CBCT and CT images for digitization of dental prostheses.

PURPOSE: State of the art computer aided implant planning procedures typically use a surgical template to transfer the digital 3D planning to the operating room. This surgical template can be generated based on an acrylic copy of the patient's removable prosthesis--the so-called radiographic guide--which is digitized using a CBCT or CT scanner. Since the same accurate fit between the surgical template and the patient as with the radiographic guide and the patient should be ensured, a procedure to accurately digitize this guide is needed. METHODS: A procedure is created to accurately digitize radiographic guides based on a calibrated segmentation. Therefore, two steps have to be executed. First, during a calibration step a calibration object is CBCT or CT scanned and a calibration algorithm which results in an optimal threshold value is executed. Next the guide is CBCT or CT scanned and a 3D model is created using the obtained optimal threshold. To validate our method, we compared a high accuracy laser scanned copy of the guide with the generated 3D model by creating a distance map between both models. RESULTS: The procedure was performed for different CBCT and CT scanners, and the digitization error for each scanner was defined. The 90th percentile error measured on average 0.15 mm, which was always less than the applied voxel size for all CBCT and CT test scans. CONCLUSIONS: The calibration procedure evaluated in this study solves the known problem of digitizing a radiographic guide based on non-standardized gray value CBCT images. The procedure can easily be executed by a clinician and allows an accurate digitization of a radiographic guide using a CBCT or CT scanner. Starting from this digitization, an accurate surgical template can be made which has a good fit on the patient's remaining teeth and surrounding soft tissues

Trans-sinusal maxillary distraction for correction of midfacial hypoplasia: long-term clinical results.

Item does not contain fulltextMaxillary distraction osteogenesis is indicated in severe angle class III malocclusions, and severe maxillary hypoplasia among some cleft patients and other craniofacial deformities. Twenty patients, aged 8-48 years (mean 17.8+/-10.5 SD) with maxillary and midfacial hypoplasia were treated. The follow-up period was 13-65 months (mean 35+/-16.3 SD). A trans-sinusal maxillary distractor was placed intraorally at each side of the maxilla. The distraction vector was predicted using specialist software, and was transferred to the patients using stereolithographic models and individual templates. A (high) Le Fort I type osteotomy was performed. The amount of activation varied from 8 to 17.5 mm (mean 13.1+/-2.9 SD). Soft and hard tissue formation resulted in complete healing across the distraction gaps. The distractors are almost completely submerged, and can be left in place as long as necessary to avoid relapse. Wit's appraisal was used to measure the stability of the long-term distraction results. Results up to 5 years after distraction showed considerable maxillary advancement with long-term stability. Ongoing growth of the facial skeleton must be considered when distraction osteogenesis is chosen in growing patients

The use of a new 3D splint and double CT scan procedure to obtain an accurate anatomic virtual augmented model of the skull.

Item does not contain fulltextThree-dimensional (3D) virtual planning of orthognathic surgery requires detailed visualization of the interocclusal relationship. The purpose of this study was to introduce the modification of the double computed tomography (CT) scan procedure using a newly designed 3D splint in order to obtain a detailed anatomic 3D virtual augmented model of the skull. A total of 10 dry adult human cadaver skulls were used to evaluate the accuracy of the automatic rigid registration method for fusion of both CT datasets (Maxilim, version 1.3.0). The overall mean registration error was 0.1355+/-0.0323 mm (range 0.0760-0.1782 mm). Analysis of variance showed a registration method error of 0.0564 mm (P < 0.001; 95% confidence interval = 0.0491-0.0622). The combination of the newly designed 3D splint with the double CT scan procedure allowed accurate registration and the set-up of an accurate anatomic 3D virtual augmented model of the skull with detailed dental surface

Predicting soft tissue deformations for a maxillofacial surgery planning system: from computational strategies to a complete clinical validation.

Item does not contain fulltextIn the field of maxillofacial surgery, there is a huge demand from surgeons to be able to pre-operatively predict the new facial outlook after surgery. Besides the big interest for the surgeon during the planning, it is also an essential tool to improve the communication between the surgeon and his patient. In this work, we compare the usage of four different computational strategies to predict this new facial outlook. These four strategies are: a linear Finite Element Model (FEM), a non-linear Finite Element Model (NFEM), a Mass Spring Model (MSM) and a novel Mass Tensor Model (MTM). For true validation of these four models we acquired a data set of 10 patients who underwent maxillofacial surgery, including pre-operative and post-operative CT data. For all patient data we compared in a quantitative validation the predicted facial outlook, obtained with one of the four computational models, with post-operative image data. During this quantitative validation distance measurements between corresponding points of the predicted and the actual post-operative facial skin surface, are quantified and visualised in 3D. Our results show that the MTM and linear FEM predictions achieve the highest accuracy. For these models the average median distance measures only 0.60 mm and even the average 90% percentile stays below 1.5 mm. Furthermore, the MTM turned out to be the fastest model, with an average simulation time of only 10 s. Besides this quantitative validation, a qualitative validation study was carried out by eight maxillofacial surgeons, who scored the visualised predicted facial appearance by means of pre-defined statements. This study confirmed the positive results of the quantitative study, so we can conclude that fast and accurate predictions of the post-operative facial outcome are possible. Therefore, the usage of a maxillofacial soft tissue prediction system is relevant and suitable for daily clinical practice

A new method of 3-D cephalometry Part I: the anatomic Cartesian 3-D reference system.

Item does not contain fulltextThe purpose of this study was to present a new innovative three-dimensional (3-D) cephalometric method. Part I deals with the set-up and validation of a voxel-based semi-automatic 3-D cephalometric reference system. The CT data (DICOM 3.0 files) of 20 control patients with normal skeletal relationships were used for this study. To investigate accuracy and reliability of the 3-D cephalometric reference system (Maxilimtrade mark, version 1.3.0) a total of 42 (14 horizontal, 14 vertical and 14 transversal) orthogonal measurements were performed on each patient twice by each of two investigators. The intra-observer measurement error was less then 0.88 mm, 0.76 mm and 0.84 mm for horizontal, vertical and transversal orthogonal measurements, respectively. The inter-observer measurement error was less as 0.78 mm, 0.86 mm and 1.26 mm for horizontal, vertical and transversal orthogonal measurements, respectively. Squared correlation coefficients showed a high intra-observer and inter-observer reliability. The presented 3-D cephalometric reference system proved to be accurate and reliable and can therefore be used for 3-D cephalometric hard and soft tissue analysis

Assessment of bone segmentation quality of cone-beam CT versus multislice spiral CT: a pilot study.

Item does not contain fulltextOBJECTIVES: The objective of this study was to quantitatively assess the quality of jawbone models generated from cone beam computed tomography (CBCT) by comparison with similar models obtained from multislice spiral computed tomography (MSCT). MATERIAL AND METHODS: Three case studies were performed involving images of anthropomorphic head phantoms and real patients acquired with 3 CBCT (NewTom 9000 DVT, Accuitomo 3D, and i-CAT) and 2 MSCT scanners (Somatom VolumeZoom and Lightspeed). Bone was segmented from the CBCT and MSCT images using global thresholding. CBCT vs MSCT segmentation differences were assessed by comparing bone thickness measurements at anatomically corresponding sites, identified automatically by CBCT to MSCT image registration. RESULTS: There was a statistically significant difference between the MSCT and CBCT segmented bone thicknesses, varying from 0.05 +/- 0.47 mm (i-CAT) up to 1.2 +/- 1.00 mm (3D Accuitomo, posterior maxilla). CONCLUSIONS: An automated, reproducible, and observer-independent method has been developed to assess the quality of CBCT bone models using MSCT as a clinically established method of reference. Our validation method is generally applicable in cases where no geometric ground-truth is available

Trans-sinusoidal maxillary distraction in three cleft patients.

Contains fulltext : 49821.pdf (publisher's version ) (Closed access)The trans-sinusoidal maxillary distractor (TS-MD) was used to achieve maxillary advancement in three patients with repaired cleft lip and palate. After preoperative computer-aided planning of the distraction vectors, each TS-MD was bent on a stereolithographic model of the maxilla of the patient. The devices were intraoperatively positioned using a methyl-methacrylate template. After standard Le Fort I osteotomy the devices were intraorally activated. After distraction the devices remained in situ for 3 months as rigid internal fixation of the maxilla. All patients were successfully distracted according to protocol. Maxillary advancement was 12, 8 and 11 mm. In two patients, additional maxillary widening of 6 and 8 mm was achieved by choosing divergent distraction vectors. After distraction a clockwise rotation of the maxilla was observed in two patients. There was no relapse during the 3 months of consolidation and 12-month follow-up. The TS-MD allows not only distraction but also rigid internal fixation after distraction. It was easy to apply but difficult to remove. Owing to preoperative 3D planning of the distraction vectors, the results were predictable, but clockwise rotation of the maxilla during distraction should be considered in planning. The distractor did not interfere with function or social activities during distraction and retention periods. After removal it left no extraoral scars

Virtual occlusion in planning orthognathic surgical procedures.

Item does not contain fulltextAccurate preoperative planning is mandatory for orthognathic surgery. One of the most important aims of this planning process is obtaining good postoperative dental occlusion. Recently, 3D image-based planning systems have been introduced that enable a surgeon to define different osteotomy planes preoperatively and to assess the result of moving different bone fragments in a 3D virtual environment, even for soft tissue simulation of the face. Although the use of these systems is becoming more accepted in orthognathic surgery, few solutions have been proposed for determining optimal occlusion in the 3D planning process. In this study, a 3D virtual occlusion tool is presented that calculates a realistic interaction between upper and lower dentitions. It enables the surgeon to obtain an optimal and physically possible occlusion easily. A validation study, including 11 patient data sets, demonstrates that the differences between manually and virtually defined occlusions are small, therefore the presented system can be used in clinical practice.1 mei 201