Room: AAPM ePoster Library
Purpose: Iron oxide nanoparticles (ION) are commonly used for biomedical applications. Their low toxicity and advantageous biodistribution are of high interest in oncology. In this study, an innovative spectral synchrotron computed tomography method was developed to simultaneously measure the ION intracerebral distribution and assess the tumor characteristics. Pre-clinical trials were performed for evaluating synchrotron radiation dose-enhancement after intracerebral delivery of ION by convection-enhanced delivery methods (CED) in a rodent glioma model.
Methods: Prior to radiotherapy, 20 µL of ION (54 mg/mL) was injected with CED in the brain of rats bearing F98 glioma. The treatment consisted of a 20 Gy irradiation delivered at the isocenter with two orthogonal monochromatic beams tuned at 35 keV. After treatment, the rats were imaged with synchrotron tomography above and below the iodine K-edge after intravenous injection of an iodinated contrast agent (Iomeron®, 350 mg/mL). The tumor dimensions, the ION distribution and the relative tumor coverage were simultaneously assessed using these images. Monte Carlo dosimetry was performed with the GATE software.
Results: The average ION distribution volume was 11.4 +/- 1.3 mm³, and the measured tumor volume was 6.9 +/- 5.7 mm³. The tumor coverage by ION was found to be 30.4% +/- 22.1%. The calculated average dose-enhancement factors were 2.1 in the ION covered area, and around 1.2 in the planning tumor volume. The survival of rats treated with radiation therapy only and ION in combination with radiotherapy were MesT 46 days and 39 days, respectively which were not significantly different (p > 0.05).
Conclusion: The distribution of ION relative to the tumor volume can explain the absence of significant therapeutic in this preclinical study. The spectral imaging method and treatment planning method developed in this study will be used to further optimize the intra-tumoral nanoparticles distribution in glioma models.