Endoscopy-Related Bleeding and Thromboembolic Events in Patients on Direct Oral Anticoagulants or Vitamin K Antagonists

1. Download : Download high-res image (232KB)
2. Download : Download full-size image

     

Motion‐compensated b‐tensor encoding for in vivo cardiac diffusion‐weighted imaging

Motion is a major confound in diffusion‐weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo‐based DWI commonly employs gradient moment‐nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2‐nulled). However, current M2‐nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b‐tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof‐of‐concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2‐nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2‐nulled LTE, where diffusion‐weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal‐to‐noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed.     

Modeling in Frequency Domain Used for Assessment of In Vivo Dissolution Profile

Purpose. To present a model-dependent approach for the assessment of the in vivo drug dissolution profile based on in vitrodata for the multiple unit dosage form, as an alternative to the numerical method proposed in the study by Hayashi et al, Pharm. Res. 12:1333–1337 (1995). Methods. The data for aspirin granules administered to healthy subjects obtained in the above mentioned study were re-evaluated. The subject dissolution system was considered to consist of two subsystems connected in series, i.e. the subsystem describing the gastric-emptying process and the subsystem describing the intestinal dissolution process. The frequency response method was used to model the subject dissolution system. Results. The model in vivodissolution profile of aspirin, assessed as the integral of the model weighting function of the subject dissolution system, was in agreement with the in vivo cumulative absorption profile calculated by the Wagner-Nelson method. Conclusions. Comparison of dynamic properties of the subject dissolution system with the subsystem describing the gastric-emptying process yielded quantitative confirmation of the decisive role of the gastric-emptying process in the in vivodrug dissolution after administration in the multi unit dosage form.     

On the synthesis of time‐varying LQG weights and noises along optimal control and state trajectories

A general approach to control non‐linear uncertain systems is to apply a pre‐computed nominal optimal control, and use a pre‐computed LQG compensator to generate control corrections from the on‐line measured data. If the non‐linear model, on which the optimal control and LQG compensator design is based, is of sufficient quality, and when the LQG compensator is designed appropriately, the closed‐loop control system is approximately optimal. This paper contributes to the selection and computation of the time‐varying LQG weighting and noise matrices, which determine the LQG compensator design. It is argued that the noise matrices may be taken time‐invariant and diagonal. Three very important considerations concerning the selection of the time‐varying LQG weighting matrices are turned into a concrete computational scheme. Thereby, the selection of the time‐varying LQG weighting matrices is reduced to selecting three scalar design parameters, each one weighting one consideration. Although the three considerations seem straightforward they may oppose one another. Furthermore, they usually result in time‐varying weighting matrices that are indefinite, rather than positive (semi) definite as required for the LQG design. The computational scheme presented in this paper addresses and resolves both problems. By two numerical examples the benefits of our optimal closed‐loop control system design are demonstrated and evaluated using Monte Carlo simulation. Copyright © 2005 John Wiley & Sons, Ltd.     

Quantifying the intra- and extravascular contributions to spin-echo fMRI at 3 T.

Functional MRI (fMRI) by means of spin-echo (SE) techniques provides an interesting alternative to gradient-echo methods because the contrast is based primarily on dynamic averaging associated with the blood oxygenation level-dependent (BOLD) effect. In this article the contributions from different brain compartments to BOLD signal changes in SE echo planar imaging (EPI) are investigated. To gain a better understanding of the underlying mechanisms that cause the fMRI contrast, two experiments are presented: First, the intravascular contribution is decomposed into two fractions with different regimes of flow by means of diffusion-weighting gradient schemes which are either flow-compensated, or will maximally dephase moving spins. Second, contributions from the intra- and extravascular space are selectively suppressed by combining flow-weighting with additional refocusing pulses. The results indicate two qualitatively different components of flowing blood which contribute to the BOLD contrast and a nearly equal share in functional signal from the intra- and extravascular compartments at TE approximately 80 ms and 3 T. Combining these results, there is evidence that at least one-half of the functional signal originates from the parenchyma in SE fMRI at 3 T. The authors suggest the use of flow-compensated diffusion weighting for SE fMRI to improve the sensitivity to the parenchyma.     

EB病毒在结外NK/T细胞淋巴瘤中的预后价值：一项淮海淋巴瘤协作组的多中心回顾性研究

目的 基于倾向性评分逆处理概率加权(IPTW)法评估EB病毒(EBV)在结外NK/T细胞淋巴瘤患者中的预后价值。方法 收集2012年10月—2021年4月淮海淋巴瘤协作组中8家医疗机构初诊为结外NK/T细胞淋巴瘤且具有全血EBV-DNA数据的468例患者的临床资料。采用IPTW法分析EBV载量对结外NK/T细胞淋巴瘤患者生存期的影响;采用Cox比例风险模型进行多因素分析;绘制Kaplan-Meier曲线,组间比较采用Log rank χ²检验。结果 468例结外NK/T细胞淋巴瘤患者中,EBV-DNA阳性266例,EBV-DNA阴性202例。EBV-DNA阳性组和阴性组患者的5年OS分别为62.5%和89.2%,两组比较,经Log rank χ²检验,差异有统计学意义(χ²=42.900,P=0.000)。IPTW前,两组的美国东部肿瘤协作组(ECOG)活动状态(PS)评分(ECOG PS评分)、原发部位、CA分期、Ann Arbor分期、白蛋白、乳酸脱氢酶、治疗方案比较,差异均有统计学意义(P<0.05)。IPT...     

Modeling cumulative incidence function for competing risks data

A frequent occurrence in medical research is that a patient is subject to different causes of failure, where each cause is known as a competing risk. The cumulative incidence curve is a proper summary curve, showing the cumulative failure rates over time due to a particular cause. A common question in medical research is to assess the covariate effects on a cumulative incidence function. The standard approach is to construct regression models for all cause-specific hazard rate functions and then model a covariate-adjusted cumulative incidence curve as a function of all cause-specific hazards for a given set of covariates. New methods have been proposed in recent years, emphasizing direct assessment of covariate effects on cumulative incidence function. Fine and Gray proposed modeling the effects of covariates on a subdistribution hazard function. A different approach is to directly model a covariate-adjusted cumulative incidence function, including a pseudovalue approach by Andersen and Klein and a direct binomial regression by Scheike, Zhang and Gerds. In this paper, we review the standard and new regression methods for modeling a cumulative incidence function, and give the sources of computer packages/programs that implement these regression models. A real bone marrow transplant data set is analyzed to illustrate various regression methods.     

Long-term outcomes of rigid ring versus De Vega annuloplasty for functional tricuspid regurgitation: A propensity score-matching analysis

ObjectiveThis study was conducted to compare the outcomes of rigid ring versus De Vega annuloplasty for the treatment of functional tricuspid regurgitation (TR).MethodsFrom 2003 to 2017, De Vega annuloplasty (group D) was used in 231 patients, and rigid ring annuloplasty (group R) was used in 204 patients for the treatment of functional TR during left-sided valve surgery. A propensity score-matching analysis was used to pair group D (n = 109) with group R (n = 109). The primary outcomes were long-term overall survival and cardiac death, and the secondary outcomes were tricuspid valve-related events and TR recurrence (TR moderate or severe). The follow-up data were complete in 99.6% (447 out of 449) of the patients with a follow-up duration of 102 months.ResultsThere were no differences in the overall survival and cardiac death between the propensity score-matched groups (P = .793 and P = .175, respectively) up to 14 years after surgery. Tricuspid valve-related events, including cardiac death, permanent pacemaker implantation, thromboembolism, bleeding and tricuspid valve reoperation were also similar between the 2 matched groups during the follow-up (P > .999). However, cumulative incidence of TR recurrence was significantly higher in group R than in group D (P = .007). Multivariate analysis indicated the annuloplasty method (De Vega) and preoperative TR grade as risk factors for late TR recurrence.ConclusionsIn functional TR, annuloplasty methods did not influence long-term overall survival, cardiac mortality, and tricuspid valve-related events. However, rigid ring annuloplasty showed less late TR recurrence. Rigid ring annuloplasty can be considered for the treatment of functional TR in terms of its better durability.