Background: In treatment planning for intensity-modulated proton therapy (IMPT), we aim to deliver the prescribed dose to the target yet minimize the dose to adjacent healthy tissue. Mixed-integer programming (MIP) has been applied in radiation therapy to generate treatment plans. However, MIP has not been used effectively for IMPT treatment planning with dose-volume constraints. In this study, we incorporated dose-volume constraints in an MIP model to generate treatment plans for IMPT. Methods: We created a new MIP model for IMPT with dose volume constraints. Two groups of IMPT treatment plans were generated for each of three patients by using MIP models for a total of six plans: one plan was derived with the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) method while the other plan was derived with our MIP model with dose-volume constraints. We then compared these two plans by dose-volume histogram (DVH) indices to evaluate the performance of the new MIP model with dose-volume constraints. In addition, we developed a model to more efficiently find the best balance between tumor coverage and normal tissue protection. Results: The MIP model with dose-volume constraints generates IMPT treatment plans with comparable target dose coverage, target dose homogeneity, and the maximum dose to organs at risk (OARs) compared to treatment plans from the conventional quadratic programming method without any tedious trial-and-error process. Some notable reduction in the mean doses of OARs is observed. Conclusions: The treatment plans from our MIP model with dose-volume constraints can meetall dose-volume constraints for OARs and targets without any tedious trial-and-error process. This model has the potential to automatically generate IMPT plans with consistent plan quality among different treatment planners and across institutions and better protection for important parallel OARs in an effective way.

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La technique de radiothérapie VMAT (Volumetric Modulated Arc Therapy), diffusée en 2009, combine les avantages des techniques d'arc thérapie dynamique aux avantages des techniques de radiothérapie conformationnelle avec modulation d'intensité (RCMI) par faisceaux stationnaires. L'objectif de la thèse est de rendre optimales les conditions de mise en œuvre du VMAT autour d'un accélérateur linéaire d'électrons Synergy/Elekta afin de sécuriser la technique et de pouvoir bénéficier de l'apport clinique potentiellement attendu. Sur la base d'une analyse de l'influence des différents paramètres de la chaîne de traitement, nous proposons des éléments d'optimisation du traitement à la fois sur la planification dosimétrique et sur le contrôle de son exécution sur la machine. Nous montrons que si la qualité de l'optimisation de la technique dépend des caractéristiques intrinsèques de l'accélérateur, elle est également fortement influencée par le paramétrage du système de planification des traitements (TPS). Nous mettons en évidence des différences comparées des collimateurs Beam Modulateur (largeur de lames de 4 mm) et MLCi2 (largeur de lames de 10 mm) tant sur le plan de la distribution de dose obtenue que sur l'efficience. Nous montrons que, si pour deux principaux TPS commercialisés (Pinnacle/Philips et Monaco/Elekta) les distributions de dose aux volumes cibles sont peu modifiées, les différences de méthodes implémentées influencent la distribution de dose aux tissus sains. Nous proposons des programmes de contrôles de qualité au niveau de l'accélérateur, des plans dosimétriques de traitement et de l'exécution des traitements. Afin de garantir un niveau de confiance élevé sur la dose délivrée, nous proposons une méthode d'évaluation de la fluence délivrée en cours de traitement basée sur l'analyse des paramètres machines. Nous établissons que le processus de traitement VMAT optimisé fournit des performances de qualité supérieure que les techniques de RCMI par faisceaux stationnaires pour quatre localisations tumorales majeures étudiées. / VMAT (Volumetric Modulated Arc Therapy) technique has been introduced in 2009, it combines advantage of arctherapy techniques with advantage of IMRT (Intensity Modulated Radio Therapy) techniques delivered with stationary beams. The purpose of the thesis is to optimise implementation conditions of VMAT for a Synergy/Elekta linear accelerator in order to secure the technique and to be able to benefit from potentially expected clinical improvement. From analysis of influence of various work flow parameters, we propose treatment optimisation factors both on dosimetric planning and on delivering control on the accelerator. We show that if optimisation quality depends on intrinsic accelerator characteristics, it also depends very much on configuration of treatment planning system (TPS). We highlight compared differences between Beam Modulateur (leaf width of 4 mm) and MLCi2 (leaf width of 10 mm) on dose distribution and on efficiency. We show that if differences of dose distributions are small for two major TPS (Pinnacle/Philips and Monao/Elekta), the differences of implemented methods affect dose distribution of healthy tissues. We suggest quality control set for accelerators, for treatment plans and for treatment delivery. In order to provide a high safety level on delivered dose, we suggest an evaluation method of the real fluence provided during treatment delivery by analysing accelerator parameters. We establish that optimised process of VMAT treatment provides better performance than RCMI techniques delivered with stationary beams for the four major cancer cases that has been studied.

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With the continued evolution of MEMS-based gas chromatography, the drive to develop new standalone systems with lower power consumptions and higher portability has increased. However, with improvements come tradeoffs, and trying to reduce the pressure drop requirements of previously reported semi-packed columns causes a significant sacrifice in separation efficiency. This thesis covers the techniques for evaluating the separation column in a gas chromatography system as well as the important parameters that have the most effect on a column’s efficiency. Ionic liquids are introduced as a stable and versatile stationary phase for micro separation columns. It then describes a MEMS-based separation column design utilizing density modulation of embedded micro-pillars which attempts to optimize the balance between separation efficiency and pressure drop. / Master of Science / Gas chromatography is a technique used by scientists to separate and identify chemical compounds present in a given test mixture. It is a versatile technique that can be used for qualitative and quantitative analysis of complex mixtures in a variety of applications. However, typical gas chromatography systems are confined to a lab because they are large and consume a lot of power. In order to overcome these problems, different research groups have focused their attention towards the development of portable MEMS-based gas chromatography systems. By miniaturizing the various components of a gas chromatography system, these two main issues can be alleviated. This thesis covers the strategies used to develop and evaluate the separation column of a gas chromatography system and introduce a new MEMS-based column design that will further reduce the power consumption.

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The objective of this thesis is to study the dynamic properties of laser diodes and the compensation for the nonlinearities of laser diodes based on the theory of Volterra series. In the first part of this thesis, an analytical expression in Volterra series is discussed to depict the nonlinear distortion of laser diodes up to the third order. The simulation results of this analytical method show that Volterra series model improves the accuracy of the description of the nonlinearity of laser diodes in comparison with small-signal analysis model. In the second part, the p^th-order inverse theory is introduced to compensate the lasers' nonlinear distortion. The compensation scheme is constructed and the simulation of the system is conducted in this thesis. The result shows that the laser nonlinear distortion can be compensated by using this technique. / Thesis / Master of Applied Science (MASc)