Quantitative MRI evaluation of whole abdomen adipose tissue volumes in healthy volunteers-validation of technique and implications for clinical studies

Objective: To explore "whole abdomen" MRI methods for quantifying adipose tissue volumes and to establish associations with body mass index (BMI) and measurement reproducibility - relative to existing "partial abdomen" methods.Methods: Fifteen healthy volunteers were scanned on a 3.0T MRI scanner using a double-echo three-point-Dixon gradient echo sequence. Whole abdomen volumes were acquired via three separate scans ("supine 1", "supine 2" and "prone"). Segmentation was applied to derive (i) "whole abdomen" visceral (VAT) and subcutaneous adipose tissue (SCAT) volumes, and (ii) "partial abdomen" volumes at the lumbar spine (L3 to L5). Root-mean-square coefficients of variation (RMS CoV) were calculated to quantify the variability of each measurement.Results: "Whole abdomen" measurements were found to correlate better with BMI (r2max= 0.74) than "partial abdomen" volumes (r2max= 0.66). Total adipose tissue (TAT) measurements correlated better with BMI (r2max= 0.74) than SCAT (r2max= 0.43) or VAT (r2max= 0.33) for both methods. Scan-to-scan RMS CoV's for "whole abdomen" VAT and SCAT measurements were 4.16 and 3.61% compared to 6.31 and 5.07% for "partial abdomen" measurements.Conclusion: "Whole abdomen" measures of abdominal adiposity are better correlated with BMI and demonstrate better scan-to-scan reproducibility than "partial abdomen" measures. It is recommended that "whole abdomen" measures be used in longitudinal MRI radiology investigations, where small volume changes may occur. Advances in knowledge: Whole abdomen adipose tissue volumes can be measured and quantified using commercial MRI sequences and post-processing software. These methods are better correlated with BMI and are more reproducible than partial abdomen measures.</p

Effect of allopurinol on phosphocreatine recovery and muscle function in older people with impaired physical function:a randomised controlled trial

Background: Allopurinol has vascular antioxidant effects and participates in purinergic signalling within muscle. We tested whether allopurinol could improve skeletal muscle energetics and physical function in older people with impaired physical performance. Methods: We conducted a randomised, double blind, parallel group, placebo-controlled trial, comparing 20 weeks of allopurinol 600 mg once daily versus placebo. We recruited community-dwelling participants aged 65 and over with baseline 6-min walk distance of &lt;400 m and no contraindications to magnetic resonance imaging scanning. Outcomes were measured at baseline and 20 weeks. The primary outcome was post-exercise phosphocreatine (PCr) recovery rate measured using 31P magnetic resonance spectroscopy of the calf. Secondary outcomes included 6-min walk distance, short physical performance battery (SPPB), lean body mass measured by bioimpedance, endothelial function and quality of life. Results: In total, 124 participants were randomised, mean age 80 (SD 6) years. A total of 59 (48%) were female, baseline 6-min walk distance was 293 m (SD 80 m) and baseline SPPB was 8.5 (SD 2.0). Allopurinol did not significantly improve PCr recovery rate (treatment effect 0.10 units [95% CI, −0.07 to 0.27], P = 0.25). No significant changes were seen in endothelial function, quality of life, lean body mass or SPPB. Allopurinol improved 6-min walk distance (treatment effect 25 m [95% 4–46, P = 0.02]). This was more pronounced in those with high baseline oxidative stress and urate. Conclusion: Allopurinol improved 6-min walk distance but not PCr recovery rate in older people with impaired physical function. Antioxidant strategies to improve muscle function for older people may need to be targeted at subgroups with high baseline oxidative stress. </p

Morphological and hemodynamical alterations in brachial artery and cephalic vein. An image‐based study for preoperative assessment for vascular access creation

The current study aims to computationally evaluate the effect of right upper arm position on the geometric and hemodynamic characteristics of the brachial artery (BA) and cephalic vein (CV) and, furthermore, to present in detail the methodology to characterise morphological and hemodynamical healthy vessels. Ten healthy volunteers were analysed in two configurations, the supine (S) and the prone (P) position. Lumen 3D surface models were constructed from images acquired from a non-contrast MRI sequence. Then, the models were used to numerically compute the physiological range of geometric (n = 10) and hemodynamic (n = 3) parameters in the BA and CV. Geometric parameters such as curvature and tortuosity, and hemodynamic parameters based on wall shear stress (WSS) metrics were calculated with the use of computational fluid dynamics. Our results highlight that changes in arm position had a greater impact on WSS metrics of the BA by altering the mean and maximum blood flow rate of the vessel. Whereas, curvature and tortuosity were found not to be significantly different between positions. Inter-variability was associated with antegrade and retrograde flow in BA, and antegrade flow in CV. Shear stress was low and oscillatory shear forces were negligible. This data suggests that deviations from this state may contribute to the risk of accelerated intimal hyperplasia of the vein in arteriovenous fistulas. Therefore, preoperative conditions coupled with post-operative longitudinal data will aid the identification of such relationships

Investigation of Ultrasound-Measured Flow Velocity, Flow Rate and Wall Shear Rate in Radial and Ulnar Arteries Using Simulation

Parameters of blood flow measured by ultrasound in radial and ulnar arteries, such as flow velocity, flow rate and wall shear rate, are widely used in clinical practice and clinical research. Investigation of these measurements is useful for evaluating accuracy and providing knowledge of error sources. A method for simulating the spectral Doppler ultrasound measurement process was developed with computational fluid dynamics providing flow-field data. Specific scanning factors were adjusted to investigate their influence on estimation of the maximum velocity waveform, and flow rate and wall shear rate were derived using the Womersley equation. The overestimation in maximum velocity increases greatly (peak systolic from about 10% to 30%, time-averaged from about 30% to 50%) when the beam-vessel angle is changed from 30° to 70°. The Womersley equation was able to estimate flow rate in both arteries with less than 3% error, but performed better in the radial artery (2.3% overestimation) than the ulnar artery (15.4% underestimation) in estimating wall shear rate. It is concluded that measurements of flow parameters in the radial and ulnar arteries with clinical ultrasound scanners are prone to clinically significant errors.</p

Allopurinol treatment adversely impacts left ventricular mass regression in patients with well-controlled hypertension

Objectives: Previous studies have demonstrated that high dose allopurinol is able to regress Left Ventricular (LV) mass in cohorts with established cardiovascular disease. The aim of this study was to assess whether treatment with high dose allopurinol would regress LV mass in a cohort with essential hypertension, LV hypertrophy and well- controlled blood pressure but without established cardiovascular disease.Methods: We conducted a mechanistic proof-of-concept randomised, placebo controlled, double-blind trial of allopurinol (600mg/day) versus placebo on LV mass regression. Duration of treatment was 12 months. LV mass regression was assessed by Cardiac Magnetic Resonance. Secondary outcomes were changes in endothelial function (flow mediated dilatation), arterial stiffness (pulse wave velocity) and biomarkers of oxidative stress. Results: 72 patients were randomised into the trial. Mean baseline urate was 362.2 ± 96.7umol/L. Despite good blood pressure control, LV mass regression was significantly reduced in the allopurinol cohort compared to placebo (LV mass -0.37 ± 6.08 g vs -3.75 ± 3.89 g; p=0.012). Oxidative stress markers (Thiobarbituric acid reactive substances) were significantly higher in the allopurinol group vs placebo (0.26 ± 0.85uM vs -0.34 ± 0.83uM; p=0.007). Other markers of vascular function were not significantly different between the two groups.Conclusions: Treatment with high dose allopurinol in normo-uricemic controlled hypertensive patients and LV hypertrophy is detrimental. It results in reduced LV mass regression and increased oxidative stress over a 12-month period. This may be due to an adverse impact on redox balance. Cohort selection for future cardiovascular trials with allopurinol is crucial.<br/

An Alumni survey of the School of Social Work, Portland State University

The alumni survey conducted at Portland State University School of Social Work by second year students had two purposes. One purpose was to fulfill the research practicum requirements of a Masters of Social Work degree by providing experience in the area of applied survey research. The other was to provide a data base for future alumni research at the school

Imaging in Vascular Access

This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention is indicated. MRI is limited by its cost and the time required for image acquisition that mainly confines it to the realm of research where high resolution is required. CT’s short acquisition times and high resolution make it useful as a problem-solving tool in complex cases, although accessibility can be an issue. All four imaging modalities have advantages and disadvantages that limit their use in this particular patient cohort. Current imaging in VA comprises an integrated approach with each modality providing particular uses dependent on their capabilities. MRI and CT, which currently have limited use, may have increasingly important future roles in complex cases where detailed analysis is required

Prevalence of unrecognised myocardial infarction in a low-intermediate risk asymptomatic cohort and its relation to systemic atherosclerosis

The study was funded by the Souter Charitable Foundation and the Chest, Heart and Stroke Scotland Charity. J.R.W.M. is supported by the Wellcome Trust through the Scottish Translational Medicine and Therapeutics Initiative (grant no. WT 085664) in the form of a clinical research fellowship.Aims :  Unrecognized myocardial infarctions (UMIs) have been described in 19-30% of the general population using late gadolinium enhancement (LGE) on cardiac magnetic resonance. However, these studies have focused on an unselected cohort including those with known cardiovascular disease (CVD). The aim of the current study was to ascertain the prevalence of UMIs in a non-high-risk population using magnetic resonance imaging (MRI). Methods and Results :  A total of 5000 volunteers aged >40 years with no history of CVD and a 10-year risk of CVD of <20%, as assessed by the ATP-III risk score, were recruited to the Tayside Screening for Cardiac Events study. Those with a B-type natriuretic peptide (BNP) level greater than their gender-specific median were invited for a whole-body MR angiogram and cardiac MR including LGE assessment. LGE was classed as absent, UMI, or non-specific. A total of 1529 volunteers completed the imaging study; of these, 53 (3.6%) were excluded because of either missing data or inadequate LGE image quality. Ten of the remaining 1476 (0.67%) displayed LGE. Of these, three (0.2%) were consistent with UMI, whereas seven were non-specific occurring in the mid-myocardium (n = 4), epicardium (n = 1), or right ventricular insertion points (n = 2). Those with UMI had a significantly higher BNP [median 116 (range 31-133) vs. 22.6 (5-175) pg/mL, P = 0.015], lower ejection fraction [54.6 (36-62) vs. 68.9 (38-89)%, P = 0.007], and larger end-systolic volume [36.3 (27-61) vs. 21.7 (5-65) mL/m(2), P = 0.014]. Those with non-specific LGE had lower diastolic blood pressure [68 (54-70) vs. 72 (46-98) mmHg, P = 0.013] but no differences in their cardiac function. Conclusion :  Despite previous reports describing high prevalence of UMI in older populations, in a predominantly middle-aged cohort, those who are of intermediate or low cardiovascular risk have a very low risk of having an unrecognized myocardial infarct.Publisher PDFPeer reviewe

Whole body cardiovascular magnetic resonance imaging to stratify symptomatic and asymptomatic atherosclerotic burden in patients with isolated cardiovascular disease

BACKGROUND: The aim of this study was to use whole body cardiovascular magnetic resonance imaging (WB CVMR) to assess the heart and arterial network in a single examination, so as to describe the burden of atherosclerosis and subclinical disease in participants with symptomatic single site vascular disease. METHODS: 64 patients with a history of symptomatic single site vascular disease (38 coronary artery disease (CAD), 9 cerebrovascular disease, 17 peripheral arterial disease (PAD)) underwent whole body angiogram and cardiac MR in a 3 T scanner. The arterial tree was subdivided into 31 segments and each scored according to the degree of stenosis. From this a standardised atheroma score (SAS) was calculated. Cine and late gadolinium enhancement images of the left ventricle were obtained. RESULTS: Asymptomatic atherosclerotic disease with greater than 50 % stenosis in arteries other than that responsible for their presenting complain was detected in 37 % of CAD, 33 % of cerebrovascular and 47 % of PAD patients. Unrecognised myocardial infarcts were observed in 29 % of PAD patients. SAS was significantly higher in PAD patients 24 (17.5-30.5) compared to CAD 4 (2–11.25) or cerebrovascular disease patients 6 (2-10) (ANCOVA p < 0.001). Standardised atheroma score positively correlated with age (β 0.36 p = 0.002), smoking status (β 0.34 p = 0.002), and LV mass (β -0.61 p = 0.001) on multiple linear regression. CONCLUSION: WB CVMR is an effective method for the stratification of cardiovascular disease. The high prevalence of asymptomatic arterial disease, and silent myocardial infarctions, particularly in the peripheral arterial disease group, demonstrates the importance of a systematic approach to the assessment of cardiovascular disease

Effects of inaccuracies in arterial path length measurement on differences in MRI and tonometry measured pulse wave velocity

Abstract Background Carotid-femoral pulse wave velocity (cf-PWV) and aortic PWV measured using MRI (MRI-PWV) show good correlation, but with a significant and consistent bias across studies. The aim of the current study was to evaluate whether the differences between cf.-PWV and MRI-PWV can be accounted for by inaccuracies of currently used distance measurements. Methods One hundred fourteen study participants were recruited into one of 4 groups: Type 2 diabetes melltus (T2DM) with cardiovascular disease (CVD) (n = 23), T2DM without CVD (n = 41), CVD without T2DM (n = 25) and a control group (n = 25). All participants underwent cf.-PWV, cardiac MRI and whole body MR angiography(WB-MRA). 90 study participants also underwent aortic PWV using MRI. cf.-PWVEXT was performed using a SphygmoCor device (Atcor Medical, West Ryde, Australia). The true intra-arterial pathlength was measured using the WB-MRA and then used to recalculate the cf.-PWVEXT to give a cf.-PWVMRA. Results Distance measurements were significantly lower on WB-MRA than on external tape measure (mean diff = −85.4 ± 54.0 mm,p < 0.001). MRI-PWV was significantly lower than cf.-PWVEXT (MRI-PWV = 8.1 ± 2.9 vs. cf.-PWVEXT = 10.9 ± 2.7 ms−1,p < 0.001). When cf.-PWV was recalculated using the inter-arterial distance from WB-MRA, this difference was significantly reduced but not lost (MRI-PWV = 8.1 ± 2.9 ms−1 vs. cf.-PWVMRA 9.1 ± 2.1 ms−1, mean diff = −0.96 ± 2.52 ms−1,p = 0.001). Recalculation of the PWV increased correlation with age and pulse pressure. Conclusion Differences in cf.-PWV and MRI PWV can be predominantly but not entirely explained by inaccuracies introduced by the use of simple surface measurements to represent the convoluted arterial path between the carotid and femoral arteries