SMALL (LESS-THAN-1.5 CM) ANGIOMYOLIPOMAS OF THE KIDNEY - CHARACTERIZATION BY THE COMBINED USE OF IN-PHASE AND FAT-ATTENUATED MR TECHNIQUES

The purpose of this study was to evaluate the ability of in-phase spoi led gradient echo combined with chemically selective fat suppression o r out-of-phase spoiled gradient echo MR images to characterize small r enal masses as angiomyolipomas, Eleven patients with a total of 35 sma ll (<1.5 cm) angiomyolipomas underwent MR examination at 1.5T. Eight p atients had solitary and three patients had multiple angiomyolipomas, One of the patients with multiple angiomyolipomas had tuberous scleros is and the number of angiomyolipomas were quantified as 20. MR examina tions included in-phase spoiled gradient echo (all patients), chemical ly selective fat suppressed spin echo (six patients), chemically selec tive fat suppressed spoiled gradient echo (three patients), selective water excitation spoiled gradient echo (one patient) and out-of-phase spoiled gradient echo (seven patients). Angiomyolipomas were minimally (4 lesions) or moderately (31 lesions) high in signal intensity relat ive to renal cortex on in-phase spoiled gradient echo images, On out-o f-phase spoiled gradient echo images, demonstration of signal void fat -water phase cancellation was present in all eight lesions in the seve n patients who were imaged with this sequence, Small lesion size rende red the entire angiomyolipoma signal void in seven of these eight lesi ons due to phase cancellation artifact, Signal void phase cancellation of lesion border or signal void of the entire angiomyolipoma resulted in high lesion conspicuity in all lesions, Mild loss of signal intens ity was observed in 7 lesions and moderate loss of signal intensity no ted in 25 lesions on chemically selective fat suppressed images, On ch emically selective fat-suppressed images, seven lesions were difficult to identify due to limited signal differences between medium intensit y cortex and low intensity angiomyolipomas (six lesions in two patient s) and moderate breathing artifact (one lesion in one patient), Charac terization of small renal masses as angiomyolipomas may be reliably pe rformed using the combination of in-phase and fat-attenuating MR seque nces, Consistent image quality and high conspicuity of fat-water phase cancellation interfaces renders out-of-phase imaging a reliable fat a ttenuating method to demonstrate the presence of fat in small angiomyo lipomas, Breath-hold fat-suppressed spoiled gradient echo is also effe ctive; however, this technique demonstrates less signal loss in fatty lesions and is subject to problems with inhomogeneity of fat suppressi on, (C) 1997 Elsevier Science Inc.