Gradient- and spin-echo T2-weighted imaging for SPIO-enhanced detection and characterization of focal liver lesions

Purpose: To evaluate superparamagnetic iron oxide (SPIO)-enhanced breathhold T2-weighted GRASE imaging in detection and characterization of focal liver lesions. Materials and Methods: In 30 patients (including 20 with cirrhosis) with 39 malignant and 25 benign lesions, gradient-and spin-echo (GRASE) images with two echo times (75 and 90 msec; GRASE₇₅ and GRASE₉₀) were obtained prior to and following administration of SPIO, and compared with respiratory-triggered and breathhold fast spin-echo (RT-FSE and BH-FSE) images. Two readers evaluated image quality and reviewed 240 liver segments for sensitivity and specificity. Signal-to-noise ratio (SNR), and its reduction in liver and spleen after administration of SPIO, and lesion-to-liver contrast-to-noise ratio (CNR) were measured. Results: Compared with RT-FSE and BH-FSE, GRASE reduced scan time by 77% to 82% and 21% to 27%, respectively. The image qualities with BH-FSE and GRASE₇₅ were higher than with BH-FSE and GRASE₉₀. BH-FSE showed higher specificity than RT-FSE and GRASE₉₀, but otherwise there were no significant differences between pulse sequences for sensitivity or specificity. The mean SNR and CNR of the lesions with RT-FSE were significantly higher than with the other methods. SPIO-induced signal reduction of liver SNR was smallest with BH-FSE. Conclusion: GRASE is faster and more sensitive to SPIO than FSE, but its sensitivity and specificity were slightly inferior to those of BH-FSE. Image quality is a current limitation.