FATTY TISSUE ON OPPOSED-PHASE MR-IMAGES - PARADOXICAL SUPPRESSION OF SIGNAL INTENSITY BY PARAMAGNETIC CONTRAST AGENTS

PURPOSE: To evaluate paradoxically decreased signal intensity on gadol inium-enhanced opposed-phase magnetic resonance (MR) images of fatty t issues. MATERIALS AND METHODS: Unenhanced and gadolinium-enhanced axia l, opposed-phase, gradient-echo images were analyzed visually and with region-of-interest measurements. Tissues measured included adipose ti ssue (n = 10), angiomyolipomas (n 8), and vertebral hemangiomas (n = 7 ). Additionally, a phantom of mayonnaise, soybean oil, agarose, and wa ter (63% lipid signal) with variable concentrations of gadolinium chel ate was imaged with similar technique. RESULTS: After administration o f gadolinium chelate, signal intensity reduction averaged 18% for adip ose tissue, 34% (72-48 units) for predominately fatty angiomyolipomas, and 39% (85-52 units) for vertebral hemangiomas. Imaging of the phant om showed a maximum of 79% reduction in signal intensity with gadolini um chelate (227-47 units). DISCUSSION: Gadolinium-enhanced opposed-pha se images depict a significant loss in signal intensity in tissues wit h MR signal predominately from lipid. Gadolinium chelate increases the signal of water within fatty tissues, which increases the amount of l ipid signal suppression due to destructive interference between water and lipid proton magnetizations.