I n North America most clinical MRI is performed at 1.5 T or 3.0 T, and some research applications have moved to 7.0 T. High field is motivated by higher polarization, promising increased signal-to-noise ratio (SNR), and resolution. However, this causes image distortion, constrained imaging efficiency, increased specific absorption rate, and higher cost. For some applications, low field strength may offer intrinsic advantages (1,2). At low field strength, short T1 and long T2* allow more efficient pulse sequence design; imaging near air-tissue interfaces is improved by virtue of reduced susceptibility gradients; and specific absorption rate is reduced, which can diminish heating of conductive devices and implants, and can eliminate pulse sequence parameter constraints (3). Commercial lower field systems have been largely overlooked as hardware and software have improved over the last 2 decades, and therefore are not well-suited for technically demanding imaging. We developed and evaluated a custom 0.55-T MRI system equipped with contemporary

BackgroundClinical treatment of cardiac arrhythmia by radiofrequency ablation (RFA) currently lacks quantitative and precise visualization of lesion formation in the myocardium during the procedure. This study aims at evaluating thermal dose (TD) imaging obtained from real-time magnetic resonance (MR) thermometry on the heart as a relevant indicator of the thermal lesion extent.MethodsMR temperature mapping based on the Proton Resonance Frequency Shift (PRFS) method was performed at 1.5 T on the heart, with 4 to 5 slices acquired per heartbeat. Respiratory motion was compensated using navigator-based slice tracking. Residual in-plane motion and related magnetic susceptibility artifacts were corrected online. The standard deviation of temperature was measured on healthy volunteers (N = 5) in both ventricles. On animals, the MR-compatible catheter was positioned and visualized in the left ventricle (LV) using a bSSFP pulse sequence with active catheter tracking. Twelve MR-guided RFA were performed on three sheep in vivo at various locations in left ventricle (LV). The dimensions of the thermal lesions measured on thermal dose images, on 3D T1-weighted (T1-w) images acquired immediately after the ablation and at gross pathology were correlated.ResultsMR thermometry uncertainty was 1.5 °C on average over more than 96% of the pixels covering the left and right ventricles, on each volunteer. On animals, catheter repositioning in the LV with active slice tracking was successfully performed and each ablation could be monitored in real-time by MR thermometry and thermal dosimetry. Thermal lesion dimensions on TD maps were found to be highly correlated with those observed on post-ablation T1-w images (R = 0.87) that also correlated (R = 0.89) with measurements at gross pathology.ConclusionsQuantitative TD mapping from real-time rapid CMR thermometry during catheter-based RFA is feasible. It provides a direct assessment of the lesion extent in the myocardium with precision in the range of one millimeter. Real-time MR thermometry and thermal dosimetry may improve safety and efficacy of the RFA procedure by offering a reliable indicator of therapy outcome during the procedure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-017-0323-0) contains supplementary material, which is available to authorized users.

The objective of this study is to determine the impact of expectation associated with placebo and caffeine ingestion. We used a three-armed, randomized, double-blind design. Two three-armed experiments varying instruction (true, false, control) investigated the role of expectations of changes in arousal (blood pressure, heart rate), subjective well-being, and reaction time (RT). In Experiment 1 (N = 45), decaffeinated coffee was administered, and expectations were produced in one group by making them believe they had ingested caffeinated coffee. In Experiment 2 (N = 45), caffeinated orange juice was given in both experimental groups, but only one was informed about the true content. In Experiment 1, a significant effect for subjective alertness was found in the placebo treatment compared to the control group. However, for RT and well-being no significant effects were found. In Experiment 2, no significant expectancy effects were found. Caffeine produced large effects for blood pressure in both treatments compared to the control group, but the effects were larger for the false information group. For subjective well-being (alertness, calmness), considerable but nonsignificant changes were found for correctly informed participants, indicating possible additivity of pharmacologic effect and expectations. The results tentatively indicate that placebo and expectancy effects primarily show through introspection.

Homeopathic proving symptoms appear to be specific to the medicine and do not seem to be due to a local process. Since this was a pilot study using a small number of provers, rival hypotheses cannot be ruled out and the study needs replication.

Findings in parapsychology suggest an effect of distant intentionality. Two laboratory set-ups explored this topic by measuring the effect of a distant intention on psychophysiological variables. The 'Direct Mental Interaction in Living Systems' experiment investigates the effect of various intentions on the electrodermal activity of a remote subject. The 'Remote Staring' experiment examines whether gazing by an observer covaries with the electrodermal activity of the person being observed. Two meta-analyses were conducted. A small significant effect size (d =.11, p =.001) was found in 36 studies on 'direct mental interaction', while a best-evidence-synthesis of 7 studies yielded d =.05 (p =.50). In 15 remote staring studies a mean effect size of d = 0.13 (p =.01) was obtained. It is concluded that there are hints of an effect, but also a shortage of independent replications and theoretical concepts.