Towards predicting biomechanical consequences of jaw reconstruction

Abstract — We are developing dynamic computer models of surgical jaw reconstructions in order to determine the effect of altered musculoskeletal structure on the biomechanics of mastication. We aim to predict post-reconstruction deficits in jaw motion and force production. To support these research goals we have extended our biomechanics simulation toolkit, ArtiSynth [1], with new methods relevant to surgical planning. The principle features of ArtiSynth include simulation of constrained rigid-bodies, volume-preserving finite-element methods for deformable bodies, contact between bodies, and muscle models. We are adding model editing capabilities and muscle activation optimization to facilitate progress on postsurgical simulation. Our software and research directions are focused on upper-airway and cranio-facial anatomy, however the toolset and methodology are applicable to other musculoskeletal systems. I

Virtual Articulator – Aid Simulator at Diagnosis, Pre-Surgical Planning and Monitoring of Bucomaxilofacial Treatment

This work presents a system for use in dentistry and medicine, that allows advance in diagnosis and planning of treatments and surgical procedures, in cases that involves the Temporomandibular Joint, TMJ. Construction of Virtual Articulator includes related research areas of computer graphics, virtual reality and medicine and tends to become a new paradigm as a tool because it will simulate and reproduce the movements of the TMJ in a realistic way, allowing a complete analysis of the case under treatment. It is a software which comes to replace and increase in an innovative way the work done by mechanical articulators. Initially Virtual Articulator reconstructs the TMJ virtually, generating a 3D model, starting from exams such as Computed Tomography and Magnetic Ressonance. Once it is obtained a virtual copy of the TMJ, software simulates real mandible movements, with great flexibility and facility of parameterization. Virtual joints model is based on points captured from the motion curve of lower incisor point. Contribution of each muscle in temporomandibular movement is approached from Hill actuators model and the new concept of curves of insertion. It will be possible to analyze in depth a particular case in a diagnostic phase or predict the results of the surgical procedure

Intensity modulated radiation therapy and arc therapy: validation and evolution as applied to tumours of the head and neck, abdominal and pelvic regions

Intensiteitsgemoduleerde radiotherapie (IMRT) laat een betere controle over de dosisdistributie (DD) toe dan meer conventionele bestralingstechnieken. Zo is het met IMRT mogelijk om concave DDs te bereiken en om de risico-organen conformeel uit te sparen. IMRT werd in het UZG klinisch toegepast voor een hele waaier van tumorlocalisaties. De toepassing van IMRT voor de bestraling van hoofd- en halstumoren (HHT) vormt het onderwerp van het eerste deel van deze thesis. De planningsstrategie voor herbestralingen en bestraling van HHT, uitgaande van de keel en de mondholte wordt beschreven, evenals de eerste klinische resultaten hiervan. IMRT voor tumoren van de neus(bij)holten leidt tot minstens even goede lokale controle (LC) en overleving als conventionele bestralingstechnieken, en dit zonder stralingsgeïnduceerde blindheid. IMRT leidt dus tot een gunstiger toxiciteitprofiel maar heeft nog geen bewijs kunnen leveren van een gunstig effect op LC of overleving. De meeste hervallen van HHT worden gezien in het gebied dat tot een hoge dosis bestraald werd, wat erop wijst dat deze “hoge dosis” niet volstaat om alle clonogene tumorcellen uit te schakelen. We startten een studie op, om de mogelijkheid van dosisescalatie op geleide van biologische beeldvorming uit te testen. Naast de toepassing en klinische validatie van IMRT bestond het werk in het kader van deze thesis ook uit de ontwikkeling en het klinisch opstarten van intensiteitgemoduleerde arc therapie (IMAT). IMAT is een rotationele vorm van IMRT (d.w.z. de gantry draait rond tijdens de bestraling), waarbij de modulatie van de intensiteit bereikt wordt door overlappende arcs. IMAT heeft enkele duidelijke voordelen ten opzichte van IMRT in bepaalde situaties. Als het doelvolume concaaf rond een risico-orgaan ligt met een grote diameter, biedt IMAT eigenlijk een oneindig aantal bundelrichtingen aan. Een planningsstrategie voor IMAT werd ontwikkeld, en type-oplossingen voor totaal abdominale bestraling en rectumbestraling werden onderzocht en klinisch toegepast

Radio telemetry devices to monitor breathing in non-sedated animals

Radio telemetry equipment has significantly improved over the last 10-15 years and is increasingly being used in research for monitoring a variety of physiological parameters in non-sedated animals. The aim of this review is to provide an update on the current state of development of radio telemetry for recording respiration. Our literature review found only rare reports of respiratory studies via radio telemetry. Much of this article will hence report our experience with our custom-built radio telemetry devices designed for recording respiratory signals, together with numerous other physiological signals in lambs. Our current radio telemetry system allows to record 24 simultaneous signals 24h/day for several days. To our knowledge, this is the highest number of physiological signals, which can be recorded wirelessly. Our devices have been invaluable for studying respiration in our ovine models of preterm birth, reflux laryngitis, postnatal exposure to cigarette smoke, respiratory syncytial virus infection and nasal ventilation, all of which are relevant to neonatal respiratory problems

Biomechanical Models of Human Upper and Tracheal Airway Functionality

The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson\u27s disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow

Development of a small animal conformal irradiator with dual energy x-ray computed tomography imaging for kilovoltage dosimetry

External beam radiotherapy has become technically sophisticated with image guided radiation therapy (IGRT) and intensity modulated radiation therapy (IMRT). These technologies allow for precise delivery of radiation to geometric targets in cancer patients. However, many questions remain on how to best define targets based on biological information, such as functional imaging, and how to combine radiation with other cancer therapies. To help answer these questions, small animal preclinical studies are needed to generate data to inform clinical trials. However, the precise radiation delivery capabilities of IGRT and IMRT have not been available in the preclinical labs. To enable translational experiments and to address the lack of preclinical radiotherapy technology, a commercial micro-CT was first developed into an image-guided conformal radiotherapy system in this thesis. Computerized asymmetric jaws were constructed, implemented and characterized for the system. A Monte Carlo dose calculation package was successfully configured for the system and verified with film measurements. Respiratory gated imaging and radiotherapy was demonstrated with a phantom and in animals. Secondly, accurate radiation dosimetry reduces uncertainties in preclinical experiments. To achieve accurate dose calculations in the kilovoltage x-ray range where photoelectric effects and Compton scattering dominate, knowledge of material composition and density is needed. Dual energy micro-CT was optimized (including choice of x-ray beam peak voltages, filtrations, and duration) and evaluated for the purpose of characterizing materials. Dual energy CT techniques developed for clinical scanners were adapted and examined for micro-CT. A set of micro-CT phantoms consisting of 11 plastic materials and solutions that spanned a relevant range of compositions was designed and constructed. Initial experiments found beam-hardening image artefacts limited accurate measurements. By switching to a more sensitive detector, x-ray spectra with additional beam filtration were possible and resulted in reduced beam-hardening effects. This improved dual energy micro-CT measurement accuracy of material composition and density. In conclusion, a small animal image-guided conformal radiotherapy system was developed and commissioned for preclinical studies. Dual energy micro-CT was demonstrated as a method to characterize materials to improve kilovoltage dose calculation. This integrated micro-CT based small animal image-guided radiation platform has enabled numerous pre-clinical studies

Articulation in time : Some word-initial segments in Swedish

Speech is both dynamic and distinctive at the same time. This implies a certain contradiction which has entertained researchers in phonetics and phonology for decades. The present dissertation assumes that articulation behaves as a function of time, and that we can find phonological structures in the dynamical systems. EMA is used to measure mechanical movements in Swedish speakers. The results show that tonal context affects articulatory coordination. Acceleration seems to divide the movements of the jaw and lips into intervals of postures and active movements. These intervals are affected differently by the tonal context. Furthermore, a bilabial consonant is shorter if the next consonant is also made with the lips. A hypothesis of a correlation between acoustic segment duration and acceleration is presented. The dissertation highlights the importance of time for how speech ultimately sounds. Particularly significant is the combination of articulatory timing and articulatory duration

Patients with head and neck cancer - aspects on treatment, complications and rehabilitation

Head and neck cancer is reported to be the fifth most common cancer globally and around 1,200 new patients are diagnosed in Sweden every year. Historically, survival rates have been rather constant but have started to improve over the last few decades as a result of new and more aggressive oncological treatments. For this reason, there is a need to re-evaluate surgical treatment—both its necessity and its morbidity in comparison to the oncological treatments available. There is also a risk of higher incidence of side effects from newer oncological regimens, which still needs to be evaluated. In this thesis, different populations of head and neck cancer patients from our institution have been analysed concerning aspects of treatment, sequelae, and rehabilitation. The material is highly applicable to everyday clinical situations. In paper I, patients diagnosed between1998 and 2002 with metastases in the neck that were treated with full-dose external beam radiotherapy (EBRT) were evaluated concerning histopathology and clinical outcome, with a view to evaluating the necessity of a planned neck dissection after EBRT. One hundred and fifty-six patients were included. Overall survival was 62% and disease-specific survival was 76%. There was a clinically complete response to radiotherapy in the neck in 63 patients (40%). Of these, 15 had viable tumor cells in the neck specimen. In patients who did not achieve a clinically complete response, 40% (37/93) had viable tumor cells in the neck specimen. Disease-specific survival in patients with viable tumor cells in the neck after EBRT was 48% (25/52), and it was 90% (93/104) in patients without viable tumor cells. Paper II describes a retrospective case-control study of patients diagnosed and treated for stricture of the upper oesophagus after EBRT for head and neck cancer between 1992 and 2005. The aim of the study was to identify possible risk factors for stricture formation. Clinical parameters were collected from the medical files. The EBRT dose delivered to the upper oesophagus was calculated using the dose-planning system data. Seventy patients with stricture and 66 patients without were identified. The incidence of upper esophageal stricture at the institution during the study period was 3.3%. A multivariate analysis showed an increased risk of stricture in patients who received enteral feeding during EBRT or with a mean dose of > 45 Gy delivered to the upper oesophagus. Treatment of the stricture with Savary-Gilliard bougienage or through-thescope balloon dilatation was found to be safe and successful, but often had to be repeated. In paper III, the morbidity of supraomohyoidal neck dissection (SOND) or modified radical neck dissection (MRND) combined with EBRT was evaluated regarding cervical range of movement, lymphoedema, mouth opening, swallowing, and shoulder disability. The patient material was collected from the study population in paper IV. Ninety-eight patients who received only EBRT were identified, 25 patients were treated with both SOND and EBRT, and 83 were treated with MRND and EBRT. The overall incidence of shoulder disability after both types of neck dissection was 18%. SOND had no other significant negative effects on the parameters under evaluation at any time 5 point, while with MRND there was significantly reduced CROM and mouth opening two months after treatment. After 12 months, only cervical rotation was still significantly reduced. In paper IV, the aim of the study was to evaluate the effect of an early preventive rehabilitation programme on functional losses and quality of life. The programme started at diagnosis before the start of treatment and was based on self-care after receiving instructions from a speech language pathologist and a physiotherapist. The patients were instructed to use the training programme during and after the treatment period. One hundred and ninety patients were included in the early experimental rehabilitation programme. A control group of 184 patients who did not receive early rehabilitation was constructed. It was shown that the programme could be implemented without delaying the start of oncological treatment, but no positive effects concerning survival, weight loss, functional loss, working ability, or quality of life were observed. The need for a neck dissection after EBRT cannot be determined by clinical examination as a high percentage of patients with clinical complete response showed viable tumor cells in the neck specimen. When performing a neck dissection, a SOND should be considered in suitable patients as morbidity of SOND is low except for shoulder disability. An EBRT dose delivered to the upper 5 cm of the oesophagus should be kept below 45 Gy to lower the risk of oesophageal stricture, and patients should be instructed to continue to swallow even if they receive enteral nutrition during treatment. Finally, even though no positive effects of early rehabilitation could be shown, the results do not contradict the idea that rehabilitation based on self-care can be effective. Efforts should be made to identify rehabilitation that can reduce functional losses and improve quality of life. Future rehabilitation programmes should also concentrate on identification of proper instruments for selection of patients and for evaluation of intervention in head and neck cancer patients