Extracellular contrast agents, such as gadopentetate dimeglumine (Gd-DTPA, Magnevist, Bayer HealthCare), have been in clinical use for more than two decades and are well established. More recently, liver-specific contrast agents have become available for the detection and characterization of focal hepatic lesions. Whereas Gd-BOPTA has been approved for liver imaging by the European authorities several years ago and certain experience and routine is available, Gd-EOB-DTPA is fairly new and has gained FDA approval only in 2008.
Brismar et al. compared liver vessel and liver parenchymal enhancement after the injection of Gd-EOB-DTPA and Gd-BOPTA using a bolus technique in ten healthy volunteers. Results showed a higher maximum of enhancement of the hepatic artery, portal vein and middle hepatic vein during the arterial, portal venous phase and delayed phase for Gd-BOPTA, while there was no significant difference in liver parenchymal contrast enhancement . So far only few studies have compared the performance of Gd-EOB-DTPA with other more established contrast agents regarding the assessment of extrahepatic tissues and vessels. Kühn et al. compared the enhancement patterns of solid organs and the abdominal aorta after the injection of gadobutrol and gadoxetate disodium in 50 patients. Mean enhancement indexes were higher for gadobutrol except for the abdominal aorta, and it has been suggested that early dynamic MRI of the upper abdomen benefits from the higher gadolinium concentration of gadobutrol than in the organ-specific contrast agent gadoxetic acid . However, patients in the two compared contrast agents groups were not the same. These results were similar to those gained by Zizka et al. earlier . A more recent intraindividual comparison of liver, abdominal and pulmonary vessel enhancement in staging for rectal carcinoma showed comparable contrast enhancement after gadoxetic acid to gadobutrol . Tamada et al. compared enhancement patterns of solid abdominal organs and vessels in 13 healthy volunteers after the injection of Gd-DTPA (Magnevist) and Gd-EOB-DTPA. It has been proposed that lower arterial vascular and parenchymal enhancement with Gd-EOB-DTPA as compared with GD-DTPA may require reassessment of its dose, despite the higher late venous phase liver parenchymal enhancement .
To the best of our knowledge, no study has so far compared the enhancement effect of extrahepatic findings in MR imaging with Gd-EOB-DTPA and Gd-BOPTA. Our results show that even though mean SNR in extrahepatic lesions, vessels and organs is significantly higher after the injection of Gd-BOPTA compared with Gd-EOB-DTPA, there is no significant difference in relative CNR with extrahepatic lesions being assessed adequately. Thus, visual impression may differ after injection of Gd-EOB-DTPA, but does not influence image interpretation, and extrahepatic findings can be assessed similarly to MRI after injection of Gd-BOPTA. The circumstance that interobserver variability for Gd-BOPTA is slightly better than for Gd-EOB-DTPA may be justified to some extent by the fact, that gadoxetate disodium is a relatively new contrast agent resulting in a different image impression and that we are in the process of gaining more routine [5–8].
Our study has a number of limitations. The time interval between MRI examination with Gd-EOB-DTPA and Gd-BOPTA was fairly long in some patients (mean 165 days). On the other hand, evaluated parenchymal lesions showed no change in size and appearance between comparative studies, so that evaluation especially of metastatic lesions could not be influenced by these factors. Also, comparative studies were performed on the same scanners using identical imaging parameters. Another limitation is the small sample size and heterogeneity of incidentally detected lesions (malignant as well as benign). As the same lesion was evaluated on two different studies, we think that this intralesional comparison is valid.