ESTIMATION OF VOLUMES OF DISTRIBUTION AND INTRATUMORAL ETHANOL CONCENTRATIONS BY COMPUTED-TOMOGRAPHY SCANNING AFTER PERCUTANEOUS ETHANOL INJECTION

Rationale and Objectives. We developed a technique for estimating the volumes of distribution and intratumoral ethanol concentrations using computed tomography (CT) scanning in patients undergoing percutaneous ethanol injection (PEI) treatment of malignant hepatic tumors. Methods . A phantom containing anhydrous ethanol diluted with deionized distil led water to concentrations of 0-100% ethanol was scanned by CT. Thirt y-seven treatment sessions were performed on eight patients with malig nant hepatic tumors undergoing PEI under CT guidance. The patients wer e scanned pre- and post-PEI, and a region of interest containing the t reated hepatic tissue was selected for pixels between -250 and 15 Houn sfield units (H). The mean density of the pixels in this range was com puted and the concentration of ethanol estimated. Volumes of distribut ion of ethanol and intratumoral concentration were then correlated wit h volume of ethanol injected during PEI. The ratios of volumes of dist ribution of ethanol to ethanol injected (adjusted in-range [IR]/volume injected) were compared for responders (n = 4) and nonresponders (n = 4). Results. CT numbers in the phantom scaled linearly with ethanol c oncentration; 100% ethanol measured -234 H. On CT scans after PEI, the volume of distribution of ethanol correlated positively with the volu me injected, Calculated intratumoral ethanol concentrations ranged fro m 4% to 31%. The adjusted IR/ volume injected was significantly higher for responders than nonresponders (p < .5). Conclusion. CT density da ta can be used to estimate volumes of ethanol distribution in tissue; a larger relative intratumoral distribution of alcohol appears to corr elate with a favorable response to PEI. However, CT measurement of int ratumoral ethanol concentrations may require more complex computationa l techniques.