超顺磁性氧化铁（SPIO）对比剂肝脾MR成像的比较研究

目的 比较两种超顺磁性氧化铁（superparamagnetic iron oxide,SPIO)对比剂，Ferumoxides及SHU－555A在肝脾MR成像中的效应。材料与方法 36例已知为肝转移癌患者于SPIO造影前后进行T2WI快速自旋回波成像（T2WI TSE）及T1WI梯度回波快去速相位成像（T1WI FLASH）。扫描伪为1．0T MR机。18例患者行Ferumoxides增强后90分钟进行MR成像；另18例行SHU－55A快速团柱增强，注药后即刻、30秒及480秒行T1WI FLASH成像，10分钟行T2WI TSE成像。测量肝脾、肝转移癌SPIO增强前后的信号强度（signal intensity,SI),计算两种SPIO对比剂在肝脾、肝转移癌增强前后SI变化的百分比（percentage signal intensity change,PSIC)及病灶肝脏对比噪声比（lesion-to-liver contrast-to-noise ratio,CNR)及其变化（ΔCNR）。结果 在T2WI TSE图像上，两种SPIO对比剂造成的肝实质SI下降无显著性差异（P＞0．05）。Ferumoxides引的脾信号下降显著大于SHU－555A（P＜0．05）。两种SPIO对比剂均导致肝实转移癌SNR显著增高。T1WI FLASH图像上，两种对比剂均可导致延迟像上肝脏SI的轻度下降及肝转移癌CNR下降，两者肝脏SIC之间无显著性差异。T1WI上两种对比剂均可导致脾脏SI显著升高，两者脾脏PSIC之间无显著性差异（P＞0．05）。结论 两种SPIO在肝脏的TI及T2增强效应相似，而脾脏的T2增强效应，Ferumoxides强于SHU－555A。

A Comparative Study of the Relaxation Effects of Two Superparamagnetic Iron Oxide Agents in MRI of the Liver and Spleen

Objective　To compare the enhancement effectiveness of two superparamagnetic iron oxide (SPIO) contrast agents, Ferumoxides and SHU-555A, in MRI of the liver and spleen.　Materials and Methods　T2W TSE and T1WI FLASH scanning were performed in 36 cases with hepatic metastases before and after SPIO contrast injection with a 1.0T MR unit. Post-Ferumoxides images were obtained 90 min. After the infusion of the agent with a dose of 15 μmol Fe/kg in 18 cases. In the other 18 cases, T1W FLASH images were obtained at 0, 30, and 480 sec. After a bolus injection of SHU-555A with a dose of 7.0～12.9 μmol Fe/kg, while T2W TSE images were obtained at 10 min. After the injection. Signal intensity of the liver, spleen and hepatic metastatic lesions was measured with an operator-defined region of interest both before and after SPIO admistration. The enhancement effects of Ferumoxides and SHU-555A were expressed as the percentage of signal intensity change (PSIC) of the liver and spleen, the PSIC of the malignant liver lesions, and the changes in lesion-to-liver contrast-to-noise ratio (ΔCNR).　Results　No significant difference in signal loss of liver parenchyma between the two agents was found on T2W TSE images, (P＞0.05). Both SPIO agents produced a significant increase in the CNR of malignant liver lesions. ΔCNR in Ferumoxides group was slightly greater than that in SHU-555A group (P＜0.05). On T1W FLASH images, a slight decrease of liver SI induced by the two agents was seen on late post-SPIO images. No significant difference in liver PSIC between two groups was noted onT1W images. The CNR of hepatic metastatic lesions was decreased in both groups on T1W images. The SI of spleen was significantly increased in both groups on T1W images and no difference in PSIC of spleen was noted (P＞0.05).　Conclusion　Ferumoxides and SHU-555A have similar T1 and T2 enhancement effects for the liver, while Ferumoxides carries a stronger T2 enhancement effects for the spleen than SHU-555A does.