Rapid acquisition spin-echo (RASE) magnetic resonance (MR) imaging allows for coverage of the entire liver with highly T1-weighted SE images during a single 23-second breath-holding period. The RASE sequence was implemented in conjunction with rapid intravenous injection of gadopentetate dimeglumine to enable performance of dynamic contrast material-enhanced MR imaging of the liver. Prospective evaluation of 24 patients with 62 liver lesions 1 cm or greater in diameter was performed. Images obtained with RASE were devoid of respiratory-related ghost artifacts or edge blurring. The dynamic contrast-enhanced RASE technique resulted in contrast-to-noise and contrast-to-artifact values and time efficiency measures significantly greater (P less than .05) than those obtained with use of conventional T1- and T2-weighted pulse sequences, indicating a higher likelihood for lesion detectability. Lesion conspicuity was maximal during or immediately following bolus administration of gadopentetate dimeglumine, with lesions often becoming obscured at delayed postcontrast imaging.

Despite rapid proliferation, the mammalian intestinal epithelium maintains precise spatial differentiation from crypt to villus tip and from duodenum to colon. During perinatal life, the rodent gut undergoes a dramatic morphogenesis, resulting in formation of the crypt-villus and duodenal-colonic axes. The ontogeny of regional differences in gene expression in the emerging vertical axis has not been well described. We used the liver fatty acid binding protein (L-FABP) and apolipoprotein (apo) AIV genes as markers of neonatal enterocytic differentiation. In situ hybridization analyses revealed that both genes exhibit unique spatial patterns of expression along the jejunal crypt-villus axis during ontogeny, characterized by increased cellular mRNA levels in villus base enterocytes. To examine the requirement for a normal luminal environment to generate these precise patterns of cellular gene expression, we employed intestinal isograft techniques. Fetal intestines were implanted as early as embryonic day 12. Appropriate expression of the apo AIV and L-FABP genes was recapitulated during villus morphogenesis in fetal life. However, spatial patterns of gene expression in the isografted postnatal cryptvillus axis were altered. The preferential accumulation of L-FABP and apo AIV mRNA in villus base enterocytes was never observed in isografts. These results suggest that a "basal" differentiation program is encoded in fetal endoderm and mesenchyme, yet extracellular substances contained in the lumen or extrinsic to the intestine play an important modulatory role in generating spatial differentiation during ontogeny.

The objective of this study was to quantitatively and qualitatively determine contrast enhancement patterns of normal abdominal organs with dynamic gadolinium-enhanced magnetic resonance (MR) imaging. Dynamic gadolinium-enhanced, T1-weighted, spin-echo imaging was performed during a 23-second breath hold in 38 patients, with images acquired before, during, and at 1,2, and 5 minutes after bolus injection of gadopentetate dimeglumine. Enhancement patterns of normal liver, spleen, pancreas, adrenal gland, kidney, aorta, inferior vena cava, and fat were determined by visual evaluation and by performance of signal intensity measurements with an electronic cursor. Time-intensity curves demonstrated peak enhancement of all abdominal organs during or immediately after bolus injection of gadopentetate dimeglumine. MR enhancement patterns included visualization of renal cortical nephrogram and heterogeneous enhancement of the spleen during the bolus phase of contrast material administration. Peak enhancement of normal liver was 72%; spleen, 172%; pancreas, 82%; adrenal gland, 85%; and kidney, 291%. This study established reference data regarding abdominal organ enhancement that will be useful as dynamic gadolinium-enhanced MR imaging becomes clinically implemented.

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