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To evaluate the reliability of MRE using a spin-echo echo-planar imaging (SE-EPI) renal MRE technique in healthy volunteers.Institutional review board approved prospective study in which all participants provided written informed consent. Sixteen healthy volunteers comprising seven males and nine females with a median age of 35 years (age range: 23 to 59 years) were included. Coronal 90 Hz and 60 Hz MRE acquisitions were performed twice within a 30-min interval between examinations. Renal MRE reliability was assessed by (i) test-retest repeatability, and (ii) inter-rater agreement between two independent readers. The MRE-measured averaged renal stiffness values were evaluated using: intraclass correlation coefficient (ICC), Bland-Altman and the within-subject coefficient of variation (COV).For test-retest repeatability, Bland-Altman showed a mean stiffness difference between examinations of 0.07 kPa (95% limits of agreement: -1.41, 1.54) at 90 Hz and 0.01 kPa (95% limits of agreement: -0.51, 0.53) at 60 Hz. Coefficient of repeatability was 1.47 kPa and 0.52 kPa at 90 Hz and 60 Hz, respectively. The within-subject COV was 13.6% and 7.7% at 90 Hz and 60 Hz, respectively. ICC values were 0.922 and 0.907 for test-retest repeatability and 0.998 and 0.989 for inter-rater agreement, respectively (P 0.001).SE-EPI renal MRE is a reliable technique.

Includes abstract., Includes bibliographical references (leaves 55-79)., The effects of long-term participation in ultra-endurance exercise on the cardiovascular system have recently been the subject of much interest. It is well known that HRV, a marker of autonomic activity, is enhanced with long-term aerobic exercise training. However, after acute exercise, HRV is reduced, but recovers over time depending on the intensity of the prior bout of exercise. A limitation of previous research is that exercise bouts of only up to 120 minutes have been studied. A modified Stroop Task is a laboratory stressor to assess executive cognitive function by means of reaction time and accuracy. The resting HRV is directly related to these prefrontal neural functions, but the effect of an altered HRV on cognitive function has never been investigated. We determined the effects of an ultra duration (10 – 15 hours) exercise event on parameters of HRV and cognitive function during a Modified Stroop Task, 60 – 200 minutes after the 2007 South African Ironman Triathlon event (3,6km swim; 180 Km cycle; 42,2 Km run). 1 Female and 13 male competing triathletes (IRON; ages 33.7±7.9) and 7 control subjects (CON; 2 female and 5 males aged 42 ±4.5) completed a Modified Stroop Task before and after the event. The individual HRV parameters, heart rate (HR), respiratory frequency (RF), reaction time (RT) and % of mistakes made were recorded via the Biopac MP150WSW System (Goletta, California, USA). Data was transformed by auto regressive analyses (Biomedical signal analysis group, University of Kuopio, Finland) into LF (0.04 - 0.15 Hz) and HF (0.15 - 0.5 Hz) components. Additional calculations included %LF and %HF as well as the central or peak frequencies in both the LF and HF bands.