03:36 PM Abstract No. 425 Iodized oil quantification using spectral computed tomography: a preclinical study

Abstract

To evaluate the accuracy of iodized oil quantification using spectral computed tomography (CT) imaging and to assess its value as an imaging biomarker after transarterial chemoembolization (TACE) of rabbit VX2 hepatomas. Phantoms were made to simulated 3 cm-sized, iodized oil-lade tumors in the liver. The artificial tumors comprised of 12 scintillation vials of 40 mL volume (diameter; 3 cm) with diverse iodized oil-water volume fractions (0%, 1%, 2%, 4%, 6%, 8%, 10%, 14%, 18%, 22%, 26% and 30%). The phantoms were scanned by a spectral CT machine and raw data were reconstructed by slice thicknesses of 1 mm and 3 mm. Circular regions of interest (ROIs) were drew to measure CT values and iodine concentration of each lesions. The animal experiment was approved by the institutional animal care and use committee at our hospital and performed in accordance with the institutional guidelines. Eighteen rabbits with a VX2 tumor in the liver were treated by conventional TACE with iodized oil and doxorubicin chemoemulsion. The rabbits were immediately imaged by a spectral CT scanner, and then euthanized to obtain tissue specimens seven days after the TACE. On the spectral CT images, ROIs were manually placed for each VX2 tumor to quantify iodized oil accumulation. Iodized oil index, which took into account both iodized oil concentration and distribution, was calculated by dividing the mean concentration by its standard deviation for each tumor. Spectral CT imaging-based quantification accurately measured true concentrations of iodized oil in the phantoms. The mean difference between true and measured values were 0.5 mg/mL, which is almost negligible given the iodine concentration of commercially available iodized oil (480 mg/mL). The image-based iodine concentration values showed very good correlation with CT values (r > 0.9). In the animal experiment, the area under the curve value to predict pathological complete response of iodized oil index was 0.839 (p = 0.038). Spectral CT based quantifications of iodized oil was very accurate and promising as an imaging biomarker of TACE.