A great deal of heterogeneity exists in fMRI data. Even within the same subject, results on successive days or scan sessions often differ in the number of significantly activated pixels and/or the intensity of activation. We sought to assess whether controllable physiologic modulators, such as dietary factors, could influence the outcome of fMRI data. A high fat diet, for example, prior to a fMRI scan could change microvascular blood rheologic factors and potentially alter brain blood oxygen-level dependent (BOLD) signal patterns. In healthy adult volunteers, we measured brain BOLD signal during bilateral finger tapping (2 Hz) in the fasted state, and at 40 and 100 minutes post-ingestion of a 235 mL can of Ensure Plus (Ross Labs), alone or supplemented with either 25 cc or 50 cc of canola oil. Both the 25 cc and 50 cc Canola oil treatments produced a significant bilateral decrease in BOLD signal 40 and 100 minutes postprandial. No significant effect was observed with Ensure in the absence of oil. Therefore, to decrease fMRI within and between subject heterogeneity, and thereby increase fMRI statistical power, it is suggested that scanning within 2 hours post high fat ingestion should be avoided. As a corollary, a thorough understanding of a subject's physiological state, prior to an fMRI exam, may reduce the impact of other confounding variables.

Purpose: To evaluate whether the BOLD signal from skeletal muscle can be modulated by exercise and ingestion of vasoactive substances. Materials and Methods:The right calf muscles of healthy adult volunteers were imaged using a GE 1.5-Tesla scanner and a gradient-echo sequence with spiral readout. Timevarying changes in the BOLD signal were induced through cyclic phases of normoxia (90 seconds of 20.8% O 2 ) and hyperoxia (45 seconds of 100% O 2 at 22 L/minute). Superimposed on this paradigm were pre-and post-exercise regimes, with and without ingestion of caffeine (100 mg) or antihistamine (4 mg chlorpheniramine). The numbers of voxels within slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles that significantly responded to the paradigms were scored and compared using the AFNI software (NIMH).Results: Cycling-inspired O 2 produced a corresponding BOLD modulation that increased in magnitude with exercise. Chlorpheniramine significantly (P Ͻ 0.01) prevented the overall increase in exercise-induced soleus muscle BOLD signal, while caffeine accentuated the increase (P Ͻ 0.05) in the gastrocnemius relative to control (no vasomodulator) conditions. Conclusion:BOLD signal changes with exercise can be modulated by standard doses of chlorpheniramine (antihistamine) and caffeine. We suggest that chlorpheniramine may act detrimentally on slow-twitch muscle contractility, while caffeine appears to improve fast-twitch muscle function. THE BLOOD OXYGEN LEVEL-DEPENDENT (BOLD) signal in MRI, which was first described by Ogawa et al (1) in 1990, is attributed to a change in the blood ratio of oxyhemoglobin (oxyHb) to deoxyhemoglobin (deoxyHb). This signal modulation is the basis for functional MRI (fMRI) studies of brain activation, in which increased local metabolism disproportionately drives increased blood flow and volume, resulting in elevated oxyHb/deoxyHb and BOLD signal enhancement. Recently the BOLD signal has been applied to the study of other tissues, including muscle (2) and tumors (3), and BOLD signal changes have been observed with inspiration of 100% O 2 . In addition, the potential for MR to characterize myocardial perfusion reserve, as indexed by the BOLD response to maximal pharmacological vasodilation, has been documented (4,5).Even though the blood volume of the brain is fairly low (on the order of 4%), BOLD signal changes with activation are still visible. Skeletal muscle at rest has a comparable blood volume; however, activation (through exercise) results in comparatively larger increases in blood flow and volume. In a previous report (2) we demonstrated that cycling inspired gas between hyperoxia (100% O 2 ) and air (20.8% O 2 ) resulted in a time-varying BOLD signal in the lower human leg that was analyzable with routine "block design" fMRI-based methods and software. Using this method we showed clear differences between the soleus (slow-twitch oxidative muscle) and gastrocnemius (fast-twitch anaerobic/glycolytic muscle), which were hypothesized to be due largely to the comparatively greater mic...

Blood-oxygen-level-dependent (BOLD) imaging was a concept introduced in 1990 for evaluating brain activation. The method relies on magnetic resonance imaging (MRI) contrast resulting from changes in the microvascular ratio of oxyhaemoglobin (oxyHb) to deoxyhaemoglobin (deoxyHb). OxyHb is diamagnetic, whereas deoxyHb is paramagnetic, which produces a local bulk magnetic susceptibility effect and subsequent MRI signal change. The changes are typically observed in T(2)*-weighted functional MRI scans. However, there has recently been interest in BOLD as a way to evaluate microcirculation of any normal or diseased tissue. This review focuses on the application of BOLD imaging in the understanding of normal and diseased skeletal muscle. In addition we present new findings showing the possible application of BOLD imaging with hyperoxia for evaluating skeletal muscle physiology.

Background: Valve-sparing aortic root replacement is an attractive option for aortic root aneurysms, avoiding valve prosthesis disadvantages and complications:the challenge for surgeons is to guarantee a durable aortic valve repair. In this study we present our early and long term results, identifying pre- and intra-operative risk factors for reoperation at follow up. Methods: From March 2002 to December 2017, 201 consecutive patients underwent conservative operation of the aortic valve and aortic root replacement, according to David reimplantation technique. Bicuspid aortic valve (BAV), Marfan syndrome and type A acute aortic dissection (AADA)-patients were included in the study. Patients were retrospectively evaluated with clinical and echocardiographic studies. Mean follow up time was 81.87 ± 59.74 months. Results: Mean age was 49.7 ± 15.2 years. Overall in-hospital mortality was 3%, if we consider only elective cases 0.5%. At discharge, aortic regurgitation was mild or lower in 87.1% of the patients. AADA (p = 0.000) and arch surgery (p = 0.004) are risk factors for early mortality. At 10 years, survival was 90.9%. At 5 years and 10 years, freedom from reoperation for severe aortic regurgitation was 92.7% and 86.2% respectively. Freedom from moderate to severe aortic regurgitation at 5 and 10 years was 97.2% and 84.4% respectively. At multivariate analysis, preoperative severe aortic regurgitation (p = 0.91), BAV (p = 0.32), Marfan syndrome (p = 0.10),cusps repair (p = 0.12) were not statistically significative risk factors. Conclusions: Our experience showed that aortic valve repair and valve-sparing aortic root surgery is a safe and effective procedure, and it can be performed with satisfactory short- and long-term results. It's important to refer the patients to high-volume center. We didn’t find risk factors for valve repair-failure.