[Magnetic resonance behavior of lipiodol--an experimental study]

To describe the characteristics of magnetic resonance (MR) signals generated by lipiodol and to assess the influence on MR imaging of hepatoma nodule.

Pure lipiodol and lipiodol emulsions mixed with 76% urografin in different ratio were imaged by both CT and MR; quantitative T(1) and T(2) measurements of lipiodol were performed. Fourty-one SD rats with transplanted walker-256 sarcoma in liver were randomly divided into six groups: 0.4-0.6 ml lipiodol emulsion was infused via hepatic artery in experimental groups by means of laparotomy under celiac anesthesia. The changes in MRI signal of hepatoma nodule were observed.

In vitro, iodized oil demonstrated high signal on T(1)-weighted images when performed at 37 degree, but all could be suppressed by the fat saturation sequence, and showed very low signal on T(2)-weighted images. The characteristic of MR signal with ultra fluid lipiodol was different from that of iodized oil (P<0.01), showing short T(1) and long T(2) signal; the high signal on T(1)-weighted images was only partially suppressed by the fat saturation sequence. With descending ratio of lipiodol in emulsion, the signal behavior was gradually similar to urografin (r -0.958, P<0.01). When rats were transarterially infused with emulsion, the intensity of the signal on MRI was nearly the same as that in the control rats, but when lipiodol was injected out of the hepatic artery and accumulated in lymphadenopathy, it demonstrated a signal similar to fat; the high intensity signal was maintained on T(1)-weighted images and T(2)-weighted images.

There are little changes in MR signal intensity when the lipiodol is accumulated in the tumor nodules. MR behavior of lipiodol is determined by its deposit area.