MR imaging of the liver: breath-hold T1-weighted MP-GRE compared with conventional T2-weighted SE imaging--lesion detection, localization, and characterization.

PURPOSE: To compare breath-hold T1-weighted magnetization-prepared gradient-echo (MP-GRE) imaging with conventional T2-weighted spin-echo (SE) imaging in evaluation of focal liver disease. MATERIALS AND METHODS: Images of 68 patients evaluated for focal liver disease were reviewed. Five sets of images were analyzed: axial, sagittal, and coronal breath-hold T1-weighted MP-GRE images, axial T2-weighted SE images, and a compilation of axial, sagittal, and coronal (three-plane) T1-weighted MP-GRE images. Lesion signal intensity (SI) and signal difference-to-noise (SD/N) ratios were calculated. RESULTS: Lesions were detected, localized, and characterize more accurately (P < .05-.001) and with greater confidence on three-plane T1-weighted MP-GRE images than on almost all single-plane images. Mean SI ratios of nonsolid and solid lesions on MP-GRE and SE images were significantly different at all lesion sizes; mean SD/N ratio was significantly different only for large lesions. CONCLUSION: Lesion detection, localization, and characterization can be accurately and confidently performed with three-plane T1-weighted MP-GRE breath-hold imaging, potentially obviating conventional T2-weighted SE imaging.

Mathematical modeling of the relationship of feed efficiency, days to market weight, and costs of production.

Decreased feed efficiency and increased days to market often occur together causing an increase in production costs. By mathematical modeling, the effect of decreased feed efficiency on the growth of an animal is given and the resulting formulas for increased days to market are derived. The most general model discussed incorporates the effects on days to market weight of variable feed efficiency (above or below normal for that species) and weight loss with a subsequent growth set-back. The resulting predicted increased days to market compares well with experimental data and examples using published data are discussed. This modeling allows a good estimate of the increased costs of production due to finishing unthrifty animals, which takes into account all the variable daily costs, not just the increased total feed consumption during the period of growth to market weight.