Purpose To evaluate the accuracy and reproducibility of quantitative chemical shift-encoded MRI (CSE-MRI) to quantify proton-density fat-fraction (PDFF) in a fat-water phantom across sites, vendors, field strengths and protocols. Methods Six sites (three vendors: GE/Philips/Siemens) participated in this study. A phantom containing multiple vials with various oil-water suspensions (PDFF:0–100%) was built, shipped to each site and scanned at 1.5T and 3T using two CSE protocols per field strength. Confounder-corrected PDFF maps were reconstructed using a common algorithm. To assess accuracy, PDFF bias and linear regression with the known PDFF were calculated. To assess reproducibility, measurements were compared across sites, vendors, field strengths and protocols using analysis of covariance (ANCOVA), Bland-Altman analysis and the intra-class correlation coefficient (ICC). Results PDFF measurements showed overall absolute bias (across sites, field strengths and protocols)=0.22% with 95% CI:(0.07%,0.38%), and R2>0.995 relative to the known PDFF at each site, field strength and protocol (slopes: 0.96–1.02, intercepts: −0.56%–1.13%). ANCOVA did not show effects of field strength (p=0.36), or protocol (p=0.19). There was a significant effect of vendor (F=25.13,p=1.07×10−10), with bias= −0.37% (Philips) and −1.22% (Siemens) relative to GE. The overall ICC was 0.999. Conclusion CSE-based fat quantification is accurate and reproducible across sites, vendors, field strengths and protocols.

Synopsis A person’s physiology is ever-changing at the structural, functional, and molecular levels as they age, and every major organ system experiences physiologic change with time. The changes to the nervous system result mostly in cognitive impairments, the cardiovascular system result in higher blood pressures with lower cardiac output, the respiratory system result in a reduction of arterial oxyhemoglobin, the gastrointestinal system result in delayed gastric emptying with a reduction of hepatic metabolism, and the renal system experiences a diminished glomerular filtration rate. All these changes are variable from patient to patient; however, combined, they create a complex physiological condition. This unique physiology must be taken into consideration for a geriatric patient undergoing general anesthesia.

The proportion of invasive methicillin-resistant Staphylococcus aureus infections caused by USA300 increased in 2006.

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