MAGNETIC-RESONANCE GUIDANCE OF PERCUTANEOUS ETHANOL INJECTION IN LIVER

Rationale and Objectives. Percutaneous ethanol injection (PEI) is used as a form of treatment for cancer, particularly malignant hepatic tum ors. Little is known about the intratumoral distributions of ethanol f ollowing PEI. We assessed, using magnetic resonance (MR) imaging, the distribution of ethanol in liver and the concentration of ethanol need ed to kill tumor cells in vivo. Methods. MR imaging studies were perfo rmed using phantoms of alcohol, ex vivo bovine liver, and healthy huma n volunteers. A variety of pulse sequences were tested for their abili ty to maximize the signal intensity from alcohol while minimizing the signal from liver tissues as well as the regions of necrosis following ethanol injection. A cell culture model of in vitro cytotoxicity was developed to predict the target concentration of alcohol necessary for killing tumor cells. Results. At 1.5 T, we found chat an inversion-re covery spin-echo sequence using an inversion time of 250 msec and an e cho time of 150 msec in combination with water saturation pulses effec tively suppressed the tissue water signal from human liver while obtai ning a clear signal from the ethanol. The cytotoxicity experiments sug gested that a concentration of 20% or more ethanol is sufficient to co mpletely kill all the tumor cells. Conclusion. A critical concentratio n of ethanol (e.g., 10%) is necessary for full tumoricidal effect. MR imaging should be able to determine the volume of distribution and the intratumoral concentrations of ethanol, thus potentially allowing res earchers to achieve the requisite concentrations for maximal tumoricid al effects.