Cancer is a leading cause of death in the world and remains a difficult disease to treat. A promising approach to image and treat cancer with the same agent is using nanoparticles (NPs). Computed tomography (CT) can offer an ideal imaging method to assist developments and test these NPs at preclinical level. However, current CT systems based on the use of energy integrating detectors, have limited contrast resolution. CT imaging can be improved by adding spectral capabilities. Our primary goal is to develop the next-generation spectral CT system and NPs for preclinical cancer research. To achieve this goal, we have established a collaboration between our academic research institution, Duke University ,and an industrial partner DxRay Inc.-a leader in developing photon-counting x-ray detectors (PCXD). We will pursue 4 specific aims. Specific aim 1 will focus on the development of PCXDs that will be integrated in a hybrid micro-CT system. The hybrid system uses a conventional high-resolution imaging chain based on an energy-integrating detector and a lower-resolution spectral imaging chain containing an x-ray photon-counting detector. The spectral imaging chain will provide multiple energy bins for the CT data, but with low spatial resolution. Through the conventional imaging chain, we will achieve high-resolution imaging with limited spectral information. DxRay will supply PCXDs with novel designs, progressively increasing the field of view. During specific aim 2, we will develop novel algorithms such as spectral diffusion and spectral deblurring allowing unprecedented spectral differentiation at high spatial resolution. Specific aim 3 will be dedicated to NP probe developments. Although our PCXD spectral micro-CT system should enable sensitive NP imaging based on a wide range of high Z-materials, we focus on NPs with high potential for clinical translation based on gold (Au) and iodine (I). We will synthesize and characterize liposomes containing iodine, gold nanoparticles (AuNPs), and vascular endothelial growth factor (VEGF)- conjugated AuNPs (VEGF-AuNPs). Finally, during specific aim 4, we will use the newly developed spectral micro-CT imaging and VEGF-AuNPs to study the augmentation effects and the increased vascular permeability caused by radiation therapy in sarcoma tumors. Our spectral micro-CT will pave the way for the translation of novel PCXDs and algorithms to clinical use. Furthermore, our results will establish how AuNPs- augmented radiation therapy can facilitate the delivery of chemotherapy into tumors to improve response. In the end, the new-generation spectral micro-CT can provide significant data required for the translational steps of NPs, generating the confidence necessary to move new cancer therapies to patients.