During an MRI scan, the radiofrequency field from the scanner's transmit coil, but also the switched gradient fields, induce currents in any conductive object in the bore. This makes any metallic ...medical implant an additional risk for an MRI patient, because those currents can heat up the surrounding tissues to dangerous levels. This is one of the reasons why implants are, until today, considered a contraindication for MRI; for example, by scanner manufacturers. Due to the increasing prevalence of medical implants in our aging societies, such general exclusion is no longer acceptable. Also, it should be no longer needed, because of a much‐improved safety‐assessment methodology, in particular in the field of numerical simulations. The present article reviews existing literature on implant‐related heating effects in MRI. Concepts for risk assessment and quantification are presented and also some first attempts towards an active safety management and risk mitigation.
Level of Evidence
5
Technical Efficacy
Stage 5
This study explored the functional connectivity between brain regions implicated in the default mode network, the sensorimotor cortex (S1/M1), and the intraparietal sulcus (IPS/MIP) at rest in ...patients with complex regional pain syndrome. It also investigated how possible alterations are associated with neuropathic pain. Our group used functional magnetic resonance imaging to investigate functional brain connectivity in 12 complex regional pain syndrome patients in comparison with that in 12 age- and sex-matched healthy controls. Data were analyzed using a seed voxel correlation analysis and an independent component analysis. An analysis of covariance was employed to relate alterations in functional connectivity with clinical symptoms. We found significantly greater reductions in functional default mode network connectivity in patients compared to controls. The functional connectivity maps of S1/M1 and IPS/MIP in patients revealed greater and more diffuse connectivity with other brain regions, mainly with the cingulate cortex, precuneus, thalamus, and prefrontal cortex. In contrast, controls showed greater intraregional connectivity within S1/M1 and IPS/MIP. Furthermore, there was a trend for correlation between alterations in functional connectivity and intensity of neuropathic pain. In our findings, patients with complex regional pain syndrome have substantial spatial alterations in the functional connectivity between brain regions implicated in the resting-state default mode network, S1/M1, and IPS/MIP; these alterations show a trend of correlation with neuropathic pain intensity.
This article presents spatial alterations in the functional resting-state connectivity of complex regional pain syndrome patients. Our results add further insight into the disease states of CRPS and into the functional architecture of the resting state brains of pain patients in general.
The PEDOT polymer electrode is a metal-free electrode, consisting of an acrylate (dental composite) and the conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The ...electrode is applied as gel onto the skin and cured with blue light for 10-20 s in order to achieve a conductive bond to the skin. The electrodes are used in combination with polymer cables consisting of a textile backbone and PEDOT:PSS. To test this new electrode and cable type under different conditions we designed two stress-tests: highly sensitive temperature recordings within a head phantom during Magnetic Resonance Imaging (MRI) and long-term stability inside a climate chamber with high humidity. To study the physical behavior inside the strong magnetic field (3 Tesla), the PEDOT polymer electrode was attached to an agarose head-phantom inside a magnetic resonance tomograph during an image sequence. MRI-safe temperature sensors were placed nearby in order to measure possible heating effects. In comparison to a metal cable, nearly no rise in temperature could be observed if the electrode was used in combination with a conductive textile cable. Furthermore, the electrode showed stable impedance values inside a climate chamber for 4 consecutive days. These results pave the way for testing the PEDOT polymer electrode as biosignal recording electrode during MRI, especially for cardio MRI and Electroencephalography in combination with functional MRI (EEG-fMRI).
The understanding of the mechanisms underlying chronic pain is of major scientific and clinical interest. This review focuses on neuroimaging studies of pain-induced neuroplastic changes in the human ...brain and discusses five major categories of pain-induced neuroplastic changes.
First, peripheral or central sensitization may result in increased nociceptive input to the brain and also changes the processing of nociceptive information within the brain. Second, chronic nociceptive input from the periphery or from lesions within the central nervous system may result in cortical reorganization and maladaptive neuroplasticity within somatosensory and motor systems. Thirdly, there is evidence for pain-induced changes in large-scale neuronal network connectivity. Fourth, in patients with chronic pain, structural brain changes may occur. Finally, there is discussion that in chronic pain patients the endogenous pain-modulatory system may function aberrantly.
Recent work has substantially broadened our insights into neuroplastic changes that are involved in pain chronification. Future research will focus on the question of whether neuroimaging techniques can be used in the individual chronic pain patient as a biomarker that would allow for an objective diagnosis of different pain conditions and for the prediction of individual responses to specific therapies.
The purpose of the present investigation was to examine the impact of blood transfusion on resource utilisation, morbidity and mortality in patients undergoing coronary artery bypass graft (CABG) ...surgery at a major university hospital. The resources we examined are time to extubation, intensive care unit length of stay (ICULOS) and postoperative length of stay (PLOS). We further examined the impact of number of units of packed red blood cells (PRBCs) transfused during PLOS. This is a retrospective observational study and includes 1746 consecutive male and female patients undergoing primary CABG (on- and off-pump) at our institution. Of these, 1067 patients received blood transfusions, while 677 did not. The data regarding the demography, blood transfusion, resource utilisation, morbidity and mortality were collected from the records of patients undergoing CABG over a period of three years. The mean time to extubation following surgery was 8.0 h for the transfused group and 4.3 h for the nontransfused group ( P <or= 0.001). The mean ICULOS for the transfused group was 1.6 d and 1.2 d for the nontransfused group ( P P <or= 0.001). In all patients and in patients with no preoperative morbidity, partial correlation coefficients were used to examine the effects of transfusion on mortality, time to extubation, ICULOS and PLOS. Linear regression model was used to assess the effect of number of PRBC units transfused on PLOS. We noted that PLOS increased with the number of PRBCs units transfused. Transfusion is significantly correlated with the increased time to extubation, ICULOS, PLOS and mortality. The transfused patients had significantly more postoperative complications than their nontransfused counterparts ( P <or= 0.001). The 30-day hospital mortality was 3.1% for the transfused group with no deaths in the nontransfused group ( P <or= 0.001). We conclude that the CABG patients receiving blood transfusion have significantly longer time for tracheal extubation, ICULOS, PLOS and higher morbidity and 30-day hospital mortality. Blood transfusion was an independent predictor of increased resource utilisation, postoperative morbidity and mortality.
A tabletop-sized Kibble balance (KIBB-g1) designed to directly realize mass at the gram-level range with uncertainties on the order of parts in 106 has been developed at the National Institute of ...Standards and Technology (NIST). The masses of a nominally 5 g and 1 g weight were determined with standard uncertainties of 9.0 g and 6.7 g, respectively. The corresponding relative uncertainties are and . The construction of the instrument, capabilities, and full uncertainty budgets are presented in this manuscript.
The insula plays a key role in brain processing of noxious and innocuous thermal stimuli. The anterior and the posterior portions of the insular cortex are involved in different ways in nociceptive ...and thermoceptive processing. Therefore, their stimulus-specific functional connectivity may also differ. Here we used functional magnetic resonance imaging (fMRI) to investigate the activity and functional connectivity of insular cortex subregions during noxious and innocuous thermal stimulation. In 11 healthy subjects, psychophysically controlled noxious and innocuous warm and cold stimuli were applied to the left forearm. To differentiate between the subregions of the insular cortex involved in pain processing and those involved in temperature processing, a 2×2 factorial fMRI analysis was performed. Pain processing insular areas (main effect of pain) were detected in bilateral aINS and contralateral pINS. Temperature processing insular areas (main effect of temperature) were also found in bilateral aINS and contralateral pINS. The individual signal time courses from the pain- and temperature processing insular activation clusters were used for calculation and comparison of stimulus-specific functional connectivity of aINS and pINS by means of a correlation analysis. As expected, both aINS and pINS were functionally connected to a large brain network — which predominantly includes areas involved in nociception and thermoception: primary (S1) and secondary (S2) somatosensory cortices, cingulate gyrus, prefrontal cortex (PFC) and parietal association cortices (PA). When statistically compared, during both noxious and innocuous stimulation, aINS was more strongly connected to PFC and to ACC than was pINS; pINS meanwhile was more strongly connected to S1 and to the primary motor cortex (M1). Interestingly, S2 was more strongly connected to aINS than to pINS during painful stimulation but not during innocuous thermal stimulation. We conclude that aINS is more strongly functionally connected to areas known for affective and cognitive processing, whereas pINS is more strongly connected with areas known for sensory-discriminative processing of noxious and somatosensory stimuli.
►The anterior insular cortex is functionally strongly connected to areas known for affective and cognitive pain processing. ►The posterior insular cortex is more strongly connected with areas known for sensory-discriminative processing of noxious and somatosensory stimuli. ►These findings support the central role of the insula in pain and thermoception and corroborate the view of the insula as a multidimensional integration side for pain.
A method for quantitative determination of the glutamate (Glu) concentration in human brain using PRESS-based single voxel MR spectroscopy (MRS) at 3 T has been developed and validated by repeatedly ...analyzing voxels comprising the anterior cingulate cortex (acc) and the left hippocampus (hc) in 40 healthy volunteer brains. At an optimum echo time of 80 ms, the C4 resonance of Glu appears well resolved and separated from major interferents, that is, glutamine and N-acetylaspartate. As a complementary method, a multiple quantum coherence filter sequence for Glu was employed. For quantification of Glu and the principal MRS-visible metabolites as well as for an estimate of the glutamine level, analysis of both types of in vivo spectra was carried out by a time domain-frequency domain method involving prior knowledge obtained from phantom spectra. Using PRESS, coefficients of variation (CV) for Glu concentration were of the order of 10%. When the concentrations were corrected by individual cerebrospinal fluid fractions obtained by segmentation using spm, CVs tended to increase and the correlation coefficients for the two MRS sessions tended to decrease, indicating that this type of correction adds uncertainty to the data. The concentrations of Glu in the two voxels studied were found to be significantly different (11.6 mmol/l in acc, 10.9 mmol/l in hc,
P = 0.023) and decrease with age (
P < 0.04). These concentrations agreed well with those determined using the quantum coherence filter method although the uncertainty of the latter limits reliable analysis.
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