MRI Guided Interventions needs new materials and contrast agents

Abstract Magnetic resonance imaging (MRI) is primary a diagnostic tool, with or without the use of contrast agents. To enable the use of MRI for interventional purposes, devices are needed that are nonmagnetic and non-conductive and visible in MRI. Fiber-composite materials provide enough strength to replace classic metal-based devices, and at the same time provide opportunity to include contrast agents as part of the matrix. Gadolinium chelates are clinically being used ad contrast agents by delivery into the vascular space, and then diffusing into the site (tumor, scar, vessel) of interest, Apart from incomplete diffusion, they are rapidly washed out of the site, and some gadolinium chelates cause specific renal toxicity Porphyrins are potential MR contrast agents, considering their stable form within chelate complexes that comprises paramagnetic metal ions and their retention by the site selectively The present study aims to evaluate the site enhancing imaging characteristics of novel metalloporphyrin derivatives. In this project we investigate the MRI characteristics of metalloporphyrin derivatives as potential biocompatible MR contrast agent. However, to enable this several technical issues have to be resolved. Hemin is sparingly soluble in aqueous media. Therefore, derivatives of Hemin have been processed for enhancing the solubility as PEGylated Hemin, Hemin Arginate or Hemin Lysinate. This new contrast agent has achieved a high molar Relaxivity in MRI allowing decrease of the required dose for in vivo applications. These derivatives suggest that the size, geometry, and polarity of hemin can be modified to optimize their relaxivities ,pharmacokinetic properties, and biocompatibility

An imbalance between specialized pro-resolving lipid mediators and pro-inflammatory leukotrienes promotes instability of atherosclerotic plaques

Chronic unresolved inflammation plays a causal role in the development of advanced atherosclerosis, but the mechanisms that prevent resolution in atherosclerosis remain unclear. Here, we use targeted mass spectrometry to identify specialized pro-resolving lipid mediators (SPM) in histologically-defined stable and vulnerable regions of human carotid atherosclerotic plaques. The levels of SPMs, particularly resolvin D1 (RvD1), and the ratio of SPMs to pro-inflammatory leukotriene B4 (LTB₄), are significantly decreased in the vulnerable regions. SPMs are also decreased in advanced plaques of fat-fed Ldlr⁻/⁻ mice. Administration of RvD1 to these mice during plaque progression restores the RvD1:LTB₄ ratio to that of less advanced lesions and promotes plaque stability, including decreased lesional oxidative stress and necrosis, improved lesional efferocytosis, and thicker fibrous caps. These findings provide molecular support for the concept that defective inflammation resolution contributes to the formation of clinically dangerous plaques and offer a mechanistic rationale for SPM therapy to promote plaque stability

The effect of Gonioscopy on keratometry and corneal surface topography

BACKGROUND: Biometric procedures such as keratometry performed shortly after contact procedures like gonioscopy and applanation tonometry could affect the validity of the measurement. This study was conducted to understand the short-term effect of gonioscopy on corneal curvature measurements and surface topography based Simulated Keratometry and whether this would alter the power of an intraocular lens implant calculated using post-gonioscopy measurements. We further compared the effect of the 2-mirror (Goldmann) and the 4-mirror (Sussman) Gonioscopes. METHODS: A prospective clinic-based self-controlled comparative study. 198 eyes of 99 patients, above 50 years of age, were studied. Exclusion criteria included documented dry eye, history of ocular surgery or trauma, diabetes mellitus and connective tissue disorders. Auto-Keratometry and corneal topography measurements were obtained at baseline and at three follow-up times – within the first 5 minutes, between the 10(th)-15(th )minute and between the 20(th)-25(th )minute after intervention. One eye was randomized for intervention with the 2-mirror gonioscope and the other underwent the 4-mirror after baseline measurements. t-tests were used to examine differences between interventions and between the measurement methods. The sample size was calculated using an estimate of clinically significant lens implant power changes based on the SRK-II formula. RESULTS: Clinically and statistically significant steepening was observed in the first 5 minutes and in the 10–15 minute interval using topography-based Sim K. These changes were not present with the Auto-Keratometer measurements. Although changes from baseline were noted between 20 and 25 minutes topographically, these were not clinically or statistically significant. There was no significant difference between the two types of gonioscopes. There was greater variability in the changes from baseline using the topography-based Sim K readings. CONCLUSION: Reversible steepening of the central corneal surface is produced by the act of gonioscopy as measured by Sim K, whereas no significant differences were present with Auto-K measurements. The type of Gonioscope used does not appear to influence these results. If topographically derived Sim K is used to calculate the power of the intraocular lens implant, we recommend waiting a minimum of 20 minutes before measuring the corneal curvature after gonioscopy with either Goldmann or Sussman contact lenses