MR Validation and Quantification of Transcatheter Arterial Chemoembolization (TACE) Treatment Through Direct Visualization of Ethiodol with Chemical Shift-Based Water-Fat Imaging

Transcatheter arterial chemoembolization (TACE) has significant utility in the treatment of malignant neoplasms of the liver, particularly hepatocellular carcinoma (HCC), that are not amenable to surgical resection or cure with transplantation. Traditionally, with TACE, several site-specific injections of chemotherapeutic agents are delivered through a hepatic arterial catheter that has been placed by an interventional radiologist under fluoroscopic guidance. A follow-up CT scan is then used to verify correspondence between the tumor and treatment sites. Because fluoroscopy provides only limited visualization of the tumor during the procedure, interventionalists will often treat large, extended volumes of hepatic tissue which can deleteriously affect liver function. Real-time MR guidance of TACE, which could potentially allow for visualization of both tumor and its supplying hepatic arterial vasculature, may thus be useful for targeting treatment and sparing normal liver. Because the chemotherapeutic agents used to treat HCC during TACE are immiscible, they must be emulsified in ethiodized oil (ethiodol) before they are delivered to the patient. Ethiodol, being principally composed of iodinated ethyl esters of the fatty acids of poppy seed oil, is radiopaque – and thus serves as a contrast agent for both fluoroscopy and CT. However, since ethiodol has NMR behavior similar to that of common oils, it can also be visualized with chemical shift-based water-fat separation methods such as IDEAL. In this study, we will explore the feasibility of using IDEAL for visualization of ethiodol distribution within the liver, and thus for validation of TACE treatment. MRI validation holds great promise to simplify the TACE procedure for future patients, as the treatment region can be verified during the TACE procedure itself, rather than weeks later as is currently done. Additionally, using MRI in place of CT for validation reduces the patient’s exposure to ionizing radiation, which reaches significant loads during management of their disease.