CT Image Electron Density Quantification in Regions with Metal Implants: Implications for Radiotherapy Treatment Planning

In radiotherapy planning, computed tomography (CT) images are used to quantify the electron density of tissues and provide spatial anatomical information. Treatment planning systems use these data to calculate the expected spatial distribution of absorbed dose in a patient. CT imaging is complicated by the presence of metal implants which cause increased image noise, produce artifacts throughout the image and can exceed the available range of CT number values within the implant, perturbing electron density estimates in the image. Furthermore, current dose calculation algorithms do not accurately model radiation transport at metal-tissue interfaces. Combined, these issues adversely affect the accuracy of dose calculations in the vicinity of metal implants. As the number of patients with orthopedic and dental implants grows, so does the need to deliver safe and effective radiotherapy treatments in the presence of implants. The Medical Physics group at the Cancer Centre of Southeastern Ontario and Queen's University has developed a Cobalt-60 CT system that is relatively insensitive to metal artifacts due to the high energy, nearly monoenergetic Cobalt-60 photon beam. Kilovoltage CT (kVCT) images, including images corrected using a commercial metal artifact reduction tool, were compared to Cobalt-60 CT images throughout the treatment planning process, from initial imaging through to dose calculation. An effective metal artifact reduction algorithm was also implemented for the Cobalt-60 CT system. Electron density maps derived from the same kVCT and Cobalt-60 CT images indicated the impact of image artifacts on estimates of photon attenuation for treatment planning applications. Measurements showed that truncation of CT number data in kVCT images produced significant mischaracterization of the electron density of metals. Dose measurements downstream of metal inserts in a water phantom were compared to dose data calculated using CT images from kVCT and Cobalt-60 systems with and without artifact correction. The superior accuracy of electron density data derived from Cobalt-60 images compared to kVCT images produced calculated dose with far better agreement with measured results. These results indicated that dose calculation errors from metal image artifacts are primarily due to misrepresentation of electron density within metals rather than artifacts surrounding the implants.

3D considerations for motion perception and visuomotor transformations

Moving through a stable, three-dimensional world is a hallmark of our motor and perceptual experience. This stability is constantly being challenged by movements of the eyes and head, inducing retinal blur and retino-spatial misalignments for which the brain must compensate. To do so, the brain must account for eye and head kinematics to transform two-dimensional retinal input into the reference frame necessary for movement or perception. The four studies in this thesis used both computational and psychophysical approaches to investigate several aspects of this reference frame transformation. In the first study, we examined the neural mechanism underlying the visuomotor transformation for smooth pursuit using a feedforward neural network model. After training, the model performed the general, three-dimensional transformation using gain modulation. This gave mechanistic significance to gain modulation observed in cortical pursuit areas while also providing several testable hypotheses for future electrophysiological work. In the second study, we asked how anticipatory pursuit, which is driven by memorized signals, accounts for eye and head geometry using a novel head-roll updating paradigm. We showed that the velocity memory driving anticipatory smooth pursuit relies on retinal signals, but is updated for the current head orientation. In the third study, we asked how forcing retinal motion to undergo a reference frame transformation influences perceptual decision making. We found that simply rolling one's head impairs perceptual decision making in a way captured by stochastic reference frame transformations. In the final study, we asked how torsional shifts of the retinal projection occurring with almost every eye movement influence orientation perception across saccades. We found a pre-saccadic, predictive remapping consistent with maintaining a purely retinal (but spatially inaccurate) orientation perception throughout the movement. Together these studies suggest that, despite their spatial inaccuracy, retinal signals play a surprisingly large role in our seamless visual experience. This work therefore represents a significant advance in our understanding of how the brain performs one of its most fundamental functions.

THE MICROSTRUCTURES OF ZR-EXCEL ALLOY: EFFECTS OF HEAVY ION IRRADIATION, PLASTIC DEFORMATION, THERMAL TREATMENT AND IN-SITU HEATING

Zr-Excel alloy (Zr-3.5Sn-0.8Nb-0.8Mo) is a dual phase (α + β) alloy in the as-received pressure tube condition. It has been proposed to be the pressure tube candidate material for the Generation-IV CANDU-Supercritical Water Reactor (CANDU-SCWR). In this dissertation, the effects of heavy ion irradiation, deformation and heat treatment on the microstructures of the alloy were investigated to enable us to have a better understanding of the potential in-reactor performance of this alloy. In-situ heavy ion (1 MeV) irradiation was performed to study the nucleation and evolution of dislocation loops in both α- and β-Zr. Small and dense type dislocation loops form under irradiation between 80 and 450 °C. The number density tends to saturate at ~ 0.1 dpa. Compared with the α-Zr, the defect yield is much lower in β-Zr. The stabilities of the metastable phases (β-Zr and ω-Zr) and the thermal-dynamically equilibrium phase, fcc Zr(Mo, Nb)2, under irradiation were also studied at different temperatures. Chemi-STEM elemental mapping was carried out to study the elemental redistribution caused by irradiation. The stability of these phases and the elemental redistribution are strongly dependent on irradiation temperature. In-situ time-of-flight neutron diffraction tensile and compressive tests were carried out at different temperatures to monitor lattice strain evolutions of individual grain families during these tests. The β-Zr is the strengthening phase in this alloy in the as-received plate material. Load is transferred to the β-Zr after yielding of the α-Zr grains. The temperature dependence of static strain aging and the yielding sequence of the individual grain families were discussed. Strong tensile/compressive asymmetry was observed in the {0002} grain family at room temperature. The microstructures of the sample deformed at 400 °C and the samples only subjected to heat treatment at the same temperature were characterized with TEM. Concentration of β phase stabilizers in the β grain and the morphology of β grain have significant effect on the stability of β- and ω-Zr under thermal treatment. Applied stress/strain enhances the decomposition of isothermal ω phase but suppresses α precipitation inside the β grains at high temperature. An α → ω/ZrO phase transformation was observed in the thin foils of Zr-Excel alloy and pure Zr during in-situ heating at 700 °C in TEM.

UNDERSTANDING ESSAY RATING AS A SOCIALLY MEDIATED ACTIVITY: THE CASE OF A HIGH-STAKES ENGLISH TEST IN CHINA

Most essay rating research in language assessment has examined human raters’ essay rating as a cognitive process, thus overlooking or oversimplifying the interaction between raters and sociocultural contexts. Given that raters are social beings, their practices have social meanings and consequences. Hence it is important to situate essay rating within its sociocultural context for a more meaningful understanding. Drawing on Engeström’s (1987, 2001) cultural-historical activity theory (CHAT) framework with a sociocultural perspective, this study reconceptualized essay rating as a socially mediated activity with both cognitive (individual raters’ goal-directed decision-making actions) and social layers (raters’ collective object-oriented essay rating activity at related settings). In particular, this study explored raters’ essay rating at one provincial rating centre in China within the context of a high-stakes university entrance examination, the National Matriculation English Test (NMET). This study adopted a multiple-method multiple-perspective qualitative case study design. Think-aloud protocols, stimulated recalls, interviews, and documents served as the data sources. This investigation involved 25 participants at two settings (rating centre and high schools), including rating centre directors, team leaders, NMET essay raters who were high school teachers, and school principals and teaching colleagues of these essay raters. Data were analyzed using Strauss and Corbin’s (1990) open and axial coding techniques, and CHAT for data integration. The findings revealed the interaction between raters and the NMET sociocultural context. Such interaction can be understood through a surface structure (cognitive layer) and a deep structure (social layer) concerning how raters assessed NMET essays, where the surface structure reflected the “what” and the deep structure explained the “how” and “why” in raters’ decision-making. This study highlighted the roles of goals and rules in rater decision-making, rating tensions and raters’ solutions, and the relationship between essay rating and teaching. This study highlights the value of a sociocultural view to essay rating research, demonstrates CHAT as a sociocultural approach to investigate essay rating, and proposes a direction for future washback research on the effect of essay rating. This study also provides support for NMET rating practices that can potentially bring positive washback to English teaching in Chinese high schools.

QUADRUPOLE CENTRAL TRANSITION NMR SPECTROSCOPY OF QUADRUPOLAR NUCLEI IN SOLUTION

This thesis reports on 17O (I = 5/2) and 59Co (I = 7/2) quadrupole central transition (QCT) NMR studies of three classes of biologically important molecules: glucose, nicotinamide and Vitamin B12 derivatives. Extensive QCT NMR experiments were performed over a wide range of molecular motion by changing solvent viscosity and temperature. 17O-labels were introduced at the 5- and 6-positions respectively: D-[5-17O]-glucose and D-[6-17O]-glucose following the literature method. QCT NMR greatly increased the molecular size limit obtained by ordinary solution NMR. It requires much lower temperatures to get the optimal spectral resolution, which are preferable for biological molecules. In addition, quadrupolar product parameter (PQ) and shielding anisotropy product parameter (PSA) were obtained for hydroxide group and amide group for the first time. For conventional NMR studies of quadrupolar nuclei, only PQ is accessible while QCT NMR obtained both PQ and PSA simultaneously. Our experiments also suggest the resolution of QCT NMR can be even better than that obtained by conventional NMR. We observed for the first time that the second-order quadrupolar interaction becomes a dominant relaxation mechanism under ultraslow motion. All these observations suggest that QCT NMR can become a standard technique for studying quadrupolar nuclei in solution.

Design and Synthesis of Acridine-Based Macrocyclic G-Quadruplex DNA Ligands

DNA sequences that are rich in the guanine nucleic base possess the ability to fold into higher order structures called G-quadruplexes. These higher level structures are formed as a result of two sets of four guanine bases hydrogen-bonding together in a planar arrangement called a guanine quartet. Guanine quartets subsequently stack upon each other to form quadruplexes. G-quadruplexes are mainly localized in telomeres as well as in oncogene promoters. One unique and promising therapeutic approach against cancer involves targeting and stabilizing G-quadruplexes with small molecules, generally in order to suppress oncogene expression and telomerase enzyme activity; the latter has been found to contribute to “out-of control” cell growth in ca. 80-85% of all cancer cells and primary tumours while being absent in normal somatic cells. In this work, we present efforts towards designing and synthesizing acridine-based macrocycles (Mh) and (Mb) with the purpose of providing potential G4 ligands that are suited for selective binding to G4 vs. duplex DNA, and stabilize G-quadruplex structures. Two ligands described in this study include an acridine core which provides an aromatic surface capable of π-π interactions with the surface of G-quadruplexes. The successful synthesis of 4,5-diaminoacridine is described in chapter 2, as an essential fragment of the macrocycles (Mh) and (Mb). In order to investigate the synthetic method for macrocyclization, model compounds composing almost half of the designed macrocycles were explored. As discussed in chapter 3, the synthesis of the model compound for (Mb) turned out to be challenging. However, as a step towards the synthesis of (Mh), the synthesis of the hydrogen-containing model compound, which is almost half of the desired macrocycle (Mh) was achieved in our group and proved to be promising.

Forging Iconographies and Casting Colonialism: Monuments and Memories in Ontario, 1850-2001

Commemorations are a critical window for exploring the social, political, and cultural trends of a specific time period. Over the past two centuries, the commemorative landscape of Ontario reaffirmed the inclusion/exclusion of particular racial groups. Intended as static markers to the past, monuments in particular visually demonstrated the boundaries of a community and acted as ongoing memorials to existing social structures. Using a specific type of iconography and visual language, the creators of monuments imbued the physical markers of stone and bronze with racialized meanings. As builders were connected with their own time periods and social contexts, the ideas behind these commemorations shifted. Nonetheless, creators were intent on producing a memorial that educated present and future generations on the boundaries of their “imagined communities.” This dissertation considers the carefully chosen iconographies of Ontario’s monuments and how visual symbolism was attached to historical memory. Through the examination of five case studies, this dissertation examines the shifting commemorative landscape of Ontario and how memorials were used to mark the boundaries of communities. By integrating the visual analysis of monuments and related images, it bridges a methodological and theoretical gap between history and art history. This dissertation opens an important dialogue between these fields of study and demonstrates how monuments themselves are critical “documents” of the past.

EXHAUSTING AFFECTS: THE NEGOTIATION OF AFFECTIVE LABOUR, NEOLIBERAL SUBJECTIVITY, AND FEMINIST POLITICS AMONG ANTI-VIOLENCE WORKERS

This thesis explores the affective and political life of anti-violence labour, with particular attention to the ways that neoliberalism comes to bear on subjectivity, embodiment, and relationality among women responding to violence. In fall of 2015, I conducted qualitative interviews with six women engaged in the work of responding to violence. The participants in this project articulated rich descriptions of the affective life of neoliberalism and the demands of neoliberal subjectivity, drawing particular attention to the affective labour involved in navigating the political complexities of anti-violence organizations, negotiating burnout, and affectively self-managing in order to meet norms of professionalism. Bringing participant narratives into conversations with feminist theories of affect, I argue for an account affective labour that centers the specific, materially embodied experiences of that work and for an account of neoliberalism as a system of embodied and affective pressures.

IMMUNE-ANGIOGENESIS MECHANISMS ASSOCIATED WITH PORCINE PREGNANCY SUCCESS AND FAILURE

Spontaneous fetal loss (25-40%) leading to decrease in litter size is a significant concern to the pork industry. A deficit in the placental vasculature has emerged as one of the important factors associated with fetal loss. During early pig pregnancy, the endometrium becomes enriched with immune cells recruited by conceptus-derived signals including specific chemokine stimuli. These immune cells assist in various aspects of placental development and angiogenesis. Recent evidence suggests that microRNAs (miRNAs: small non-coding RNAs that regulate gene expression) regulate immune cell development and their functions. In addition, intercellular communication including exchange of biomolecules (e.g. miRNAs) between the conceptus and endometrium regulate key developmental processes during pregnancy. To understand the biological significance of immune cell enrichment, regulation of their functions by miRNAs and transfer of miRNAs across the maternal fetal-interface, we screened specific sets of chemokines and pro- and anti-angiogenic miRNAs in endometrial lymphocytes (ENDO LY), endometrium, and chorioallantoic membrane (CAM) isolated from conceptus attachment sites (CAS) during early, gestation day (gd)20 and mid-pregnancy (gd50). We report increased expression of selected chemokines including CXCR3 and CCR5 in ENDO LY and CXCL10, CXCR3, CCL5, CCR5 in endometrium associated with arresting CAS at gd20. Some of these differences were also noted at the protein level (CXCL10, CXCR3, CCL5, and CCR5) in endometrium and CAM. We report for the first time significant differences for miRNAs involved in immune cell-derived angiogenesis (miR-296-5P, miR-150, miR-17P-5P, miR-18a, and miR-19a) between ENDO LY associated with healthy and arresting CAS. Significant differences were also found in endometrium and CAM for some miRNAs (miR-17-5P, miR-18a, miR-15b-5P, and miR-222). Finally, we confirm that placenta specific-exosomes contain proteins and 14 select miRNAs including miR-126-5P, miR-296-5P, miR-16, and miR-17-5P that are of relevance to early implantation events. We further demonstrated the bidirectional exosome shuttling between porcine trophectoderm cells (PTr2) and porcine aortic endothelial cells (PAOEC). PTr2-derived exosomes were able to modulate the endothelial cell proliferation that is crucial for the establishment of pregnancy. Our data unravels the selected chemokines and miRNAs associated with immune cell-regulated angiogenesis and reconfirm that exosome mediated cell-cell communication opens-up new avenues to understand porcine pregnancy.

A cloud-based system for measuring radiation treatment plan similarity

PURPOSE: Radiation therapy is used to treat cancer using carefully designed plans that maximize the radiation dose delivered to the target and minimize damage to healthy tissue, with the dose administered over multiple occasions. Creating treatment plans is a laborious process and presents an obstacle to more frequent replanning, which remains an unsolved problem. However, in between new plans being created, the patient's anatomy can change due to multiple factors including reduction in tumor size and loss of weight, which results in poorer patient outcomes. Cloud computing is a newer technology that is slowly being used for medical applications with promising results. The objective of this work was to design and build a system that could analyze a database of previously created treatment plans, which are stored with their associated anatomical information in studies, to find the one with the most similar anatomy to a new patient. The analyses would be performed in parallel on the cloud to decrease the computation time of finding this plan. METHODS: The system used SlicerRT, a radiation therapy toolkit for the open-source platform 3D Slicer, for its tools to perform the similarity analysis algorithm. Amazon Web Services was used for the cloud instances on which the analyses were performed, as well as for storage of the radiation therapy studies and messaging between the instances and a master local computer. A module was built in SlicerRT to provide the user with an interface to direct the system on the cloud, as well as to perform other related tasks. RESULTS: The cloud-based system out-performed previous methods of conducting the similarity analyses in terms of time, as it analyzed 100 studies in approximately 13 minutes, and produced the same similarity values as those methods. It also scaled up to larger numbers of studies to analyze in the database with a small increase in computation time of just over 2 minutes. CONCLUSION: This system successfully analyzes a large database of radiation therapy studies and finds the one that is most similar to a new patient, which represents a potential step forward in achieving feasible adaptive radiation therapy replanning.

Autonomy-Oriented Social Movements and the Politics of Affect

Abstract This dissertation explores damaging tendencies that exist within autonomy-oriented activism in the West. I examine how affect shapes the way that internal conflict is approached and internal strife is dealt with in radical communities. I adopt Sara Ahmed’s proposition “that our emotions are bound up with the securing of the social hierarchy” (Ahmed, 2004b: 4) and given that autonomy-oriented practices are committed to dismantling existing hierarchies, it follows that the less oppressive social configurations sought by autonomous social movements must have different emotional underpinnings. My thesis involves applying critical theory on affect and emotion in social movements to interview data gathered from activists both currently and historically involved in autonomy-oriented social movement communities in Kingston, Ontario. I ask whether anglophone, western-based, autonomy-oriented social movements reproduced understandings of affect/emotions/feelings that underwrite the social order they are working against? I also ask, “how are our emotions conditioned by capitalism?”. The research that I engage with provides responses to these questions by pointing out how the dominant discourse on emotions in the West encourages and informs certain modes of identity production that affect the diminishing and sad practices of autonomy-oriented communities and the (re)production of oppressive practices found in the dominant order. My work critically places this psychologizing view of emotions, and its damaging effects on resistance, within the context of neoliberal capitalism. I argue that the way we understand the politics of affect is an important dimension of radical struggle, and will inform and impact upon our individual and collective capacities to respond to, and refuse to reproduce relations of control and domination. I look for an understanding of “why” and to “what extent” these determinations exists, and look for hope in a politics of affect which supports an autonomy-oriented ethic.

CRISPR/Cas9-Mediated Gene Editing of ARG1 in Cell Lines and Primary Cells

Arginase 1 deficiency, a urea cycle disorder resulting from an inability of the body to convert arginine into urea, results in hyperargininemia and sporadic episodes of hyperammonemia. Arginase 1 deficiency can lead to a range of developmental disorders and progressive spastic diplegia in children, and current therapeutic options are limited. Clustered regularly interspaced short palindromic repeat (CRISPR) /CRISPR associated protein (Cas) 9 gene editing systems serve as a novel means of treating genetic disorders such as Arginase 1 (ARG1) deficiency, and must be thoroughly examined to determine their curative capabilities. In these experiments numerous guide RNAs and CRISPR/Cas9 systems targeting the ARG1 gene were designed and observed by heteroduplex assay for their targeting capabilities and cleavage efficiencies in multiple cell lines. The CRISPR/Cas9 system utilized in these experiments, along with a panel of guide RNAs targeting various locations in the arginase 1 gene, successfully produced targeted cleavage in HEK293, MCF7, A549, K562, HeLa, and HepG2 cells; however, targeted cleavage in human dermal fibroblasts, blood outgrowth endothelial cells, and induced pluripotent stem cells was not observed. Additionally, a CRISPR/Cas system involving partially inactivated Cas9 was capable of producing targeted DNA cleavage in intron 1 of ARG1, while a Cas protein termed Cpf1 was incapable of producing targeted cleavage. These results indicate a complex set of variables determining the CRISPR/Cas9 systems’ capabilities in the cell lines and primary cells tested. By examining epigenetic factors and alternative CRISPR/Cas9 gene targeting systems, the CRISPR/Cas9 system can be more thoroughly considered in its ability to act as a means towards editing the genome of arginase 1-deficient individuals.

EDUCATING THE PUBLIC THROUGH NEWS MEDIA: CASE STUDIES OF NEWS LITERACY IN THE NEW MEDIA LANDSCAPE

Two decades of unprecedented changes in the media landscape have increased the complexity of informing the public through news media. With significant changes to the way the news industry does business and the way news consumers access this information, a new set of skills is being proposed as essential for today’s news consumer. News literacy is the use of critical thinking skills to assess the reliability and source of the information that people consume on a daily basis, as well as fostering self-awareness of personal news consumption habits and how it can create audience bias. The purpose of this study was to examine how adults experience the news in their everyday lives and to describe the nature of the news literacy skills people employ in their daily news consumption. This study purposefully selected four adults who have completed high school, and who regularly consume news information across a number of platforms, both traditional and digital. Two of the participants, one man and one woman, were over 50 years old. One other male participant was in his 30’s and the final participant, a young woman, was in her 20’s. They all utilized both traditional and digital media on a regular basis and all had differing skill levels when using social media for information. Their news experiences were documented by in-depth interviews and the completion of seven daily news logs. In their daily logs the participants differentiated news information from other information available on-line but the interviews revealed a contradiction between their intentions and their news consumption practices. All four participants had trouble distinguishing between news and opinion pieces in the news information realm. In addition all but one seemed unaware of their personal bias and any possible effect it was having on their news consumption. Further research should explore the benefits of an adult-centered news literacy curriculum on news consumers similar to the participants, and should examine the development of audience bias and its relationship to the daily exposure people have to the torrent of information that is available to them on a daily basis.

DEVELOPMENT OF AN ADJUSTABLE SUTURE TECHNIQUE FOR TRABECULECTOMY

This research presents a new design of an adjustable suture that could provide a better intraocular pressure (IOP) control in the post treatment of trabeculectomy surgery and limit associated complication with the current suturing techniques. A better control in tension suture brings a great deal of advantages to this surgical technique compared with the traditional adjustable suture. A length adjustment can be added in advance to a 10-0 nylon suture which enables suture tension to be released during the postoperative period of trabeculectomy surgery. This adjustment has a D-ring geometry made of 10-0 nylon suture adhered to a 10-0 nylon surgical suture which is used to close the scalar flap. The D ring was adhered with about 180 microdroplet of Loctite 4311that was found to form a strong joint to connect the D ring to the main 10-0 nylon suture and strong enough to carry the added tension instead after cutting the central suture between the two joints of the D ring. The geometry of adjustment is the key factor of maintaining the IOP at the normal range and keeping the scleral flap tight enough and secure so that aqueous humor continues to percolate under the subconjunctiva. It has been found that a 365, and 450 µm length extensions can release suture tension postoperatively and relieve the intraocular pressure within the eye by 33, and 66% respectively. The fabrication process of the new adjustable suture was divided into two steps: fabrication of micro jig and forming microdroplets. A micro jig was fabricated in order to form and bond a precise length extension to the new design of the adjustable suture. In addition, a new liquid separation technique has been followed in this study in order to generate micro adhesive droplets as small as 50µm for bonding the new adjustable suture structure.

SINGLE STAGE LED DRIVER TECHNOLOGY WITH LOW FREQUENCY RIPPLE CANCELLATION

Because of high efficacy, long lifespan, and environment-friendly operation, LED lighting devices become more and more popular in every part of our life, such as ornament/interior lighting, outdoor lightings and flood lighting. The LED driver is the most critical part of the LED lighting fixture. It heavily affects the purchasing cost, operation cost as well as the light quality. Design a high efficiency, low component cost and flicker-free LED driver is the goal. The conventional single-stage LED driver can achieve low cost and high efficiency. However, it inevitably produces significant twice-line-frequency lighting flicker, which adversely affects our health. The conventional two-stage LED driver can achieve flicker-free LED driving at the expenses of significantly adding component cost, design complexity and low the efficiency. The basic ripple cancellation LED driving method has been proposed in chapter three. It achieves a high efficiency and a low component cost as the single-stage LED driver while also obtaining flicker-free LED driving performance. The basic ripple cancellation LED driver is the foundation of the entire thesis. As the research evolving, another two ripple cancellation LED drivers has been developed to improve different aspects of the basic ripple cancellation LED driver design. The primary side controlled ripple cancellation LED driver has been proposed in chapter four to further reduce cost on the control circuit. It eliminates secondary side compensation circuit and an opto-coupler in design while at the same time maintaining flicker-free LED driving. A potential integrated primary side controller can be designed based on the proposed LED driving method. The energy channeling ripple cancellation LED driver has been proposed in chapter five to further reduce cost on the power stage circuit. In previous two ripple cancellation LED drivers, an additional DC-DC converter is needed to achieve ripple cancellation. A power transistor has been used in the energy channeling ripple cancellation LED driving design to successfully replace a separate DC-DC converter and therefore achieved lower cost. The detailed analysis supports the theory of the proposed ripple cancellation LED drivers. Simulation and experiment have also been included to verify the proposed ripple cancellation LED drivers.