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Coming dissertations at MedFak

  • CT Guided Ablation of T1 Renal Tumors Author: Vanessa Acosta Ruiz Link: Publication date: 2019-10-11 10:06

    The widespread use of medical imaging contributes to the increased detection of incidentally detected small renal tumors, a majority which are often indolent masses found in elderly patients with preexisting chronic kidney disease. In Sweden, partial nephrectomy with minimal invasive surgical approach is the current standard for removing these tumors, although another option is percutaneous image-guided tumor ablation that allows treatment of elderly patients with comorbidities for who surgery is a risk. Due to the lack of long-term follow-up studies and prospective randomized trials, ablation is still considered an alternative option to surgery in Sweden. The aim of this thesis was to evaluate treatment of T1 renal tumors with CT guided radiofrequency (RFA) and microwave ablation (MWA).

    Factors affecting the efficacy rate of complete tumor ablation with RFA after a single session were evaluated (Paper I). Optimal electrode placement and a long tumor distance to the collecting system were associated with an increased primary efficacy. Renal tumor RFA was compared with laparoscopic partial nephrectomy (LPN: Papers II-III): both methods had comparable secondary efficacy rates, but RFA involved several treatment sessions. Total session times and hospitalization times were shorter and complications less frequent for RFA than for LPN (Paper II). After treatment, renal function impact was assessed by evaluation of both renal function quantity and quality through determination of the split renal function (SRF: Paper III). Standard renal function measurements were assessed and both RFA and LPN were nephron sparing when treating small renal tumors and did not affect creatinine or GFR. However, LPN involved greater SRF reduction in the affected kidney than RFA. Initial experience with microwave ablation was evaluated and this new ablation technique demonstrated high efficacy rates with fewer complications, and was comparable with the mid-term results of now established ablation techniques (Paper IV).

    In conclusion, CT guided RFA and MWA are safe and effective treatments for the removal of T1 renal tumors. This thesis provides further insights into the field of thermal ablation of small renal masses, which can aid future treatment selection and patient management.

  • Brain, consciousness and disorders of consciousness at the intersection of neuroscience and philosophy Author: Michele Farisco Link: Publication date: 2019-10-07 13:12

    The present dissertation starts from the general claim that neuroscience is not neutral, with regard to theoretical questions like the nature of consciousness, but it needs to be complemented with dedicated conceptual analysis. Specifically, the argument for this thesis is that the combination of empirical and conceptual work is a necessary step for assessing the significant questions raised by the most recent study of the brain. Results emerging from neuroscience are conceptually very relevant in themselves but, notwithstanding its theoretical sophistication, neuroscience is not sufficient to provide a complete interpretation or an appropriate understanding of their impact. Consequently, the present thesis starts from the need for an interdisciplinary and hybrid field of research, i.e. fundamental neuroethics.

    Within this framework, the thesis takes consciousness and related disorders (i.e. Vegetative State/Unresponsive Wakefulness Syndrome, Minimally Conscious State and Coma) and the addicted brain as illustrative cases of the potential fruitful collaboration between empirical and conceptual investigations.

    The general goal of the thesis is to contribute to the overall development of bridging the gap between empirical and conceptual understandings of consciousness. The first paper sets the theoretical framework, providing an empirically-based description of the brain with significant philosophical implications for an understanding of consciousness. The last three papers of the thesis try to apply the theoretical framework to illustrative cases. Papers II and III analyse the possible application of science and technology for an easier detection and clinical care of patients with disorders of consciousness, with particular attention to communication mediated by neurotechnology and the simulation of the conscious brain, respectively; paper IV provides a potentially new ethical analysis of addiction within the elaborated general conceptual framework.

    The conclusion of the thesis is that the impact of neuroscientific results needs that a dedicated conceptual approach reveals and investigates their conceptual meaning. This conceptual analysis is not exclusive but integrative and complementary to the empirical science. The case of consciousness, analysed from both an ethical and conceptual point of view, is highly illustrative in this respect. In the end, a conceptual/linguistic work of clarification is urgently needed.

  • Clinically-driven angiography after coronary artery bypass surgery : Results from the SWEDEHEART registry Author: Mikael Janiec Link: Publication date: 2019-10-03 14:21

    The success of coronary artery bypass grafting (CABG) arguably depends on the patency rate of the conduits. The saphenous vein grafts (SVGs) most often used are subject to graft disease and their reduced long-term patency compared to left internal mammary artery (IMA) grafts is well established. Postoperative coronary artery disease (CAD) symptoms, such as angina or myocardial infarction can undoubtedly be linked to graft failure or progression of atherosclerosis in the native coronary vessels, but the contribution from each of these processes is not completely understood.

    The aim of this thesis was to use clinically-driven angiography as the main outcome measure in studying different bypass conduits and surgical techniques. This endpoint has a very low risk of misclassification, and is likely to have a high association with recurrence of CAD symptoms. The SWEDEHEART registry provides extensive data on all patients undergoing cardiac surgery in Sweden as well as records of angiographies and coronary interventions.

    We studied the incidence of postoperative angiography in 46 663 CABG patients operated with IMA and SVGs. Young age, female sex, presence of diabetes, normal left ventricle function, previous PCI, prior MI, emergency surgery and one or two distal anastomoses were associated with a higher risk. We also studied 6 977 CABG operated individuals with three or more grafted vessels that experienced a postoperative angiography and had available records on individual graft patency. Almost one third of catheterized individuals with CAD symptoms did not demonstrate any failed grafts and in 18% of early and 10% of late angiographies the IMA-graft had failed.

    We compared 862 patients operated with bilateral IMA grafts and 1036 cases of IMA and radial artery grafts with 46 343 cases of IMA and SVGs. When adjusted for risk factors no improvement in outcome could be seen for patients operated with multiple arterial grafts. We also compared 1371 patients operated with “no-touch” SVGs with a propensity-matched cohort of patients with conventional SVGs. An improvement in the risk for angiography could be seen for the “no-touch” group but not for the need of repeat intervention or survival.

    Postoperative angiography is a useful endpoint in studying long-term outcome after CABG surgery. It is less sensitive than mortality to variations in the baseline covariates and thereby possibly less susceptible to confounding by indication. The causation behind the return of CAD symptoms after CABG surgery and the relative importance of the individual contributions from vein graft failures, failure of the IMA graft, as well as from progression of atherosclerotic plaques in both grafted and non-grafted coronary arteries, remains to be determined.