Do we need real-time MRI for diagnosis of temporomandibular joint disorders?

INTRODUCTION

Magnetic resonance imaging (MRI) has been approved as an appropriate radiological modality for temporomandibular joint (TMJ) diagnosis, whereas the results of international multicenter studies impressively show the limitations of static three-dimensional MRI. The state of the art for dynamic imaging of the TMJ in real-time are TrueFISP sequences in one sagittal plane. In order to support the diagnostics, a computer-assisted visualization procedure has been developed by the authors for both the static and dynamic MRI.

METHODS

A number of validated sequences are available for the static 3D-MRI within the clinical routine. For dynamic MRI in real-time, True-FISP sequences in one sagittal plane with a slice thickness of 5-10 mm and 1.3 mm x 1.3 mm spatial resolution were applied. Both the dynamic and static MRI datasets are animated and visualized using the computer-assisted procedure.

RESULTS

The computer-assisted procedure reliably supported the clinical diagnosis, especially the visibility of the articular disc was enhanced. On the basis of the static MRI, a 60-year-old patient was diagnosed with anterior disc displacement without reduction. In contrast, by the dynamic MRI, it was recognized how the articular disc was firstly somehow stretched and flattened before the mandibular condyle again glided under the disc, thus resulting in an anterior disc displacement with reduction.

CONCLUSION

These results endorse the relevance of real-time diagnosis for the TMJ. The computer-assisted visualization has been approved as a reliable help for clinical diagnosis.

Finite element simulation of the human mandible: the role of (natural) teeth

INTRODUCTION

Individual bone quality depends on genetic, biological, and mechanical influencing factors, where the latter is accessible via Finite Element Simulation. This work is part of an interdisciplinary research project with the purpose of stepwise refinement towards anatomical reality. This approach opened the door for many interrelated applications such as atrophy of the jaw bone, periodontology, implantology, or TMJ disorders. This lecture is dedicated to the influence of dental anatomy on mandibular biomechanics.

MATERIALS AND METHODS

In general, biomechanical simulation requires reconstruction of the individual anatomy, implementation of the inhomogeneous and anisotropic material law of bone, and realization of the load case due to tooth, muscle and joint forces. The simulation chain ranges from image processing of CT data up to specifically adapted post-processing of the simulation results. In spite of ongoing research, there is still a fundamental difference of dental implants compared to natural teeth: the periodontal ligament (PDL) present at the interface between teeth and mandibular corpus. Due to its thickness of about 0.2 mm, the PDL was introduced to the simulation model by a special semiautomatic procedure.

RESULTS

Simulations "with and without PDL" proved remarkable force absorption due to the PDL, as well as qualitative changes of the stress/strain profiles of the alveolar ridge. Concerning the simulation without PDL, the observed high compressive strains at the adjacent bone were in agreement with regions of frequent implant failure.

CONCLUSION

The PDL is essential for the structural behavior of the human mandible. Based on the mechanical adaptation of bone, the comparison of the simulation with and without PDL provided special insight to the changes due to dental implants, in particular implant loss and bone resorption. Finally, the simulation will serve as a virtual platform for further evaluation (a) of implant design (b) of implant placement.

Mandibular finite element simulation as a tool for trauma surgery

PURPOSE

Despite remarkable progress within the last decade, the treatment of mandibular fractures is still a highly discussed topic in oral and cranio-maxillofacial surgery. The possible traumatologic scenarios are characterized by high variability. A current project is focused on "resimulation" of traumatologic cases given by clinical radiographs by means of finite element method.

METHODS

The applied finite element model of the mandible is very refined, providing detailed dental anatomy especially of the periodontal ligament. The mandible was modelled as inhomogeneous and anisotropic. The temporomandibular joints were realized as simplified joint capsules, wherein the mandibular condyles are freely mobile with certain limitations. The user has the choice of 5 regions on the mandibular surface where the virtual injury can be inflicted. Power and direction of the impact force vector can be set at will. The masticatoy system including the digastrics and the mylohyoid muscles can be activated.

RESULTS

The situations given by radiographs could be "reproduced" by a simulation scenario characterized by high compressive strain at the location of fractures. If masticatory muscles were activated and teeth clenched, the stress/strain profiles were qualitatively changed.

DISCUSSION

The approach may be of benefit for optimized behavior with regard to certain sports or vocations. For forensic analysis, the method will contribute by elimination of scenarios not matching the given fracture locations. Nevertheless, the immediate purpose of our approach is a better understanding of the injured organ's condition. Fractures of bone as an adaptive biological tissue differ fundamentally from mechanical failure in engineering. Many of our trauma simulations showed elevated stress/strain around the fracture, leading to the suggestion of weakened bone there. This finding was confirmed by surgical observation.

Three-dimensional recording of the human face with a 3D laser scanner

Three-dimensional recording of the surface of the human body or of certain anatomical areas has gained an ever increasing importance in recent years. When recording living surfaces, such as the human face, not only has a varying degree of surface complexity to be accounted for, but also a variety of other factors, such as motion artefacts. It is of importance to establish standards for the recording procedure, which will optimise results and allow for better comparison and validation. In the study presented here, the faces of five male test persons were scanned in different experimental settings using non-contact 3D digitisers, type Minolta Vivid 910). Among others, the influence of the number of scanners used, the angle of recording, the head position of the test person, the impact of the examiner and of examination time on accuracy and precision of the virtual face models generated from the scanner data with specialised software were investigated. Computed data derived from the virtual models were compared to corresponding reference measurements carried out manually between defined landmarks on the test persons' faces. We describe experimental conditions that were of benefit in optimising the quality of scanner recording and the reliability of three-dimensional surface imaging. However, almost 50% of distances between landmarks derived from the virtual models deviated more than 2mm from the reference of manual measurements on the volunteers' faces.

Accuracy and precision of the three-dimensional assessment of the facial surface using a 3-D laser scanner

Three-dimensional (3-D) recording of the surface of the human body or anatomical areas has gained importance in many medical specialties. Thus, it is important to determine scanner precision and accuracy in defined medical applications and to establish standards for the recording procedure. Here we evaluated the precision and accuracy of 3-D assessment of the facial area with the Minolta Vivid 910 3D Laser Scanner. We also investigated the influence of factors related to the recording procedure and the processing of scanner data on final results. These factors include lighting, alignment of scanner and object, the examiner, and the software used to convert measurements into virtual images. To assess scanner accuracy, we compared scanner data to those obtained by manual measurements on a dummy. Less than 7% of all results with the scanner method were outside a range of error of 2 mm when compared to corresponding reference measurements. Accuracy, thus, proved to be good enough to satisfy requirements for numerous clinical applications. Moreover, the experiments completed with the dummy yielded valuable information for optimizing recording parameters for best results. Thus, under defined conditions, precision and accuracy of surface models of the human face recorded with the Minolta Vivid 910 3D Scanner presumably can also be enhanced. Future studies will involve verification of our findings using test persons. The current findings indicate that the Minolta Vivid 910 3D Scanner might be used with benefit in medicine when recording the 3-D surface structures of the face.

Foetal surgery and cleft lip and palate: current status and new perspectives

Now-a-days, high-resolution ultrasound allows an accurate and relatively early diagnosis of congenital malformations. In a limited number of such conditions foetal surgery may be lifesaving. However, premature labour has been the major drawback for open foetal surgery. Recently, improvement of video-endoscopic technology has boosted the development of operative techniques for feto-endoscopic surgery, which has been demonstrated to be less invasive than the open approach. Main clinical application of fetoscopic procedures today is the treatment of feto-foetal transfusion syndrome. Although still in development, feto-endoscopic surgery seems to offer new hope for surgical foetal therapy not only in cases of life threatening conditions. Experimental intrauterine correction of cleft lip and palate (CLP) has been lately performed using the feto-endoscopic approach. This procedure offers two major advantages: first, scarless foetal wound healing and bone healing without callus formation, which would also allow a better/normal maxillary growth, and second, significant decrease of foetal and maternal morbidity. Herein, we report the current status of experimental and clinical foetal surgery and propose possible directions for continuing research to make intrauterine procedures safer. Furthermore, we discuss current knowledge and new perspectives of experimental foetal cleft lip and palate repair, which in the future may lead to such excellent results in the operative treatment of clefts, that less or no secondary corrections and therapies, such as orthodontic, dental, logopedic, etc. would be needed. Only if these conditions can be fulfilled, will we be able to improve substantially our therapy for the human foetus with a cleft lip and palate. In spite of all efforts, however, it must be considered that it may not ever be possible to find the optimal treatment method for this or other craniofacial malformations.

Computer aided surgical reconstruction after complex facial burn injuries – opportunities and limitations

In severe facial burn injuries with extensive destruction of anatomical structures, cosmetic and functional outcome of treatment are frequently not satisfactory. Although operative therapy is being continuously refined, the variety and proximity of structures in the facial region is considered a major challenge in reconstructive surgery. We present the case of a 16-year-old patient with a severe facial burn injury. In planning the reconstructive procedures, we used a multimodal approach employing data from computerized tomography imaging, as well as from surface laser scanning, which provided three-dimensional visualization of facial soft tissues. Amount and pattern of structural loss could thus be determined more precisely and studied more vividly than by inspection of two-dimensional imaging alone. Anatomical features to be reconstructed could be projected onto the skin area of the prelaminated vertical rectus abdominis muscle (VRAM) flap that has been chosen to cover the defect. Prior to surgery, correction of the defects was simulated and the results of the virtual procedure superimposed on a three-dimensional head model of the patient. Tissue elasticity and thickness of the flap, however, could not be ascertained in advance, indicating the limitations of the method.

Fetale Wundheilung

The characteristic of fetal wound healing is scarless wound repair in early gestation. During the last two decades, intensive research efforts have focused on unraveling the molecular regulations underlying the phenomenon of scarless wound healing. Better understanding of synthesis and degradation will enable us to develop important therapeutic options for the prevention and reduction of scarring. The aim of this article is to present an overview, discuss the most important research works of the last two decades on the field of fetal wound healing, and report current therapeutic developments for the modulation of adult wound repair. Recent experimental results using these new therapeutic approaches are very promising and present great possibilities and chances for future surgery.

[Urokinase-type plasminogen activator (uPA) and its inhibitor--new prognostic factors in oral squamous cell carcinoma]

Several cell biological studies have shown that the invasiveness of different malignant tumors (breast, renal, prostate, gastric, ovarian cancers) depends at least in part on the urokinase type plasminogen activator (uPA) and its inhibitor PAI1. uPA converts plasminogen into plasmin. Plasmin degrades tumor matrix components and starts invasion and metastasis. Our target was to see the possible prognostic relevance of the tumor-associated proteolytic factors and to compare with tumor size, nodal status and grading. Our results suggest that the invasive and metastatic potential of squamous cell carcinoma is correlated with overexpression of uPA and PAI1.

Surgery planning tools for the osseous grafting treatment

This paper presents a method for computer assisted selection of optimal donor sites for autologous grafts in the craniofacial surgery planning. The method consists of two stages. The non-automatic graft design step is followed by a fully automatic procedure to find the best harvesting site in the predefined donor region. The main idea of the proposed method is based on the registration paradigm. The optimal donor site is identified by performing an optimization of the surface based similarity measure between the donor region and the designed graft template. An efficient optimization method based on the Levenberg-Marquardt algorithm has been implemented. It enables, once the preprocessing step has been performed, selection of the optimal donor site in time less than one minute.

[Speech outcome after simple and multiple cleft palate operations]

OBJECTIVES

If the primary palatal closure in a patient with cleft lip and palate is unsuccessful, defects such as palatal fistulas and a short velum have to be corrected by secondary operations. It is an informal belief among surgeons that these reoperations can have detrimental effects on the patients' nasal resonance and articulation. It was our aim to critically evaluate the validity of this belief.

MATERIAL AND METHODS

One hundred and twenty-four patients with cleft lip and palate were divided into three groups. The 70 patients in group 1 had only undergone a primary palatal closure operation. The 33 patients in group 2 had undergone one or more palatal reoperations. The 21 patients in group 3 had undergone an additional pharyngeal flap operation. Resonance and articulation were evaluated perceptually. Nasalance was assessed with the NasalView system, and the mean speech rate was analyzed with the MODIAS software.

RESULTS

There were no significant differences for any of the speech measures between groups 1 and 2. Patients in group 3 had significantly worse results for all speech measures.

CONCLUSIONS

The speech outcomes for patients with multiple palatal reoperations were no different from those of patients with single palatal closure operations. The pharyngeal flap operation did not lead to sufficient improvements in the speech of the patients in group 3.

Levatorplasty, a new technique to treat hypernasality: anatomical investigations and preliminary clinical results

BACKGROUND

Velopharyngoplasty is the most commonly used operative technique for the treatment of velopharyngeal insufficiency. By attaching a posterior pharyngeal flap to the velum, a nonphysiological situation is created in the upper airway.

PURPOSE

The aim of this investigation was to find a new surgical approach to physiological reconstruction of the velopharyngeal sphincter.

MATERIAL

Anatomical investigations were performed in four cadavers. From this study a new surgical technique was developed and called 'levatorplasty': the musculus longus capitis was taken to create a new muscular loop leading to (a) an augmentation of the posterior wall, (b) a medial shift of the lateral pharyngeal wall; and (c) stretching of the velum posteriorly. Thus, the velopharyngeal space was reduced and a physiological closure of the nasal airway space could be obtained.

STUDY DESIGN

The levatorplasty was employed in nine cleft palate patients with velopharyngeal insufficiency. Pre- and postoperatively the velopharyngeal closure was evaluated by phonetic and radiological examination.

RESULTS

The operation was easily performed without major complications. A concentric constriction with decrease of the velopharyngeal space was achieved and a definitive decrease of nasalance and hypernasality resulted.

CONCLUSION

Long-term follow-ups have to verify whether these results will be stable. They also have to be compared with functional improvements following velopharyngoplasty or pharyngoplasty. Of special interest will be evaluation of the altered mobility of the lateral pharyngeal walls.

[Stress analysis of the human mandible in standard trauma situations with numerical simulation]

For the stress analysis of the human mandible a flexible simulation concept basing on finite element-method has been developed. One of the main issues is the prediction of fractures as a consequence of known forces as well as the forensic reconstruction of the traumatologic situation. At first, the individual geometry was reconstructed by 3D-CT-Scans. To reduce the simulation efforts, for the time being the anisotropic structural mechanics of the jaw bone was neglected in favour of an homogeneous and isotropic material law. Assuming the Von-Mises-Stress as a failure indicator the results of the simulations were in good agreement with typical traumatologic situations. For further validation of the model, a real failure case, shown on a radiograph of a injured human mandible with three fractures, was simulated and, by this, the real incident was reconstructed. Reasonable planned extensions of the actual simulation concept have the regard on the nerve channel, the temporomandibular joint's function, the paradontal apparatus and the individual mechanical properties of the bone.

[Numerical simulation (FEM) of the human mandible: validation of the function of the masticatory muscles]

The article describes part of a research project aiming to develop a new modular software tool for the individual dynamic numerical simulation of the human mandible using the finite element method (FEM). Its planned use in the clinical setting makes it very important to validate the results of the simulations. Here, the function of the masticatory muscles is to be tested. On the basis of biomechanical data from the literature, standard movements, such as closing the mouth, forward movement, lateral movement or backward movement, were dynamically simulated. Apart from muscle activity, the movements of the mandible are defined by the temporomandibular joint. At present, translating the condylar dynamics to the simulation still poses problems. For this reason, therefore, simulations of the two extreme cases "fixed" and "force-free" condyles are compared. While in the case of fixed condyles, some of the movements could be reproduced either not at all or only weakly, in the case of force-free condyles, all standard movements were reproduced qualitatively, albeit without the guiding effect of the joint capsule or the articular disc.

[A modular software concept for individual numerical simulation (FEM) of the human mandible]

A new modular software concept for individual numerical simulation of the human mandible using the finite element method (FEM) is presented. The main task is an individual analysis of regional stress and stress-compatibility on the basis of computed tomographic data in individual patients. Simulation should, however, also be possible in parallel with biomechanical experiments, or for further research projects. For this purpose, rapid and uncomplicated generation of the FEM model, easy modification of input data, and short computation times are required. Practical use in the clinical setting makes appreciable additional demands on the individual software components.

Nasalance distance and ratio: two new measures

OBJECTIVES

Mean nasalance in speakers with perceptually normal nasal resonance can differ in magnitude considerably. In addition, categorizations of speech based on nasalance scores may not agree with perceptual judgments. To overcome this limitation, we evaluated two new simple measures derived from mean nasalance data: the nasalance distance (range between maximum and minimum nasalance) and the nasalance ratio (minimum nasalance divided by maximum nasalance).

SETTING

Department of Oral and Maxillofacial Surgery, University of Technology, Munich, Germany.

SUBJECTS

The sample consisted of 133 cleft lip and palate patients with normal nasal resonance or varying degrees of hypernasality.

PROCEDURES

Oral and nasal acoustic measurements were made using the NasalView system. Nasalance distance and nasalance ratio were calculated for five non-nasal and three nasal sentences from the modified Heidelberg Rhinophonia Assessment Form.

RESULTS

Optimum cutoffs were derived from receiver-operating characteristics. Results for the sentence stimuli ranged from 64.4% to 89.6% sensitivity and from 91.2% to 94.1% specificity. When the analysis was limited to only one nonnasal and one nasal sentence, results ranged from 79.7% to 87.5% sensitivity and from 88.2% to 97.1% specificity.

CONCLUSIONS

We conclude that the two new measurements are valuable in routine clinical examinations. Nasalance distance and ratio derived from sentence stimuli are two useful and easily applicable measures that can be used to supplement the nasalance mean value.

[Speech rate of compensatory articulation in patients with cleft lip and palate]

Infolge eines primären Defizits der velopharyngealen Funktion liegen bei vielen Patienten mit Lippen-Kiefer-Gaumenspalten sekundäre kompensatorische Lautbildungen vor. Mit zwei neuen Computerprogrammen werden die Auswirkungen der kompensatorischen Artikulation auf die durchschnittliche Sprechgeschwindigkeit von 146 Patienten mit Lippen-Kiefer-Gaumen-spalten untersucht. Die Patienten wurden dabei nach dem Schweregrad der artikulatorischen Auffälligkeit gruppiert. Bei der schnellen Silbenwiederholung zeigte sich, dass die durchschnittliche Silbenrate pro Sekunde bei Patienten mit deutlich auffälliger Artikulation signifikant reduziert war. Beim Nachsprechen von Sätzen war die zum Nachsprechen benötigte Gesamtzeit bei dieser Patientengruppe signifikant erhöht, und das Zielwort des Satzes wurde signifikant später begonnen. Die Ergebnisse zeigen, dass die mittlere Sprechgeschwindigkeit von Patienten mit Lippen-Kiefer-Gaumenspalten mit kompensatorischer palatolalischer Artikulation niedriger ist.

Rapid protyping technology in medicine--basics and applications

Using medical models built with Rapid Prototyping (RP) technologies represents a new approach for surgical planning and simulation. These techniques allow one to reproduce anatomical objects as 3D physical models, which give the surgeon a realistic impression of complex structures before a surgical intervention. The shift from the visual to the visual-tactile representation of anatomical objects introduces a new kind of interaction called 'touch to comprehend'. As can be seen, from the presented case studies of maxillo-cranio-facial surgery, the RP models are very well suited for use in the diagnosis and the precise preoperative simulation of skeleton modifying interventions.

[Quality of life research in patients with cleft lip and palate: preliminary results]

While esthetic and functional outcomes of treatment have improved for patients with cleft lip and palate (CLP), a CLP remains a severe problem for patients and relatives. To date, psychological research has dealt with issues such as intelligence, self-consciousness or treatment satisfaction but the long-term impact of a CLP on a psychological construct such as quality of life has yet to be explored. From a pool of 156 patients with CLP, subgroups of varying sizes were examined with a set of standardized questionnaires (KINDL, SF-36, Social Support Survey). In all patients, primary operative treatment had been accomplished. Long-term impact of the CLP on family life was assessed by 112 of the patients' parents by filling in the Impact on Family Scale. A set of questionnaires, especially developed for patients with CLP, was administered as well. For all patients who have been being treated in an interdisciplinary cleft center for their entire life, the results presented indicate that quality of life is good and within a normal range. Social support appears to be within a normal range. Parents report only minor long-term impact of the CLP on family life and family planning. Treatment satisfaction is high in the CLP patients. The questionnaires especially aimed at CLP patients indicate more specific problems mainly concerning social acceptance, where patients think the CLP had a negative impact. The standardized questionnaires employed so far failed to capture these problems. The combination of the two types of questionnaires is a sufficiently sensitive assessment procedure.

[Significance of profile prognosis in implant management of the atrophic maxilla]

Postoperative cosmetic results in soft tissue after combined surgical and prosthetic treatment of the extremely atrophic edentulous maxilla by maxillary advancement, sinus lift, and insertion of enosseous implants are rarely considered during preoperative planning. In a prospective study that began in 1993 in 23 patients, the treatment concept was determined by a medical rapid prototyping model and video imaging to predict the soft tissue profile, taking into consideration the appearance of the front teeth. In eight patients, the surgical and/or the prosthetic concept was modified according to the treatment plan decided on with the patient. All patients were highly satisfied with the aesthetic and functional result achieved. Profile prediction using video imaging is a useful tool in planning rehabilitation of the atrophic maxilla and takes into account the interplay of various factors--the amount of maxillary advancement, the direction of insertion of enosseous implants, and the type of supraconstruction. This procedure shows a very high level of acceptance by patients.

[Quantitative diagnosis of hypernasality in cleft lip and palate patients by computerized nasal quality assessment]

In patients with cleft lip and palate (CLP), the assessment of velopharyngeal morphology and function and the quantitative analysis of perceptual consequences of velopharyngeal insufficiency are of major importance regarding the effective planning of velopharyngoplasties for speech improvement. The NasalView, a new instrument for the objective assessment of rhinophonia, is presented. The NasalView measures nasalance, the relative sound pressure level of the nasal signal in speech, expressed as a percentage. In order to evaluate the effectiveness of the computerised measurement of nasalance, 156 patients with surgically treated CLP were examined. The NasalView differentiated with high sensitivity and specificity between patients with normal nasal resonance and patients with varying degrees of hypernasality. To illustrate the importance of the NasalView for making the decision for a velopharyngoplasty, a single case is presented.

[Perceptive and instrumental examination of voice quality in patients with lip-jaw-palate clefts]

BACKGROUND

In Anglo-American literature, prevalences as high as 41% are reported for voice disorders in cleft lip and palate (CLP) patients. Because of considerable variability in the reported findings and because no prevalence data are available for the German-speaking area, a screening study was conducted.

METHOD

154 patients with CLP were examined. Voice quality was assessed perceptively according to the rbh-system (roughness, breathiness, hoarseness). Suprasegmentals and nasal resonance were also assessed. Using a new computer programme for the apparative analysis of voice quality, data for pitch, intensity and pertubation (jitter and shimmer) were obtained for 4 sustained vowels.

RESULTS

Based on perceptual analysis, we found that the prevalence of severe voice disorders in CLP patients was 6.5% which is lower than reported in most other studies. The incidence of voice disorders in CLP patients is numerically only slightly higher than in the normal population. The acoustic measurements confirm the results of perceptual analysis. Since the prevalence of severe voice disorders was low, none of the pertubation quotients differentiated between modal and disordered voices. A weak correlation was found between jitter and the ratings for hoarseness.

CONCLUSIONS

1. While it is appropriate to assume a higher potential risk for vocal dysfunction in CLP patients the actual prevalence in the patients examined is numerically only slightly higher than in normals. 2. For patients with voice disorders, apparative diagnostics of voice quality is a useful and practical adjunct to perceptual analysis which helps profiling individual patients and helps the professional to make decisions for therapy.

[Video matching as intraoperative navigation aid in operations to improve the facial profile]

Planning and simulation of individual interventions are not yet the common standard treatment in general surgery. Improvements in planning and simulation of individual orthognatic and craniofacial interventions have led to the need to transfer the results of preoperative planning to the location. Videomatching offers a new approach to the surgeon so that simulation output can be used in a highly intuitive way. Congruent video superimposition of the real site and a view of the simulation give the surgeon a unified view of both domains. Visual merging is immediately accepted by the surgeon who prefers the intuitive, non-tactile nature of this highly informative navigational aid. Application and positioning of anatomical markers and time-consuming calibration procedures can be reduced to a minimum. Alternative plans can be discussed among several surgeons preoperatively, and different therapeutic concepts solidified in various simulation models can be selected intraoperatively. We concentrate on the application of this new method in craniomaxillofacial surgery, but it is applicable in other disciplines as well.

[Precision of 3D-assisted surgical planning with rapid prototype techniques]

Our clinical results show that 3D model building is an excellent method for 3D preoperative planning. Dependent on the number of steps, however, there are many possibilities of failures. Standardization and quality control of data acquisition and industrial manufacturing must be recommended. This is especially important for stereolithography, as it is definitely more complex than the milling technique. One possibility seems to be the use of phantom models. Another factor is that the surgeon has to be involved in the essential steps of data analysis and segmentation. Based on our experience, the building of 3D CT skull models is a clinically efficient method that is mature enough for clinical use, but cannot yet be accepted as the clinical routine. Quality assurance is urgently necessary.

[Equipment and transducer-independent 3D ultrasound in the maxillofacial area]

AIM

The use of a new 3D ultrasound system should reduce the drawbacks of former 3D workstations (long image generation time, limited use due to the need for special 3D transducers), so that it is now applicable in daily clinical routine.

METHOD

An ultrasound 3D workstation was used based on a pentium PC platform, employing a magnetoelectronic position detection system for spatial reconstruction of conventional 2D B-scan image sequences.

RESULTS

Better assessment of topographico-anatomical spatial relationships was achieved when presenting pathological findings, especially in assessing lymph nodes and salivary stones. Pathological processes in the maxillofacial area occurring during a period of five months were visualised.

CONCLUSION

The method of 3D reconstruction of standard two-dimensional electronic scans, as presented here, is the first method of its kind enabling applicability in daily clinical routine thanks to rapid imaging. The images can be produced with any ultrasound unit or transducer. First clinical results in maxillofacial surgery clearly show improved diagnostic possibilities although there still room for an improvement of the image quality. The possibility of semi-automatic exact volumetry appears meaningful especially in the investigation of lymph nodes. Integration of colour duplex sonography will further enhance the diagnostic value of this method.

[New possibilities in computer-assisted image processing for ultrasound diagnosis in mouth-jaw-facial surgery]

The use of a digital image processing system in ultrasound diagnostics offers not only the advantage of a space-saving archiving without loss of quality, but also a clearly higher efficacy of the examination is achieved. An interactive of system findings leads to a more complete examination and evaluation, thus increasing the reliability and the objectivity of the examination. The standardized findings by use of text components mean at the same time a clear saving of time. Moreover, this system is very comfortable not only for the comparison of different images, but also for the scientific evaluation and processing of the image data. By digitalizing the sonographic images the visual data can be processed in a personal computer. Thereby, for maxillofacial surgery a simple and fast dynamic-functional evaluation of the temporomandibular joint was made possible. By archiving without loss of quality and by higher reliability, objectivity and efficacy of the sonographic examination important preconditions for quality care in ultrasound diagnostics have been achieved.

[High-frequency videocinematograpphy for the objective imaging of the velopharyngeal closure mechanism in cleft palate patients]

The use of high-frequency video cineradiography makes possible an objective and dynamic rendering of the individual velopharyngeal closer pattern. The high resolution and the depiction of the finest mucosal structures while in motion achieved by this technique opens up the possibility of exact and objective 3-dimensional evaluation of the velopharyngeal gap. Following secondary velopharyngoplasty on 80 cleft palate patients, the velopharyngeal closure was studied by means of high-frequency video cineradiography and this rendering was then compared to results obtained by nasoendoscopy and to the clinical findings. It became definitely apparent that the radiological technique is markedly superior in relation to clearness of depiction and ease of use, especially in young children. This imaging technique can be recommended without reservation for pre- and postoperative control of speech-improving procedures.