Search results for " Magnetic resonance"

Effect of electron-withdrawing substituents on the electrophilicity of carbonyl carbons

2005

Indexación: Scopus The substituent effects on the carbonyl carbon atom for a series of twelve substituted phenyl acetates have been rationalized using a global electrophilicity index. This index is linearly correlated with the experimental reaction rate coefficients. We found that, in contrast to the proposed interpretation based on experimental 13C NMR chemical shifts and ground state destabilization calculations, the electrophilicity of carbonyl compounds increases due to the effect promoted by electron-withdrawing groups in these systems. https://www.sciencedirect.com/science/article/pii/S0040402004018046?via%3Dihub

An ab initio study of the relation between NMR chemical shifts and solid-state structures: hexabenzocoronene derivatives

2000

The assignment of solid-state NMR spectra is studied by the use of model systems computed with ab initio methods. The investigated system is a hexabenzocoronene derivative, for which a T-like arrangement of dimer units is found in the solid-state structure. Here, a tetramer model is required to explain the intermolecular interactions influencing the spectrum, whereas a dimer model is found to be inadequate. For the tetramer model, agreement of the computed NMR spectrum with the experimental solid-state magic angle spinning MAS-NMR data is observed. This study implies that the combination of experimental NMR data with quantum chemical calculations can be employed as a useful tool in determin…

Morpho-volumetric assessment of the right ventricle: a comparison between three-dimensional echocardiography and cardiac magnetic resonance

2013

The morpho-volumetric assessment of the right ventricle (RV) is useful in the diagnosis and prognosis of many congenital and acquired cardiovascular diseases. The complexity of the right ventricular shape does not allow an adequate and satisfactory evaluation of the RV. Two-dimensional (2D) echocardiography is the most used tool for the assessment of RV function, as it is a noninvasive, reproducible and widespread technique, but the geometric assumptions required for measurement of RV volumes reduce its accuracy. At present, cardiac magnetic resonance is the gold standard for the evaluation of RV volumes because it does not need any assumption and is reproducible, though not always availabl…

[Coronary microvascular dysfunction: past, present, and future of an evolving disease].

2017

Coronary atherosclerosis is the main cause of myocardial ischemia. Nevertheless 10-30% of patients with angina has angiographically normal coronary arteries. In the last 30 years, several studies showed that in these patients the symptoms can be caused by dysfunction of the coronary microcirculation. Coronary microvascular dysfunction (CMVD) occurring in patients affected by specific cardiac or systemic diseases may be due to mechanisms of the underlying disease. On the other hand, in several patients affected by angina with angiographically normal coronary arteries, there is no specific disease, and CMVD only is responsible for the clinical picture. This condition can be defined as leading…

Heart Failure and Left Ventricular Dysfunction

2018

Heart failure (HF) and left ventricular (LV) dysfunction are the most concerning and serious cardiovascular complications of cancer therapies and cause an increase in morbidity and mortality. Some cancer treatments induce left ventricular dysfunction that appears early after exposure and therefore may adversely affect oncological therapy, while others generate cardiac injuries resulting in clinical problems only years later.

Cardiovascular magnetic resonance characterization of a hamartoma in an asymptomatic child

2009

Pressure–volume relationship by pharmacological stress cardiovascular magnetic resonance

2021

Abstract Background. The variation between rest and peak stress end-systolic pressure-volume relation (ΔESPVR) is an index of myocardial contractility, easily obtained during routine stress echocardiography and never tested during dipyridamole stress-cardiac magnetic resonance (CMR). We assessed the ΔESPVR index in patients with known/suspected coronary artery disease (CAD) who underwent dipyridamole stress-CMR.Methods. One-hundred consecutive patients (24 females, 63.76±10.17 years) were considered. ESPVR index was evaluated at rest and stress from raw measurement of systolic arterial pressure and end-systolic volume by biplane Simpson’s method. Results. The ΔESPVR index showed a good inte…

Everything you wanted to know about phase and reference frequency in one- and two-dimensional NMR spectroscopy

2019

The fundamental concept of phase discussed in this tutorial aimed at providing students with an explanation of the delays and processing parameters they may find in nuclear magnetic resonance (NMR) pulse programs. We consider the phase of radio-frequency pulses, receiver, and magnetization and how all these parameters are related to phases and offsets of signals in spectra. The impact of the off-resonance effect on the phase of the magnetization is discussed before presenting an overview of how adjustment of the time reference of the free induction decay avoids first-order correction of the phase of spectra. The main objective of this tutorial is to show how the relative phase of a pulse an…

Computed tomography detects changes in contrast agent diffusion after collagen cross-linking typical to natural aging of articular cartilage

2011

SummaryObjectiveThe effect of threose-induced collagen cross-linking on the mechanical and diffusive properties of cartilage was investigated in vitro. In particular, we investigated the potential of Contrast Enhanced Computed Tomography (CECT) to detect changes in articular cartilage after increased collagen cross-linking, which is an age-related phenomenon.MethodsOsteochondral plugs (Ø=6.0mm, n=28) were prepared from intact bovine patellae (n=7). Two of the four adjacent samples, prepared from each patella, were treated with threose to increase the collagen cross-linking, while the other two specimen served as paired controls. One sample pair was mechanically tested and then mechanically …

Physical Activity Is Related with Cartilage Quality in Women with Knee Osteoarthritis

2017

Purpose To study the relationship between 12-month leisure-time physical activity (LTPA) level and changes in estimated biochemical composition of tibiofemoral cartilage in postmenopausal women with mild knee osteoarthritis (OA). Methods Originally, 87 volunteer postmenopausal women, age 60 to 68 yr, with mild knee OA (Kellgren Lawrence I/II and knee pain) participated in a randomized controlled, 4-month aquatic training trial (RCT), after which 76 completed the 12-month postintervention follow-up period. Self-reported LTPA was collected along the 12-month period using a diary from which MET task hours per month were calculated. Participants were divided into MET task hour tertiles: 1, lowe…