1,721,132 research outputs found
Detecting breast cancer tissue with diffuse reflectance spectroscopy
Full text linkNowadays, the majority of patients with small tumors undergo breast-conserving surgery which aims at conserving the shape of the breast by resecting only a small portion of the breast including the tumor followed by radiation therapy. There is one very important condition that has to be met during breast-conserving surgery in order to minimize the risk of a local recurrence, which is complete removal of the tumor, or in other words, the absence of positive resection margins. Currently, there are no sufficient margin assessment technologies available that can provide the surgeon with real-time feedback on whether margins are positive for tumor. Diffuse Reflectance Spectroscopy is an optical technology that reflects the composition and morphology of tissue by measuring the interaction between light and tissue. A DRS measurement will provide information on the optical characteristics of tissue which can be used to discriminate different tissue types. Potentially DRS measurements can help the surgeon in characterizing tissue and thereby provide guidance during breast-conserving surgery. The aim of this thesis was to address some of the challenges that hamper progressing DRS into the OR room for the detection of positive resection margins. First, the optical differences between DRS measurements of healthy tissue and tumor tissue are compared. Second, the influence of tissue status (in vivo or ex vivo) and patient-specific characteristics (i.e. neo-adjuvant chemotherapy) are examined. Furthermore, the ability of DRS to classify measurements of locations with a mixture of tissue types is investigated. Finally, also the feasibility of translating the technology into the clinic is investigated in an in vivo study in which biopsies were acquired with an optical biopsy needle
Colorectal liver metastases: spectroscopy, immune response and radiofrequency ablation
Full text linkColorectal cancer is the most common form of cancer and the 2nd most frequent cancer related death in Europe. Up to half of patients with colorectal cancer develop liver metastases during their lifetime. This thesis concerns quality improvements in care of patients with colorectal liver metastases
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Current advances in colorectal cancer treatment
Full text linkThe general aim of this thesis was to examine current advances in the treatment of colorectal cancer. The first part of this thesis is focused on new application of existing treatment in patients with stage IV CRC. Chapter 2 evaluates the feasibility and effectiveness of short-course pelvic radiotherapy (5 x 5 Gy) followed by systemic therapy and local treatment of all tumor sites in potentially curable stage IV rectal cancer patients in daily practice. A multicenter retrospective study is performed, evaluating the completion rate of the full treatment schedule, symptom control of the primary tumor and survival. 16 Chapter 1 In Chapter 3, high dose Stereotactic Body Radiation Therapy (SBRT) is compared to low dose SBRT for hepatic metastases. The aim of this study is to evaluate the efficacy and safety of high versus low dose SBRT in patients with liver metastases and to determine prognostic variables on local control and overall survival. Chapter 4 describes a prospective, randomized controlled pilot study conducted in the Netherlands Cancer Institute and examines if neoadjuvant chemotherapy and/or targeted therapy in patients with unresectable liver metastases can inhibit the growth of the metastases induced by the primary tumor resection. The second part of this thesis is focused on new surgical techniques for localized CRC surgery. Chapter 5 includes an ex vivo study investigating the use of hyperspectral imaging for tissue classification in CRC. Tissue samples from CRC surgery were imaged with two hyperspectral cameras. The ultimate goal is to develop a real-time technique for tissue identification in colorectal surgery. In Chapter 6 and 7, a different intraoperative imaging technique is evaluated. Chapter 6 evaluates whether image-guided navigation during locally advanced primary or recurrent rectal cancer surgery can improve resection margin rates compared to rectal surgery without navigation. The study compares the clinical outcomes of patients from a prospective, single-arm study with patients from a historical cohort. Chapter 7 explores the feasibility of real-time tumor tracking with image-guided navigation in patients with non-fixed mobile rectal tumors. An electromagnetic tracking system is used to real-time track the rectal tumor during the course of surgery
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Optical tissue identification: weefseldifferentiatie met behulp van licht
Full text linkThis thesis describes the evaluation of optical tissue identification for surgical applications. Three promising techniques are examined. After exploration of near infra-red fluorescence imaging and photoacoustic imaging, the thesis will focus on diffuse reflectance spectroscopy (DRS) for surgical tissue identification. Chapter two describes the use of an intraoperative fluorescence camera in breast cancer phantoms. The technique provides the surgeon with an image overlay of the fluorescent contrast agent in phantoms mimicking absorption and scattering properties of human breast tissue. Important benefits and drawbacks are described. Chapter three covers the application of photoacoustic imaging in surgery. The research is focused on lymph nodes in melanoma patients. Melanin, a strong optical absorber is imaged photoacoustically. The spectral identification of both tumor and blood vessels is demonstrated in phantoms and human lymph nodes ex vivo. The photoacoustic imager used is a reflective type, with the light source incorporated in the ultrasound detector. Diffuse reflection spectroscopy is presented as an optical technique able to identify both tumor and vital surrounding structures like blood vessels and nerves. Colorectal tumors are frequently in close relation with vital structures. In oncologic rectum surgery, bladder- and sexual dysfunctions are both feared and high in incidence. Chapter four describes the identification of colorectal tumor using DRS. Chapter five and six describe the identification of peripheral nerves in human during surgery. Peripheral nerves are often part of the vital structures surrounding a tumor. Ideally, image guided surgery depicts both tumor and vital surrounding tissue. Chapter five describes the identification of larger nerves as proof of principle. Chapter six is committed to the detection of smaller peripheral nerves. Optimization and validation is not necessarily executed in humans in vivo. Logistically, and patient friendly, more suited for extensive measurements are a post mortem- or animal studies. However, DRS is subject to the morphological composition and biochemical make-up of the tissue, and both will change post mortem and may differ between human and animal. Chapter seven describes the optical similarities and differences between in vivo versus post mortem and human versus swine, focused on nerve identification. In chapter eight we explore to possibilities to incorporate the DRS technique into a clinical device. We choose a bronchoscopic tool to fully utilize the small size and flexibility of the DRS optical fibers. This thesis concludes with a general discussion and outlook on a use of optical tissue identification
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
"Cutting-edge" technology for oncological oral surgery
Full text linkCutting-edge technology has the potential to provide guidance during oncological oral surgery. Guidance could be considered in two ways: to evaluate the cutting edge of the resected specimen after the resection (resection margin assessment) or to indicate where to cut during the resection (surgical guidance). To determine whether the tumor is completely excised during surgery, there is a need for technologies that provide intra-operative feedback on the status of the resection margin. In this thesis, the status of the resection margin of fresh surgical specimens from patients with oral cavity cancer was evaluated with ultrasound, diffuse reflectance spectroscopy (DRS) and hyperspectral imaging (HSI). Ultrasound works fast, reaches a sampling depth of several centimetres and is widely available. However, it is user dependent and cannot detect microscopic tumor infiltrations. DRS is suitable for microscopic tumor detection at specific suspicious locations build into a surgical instrument, whereas HSI could be used for evaluation of the whole resection surface in one view. However, these optical technologies require more research to increase the robustness. Surgical guidance is relevant in patients undergoing surgery for malignant disease invading the mandible, where osteotomies (i.e., the resection through bone) of the involved part of the mandible must be determined accurately to ensure clear resection margins, but also to allow precise placement of bone segments for reconstruction. At the moment, these surgeries are prepared virtually, and patient-specific cutting guides are used to translate the position of the osteotomies from the virtual surgical plan to the clinical situation in the operating room. It is hypothesised that the use of surgical navigation could expedite the preparation of the procedure and improve the accuracy. The accuracy of the surgical navigation system was evaluated with a patient study and inaccuracies of 2.6 ± 1.5 mm were achieved. A dental splint was designed to improve the accuracy further (inaccuracy of 0.83 mm). Furthermore, to achieve both guidance in localization of the osteotomy as well as guidance during sawing, a navigated cutting guide was developed
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
