Development of Kinetic Modeling to Assess Multi-functional Vascular Response to Low Dose Radiation in Leukemia

Vascular permeability, tissue transfer rate (Ktrans), fractional extracellular tissue space ({nu}ec) and blood perfusion are crucial parameters to assess bone marrow vasculature (BMV) function. However, quantitative measurements of these parameters in a mouse model are difficult because of limited resolution of standard macroscopic imaging modalities. Using intravital multiphoton microscopy (MPM), live imaging of dextran transfer from BMV to calvarium tissue of mice bearing acute lymphoblastic leukemia (ALL) was performed to obtain BMV parameters. Mice bearing ALL had increased BMV permeability, altered Ktrans, increased {nu}ec, decreased blood perfusion, and increased BMV permeability resulting in reduced drug uptake. Targeted 2 Gy radiation therapy (RT) to mice bearing ALL increased local BMV perfusion and ALL chemotherapy uptake (P<0.0001 and P=0.0036, respectively), suggesting RT prior to chemotherapy treatment may increase treatment efficacy. Developed MPM techniques allow for a quantitative assessment of BMV functional parameters not previously performed with microscopic or macroscopic imaging.