Motion Calculations on Stent Grafts in AAA

Endovascular aortic repair (EVAR) is a technique which uses stent grafts to treat aortic aneurysms in patients at risk of aneurysm rupture. Although this technique has been shown to be very successful on the short term, the long term results are less optimistic due to failure of the stent graft. The pulsating blood flow applies stresses and forces to the stent graft, which can cause problems such as breakage, leakage, and migration. Therefore it is of importance to gain more insight into the in vivo motion behavior of these devices. If we know more about the motion patterns in well-behaved stent graft as well as ill-behaving devices, we shall be better able to distinguish between these type of behaviors These insights will enable us to detect stent-related problems and might even be used to predict problems beforehand. Further, these insights will help in designing the next generation stent grafts. Firstly, this work discusses the applicability of ECG-gated CT for measuring the motions of stent grafts in AAA. Secondly, multiple methods to segment the stent graft from these data are discussed. Thirdly, this work proposes a method that uses image registration to apply motion to the segmented stent mode

Percutaneous Radiofrequency Ablation of Osteoid Osteomas with Use of Real-Time Needle Guidance for Accurate Needle Placement: A Pilot Study

Contains fulltext : 97211.pdf (publisher's version ) (Open Access)PURPOSE: To evaluate the accuracy and technical success of positioning a radiofrequency ablation (RFA) electrode in osteoid osteomas by use of a new real-time needle guidance technology combining cone-beam computed tomography (CT) and fluoroscopy. MATERIALS AND METHODS: Percutaneous RFA of osteoid osteomas was performed in five patients (median age 18 years), under general anesthesia, with the use of cone-beam CT and fluoroscopic guidance for electrode positioning. The outcome parameters were technical success, meaning correct needle placement in the nidus; accuracy defined as the deviation (in mm) from the center of the nidus; and clinical outcome at follow-up. RESULTS: In all five cases, positioning was possible within 3 mm of the determined target location (median nidus size 6.8 mm; range 5-10.2 mm). All procedures were technically successful. All patients were free of pain at clinical follow-up. No complications were observed. CONCLUSION: Real-time fluoroscopy needle guidance based on cone-beam CT is a useful tool to accurately position radiofrequency needles for minimally invasive treatment of osteoid osteomas

Detectability of motions in AAA with ECG-gated CTA: A quantitative study

Purpose: ECG-gated CT enables the visualization of motions caused by the beating of the heart. Although ECG gating is frequently used in cardiac CT imaging, this technique is also very promising for evaluating vessel wall motion of the aortic artery and the motions of (stent grafts inside) abdominal aortic aneurysms (AAA). Late stent graft failure is a serious complication in endovascular repair of aortic aneurysms. Better understanding of the motion characteristics of stent grafts will be beneficial for designing future devices. In addition, these data can be valuable in predicting stent graft failure in patients. To be able to reliably quantify the motion, however, it is of importance to know the performance and limitations of ECG gating, especially when the motions are small, as is the case in AAA. Since the details of the reconstruction algorithms are proprietary information on the CT manufacturers and not in the public domain, empirical experiments are required. The goal of this study is to investigate as to what extent the motions in AAA can be measured using ECG-gated CT. The authors quantitatively investigate four aspects of motion in ECG-gated CT: The detectability of the motion of objects at different amplitudes and different periodic motions, the temporal resolution, and the volume gaps that occur as a function of heart rate.\ud \ud Methods: They designed an experiment on a standard static phantom to empirically determine temporal resolution. To investigate motion amplitude and frequency, as well as patient heart rate, they designed dynamic experiments in which a home-made phantom driven by a motion unit moves in a predetermined pattern.\ud \ud Results: The duration of each ECG-gated phase was found to be 185 ms, which corresponds to half of the rotation time and is thus in accordance with half scan reconstruction applied by the scanner. By using subpixel localization, motions become detectable from amplitudes of as small as 0.4 mm in the x direction and 0.7 mm in the z direction. With the rotation time used in this study, motions up to 2.7 Hz can be reliably detected. The reconstruction algorithm fills volume gaps with noisy data using interpolation, but objects within these gaps remain hidden.\ud \ud Conclusions: This study gives insight into the possibilities and limitations for measuring small motions using ECG-gated CT. Application of the experimental method is not restricted to the CT scanner of a single manufacturer. From the results, they conclude that ECG-gated CTA is a suitable technique for studying the expected motions of the stent graft and vessel wall in AAA.\u

MRI compared to conventional diagnostic work-up in the detection and evaluation of invasive lobular carcinoma of the breast: a review of existing literature

Item does not contain fulltextPURPOSE: The clinical diagnosis and management of invasive lobular carcinoma (ILC) of the breast presents difficulties. Magnetic resonance imaging (MRI) has been proposed as the imaging modality of choice for the evaluation of ILC. Small studies addressing different aspects of MRI in ILC have been presented but no large series to date. To address the usefulness of MRI in the work-up of ILC, we performed a review of the currently published literature. MATERIALS AND METHODS: We performed a literature search using the query "lobular AND (MRI OR MR OR MRT OR magnetic)" in the Cochrane library, PubMed and scholar.google.com, to retrieve all articles that dealt with the use of MRI in patients with ILC. We addressed sensitivity, morphologic appearance, correlation with pathology, detection of additional lesions, and impact of MRI on surgery as different endpoints. Whenever possible we performed meta-analysis of the pooled data. RESULTS: Sensitivity is 93.3% and equal to overall sensitivity of MRI for malignancy in the breast. Morphologic appearance is highly heterogeneous and probably heavily influenced by interreader variability. Correlation with pathology ranges from 0.81 to 0.97; overestimation of lesion size occurs but is rare. In 32% of patients, additional ipsilateral lesions are detected and in 7% contralateral lesions are only detected by MRI. Consequently, MRI induces change in surgical management in 28.3% of cases. CONCLUSION: This analysis indicates MRI to be valuable in the work-up of ILC. It provides additional knowledge that cannot be obtained by conventional imaging modalities which can be helpful in patient treatment

HMG-coenzyme A reductase inhibition, type 2 diabetes, and bodyweight: evidence from genetic analysis and randomised trials.

BACKGROUND: Statins increase the risk of new-onset type 2 diabetes mellitus. We aimed to assess whether this increase in risk is a consequence of inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the intended drug target. METHODS: We used single nucleotide polymorphisms in the HMGCR gene, rs17238484 (for the main analysis) and rs12916 (for a subsidiary analysis) as proxies for HMGCR inhibition by statins. We examined associations of these variants with plasma lipid, glucose, and insulin concentrations; bodyweight; waist circumference; and prevalent and incident type 2 diabetes. Study-specific effect estimates per copy of each LDL-lowering allele were pooled by meta-analysis. These findings were compared with a meta-analysis of new-onset type 2 diabetes and bodyweight change data from randomised trials of statin drugs. The effects of statins in each randomised trial were assessed using meta-analysis. FINDINGS: Data were available for up to 223 463 individuals from 43 genetic studies. Each additional rs17238484-G allele was associated with a mean 0·06 mmol/L (95% CI 0·05-0·07) lower LDL cholesterol and higher body weight (0·30 kg, 0·18-0·43), waist circumference (0·32 cm, 0·16-0·47), plasma insulin concentration (1·62%, 0·53-2·72), and plasma glucose concentration (0·23%, 0·02-0·44). The rs12916 SNP had similar effects on LDL cholesterol, bodyweight, and waist circumference. The rs17238484-G allele seemed to be associated with higher risk of type 2 diabetes (odds ratio [OR] per allele 1·02, 95% CI 1·00-1·05); the rs12916-T allele association was consistent (1·06, 1·03-1·09). In 129 170 individuals in randomised trials, statins lowered LDL cholesterol by 0·92 mmol/L (95% CI 0·18-1·67) at 1-year of follow-up, increased bodyweight by 0·24 kg (95% CI 0·10-0·38 in all trials; 0·33 kg, 95% CI 0·24-0·42 in placebo or standard care controlled trials and -0·15 kg, 95% CI -0·39 to 0·08 in intensive-dose vs moderate-dose trials) at a mean of 4·2 years (range 1·9-6·7) of follow-up, and increased the odds of new-onset type 2 diabetes (OR 1·12, 95% CI 1·06-1·18 in all trials; 1·11, 95% CI 1·03-1·20 in placebo or standard care controlled trials and 1·12, 95% CI 1·04-1·22 in intensive-dose vs moderate dose trials). INTERPRETATION: The increased risk of type 2 diabetes noted with statins is at least partially explained by HMGCR inhibition. FUNDING: The funding sources are cited at the end of the paper

Causal Effects of Body Mass Index on Cardiometabolic Traits and Events: A Mendelian Randomization Analysis

(The American Journal of Human Genetics 94, 198–208; February 6, 2014

Mendelian randomization of blood lipids for coronary heart disease

Aims To investigate the causal role of high-density lipoprotein cholesterol (HDL-C) and triglycerides in coronary heart disease (CHD) using multiple instrumental variables for Mendelian randomization. Methods and results We developed weighted allele scores based on single nucleotide polymorphisms (SNPs) with established associations with HDL-C, triglycerides, and low-density lipoprotein cholesterol (LDL-C). For each trait, we constructed two scores. The first was unrestricted, including all independent SNPs associated with the lipid trait identified from a prior meta-analysis (threshold P < 2 × 10−6); and the second a restricted score, filtered to remove any SNPs also associated with either of the other two lipid traits at P ≤ 0.01. Mendelian randomization meta-analyses were conducted in 17 studies including 62,199 participants and 12,099 CHD events. Both the unrestricted and restricted allele scores for LDL-C (42 and 19 SNPs, respectively) associated with CHD. For HDL-C, the unrestricted allele score (48 SNPs) was associated with CHD (OR: 0.53; 95% CI: 0.40, 0.70), per 1 mmol/L higher HDL-C, but neither the restricted allele score (19 SNPs; OR: 0.91; 95% CI: 0.42, 1.98) nor the unrestricted HDL-C allele score adjusted for triglycerides, LDL-C, or statin use (OR: 0.81; 95% CI: 0.44, 1.46) showed a robust association. For triglycerides, the unrestricted allele score (67 SNPs) and the restricted allele score (27 SNPs) were both associated with CHD (OR: 1.62; 95% CI: 1.24, 2.11 and 1.61; 95% CI: 1.00, 2.59, respectively) per 1-log unit increment. However, the unrestricted triglyceride score adjusted for HDL-C, LDL-C, and statin use gave an OR for CHD of 1.01 (95% CI: 0.59, 1.75). Conclusion The genetic findings support a causal effect of triglycerides on CHD risk, but a causal role for HDL-C, though possible, remains less certain.M.V.H. was funded by a UK Medical Research Council Population Health Scientist Fellowship (G0802432). F.W.A. is supported by UCL Hospitals NIHR Biomedical Research Centre. D.I.S. is supported by a Medical Research Council Doctoral Training Award and a grant from the Rosetrees Foundation. ME.K. is supported by the National Institute of Aging and the National Heart, Lung and Blood Institute (HL36310). S.E.H. and P.J.T. are supported by the British Heart Foundation (BHF RG 08/008, PG/07/133/24260), UK Medical Research Council, the US National Institutes of Health (grant NHLBI 33014) and Du Pont Pharma, Wilmington, USA. N.J.S. holds a Chair funded by the British Heart Foundation and is an NIHR Senior Investigator. MI.K. is supported by the National Institute of Aging, the Medical Research Council, the British Heart Foundation, and the National Heart, Lung and Blood Institute and the Academy of Finland. A.D.H. and J.P.C. are supported by the National Institute of Health Research University College London Hospitals Biomedical Research Centre. Funding to pay the Open Access publication charges for this article was provided by RCUK

Effects of sera from patients with Hodgkin's disease and of cytokines on the expression of parallel tubular structures and cell surface antigens in lymphocytes

The key terms which form the basis of this thesis are Hodgkin's disease (HD), granular lymphocytes, parallel tubular structured (PTS), induction, serum factor(s), interferon-a (IFNa), immunoelectron microscopy (IEM), and natural killer (NK) activity. The main aims of the present investigation were to reveal the identity of the unknown factor responsible for the granular lymphocyte induction and NK activity enhancement, determine the subpopulations(s) to which the granular cells belong, and gain insight into the function of these cells in HD patients. Zie: Discusion and conclusions