Comparison of different compressed sensing algorithms for low SNR 19F MRI applications—Imaging of transplanted pancreatic islets and cells labeled with perfluorocarbons

Transplantation of pancreatic islets is a possible treatment option for patients suffering from Type I diabetes. In vivo imaging of transplanted islets is important for assessment of the transplantation site and islet distribution. Thanks to its high specificity, the absence of intrinsic background signal in tissue and its potential for quantification, ¹⁹F MRI is a promising technique for monitoring the fate of transplanted islets in vivo. In order to overcome the inherent low sensitivity of ¹⁹F MRI, leading to long acquisition times with low signal‐to‐noise ratio (SNR), compressed sensing (CS) techniques are a valuable option. We have validated and compared different CS algorithms for acceleration of ¹⁹F MRI acquisition in a low SNR regime using pancreatic islets labeled with perfluorocarbons both in vitro and in vivo. Using offline simulation on both in vitro and in vivo low SNR fully sampled ¹⁹F MRI datasets of labeled islets, we have shown that CS is effective in reducing the image acquisition time by a factor of three to four without seriously affecting SNR, regardless of the particular algorithms used in this study, with the exception of CoSaMP. Using CS, signals can be detected that might have been missed by conventional ¹⁹F MRI. Among different algorithms (SPARSEMRI, OMMP, IRWL1, Two‐level and CoSAMP), the two‐level l₁ method has shown the best performance if computational time is taken into account. We have demonstrated in this study that different existing CS algorithms can be used effectively for low SNR ¹⁹F MRI. An up to fourfold gain in SNR/scan time could be used either to reduce the scan time, which is beneficial for clinical and translational applications, or to increase the number of averages, to potentially detect otherwise undetected signal when compared with conventional ¹⁹F MRI acquisitions. Potential applications in the field of cell therapy have been demonstrated.     

Vertebral bone quality score predicts fragility fractures independently of bone mineral density

BackgroundCurrent evidence suggests that dual-energy x-ray absorptiometry (DXA) scans, the conventional method defining osteoporosis, is underutilized and, when used, may underestimate patient risk for skeletal fragility. It has recently been suggested that other imaging modalities may better estimate bone quality, such as the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score which also may assess vertebral compression fracture risk in patients with spine metastases.PurposeTo evaluate whether VBQ score is predictive of fragility fractures in a population with pre-existing low bone density and at high-risk for fracture.Study Design/SettingRetrospective single-center cohort.Patient SamplePatients followed at a metabolic bone clinic for osteopenia and/or osteoporosis.Outcome MeasuresRadiographically-documented new-onset fragility fracture.MethodsPatients with a DXA and MRI scans at the time of consultation and ≥2-year follow-up were included. Details were gathered about patient demographics, health history, current medication use, and serological studies of kidney function and bone turnover. For each patient, VBQ score was calculated using T1-weighted lumbar MRI images. Univariable and multivariable analyses were used to identify the independent predictors of a new fragility fracture. To support the construct validity of VBQ, patient VBQ scores were compared to those in a cohort of 45 healthy adults.ResultsSeventy-two (39.1%) study participants suffered fragility fractures, the occurrence of which was associated with higher VBQ score (3.50 vs. 3.01; p<.001), chronic glucocorticoid use (30.6% vs. 15.2%; p=.014), and a history of prior fragility fracture (36.1% vs. 21.4%; p=.030). Mean VBQ score across all patients in the study cohort was significantly higher than the mean VBQ score in the healthy controls (p<.001). In multivariable analysis, new-onset fracture was independently associated with history of prior fracture (OR=6.94; 95% confidence interval [2.48–19.40]; p<.001), higher VBQ score (OR=2.40 per point; [1.30–4.44]; p=.003), higher body mass index (OR=1.09 per kg/m²; [1.01–1.17]; p=.03), and chronic glucocorticoid use (OR=2.89; [1.03–8.17]; p=0.043). Notably, DXA bone mineral density (BMD) was not found to be significantly predictive of new-onset fractures in the multivariable analysis (p=.081).ConclusionsHere we demonstrate the novel, MRI-derived VBQ score is both an independent predictor of fragility fracture in at-risk patients and a superior predictor of fracture risk than DXA-measured BMD. Given the frequency with which MRIs are obtained by patients undergoing spine surgery consultation, we believe the VBQ score could be a valuable tool for estimating bone quality in order to optimize the management of these patients.     

Heart Failure Management in Nursing Homes: A Scoping Literature Review

Heart failure (HF) affects 20% of nursing home (NH) residents, causing high morbidity and mortality. The optimal approach to HF management in NHs remains elusive. We conducted a scoping review of published guidelines and HF management interventions in NHs. A search for English publications since 1990 was conducted using PubMed, EMBASE, CINAHL, and Scopus, for scientific statements, guidelines, recommendations, or intervention studies that addressed at least 1 principle of HF management. Of 2545 records retrieved, 19 articles were retained after screening, and 2 additional articles identified through reference list manual searches. Six articles represented 5 guidelines and 15 described interventions. All guidelines endorsed the applicability of general HF guidelines to NH residents, tailored to comorbidities, frailty, and advance care preferences. Four addressed quality assurance but not feasibility and sustainability. Methodological quality of the interventions was poor, although results suggest that guideline-based HF management in NHs can improve nursing staff knowledge and job satisfaction, prescribing, and reduce acute care utilization. Clinically-based education for staff, and access to specialist mentorship are important. NH physician involvement was limited, and resident/family education potentially ineffective. Concerns about feasibility, sustainability, and quality assurance were identified in most interventions, and advance care planning was rarely addressed. HF guidelines for NH support the applicability of general HF guidelines to the care of NH residents, and published interventions suggest that guideline-based HF management in NHs is effective. Future work should support greater physician and resident engagement, advance care planning, and provide robust guidelines on developing feasible and sustainable interventions.     

继续医学教育活动的有效性

继续医学教育的目的是通过向医生提供最新的医学知识和技能,使医生在其整个职业生涯中,一直保持较高的医疗水平.但目前还没有充足的证据能证明继续医学教育活动的有效性,以及在继续医学教育活动中哪些教育方法和技术能最有效地传播和记忆医学知识.为了全面、系统地评估继续医学教育活动的有效性,以及了解不同的教育手段对医生知识、态度、技能、临床表现和临床效果的作用.美国约翰·霍普金斯大学医学院、美国医疗保健研究与质量管理署和美国胸科医师学会的专家共同进行了一项系统回顾性研究.     

The effects of troglitazone,an insulin-sensitizing agent,on the endothelial function in early and late type 2 diabetes: a placebo-controlled randomized clinical trial

Activation of the peroxisome proliferator-activator receptor gamma (PPARgamma) improves insulin resistance and glycemic control in patients with diabetes. As PPARgamma is expressed in the endothelial cell, we have investigated the effect of troglitazone, a PPARgamma activator, on the endothelial function in people with type 2 diabetes in a 12-week, prospective, randomized, double-blinded clinical trial. We studied 87 type 2 diabetic patients who were divided into 3 groups. Group A consisted of 27 patients with recently diagnosed diabetes and no clinical manifestations of macrovascular disease; group B, 29 patients with long-term diabetes and no clinically evident macrovascular disease; and group C, 31 diabetic patients with documented macrovascular disease (cardiovascular, cerebrovascular, or peripheral vascular disease). High-resolution ultrasound images were used to measure the flow-mediated dilation (FMD, endothelium-dependent) and nitroglycerin-induced dilation (NID, endothelium-independent) in the brachial artery. Laser Doppler perfusion imaging was used to measure vasodilation in the forearm skin in response to iontophoresis of 1% acetylcholine (Ach, endothelium-dependent) and 1% sodium nitroprusside (NaNP, endothelium-independent). The plasma concentrations of von Willebrand factor (vWF), soluble intercellular adhesion molecule (sICAM), and soluble vascular cell adhesion molecule (sVCAM) were also measured as indicators of endothelial cell activation. The FMD improved in the troglitazone-treated patients in group A (7.72 +/- 3.4 v 5.27 +/- 2.0, P <.05 [exit visit v baseline, percent of increase in brachial artery diameter, mean +/- SD]). The fasting insulin level also improved in this group (15.6 +/- 10 v 19.7 +/- 10, P <.05) and was strongly correlated to changes in FMD (r = -.73, P <.01). No changes were found in the FMD or the fasting insulin levels in the troglitazone-treated patients in groups B or C. The NID was not changed by troglitazone treatment in any of the 3 groups. Also, no differences were found in the microcirculation reactivity measurements or in the biochemical markers of endothelial dysfunction in all 3 groups. A small, but significant, improvement of the FMD was found in placebo-treated patients in group B, probably related to the low FMD levels at baseline in the patients (5.40 +/- 3.0 v 4.36 +/- 2.4, P <.05). We concluded that troglitazone treatment for 12 weeks improved endothelial function in the macrocirculation of patients with recently diagnosed type 2 diabetes and no clinical evidence of macrovascular disease. This improvement was strongly associated with the improvement of fasting plasma insulin concentrations.     

Powdered infant formula as a source of Salmonella infection in infants.

Powdered infant formula is not sterile and may be intrinsically contaminated with pathogens, such as Salmonella enterica, that can cause serious illness in infants. In recent years, at least 6 outbreaks of Salmonella infection in infants that have been linked to the consumption of powdered infant formula have been reported. Many of these outbreaks were identified because the Salmonella strains were unique in some way (e.g., a rare serotype) and a well-established Salmonella surveillance network, supported by laboratories capable of serotyping isolates, was in place. Another common feature of the outbreaks was the low level of salmonellae detected in the implicated formula (salmonellae may be missed in routine testing). These outbreaks likely represent only a small proportion of the actual number of Salmonella infections in infants that have been linked to powdered infant formula. Managing this problem requires a multidimensional approach in which manufacturers, regulators, and caregivers to infants can all play a role.