Purpose:To identify, with noninvasive imaging, the zone of radiopharmaceutical uptake after combination therapy with radiofrequency (RF) ablation and intravenous administration of technetium 99m ( 99m Tc) liposomal doxorubicin in a small-animal tumor model, and to quantify and correlate the uptake by using imaging and tissue counting of intratumoral doxorubicin accumulation.
Materials and Methods:This study was approved by the animal care committee. Two phases of animal experiments were performed. In the fi rst experiment, a single human head-and-neck squamous cell carcinoma tumor was grown in each of 10 male nude rats. Seven of these animals were treated with intravenous 99m Tc-liposomal doxorubicin followed by RF tumor ablation at a mean temperature of 70°C 6 2 for 5 minutes, and three were treated with intravenous 99m Tc-liposomal doxorubicin only. Combination single photon emission computed tomography-computed tomography (SPECT/CT) was performed at 15 minutes, 4 hours, and 20 hours after therapy. In the second experiment, two tumors each were grown in 11 rats, but only one of the tumors was ablated after intravenous administration of 99m Tc-liposomal doxorubicin. SPECT/CT and planar scintigraphy were performed at the same posttreatment intervals applied in the fi rst experiment, with additional planar imaging performed at 44 hours. After imaging, tissue counting in the excised tumors was performed. Radiotracer uptake, as determined with imaging and tissue counting, was quantifi ed and compared. In a subset of three animals, intratumoral doxorubicin accumulation was determined with fl uorimetry and correlated with the imaging and tissue-counting data.
Results:At both SPECT/CT and planar scintigraphy, increased uptake of
Conclusion:Study results show that increased delivery of intravenous liposomal doxorubicin to tumors combined with RF ablation can be depicted and quantifi ed with noninvasive imaging.