SPECT/CT imaging of temperature-sensitive liposomes for MR-image guided drug delivery with high intensity focused ultrasound.

The goal of this study was to investigate the blood kinetics and biodistribution of temperature-sensitive liposomes (TSLs) for MR image-guided drug delivery. The co-encapsulated doxorubicin and [Gd(HPDO3A)(H2O)] as well as the 111In-labeled liposomal carrier were quantified in blood and organs of tumor bearing rats. After TSL injection, mild hyperthermia (T=42°C) was induced in the tumor using high intensity focused ultrasound under MR image-guidance (MR-HIFU). The biodistribution of the radiolabeled TSLs was investigated using SPECT/CT imaging, where the highest uptake of 111In-labeled TSLs was observed in the spleen and liver. The MR-HIFU-treated tumors showed 4.4 times higher liposome uptake after 48h in comparison with controls, while the doxorubicin concentration was increased by a factor of 7.9. These effects of HIFU-treatment are promising for applications in liposomal drug delivery to tumors.