Differentiation of hypointense nodules on gadoxetic acid-enhanced hepatobiliary-phase MRI using T₂ enhanced spin-echo imaging with the time-reversed gradient echo sequence: An initial experience

Purpose To optimize the flip angle (FA) of the T₂ enhanced spin-echo imaging using the time reversed gradient echo (T2FFE) and evaluate its utility for differentiating hypointensity nodules in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced (Gd-EOB) MRI. Materials and methods First, FA optimization of the T2FFE in the HBP was investigated by comparing signal-to-noise ratio (SNR) among different FAs using phantoms. The liver-to-muscle contrast ratios (CR_Liver-Muscle) and image quality among three FAs (20°, 50° and 80°) were compared using images of 10 patients. Next, the utility of the T2FFE with an optimized FA for differentiating hypointensity nodules in the HBP was assessed by comparing the lesion-to-liver contrast ratio (CR_Lesion-Liver) among cysts, hemangiomas, hepatocellular carcinomas, and metastatic tumors in 32 patients. Results SNR increased as FA increased, but leveled off at FAs of 50° and greater. The FA of 50° showed significantly better image quality scores than that of 80° (p < 0.05). After employing an FA of 50°, the CR_Lesion-Liver value indicated that the T2FFE depicted benign lesions as hyperintense and most malignant lesions as hypointense in relation with the liver parenchyma (p < 0.05). Conclusion The T2FFE in the HBP of Gd-EOB-MRI is useful for differentiating benign and malignant liver lesions.