Citations

Abstract Due to engineering limitations, the spatial encoding gradient fields in conventional magnetic resonance imaging cannot be perfectly linear and always contain higher-order, nonlinear components. If ignored during image reconstruction, gradient nonlinearity (GNL) manifests as image geometric distortion. Given an estimate of the GNL field, this distortion can be corrected to a degree proportional to the accuracy of the field estimate. The GNL of a gradient system is typically characterized using a spherical harmonic polynomial model with model coefficients obtained from electromagnetic simulation. Conventional whole-body gradient systems are symmetric in design; typically, only odd-order terms up to the 5th-order are required for GNL modeling. Recently, a high-performance, asymmetric gradient system was developed, which exhibits more complex GNL that requires higher-order terms including both odd- and even-orders for accurate modeling. This work characterizes the GNL of this system using an iterative calibration method and a fiducial phantom used in ADNI (Alzheimer’s Disease Neuroimaging Initiative). The phantom was scanned at different locations inside the 26 cm diameter-spherical-volume of this gradient, and the positions of fiducials in the phantom were estimated. An iterative calibration procedure was utilized to identify the model coefficients that minimize the mean-squared-error between the true fiducial positions and the positions estimated from images corrected using these coefficients. To examine the effect of higher-order and even-order terms, this calibration was performed using spherical harmonic polynomial of different orders up to the 10th-order including even- and odd-order terms, or odd-order only. The results showed that the model coefficients of this gradient can be successfully estimated. The residual root-mean-squared-error after correction using up to the 10th-order coefficients was reduced to 0.36 mm, yielding spatial accuracy comparable to conventional whole-body gradients. The even-order terms were necessary for accurate GNL modeling. In addition, the calibrated coefficients improved image geometric accuracy compared with the simulation-based coefficients.

Purpose In the surgical treatment of thumb carpometacarpal (CMC) joint arthritis, the effect of mild preoperative metacarpophalangeal (MCP) hyperextension on postoperative functional outcomes is unknown. We sought to examine outcomes after surgical treatment of CMC arthritis in patients with and without mild preexisting MCP deformity. Methods A retrospective review was conducted to analyze the functional outcomes of patients treated for CMC arthritis at a single institution from March 1998 to May 2009. All patients were treated with one of two standard CMC arthroplasty procedures—either ligament reconstruction tendon interposition (LRTI) or a Weilby procedure—and none had additional procedures to address MCP hyperextension. Pre- and postoperative assessments included pinch and grip strength, degree of MCP hyperextension, and thumb radial and palmar abduction. A t-test was used to assume unequal variances. Results A total of 203 patients were followed for an average of 27.3 months. Patients were divided into two groups: (1) patients without preoperative MCP hyperextension (167 patients) and (2) patients with mild but untreated preoperative MCP hyperextension (≤ 30 degrees; 36 patients). All patients underwent either a Weilby procedure (118 patients) or an LRTI; 85 patients). The main difference between techniques was the use of the abductor pollicis longus tendon as a post to secure the flexor carpi radialis (Weilby) or the use of a bone tunnel in the first metacarpal (LRTI). Analysis of the preoperative data showed no difference in the baseline parameters among both the groups, with the exception of MCP hyperextension. Postoperatively, neither the type of CMC procedure nor the presence of MCP hyperextension demonstrated any significant differences in key pinch, tip pinch, grip strength, and radial or palmar abduction of the thumb between the groups. Conclusion There were no statistically significant differences in improvement of functional outcomes after surgery when comparing patients without preoperative MCP hyperextension to patients with untreated MCP hyperextension of less than 30 degrees. Level of Evidence Level III, retrospective comparative study.

A 65-year-old male resident of Guatemala presented with a 5-month history of distal symmetric arthritis and generalized fatigue. This was associated with night sweats, chills, and weight loss. Symptoms were refractory to oral prednisone and hydroxychloroquine.

ObjectiveTo describe the perception of the current role of systemic glucocorticoids in the management of rheumatoid arthritis (RA) by examining their importance and the current level of evidence in recent guidelines, and to identify open questions to be addressed in future guidelines and research projects.MethodsWe conducted a systematic literature review using the databases Ovid Embase, PubMed Medline, and Cochrane Library for guidelines on the pharmacologic treatment of RA. Retrieved articles were evaluated regarding their quality using the Appraisal of Guidelines for Research and Evaluation II tool and scrutinized for all relevant information concerning the use of glucocorticoids.ResultsAll guidelines agree that glucocorticoids, especially if given at low doses and for a short duration, are an appropriate option in the treatment of RA. However, many recommendations remain vague, as reliable and detailed evidence is scarce. Important aspects of glucocorticoid therapy are partially or completely neglected, and the existing nomenclature is not used uniformly. Quality evaluation revealed flaws in many articles, concerning not only glucocorticoid‐specific recommendations but also guideline quality in general.ConclusionCurrent recommendations for use of glucocorticoids in the management of RA are suboptimal. More rigorous evaluation of doses, timing, and duration of their use is needed. Existing nomenclature on glucocorticoid therapy should be used uniformly.

Objective To identify risk alleles relevant to the causal and biologic mechanisms of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV). Methods A genome‐wide association study and subsequent replication study were conducted in a total cohort of 1,986 cases of AAV (patients with granulomatosis with polyangiitis [Wegener's] [GPA] or microscopic polyangiitis [MPA]) and 4,723 healthy controls. Meta‐analysis of these data sets and functional annotation of identified risk loci were performed, and candidate disease variants with unknown functional effects were investigated for their impact on gene expression and/or protein function. Results Among the genome‐wide significant associations identified, the largest effect on risk of AAV came from the single‐nucleotide polymorphism variants rs141530233 and rs1042169 at the HLA–DPB1 locus (odds ratio [OR] 2.99 and OR 2.82, respectively) which, together with a third variant, rs386699872, constitute a triallelic risk haplotype associated with reduced expression of the HLA–DPB1 gene and HLA–DP protein in B cells and monocytes and with increased frequency of complementary proteinase 3 (PR3)–reactive T cells relative to that in carriers of the protective haplotype. Significant associations were also observed at the SERPINA1 and PTPN22 loci, the peak signals arising from functionally relevant missense variants, and at PRTN3 , in which the top‐scoring variant correlated with increased PRTN3 expression in neutrophils. Effects of individual loci on AAV risk differed between patients with GPA and those with MPA or between patients with PR3‐ANCAs and those with myeloperoxidase‐ANCAs, but the collective population attributable fraction for these variants was substantive, at 77%. Conclusion This study reveals the association of susceptibility to GPA and MPA with functional gene variants that explain much of the genetic etiology of AAV, could influence and possibly be predictors of the clinical presentation, and appear to alter immune cell proteins and responses likely to be key factors in the pathogenesis of AAV.

Pediatric cancers rarely exhibit recurrent mutational events when compared to most adult cancers. This poses a challenge in understanding how cancers initiate, progress, and metastasize in early childhood. Also, due to limited detected driver mutations, it is difficult to benchmark key genes for drug development. In this review, we use neuroblastoma, a pediatric solid tumor of neural crest origin, as a paradigm for exploring “big data” applications in pediatric oncology. Computational strategies derived from big data science–network- and machine learning-based modeling and drug repositioning—hold the promise of shedding new light on the molecular mechanisms driving neuroblastoma pathogenesis and identifying potential therapeutics to combat this devastating disease. These strategies integrate robust data input, from genomic and transcriptomic studies, clinical data, and in vivo and in vitro experimental models specific to neuroblastoma and other types of cancers that closely mimic its biological characteristics. We discuss contexts in which “big data” and computational approaches, especially network-based modeling, may advance neuroblastoma research, describe currently available data and resources, and propose future models of strategic data collection and analyses for neuroblastoma and other related diseases.

Abstract This brief review summarizes factors associated with elite endurance performance, trends in distance running training, and participation by men and more recently women. It is framed in the context of key ideas about the physiological determinants of endurance performance but also touches on some historical and sociological factors relevant to the overall topic. Historical trends that served to increase women's participation in elite endurance events are also discussed as is the role of increased volume and intensity of training. The rapid improvement in women's world record marathon times in the 1970s and 80s are emblematic of these trends and represent a combination of increased training volume and intensity and more competitive opportunities. This occurred as bans on participation by women in endurance events were lifted. For men these same trends evolved over a much longer time frame. The main physiological factor responsible for 10–12% slower times in women compared to men at the elite level are also considered and probably centre around . image

AbstractMalignancy represents substantial morbidity and mortality in patients with primary sclerosing cholangitis (PSC). This subset of patients has been proven to be at increased risk for developing cholangiocarcinoma, gallbladder carcinoma and colorectal cancer in those with overlapping inflammatory bowel disease. Herein, we review the prevalence of these malignancies and recommend screening tools and current knowledge to reduce the disease burden in this population. Cholangiocarcinoma is the most dominant malignancy affecting PSC patients, with a lifetime risk ranging from 5% to 20%. We advocate for serial US or MRI/MRCP and CA 19‐9 to screen for cholangiocarcinoma. Gallbladder cancer has a lifetime risk around 2% in this population and we agree with annual imaging for lesions as recommended by national guidelines. Patients with PSC and concomitant IBD are at increased risk of colorectal carcinoma from time of diagnosis and therefore should likely undergo annual surveillance. The low rates of hepatocellular cancer and pancreatic cancer indicate surveillance for these malignancies is less advantageous.