Characterization of perfluorocarbon relaxation times and their influence on the optimization of fluorine-19 MRI at 3 tesla.

To characterize and optimize javax.xml.bind.JAXBElement@7524a985 F MRI for different perfluorocarbons (PFCs) at 3T and quantify the loss of acquisition efficiency as a function of different temperature and cellular conditions. The T javax.xml.bind.JAXBElement@1ef4ca84 and T javax.xml.bind.JAXBElement@295b7e6f relaxation times of the commonly used PFCs perfluoropolyether (PFPE), perfluoro-15-crown-5-ether (PFCE), and perfluorooctyl bromide (PFOB) were measured in phantoms and in several different conditions (cell types, presence of fixation agent, and temperatures). These relaxation times were used to optimize pulse sequences through numerical simulations. The acquisition efficiency in each cellular condition was then determined as the ratio of the signal after optimization with the reference relaxation times and after optimization with its proper relaxation times. Finally, PFC detection limits were determined. The loss of acquisition efficiency due to parameter settings optimized for the wrong temperature and cellular condition was limited to 13%. The detection limits of all PFCs were lower at 24 °C than at 37 °C and varied from 11.8 ± 3.0 mM for PFCE at 24 °C to 379.9 ± 51.8 mM for PFOB at 37 °C. Optimizing javax.xml.bind.JAXBElement@30187e57 F pulse sequences with a known phantom only leads to moderate loss in acquisition efficiency in cellular conditions that might be encountered in in vivo and in vitro experiments. Magn Reson Med 77:2263-2271, 2017. © 2016 International Society for Magnetic Resonance in Medicine

Coronary reserve in patients with aortic valve disease before and after successful aortic valve replacement

In patients with aortic valve disease and normal coronary angiograms coronary reserve was determined by the coronary sinus thermodilution technique. Three groups of patients were studied: 37 preoperative patients; 18 different patients 12.52 months after aortic valve replacement and seven control subjects with no cardiac disease. Coronary flow ratio (dipyridamole/rest) was diminished in preoperative compared with postoperative patients (1.66±0.44 vs 2.22±0.85; P<0.05) as well as with controls (2.80±0.84; P<0.01), and corresponding coronary resistance ratio (dipyridamolej rest) was higher in preoperative patients than in both other groups (0.61±0.17 vs 0.48±0.14; P<0.05 vs 0.37±0.10; P<0.01). Differences in the flow ratio, but not in the resistance ratio, were significant (P<0.05) in patients after aortic valve replacement compared with controls. Total coronary sinus blood flow at rest was elevated in preoperative compared with both postoperative patients and controls (252±99 vs 169±63; P<0.01; vs 170±35 ml.min−1, P<0.05), whereas flows after maximal vasodilation did not differ among the three groups (416± 184 vs 361 ± 150 vs 488± 235 ml.min−1). Postoperative patients showed a distinct, though not total regression of left ventricular angiographic muscle mass index and wall thickness. Nine of the 18 postoperative patients showed a normal coronary flow reserve and nine showed subnormal response. These two subgroups did not differ with respect to preoperative macroscopic and microscopic measures of hypertrophy. Thus in aortic valve disease, the reduced coronary vasodilator capacity is mainly due to an elevated coronary flow at rest, while the maximal coronary blood flow achieved is identical to that of postoperative patients and controls. With regression of left ventricular hypertrophy, flow at rest decreases and this leads to a distinct improvement of coronary flow reserv

Three-Dimensional Self-Navigated T2 Mapping for the Detection of Acute Cellular Rejection After Orthotopic Heart Transplantation.

T2 mapping is a magnetic resonance imaging technique measuring T2 relaxation time, which increases with the myocardial tissue water content. Myocardial edema is a component of acute cellular rejection (ACR) after heart transplantation. This pilot study compares in heart transplantation recipients a novel high resolution 3-dimensional (3D) T2-mapping technique with standard 2-dimensional (2D) T2-mapping for ACR detection. Consecutive asymptomatic patients (n = 26) underwent both 3D T2 mapping and reference 2D T2 mapping magnetic resonance imaging on the day of endomyocardial biopsy (EMB). 3D T2 maps were obtained at an isotropic spatial resolution of 1.72 mm (voxel volume 5.1 mm(3)). 2D and 3D maps were matched anatomically, and maximum segmental T2 values were compared blinded to EMB results. In addition, all 3D T2 maps were rendered as 3D images and inspected for foci of T2 elevation. T2 values of segments from 2D and reformatted 3D T2 maps agreed (p &gt; 0.5). The highest 2D segmental T2 values were 49.9 ± 4.0 ms (no ACR = 0R, n = 18), 48.9 ± 0.8 ms (mild ACR = 1R, n = 3), and 65.0 ms (moderate ACR = 2R). Rendered 3D T2 maps of cases with 1R showed foci with significantly elevated T2 signal (T2 = 58.2 ± 3.6 ms); 5 cases (28%) in the 0R group showed foci with increased T2 values (&gt;2 SD above adjacent tissue) that were not visible on the 2D T2 maps. This pilot study in a small cohort suggests equivalency of standard segmental analysis between 3D and 2D T2-mapping. 3D T2 mapping provides a spatial resolution that permits detection of foci with elevated T2 in patients with mild ACR

Churg-Strauss syndrome with cardiac involvement: case illustration and contribution of CMR in the diagnosis and clinical follow-up.

This report summarises three cases of Churg-Strauss syndrome (CSS) illustrating the diagnostic challenges associated with the cardiac manifestation of this disease. Here, we illustrate the role of cardiac magnetic resonance (CMR) for diagnosis and follow-up of CSS with a focus on new non-contrast T &lt;sub&gt;2&lt;/sub&gt; -weighted imaging sequences for quantification of myocardial scar tissue and quantitative T &lt;sub&gt;2&lt;/sub&gt; mapping techniques, which allow the detection of myocardial edema

Feasibility of perfusion cardiovascular magnetic resonance in paediatric patients

AIMS: As coronary artery disease may also occur during childhood in some specific conditions, we sought to assess the feasibility and accuracy of perfusion cardiovascular magnetic resonance (CMR) in paediatric patients. METHODS AND RESULTS: First-pass perfusion CMR studies were performed under pharmacological stress with adenosine and by using a hybrid echo-planar pulse sequence with slice-selective saturation recovery preparation. Fifty-six perfusion CMR examinations were performed in 47 patients. The median age was 12 years (1 month-18 years), and weight 42.8 kg (2.6-82 kg). General anaesthesia was required in 18 patients. Mean examination time was 67 +/- 19 min. Diagnostic image quality was obtained in 54/56 examinations. In 23 cases the acquisition parameters were adapted to patient's size. Perfusion CMR was abnormal in 16 examinations. The perfusion defects affected the territory of the left anterior descending coronary artery in 11, of the right coronary artery in 3, and of the circumflex coronary artery in 2 cases. Compared to coronary angiography, perfusion CMR showed a sensitivity of 87% (CI 52-97%) and a specificity of 95% (CI 79-99%). CONCLUSION: In children, perfusion CMR is feasible and accurate. In very young children (less than 1 year old), diagnostic image quality may be limited

Detection of coronary artery disease by magnetic resonance myocardial perfusion imaging with various contrast medium doses: first european multi-centre experience

Aims Magnetic resonance (MR) first-pass myocardial perfusion imaging during hyperaemia detects coronary artery stenoses in humans with test sensitivity depending on contrast medium (CM)-induced signal change in myocardium. In this prospective multi-centre study, the effect of CM dose on myocardial signal change and on diagnostic performance was evaluated using a stress-only approach. Methods and results Ninety-four patients with known or suspected coronary artery disease (CAD) were randomised to 0.05,0.10, or 0.15 mmol/kg body weight of an extravascular CM (Gd-DTPA) and X-ray coronary angiography was performed within 30 days prior/after the MR examination. A multi-slice MR technique with identical hardware and software in all centres was used during hyperaemia (adenosine 0.14 mg/kg/min) to monitor myocardial CM wash-in kinetics and data were analysed semi-automatically in a core laboratory. Protocol violations resulted in 80 complete studies with CAD (defined as ⩾1 vessel with diameter stenosis ⩾50% on quantitative coronary angiography) present in 19/29, 13/24, and 20/27 patients for doses 1, 2, and 3, respectively. In normal myocardium, the upslope increased with CM dose (overall-p<0.0001, ANOVA). For CAD detection the area under the receiver operator characteristics curve for subendocardial data (3 slices with quality score<4 representing 86% of cases) was 0.91±0.07 and 0.86±0.08 for doses 2 and 3, respectively, and was lower for dose 1 (0.53±0.13, p<0.01 and p<0.02 vs. doses 2 and 3, respectively). Corresponding sensitivities/specificities (95% confidence intervals) for pooled doses 2/3 were 93% (77-99%; ns vs. dose 1) and 75% (48-92%;p<0.05 vs. dose 1), respectively. Conclusions With increasing doses of CM, a higher signal response in the myocardium was achieved and consequently this stress-only protocol, with CM doses of 0.10-0.15 mmol/kg combined with a semi-automatic analysis, yielded a high diagnostic performance for the detection of CA

e-Social Science and Evidence-Based Policy Assessment : Challenges and Solutions

Peer reviewedPreprin

Full-Body MRI in Patients With an Implantable Cardioverter-Defibrillator Primary Results of a Randomized Study

AbstractBackgroundMagnetic resonance imaging (MRI) of patients with conventional implantable cardioverter-defibrillators (ICD) is contraindicated.ObjectivesThis multicenter, randomized trial evaluated safety and efficacy of a novel ICD system specially designed for full-body MRI without restrictions on heart rate or pacing dependency. The primary safety objective was >90% freedom from MRI-related events composite endpoint within 30 days post-MRI. The primary efficacy endpoints were ventricular pacing capture threshold and ventricular sensing amplitude.MethodsSubjects received either a single- or dual-chamber ICD. In a 2:1 randomization, subjects either underwent MRI at 1.5-T of the chest, cervical, and head regions to maximize radiofrequency exposure up to 2 W/kg specific absorption rate and gradient field exposure to 200 T/m/s per axis (MRI group, n = 175), or they underwent a 1-h waiting period without MRI (control group, n = 88). A subset of MRI patients underwent ventricular fibrillation induction testing post-MRI to characterize defibrillation function.ResultsIn 42 centers, 275 patients were enrolled (76% male, age 60.4 ± 13.8 years). The safety endpoint was met with 100% freedom from the composite endpoint (p < 0.0001). Both efficacy endpoints were met with minimal differences in the proportion of MRI and control patients who demonstrated a ≤0.5 V increase in ventricular pacing capture threshold (100% MRI vs. 98.8% control, noninferiority p < 0.0001) or a ≤50% decrease in R-wave amplitude (99.3% MRI vs. 98.8% control, noninferiority p = 0.0001). A total of 34 ventricular tachyarrhythmia/ventricular fibrillation episodes (20 induced; 14 spontaneous) occurred in 24 subjects post-MRI, with no observed effect on sensing, detection, or treatment.ConclusionsThis is the first randomized clinical study of an ICD system designed for full-body MRI at 1.5-T. These data support that the system is safe and the MRI scan does not adversely affect electrical performance or efficacy. (Confirmatory Clinical Trial of the Evera MRI System for Conditionally-Safe MRI Access; NCT02117414

Long-Term Consequences of COVID-19: A 1-Year Analysis.

Long-lasting symptoms after SARS-CoV-2 infection have been described many times in the literature and are referred to as Long COVID. In this prospective, longitudinal, monocentric, observational study, we collected the health complaints of 474 patients (252 ambulatory and 222 hospitalized) at Lausanne University Hospital 1 year after COVID-19 diagnosis. Using a self-reported health survey, we explored cardiopulmonary, vascular, neurological, and psychological complaints. Our results show that age, Charlson comorbidity index, and smoking habits were associated with hospital admission. Regarding the vascular system, we found that having had thromboembolism before SARS-CoV-2 infection was significantly associated with a higher risk of recurrence of thromboembolism at 1 year. In the neurologic evaluation, the most frequent symptom was fatigue, which was observed in 87.5% of patients, followed by "feeling slowed down", headache, and smell disturbance in 71.5%, 68.5%, and 60.7% of cases, respectively. Finally, our cohort subjects scored higher overall in the STAI, CESD, Maastricht, and PSQI scores (which measure anxiety, depression, fatigue, and sleep, respectively) than the healthy population. Using cluster analysis, we identified two phenotypes of patients prone to developing Long COVID. At baseline, CCS score, prior chronic disease, stroke, and atrial fibrillation were associated with Long COVID. During COVID infection, mechanical ventilation and five neurological complaints were also associated with Long COVID. In conclusion, this study confirms the wide range of symptoms developed after COVID with the involvement of all the major systems. Early identification of risk factors associated with the development of Long COVID could improve patient follow-up; nevertheless, the low specificity of these factors remains a challenge to building a systematic approach

Probing cardiac metabolism by hyperpolarized 13C MR using an exclusively endogenous substrate mixture and photo-induced nonpersistent radicals.

To probe the cardiac metabolism of carbohydrates and short chain fatty acids simultaneously in vivo following the injection of a hyperpolarized &lt;sup&gt;13&lt;/sup&gt; C-labeled substrate mixture prepared using photo-induced nonpersistent radicals. Droplets of mixed [1- &lt;sup&gt;13&lt;/sup&gt; C]pyruvic and [1- &lt;sup&gt;13&lt;/sup&gt; C]butyric acids were frozen into glassy beads in liquid nitrogen. Ethanol addition was investigated as a means to increase the polarization level. The beads were irradiated with ultraviolet light and the radical concentration was measured by ESR spectroscopy. Following dynamic nuclear polarization in a 7T polarizer, the beads were dissolved, and the radical-free hyperpolarized solution was rapidly transferred into an injection pump located inside a 9.4T scanner. The hyperpolarized solution was injected in healthy rats to measure cardiac metabolism in vivo. Ultraviolet irradiation created nonpersistent radicals in a mixture containing &lt;sup&gt;13&lt;/sup&gt; C-labeled pyruvic and butyric acids, and enabled the hyperpolarization of both substrates by dynamic nuclear polarization. Ethanol addition increased the radical concentration from 16 to 26 mM. Liquid-state &lt;sup&gt;13&lt;/sup&gt; C polarization was 3% inside the pump at the time of injection, and increased to 5% by addition of ethanol to the substrate mixture prior to ultraviolet irradiation. In the rat heart, the in vivo &lt;sup&gt;13&lt;/sup&gt; C signals from lactate, alanine, bicarbonate, and acetylcarnitine were detected following the metabolism of the injected substrate mixture. Copolarization of two different &lt;sup&gt;13&lt;/sup&gt; C-labeled substrates and the detection of their myocardial metabolism in vivo was achieved without using persistent radicals. The absence of radicals in the solution containing the hyperpolarized &lt;sup&gt;13&lt;/sup&gt; C-substrates may simplify the translation to clinical use, as no radical filtration is required prior to injection