Magnetic susceptibility anisotropy of myocardium imaged by cardiovascular magnetic resonance reflects the anisotropy of myocardial filament α-helix polypeptide bonds

BACKGROUND: A key component of evaluating myocardial tissue function is the assessment of myofiber organization and structure. Studies suggest that striated muscle fibers are magnetically anisotropic, which, if measurable in the heart, may provide a tool to assess myocardial microstructure and function. METHODS: To determine whether this weak anisotropy is observable and spatially quantifiable with cardiovascular magnetic resonance (CMR), both gradient-echo and diffusion-weighted data were collected from intact mouse heart specimens at 9.4 Tesla. Susceptibility anisotropy was experimentally calculated using a voxelwise analysis of myocardial tissue susceptibility as a function of myofiber angle. A myocardial tissue simulation was developed to evaluate the role of the known diamagnetic anisotropy of the peptide bond in the observed susceptibility contrast. RESULTS: The CMR data revealed that myocardial tissue fibers that were parallel and perpendicular to the magnetic field direction appeared relatively paramagnetic and diamagnetic, respectively. A linear relationship was found between the magnetic susceptibility of the myocardial tissue and the squared sine of the myofiber angle with respect to the field direction. The multi-filament model simulation yielded susceptibility anisotropy values that reflected those found in the experimental data, and were consistent that this anisotropy decreased as the echo time increased. CONCLUSIONS: Though other sources of susceptibility anisotropy in myocardium may exist, the arrangement of peptide bonds in the myofilaments is a significant, and likely the most dominant source of susceptibility anisotropy. This anisotropy can be further exploited to probe the integrity and organization of myofibers in both healthy and diseased heart tissue

Pattern of Esophageal Injuries and Surgical Management: A Retrospective Review

Background: The consequence of significant injury to the esophagus is devastating. The initial management when timely and appropriate is  rewarding and often prevents lethal complications. The objective of this study is to describe the etiology of esophageal injury in our institution, the management procedures and the mid‑term results. Method: Consecutive patients diagnosed and managed for esophageal injury from January 2005 to March 2015 were retrospectively reviewed. Results: One hundred and eleven patients were seen and treated during this period; 85 (76.6%) predominantly children were corrosive esophageal injuries who accidentally ingested caustic soda and 26 (24.4%) were traumatic esophageal injuries. Patients with corrosive esophageal injuries were predominantly male (2:1), mean age 12.8 ± 14.2 years (2–58 years) and predominantly children (53% ≤5 years; 18.8% ≥ 18 years). Patients with non‑corrosive esophageal injury were also predominantly male (4:1) with a mean age of 34.4 ± 20.1 years (1–73 years). The treatment procedures for corrosive esophageal injuries included esophagocoloplasty 64 (75.3%), colopharyngoplasty 10 (11.8%), colon‑flap augmentation  pharyngo‑esophagoplasty 4 (4.7%), colopharyngoplasty with tracheostomy 4 (4.7%) and esophagoscopy and dilatation 3 (3.5%). Mortality was 5.9% and 5 patients were lost to follow‑up. In patients with noncorrosive esophageal injury, esophageal perforation from instrumentation accounted for 14 (53.9%), foreign body impaction 11 (42.3%) and spontaneous perforation 1 (3.8%) making up the rest. Management of these patients includedesophagotomy and removal of foreign body 7 (26.9%), esophagectomy, cervical esophagostomy and feeding gastrostomy 10 (38.6%), primary repair 7 (26.9%), Ivor Lewis procedure 1 (3.8%) and emergency esophagectomy with colon replacement 1 (3.8%). Mortality in this group of patients was 7.7% and 4 patients were lost to follow‑up. Conclusion: Corrosive esophageal injuries were the most frequent form of esophageal injury at our center due to unrestricted access to corrosive substances. Generally, appropriate surgical intervention in patients with esophageal injury based on individualization of care yields excellent early  and  mid‑term results. Keywords: Colon‑flap, colopharyngoplasty, esophageal injury, pharyngoesophagoplast

Two-site exchange revisited: a new method for extracting exchange parameters in biological systems.

A new analysis is presented which links real volume fractions, relaxation rates, and intracompartmental exchange rates directly with apparent volume fractions and relaxation rates obtained from biexponential fits of transverse magnetization decay curves. The analysis differs from previous methods in that measurements from two paramagnetic doping levels are used to close the two-site exchange equations. Both the new method and one previously described by Herbst and Goldstein (HG) have been applied to paramagnetically doped whole-blood data sets. Significant differences in the calculated exchange parameters are found between the two methods. A small dependence of the intracellular relaxation rate on extracellular paramagnetic agent concentration, assumed nonexistent with the HG method, is inferred from the new analysis. The analysis was also applied to published data on perfused rat hearts, and we obtained a limited assessment of two-site exchange in this system