Virtual simulation of the postsurgical cosmetic outcome in patients with pectus excavatum

Pectus excavatum is the most common congenital deformity of the anterior chest wall, in which several ribs and the sternum grow abnormally. Nowadays, the surgical correction is carried out in children and adults through Nuss technic. This technic has been shown to be safe with major drivers as cosmesis and the prevention of psychological problems and social stress. Nowadays, no application is known to predict the cosmetic outcome of the pectus excavatum surgical correction. Such tool could be used to help the surgeon and the patient in the moment of deciding the need for surgery correction. This work is a first step to predict postsurgical outcome in pectus excavatum surgery correction. Facing this goal, it was firstly determined a point cloud of the skin surface along the thoracic wall using Computed Tomography (before surgical correction) and the Polhemus FastSCAN (after the surgical correction). Then, a surface mesh was reconstructed from the two point clouds using a Radial Basis Function algorithm for further affine registration between the meshes. After registration, one studied the surgical correction influence area (SCIA) of the thoracic wall. This SCIA was used to train, test and validate artificial neural networks in order to predict the surgical outcome of pectus excavatum correction and to determine the degree of convergence of SCIA in different patients. Often, ANN did not converge to a satisfactory solution (each patient had its own deformity characteristics), thus invalidating the creation of a mathematical model capable of estimating, with satisfactory results, the postsurgical outcome.Fundação para a Ciência e a Tecnologia, Portugal (FCT) through the Postdoc grant referenced SFRH/BPD/46851/2008 and R&D project referenced PTDC/SAU-BEB/103368/2008

Optimization of craniosynostosis surgery: virtual planning, intraoperative 3D photography and surgical navigation

Mención Internacional en el título de doctorCraniosynostosis is a congenital defect defined as the premature fusion of one or more cranial sutures. This fusion leads to growth restriction and deformation of the cranium, caused by compensatory expansion parallel to the fused sutures. Surgical correction is the preferred treatment in most cases to excise the fused sutures and to normalize cranial shape. Although multiple technological advancements have arisen in the surgical management of craniosynostosis, interventional planning and surgical correction are still highly dependent on the subjective assessment and artistic judgment of craniofacial surgeons. Therefore, there is a high variability in individual surgeon performance and, thus, in the surgical outcomes. The main objective of this thesis was to explore different approaches to improve the surgical management of craniosynostosis by reducing subjectivity in all stages of the process, from the preoperative virtual planning phase to the intraoperative performance. First, we developed a novel framework for automatic planning of craniosynostosis surgery that enables: calculating a patient-specific normative reference shape to target, estimating optimal bone fragments for remodeling, and computing the most appropriate configuration of fragments in order to achieve the desired target cranial shape. Our results showed that automatic plans were accurate and achieved adequate overcorrection with respect to normative morphology. Surgeons’ feedback indicated that the integration of this technology could increase the accuracy and reduce the duration of the preoperative planning phase. Second, we validated the use of hand-held 3D photography for intraoperative evaluation of the surgical outcome. The accuracy of this technology for 3D modeling and morphology quantification was evaluated using computed tomography imaging as gold-standard. Our results demonstrated that 3D photography could be used to perform accurate 3D reconstructions of the anatomy during surgical interventions and to measure morphological metrics to provide feedback to the surgical team. This technology presents a valuable alternative to computed tomography imaging and can be easily integrated into the current surgical workflow to assist during the intervention. Also, we developed an intraoperative navigation system to provide real-time guidance during craniosynostosis surgeries. This system, based on optical tracking, enables to record the positions of remodeled bone fragments and compare them with the target virtual surgical plan. Our navigation system is based on patient-specific surgical guides, which fit into the patient’s anatomy, to perform patient-to-image registration. In addition, our workflow does not rely on patient’s head immobilization or invasive attachment of dynamic reference frames. After testing our system in five craniosynostosis surgeries, our results demonstrated a high navigation accuracy and optimal surgical outcomes in all cases. Furthermore, the use of navigation did not substantially increase the operative time. Finally, we investigated the use of augmented reality technology as an alternative to navigation for surgical guidance in craniosynostosis surgery. We developed an augmented reality application to visualize the virtual surgical plan overlaid on the surgical field, indicating the predefined osteotomy locations and target bone fragment positions. Our results demonstrated that augmented reality provides sub-millimetric accuracy when guiding both osteotomy and remodeling phases during open cranial vault remodeling. Surgeons’ feedback indicated that this technology could be integrated into the current surgical workflow for the treatment of craniosynostosis. To conclude, in this thesis we evaluated multiple technological advancements to improve the surgical management of craniosynostosis. The integration of these developments into the surgical workflow of craniosynostosis will positively impact the surgical outcomes, increase the efficiency of surgical interventions, and reduce the variability between surgeons and institutions.Programa de Doctorado en Ciencia y Tecnología Biomédica por la Universidad Carlos III de MadridPresidente: Norberto Antonio Malpica González.- Secretario: María Arrate Muñoz Barrutia.- Vocal: Tamas Ung

Feasibility assessment of the interactive use of a Monte Carlo algorithm in treatment planning for intraoperative electron radiation therapy

This work analysed the feasibility of using a fast, customized Monte Carlo (MC) method to perform accurate computation of dose distributions during pre- and intraplanning of intraoperative electron radiation therapy (IOERT) procedures. The MC method that was implemented, which has been integrated into a specific innovative simulation and planning tool, is able to simulate the fate of thousands of particles per second, and it was the aim of this work to determine the level of interactivity that could be achieved. The planning workflow enabled calibration of the imaging and treatment equipment, as well as manipulation of the surgical frame and insertion of the protection shields around the organs at risk and other beam modifiers. In this way, the multidisciplinary team involved in IOERT has all the tools necessary to perform complex MC dosage simulations adapted to their equipment in an efficient and transparent way. To assess the accuracy and reliability of this MC technique, dose distributions for a monoenergetic source were compared with those obtained using a general-purpose software package used widely in medical physics applications. Once accuracy of the underlying simulator was confirmed, a clinical accelerator was modelled and experimental measurements in water were conducted. A comparison was made with the output from the simulator to identify the conditions under which accurate dose estimations could be obtained in less than 3 min, which is the threshold imposed to allow for interactive use of the tool in treatment planning. Finally, a clinically relevant scenario, namely early-stage breast cancer treatment, was simulated with pre- and intraoperative volumes to verify that it was feasible to use the MC tool intraoperatively and to adjust dose delivery based on the simulation output, without compromising accuracy. The workflow provided a satisfactory model of the treatment head and the imaging system, enabling proper configuration of the treatment planning system and providing good accuracy in the dosage simulation

Craniofacial Growth Series Volume 56

https://deepblue.lib.umich.edu/bitstream/2027.42/153991/1/56th volume CF growth series FINAL 02262020.pdfDescription of 56th volume CF growth series FINAL 02262020.pdf : Proceedings of the 46th Annual Moyers Symposium and 44th Moyers Presymposiu

Comparative validation of single-shot optical techniques for laparoscopic 3-D surface reconstruction

Intra-operative imaging techniques for obtaining the shape and morphology of soft-tissue surfaces in vivo are a key enabling technology for advanced surgical systems. Different optical techniques for 3-D surface reconstruction in laparoscopy have been proposed, however, so far no quantitative and comparative validation has been performed. Furthermore, robustness of the methods to clinically important factors like smoke or bleeding has not yet been assessed. To address these issues, we have formed a joint international initiative with the aim of validating different state-of-the-art passive and active reconstruction methods in a comparative manner. In this comprehensive in vitro study, we investigated reconstruction accuracy using different organs with various shape and texture and also tested reconstruction robustness with respect to a number of factors like the pose of the endoscope as well as the amount of blood or smoke present in the scene. The study suggests complementary advantages of the different techniques with respect to accuracy, robustness, point density, hardware complexity and computation time. While reconstruction accuracy under ideal conditions was generally high, robustness is a remaining issue to be addressed. Future work should include sensor fusion and in vivo validation studies in a specific clinical context. To trigger further research in surface reconstruction, stereoscopic data of the study will be made publically available at www.open-CAS.com upon publication of the paper

Determining the Influence of Environment and Minimizing Residual Roughness in Laser Corneal Refractive Surgery

Aims: This dissertation deals with multiple topics, with a global aim of determining the influence of environment and minimizing residual roughness in laser corneal refractive surgery. The multiple topics under consideration are listed below: •TOPIC A: To analyze the effect of seasonal changes in PMMA Performance using the SCHWIND AMARIS laser system •TOPIC B: To analyze impact of various humidity and temperature settings on excimer laser ablation of PET, PMMA and porcine corneal tissue •TOPIC C: To analyze the impact of residual roughness after corneal ablation in perception and vision •TOPIC D: To outline a rigorous simulation model for simulating shot-by-shot ablation process. Furthermore, to simulate the impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap and lattice geometry on ablation smoothness. •TOPIC E: To test the impact of laser beam truncation, dithering, and jitter on residual roughness after PMMA ablations, using a close-to-Gaussian beam profile. Methods: TOPIC A: By analyzing PMMA and PET ablation performance by a large series of AMARIS laser systems (Schwind eye-tech solutions, Germany) inside a climate controlled environment, the influence purely coming from the seasonal changes was investigated in a large scale retrospective cross sectional review. Seasonal outcomes were evaluated in terms of PMMA and PET Performance stratified for every month in a year, as well as stratified for each season in a year. TOPIC B: A Study was conducted using AMARIS system placed inside a climate chamber. Ablations were performed on PET, PMMA and porcine cornea. Impact of wide range of temperature (~18°C to ~30°C) and relative humidity (~25% to ~80%) on laser ablation outcomes was tested using nine climate test settings. Multiple linear regression was performed using least square method with predictive factors: Temperature, Relative Humidity, Time stamp. Influence of climate settings was modelled for Pulse Energy, Pulse Fluence, ablation efficiency on PMMA and porcine cornea tissue. TOPIC C: The Indiana Retinal Image Simulator (IRIS) was used to simulate the polychromatic retinal image. Using patient-specific Zernike coefficients and pupil diameter, the impact of different levels of chromatic aberrations was calculated. Corneal roughness was modeled via both random and filtered noise, using distinct pre-calculated higher order Zernike coefficient terms. The outcome measures for the simulation were simulated retinal image, Strehl Ratio and Visual Strehl Ratio computed in frequency domain. The impact of varying degree of roughness, spatial frequency of the roughness, and pupil dilation was analyzed on these outcome measures. TOPIC D: Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical, beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or PMMA). The roughness in ablation was determined by the root-mean-square per square root of layer depth. TOPIC E: A study was conducted using a modified AMARIS system. For the PMMA ablations, two configurations (with a 0.7mm pinhole and 0.75mJ and without pinhole and 0.9mJ (for fluences of 329mJ/cm2 and 317mJ/cm2 and corneal spot volumes of 174pl and 188pl)) were considered, along with two types of lattices (with and without ordered dithering to select the optimum pulse positions), and two types of spot placement (with and without jitter). Real ablations on PMMA (ranging from -12D to +6D with and without astigmatism) completed the study setup. The effect of the 2x2x2 different configurations was analyzed based on the roughness in ablation estimated from the root mean square error in ablation. Results: TOPIC A: The seasons winter and summer showed statistical significant variations with respect to the global values for all the tested parameters except the nominal number of laser pulses for high and low fluence setting. The metric technical performance of the analyzed systems showed a stronger PMMA ablation performance in summer time compared to a weaker performance in the winter time, with the maximum seasonal deviation of 6%. The results were consistently confirmed in seasonal as well as monthly analyses. TOPIC B: Temperature changes did not affect laser pulse energy, pulse fluence (PET), and ablation efficiency (on PMMA or porcine corneal tissue) significantly. Changes in relative humidity were more critical and significantly affected laser pulse energy, high fluence and low fluence. Opposite trend was observed between the ablation performance on PMMA and porcine cornea. TOPIC C: In case of a constant roughness term, reducing the pupil size resulted in improved outcome measures and simulated retinal image. The calculated image quality metrics deteriorated dramatically with increasing roughness. Clear distinction was observed in outcome measures for corneal roughness simulated as random noise compared to filtered noise, further influenced by the spatial frequency of filtered noise. TOPIC D: Truncating the beam profile increased the roughness in ablation, Gaussian profiles theoretically resulted in smoother ablations, round spot geometries produced lower roughness in ablation compared to square geometry, triangular lattices theoretically produced lower roughness in ablation compared to the reticular lattice, theoretically modelled beam profiles showed lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tend to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness has been found. TOPIC E: Truncation of the beam was negatively associated to a higher level of residual roughness; ordered dithering to select the optimum pulse positions was positively associated to a lower level of residual roughness; jitter was negatively associated to a higher level of residual roughness. The effect of dithering was the largest, followed by truncation, and jitter had the lowest impact on results. Conclusions: The large scale retrospective cross sectional study presented in this work, demonstrated a cyclic winter-summer variation in PMMA ablation using the AMARIS lasers. These seasonal variations were further substantiated with the experiments conducted in the climate chamber, over a wide range of temperature and humidity. Temperature changes did not affect laser pulse energy, pulse fluence, and ablation efficiency (on PMMA or porcine corneal tissue) significantly. However, changes in relative humidity were more critical and significantly affected laser pulse energy, high fluence and low fluence. The proposed well-fitting multi-linear model can be utilized for compensation of temperature and humidity changes on ablation efficiency. The relationship between calibration materials like PMMA and corneal tissue shall be analyzed cautiously before designing the calibration routine, in order to obtain optimum outcomes with minimum deviations. Despite its limitations, the simple and robust method proposed here for quantifying the influence of post-ablation roughness on vision and perception, can be utilized in different applications. From the simulations of the shot-by-shot ablation process, a theoretical proper optimum configuration was found for minimizing the roughness in ablation for defined input parameters. The PMMA experiments confirmed the theoretical proper optimum settings in real world conditions. The results and improvements derived out of this work can be directly applied to the laser systems for corneal refractive surgery, to help reduce the complications and occurrence of adverse events during and after refractive surgery, and improve the short term and long term postoperative clinical outcomes