A non-invasive optical method for mapping temperature polarization in direct contact membrane distillation

Membrane Distillation (MD) is a thermal membrane process allowing for a theoretical 100% rejection of non-volatile compounds (i.e. ions, macromolecules, colloids, cells), whereas vapour molecules permeate through a micro-porous hydrophobic membrane due to a difference of vapour pressure established across the membrane-self. The effective driving force and, then, the vapour trans-membrane flux is affected by temperature polarization phenomena occurring in the boundary layers adjacent to the membrane. The temperature values at the membrane surface are usually difficult to measure and only recently some invasive techniques were adopted for this scope. The aim of this work was to introduce luminescent molecular probing as an innovative technology for non-invasive and in-situ monitoring of thermal polarization in MD. Tris(phenantroline)ruthenium(II) chloride (Ru(phen)3) was selected as temperature sensitive luminescent probe and immobilized in a flat poly(vinylidene fluoride) electrospun nanofibrous membrane (PVDF ENM). Experiments showed the key role of the Ru(phen)3 and Lithium Chloride (LiCl) in the preparation of homogeneous PVDF ENM due to their ionic nature that improved the electrical conductivity of the polymeric solution favouring the electrospinning. Furthermore, PVDF ENM showed a good performance in Direct Contact Membrane Distillation (DCMD) process. The immobilization of the molecular probe allowed to optically monitoring the membrane surface temperature during DCMD experiments. On the other hand, the employment of an IR-camera permitted the evaluation of the temperature of the bulk of liquid streams. Therefore, the combination of these two optical techniques enabled to evaluate, in a direct and non-invasive way, the thermal polarization along the membrane module during DCMD experiments

Reduction of motion effects in myocardial arterial spin labeling

Purpose To evaluate the accuracy and reproducibility of myocardial blood flow measurements obtained under different breathing strategies and motion correction techniques with arterial spin labeling. Methods A prospective cardiac arterial spin labeling study was performed in 12 volunteers at 3 Tesla. Perfusion images were acquired twice under breath-hold, synchronized-breathing, and free-breathing. Motion detection based on the temporal intensity variation of a myocardial voxel, as well as image registration based on pairwise and groupwise approaches, were applied and evaluated in synthetic and in vivo data. A region of interest was drawn over the mean perfusion-weighted image for quantification. Original breath-hold datasets, analyzed with individual regions of interest for each perfusion-weighted image, were considered as reference values. Results Perfusion measurements in the reference breath-hold datasets were in line with those reported in literature. In original datasets, prior to motion correction, myocardial blood flow quantification was significantly overestimated due to contamination of the myocardial perfusion with the high intensity signal of blood pool. These effects were minimized with motion detection or registration. Synthetic data showed that accuracy of the perfusion measurements was higher with the use of registration, in particular after the pairwise approach, which probed to be more robust to motion. Conclusion Satisfactory results were obtained for the free-breathing strategy after pairwise registration, with higher accuracy and robustness (in synthetic datasets) and higher intrasession reproducibility together with lower myocardial blood flow variability across subjects (in in vivo datasets). Breath-hold and synchronized-breathing after motion correction provided similar results, but these breathing strategies can be difficult to perform by patients

Multiparametric renal magnetic resonance imaging: A reproducibility study in renal allografts with stable function

Monitoring renal allograft function after transplantation is key for the early detection of allograft impairment, which in turn can contribute to preventing the loss of the allograft. Multiparametric renal MRI (mpMRI) is a promising noninvasive technique to assess and characterize renal physiopathology; however, few studies have employed mpMRI in renal allografts with stable function (maintained function over a long time period). The purposes of the current study were to evaluate the reproducibility of mpMRI in transplant patients and to characterize normal values of the measured parameters, and to estimate the labeling efficiency of Pseudo-Continuous Arterial Spin Labeling (PCASL) in the infrarenal aorta using numerical simulations considering experimental measurements of aortic blood flow profiles. The subjects were 20 transplant patients with stable kidney function, maintained over 1 year. The MRI protocol consisted of PCASL, intravoxel incoherent motion, and T1 inversion recovery. Phase contrast was used to measure aortic blood flow. Renal blood flow (RBF), diffusion coefficient (D), pseudo-diffusion coefficient (D*), flowing fraction ( f ), and T1 maps were calculated and mean values were measured in the cortex and medulla. The labeling efficiency of PCASL was estimated from simulation of Bloch equations. Reproducibility was assessed with the within-subject coefficient of variation, intraclass correlation coefficient, and Bland-Altman analysis. Correlations were evaluated using the Pearson correlation coefficient. The significance level was p less than 0.05. Cortical reproducibility was very good for T1, D, and RBF, moderate for f , and low for D*, while medullary reproducibility was good for T1 and D. Significant correlations in the cortex between RBF and f (r = 0.66), RBF and eGFR (r = 0.64), and D* and eGFR (r = -0.57) were found. Normal values of the measured parameters employing the mpMRI protocol in kidney transplant patients with stable function were characterized and the results showed good reproducibility of the techniques

Successful working memory processes and cerebellum in an elderly sample: A neuropsychological and fMRI study

Background Imaging studies help to understand the evolution of key cognitive processes related to aging, such as working memory (WM). This study aimed to test three hypotheses in older adults. First, that the brain activation pattern associated to WM processes in elderly during successful low load tasks is located in posterior sensory and associative areas; second, that the prefrontal and parietal cortex and basal ganglia should be more active during high-demand tasks; third, that cerebellar activations are related to high-demand cognitive tasks and have a specific lateralization depending on the condition. Methods We used a neuropsychological assessment with functional magnetic resonance imaging and a core N-back paradigm design that was maintained across the combination of four conditions of stimuli and two memory loads in a sample of twenty elderly subjects. Results During low-loads, activations were located in the visual ventral network. In high loads, there was an involvement of the basal ganglia and cerebellum in addition to the frontal and parietal cortices. Moreover, we detected an executive control role of the cerebellum in a relatively symmetric fronto-parietal network. Nevertheless, this network showed a predominantly left lateralization in parietal regions associated presumably with an overuse of verbal storage strategies. The differential activations between conditions were stimuli-dependent and were located in sensory areas. Conclusion Successful WM processes in the elderly population are accompanied by an activation pattern that involves cerebellar regions working together with a fronto-parietal network

Incumplimiento terapéutico en pacientes sometidos a trasplante cardiaco

• Introduction: Heart transplant patients are required to take medication for life, both immunosuppressant to prevent rejection, as required for other illnesses. It is essential to modify the plasma levels of immunosuppressive drugs on an ongoing basis to achieve the desired effect with minimal side effects. Several studies show that the degree of non-compliance with therapy ranges in Spain, over 45% for hypertension. For other diseases such as diabetes and dialysis studies are variable percentages. Treatment compliance can be measured quantitatively and / or qualitative. Compliance measurement is not easy because different factors. • Objective: The aim of the study was to assess the prevalence of the therapeutic compliance in heart transplanted patients. • Material and Methods: One hundred patients subject to heart transplantation in our hospital until December 2007 were included. The extended Morisky-Green test as indirect method and the immunosuppressant blood levels as direct method were applied. • Results: Patients had a mean age of 61 ± 10, and 78% of men. Mostly with primary and sick leave and disability. According to the Morisky-Green test 47% of patients are non-compliant, of which 89% said they rarely forget to take medication. Patients take an average of 10.69 ± 2.99 medications per day, and only 55% known for serving the medicines they take. 3A rejection showed 56% of patients, of who half were noncompliant. 57% of patients who required immunosuppressive medication changes were defaulters. • Conclusions: Transplant recipients have a high level of therapeutic failure, not unlike the levels for other diseases. Although 80% of patients transplanted electively and with the knowledge of the process and subsequent treatment, we must insist more on the importance of adherence, as this directly influences the onset of rejection. The role of nursing is very important and basic to help achieve more optimal results.• Introducción: Los pacientes sometidos a trasplante cardiaco requieren tomar medicación de por vida, tanto inmunosupresora para evitar el rechazo, como la necesaria para otras enfermedades concomitantes. Es imprescindible modificar los niveles plasmáticos de los inmunosupresores de forma continuada, para conseguir el efecto deseado con los mínimos efectos secundarios. Diversos estudios muestran que el grado de incumplimiento terapéutico oscila, en España, sobre el 45% para hipertensos. Para otras enfermedades como diabetes y pacientes en diálisis se encuentran estudios con porcentajes variables. El cumplimiento terapéutico se puede medir de forma cuantitativa y/o cualitativa. La medición del cumplimiento no es fácil puesto que intervienen diferentes factores. • Objetivo: El objetivo del estudio es determinar la prevalencia del cumplimiento terapéutico en el paciente trasplantado de corazón. • Material y método: Se han incluido 100 pacientes que fueron sometidos a trasplante de corazón en nuestro hospital hasta diciembre de 2007. Utilizamos como método indirecto el test de Morisky-Green ampliado y como método directo los niveles de inmunosupresores en sangre. • Resultados: Los pacientes tienen una media de edad de 61±10, y un 78% de hombres. Mayoritariamente con estudios primarios y en situación de baja laboral o invalidez. Según el test de Morisky-Green el 47% de los pacientes son incumplidores; de éstos el 89% afirma que olvida en pocas ocasiones tomar la medicación. Los pacientes toman una media de 10,69±2,99 medicaciones al día, y solo el 55% conoce para qué sirve la medicación que toma. Presentaron rechazo 3A un 56% de los pacientes, de los cuales la mitad eran no cumplidores. Un 57% de los pacientes que precisaron cambios en medicación inmunosupresora eran incumplidores. • Conclusiones: Los pacientes trasplantados presentan un alto nivel de incumplimiento terapéutico, que no difiere de los niveles para otras enfermedades. Pese a que el 80% de los pacientes se trasplantaron de forma electiva y con el conocimiento de todo el proceso y tratamiento posterior, debemos incidir más en la importancia del cumplimiento terapéutico, ya que esto influye directamente en la aparición de rechazo. La función de Enfermería es muy importante y básica para lograr conseguir unos resultados más óptimos

Fully Automated Attenuation Measurement and Motion Correction in FLIP Image Sequences

Radiolog

Assessment of splenic switch-off with arterial spin labeling in adenosine perfusion cardiac MRI

Background: In patients with suspected coronary artery disease (CAD), myocardial perfusion is assessed under rest and pharmacological stress to identify ischemia. Splenic switch-off, defined as the stress to rest splenic perfusion attenuation in response to adenosine, has been proposed as an indicator of stress adequacy. Its occurrence has been previously assessed in first-pass perfusion images, but the use of noncontrast techniques would be highly beneficial. Purpose: To explore the ability of pseudo-continuous arterial spin labeling (PCASL) to identify splenic switch-off in patients with suspected CAD. Study type: Prospective. Population: Five healthy volunteers (age 24.8 ± 3.8 years) and 32 patients (age 66.4 ± 8.2 years) with suspected CAD. Field strength/sequence: A 1.5-T/PCASL (spin-echo) and first-pass imaging (gradient-echo). Assessment: In healthy subjects, multi-delay PCASL data (500-2000 msec) were acquired to quantify splenic blood flow (SBF) and determine the adequate postlabeling delay (PLD) for single-delay acquisitions (PLD > arterial transit time). In patients, single-delay PCASL (1200 msec) and first-pass perfusion images were acquired under rest and adenosine conditions. PCASL data were used to compute SBF maps and SBF stress-to-rest ratios. Three observers classified patients into "switch-off" and "failed switch-off" groups by visually comparing rest-stress perfusion data acquired with PCASL and first-pass, independently. First-pass categories were used as reference to evaluate the accuracy of quantitative classification. Statistical tests: Wilcoxon signed-rank, Pearson correlation, kappa, percentage agreement, Generalized Linear Mixed Model, Mann-Whitney, Pearson Chi-squared, receiver operating characteristic, area-under-the-curve (AUC) and confusion matrix. Significance: P value < 0.05. Results: A total of 27 patients (84.4%) experienced splenic switch-off according to first-pass categories. Comparison of PCASL-derived SBF maps during stress and rest allowed assessment of splenic switch-off, reflected in a reduction of SBF values during stress. SBF stress-to-rest ratios showed a 97% accuracy (sensitivity = 80%, specificity = 100%, AUC = 85.2%). Data conclusion: This study could demonstrate the feasibility of PCASL to identify splenic switch-off during adenosine perfusion MRI, both by qualitative and quantitative assessments. Evidence level: 2 TECHNICAL EFFICACY: 2

Cortical hypoperfusion in Parkinson's disease assessed using arterial spin labeled perfusion MRI

Alterations in cerebral perfusion and metabolism in Parkinson's disease have been assessed in several studies, using nuclear imaging techniques and more recently magnetic resonance imaging. However, to date there is no consensus in the literature regarding the extent and the magnitude of these alterations. In this work, arterial spin labeled perfusion MRI was employed to quantify absolute cerebral blood flow in a group of earlyto- moderate Parkinson's disease patients and age-matched healthy controls. Perfusion comparisons between the two groups showed that Parkinson's disease is characterized by wide-spread cortical hypoperfusion. Subcortically, hypoperfusion was also found in the caudate nucleus. This pattern of hypoperfusion could be related to cognitive dysfunctions that have been previously observed even at the disease early stages. The present results were obtained by means of whole brain voxel-wise comparisons of absolute perfusion values, using statistical parametric mapping, thus avoiding the potentially biased global mean normalization procedure. In addition, this work demonstrates that between-group comparison of relative perfusion values after global mean normalization, introduced artifactual relative perfusion increases, where absolute perfusion was in fact preserved. This has implications for perfusion studies of other brain disorders