Objectives:
The characterization of tumor vasculature is essential in studying tumor physiology. the aim of this study was to develop a new method - based on water proton mr density measurements, in combination with ultrasmall superparamagnetic iron oxide (uspio) administration - to measure absolute blood volume (bv) in murine colon carcinoma.
Materials and methods:
Mri experiments were performed at 7 t. cpmg imaging was performed on subcutaneous murine colon carcinoma in six mice before and after administration of an uspio blood-pool contrast agent. density maps were obtained from the signal amplitude at te=0 of the cpmg decay fit. post-uspio density maps were subtracted from pre-uspio density maps to quantitatively yield absolute tumor bv maps. in a separate group of mice (n=6), the relative vascular area (rva) of tumors was determined by immunohistochemistry.
Results:
Ultrasmall superparamagnetic iron oxide administration resulted in a small decrease in the water proton mr density. the bv averaged over the six tumors was 4.6+/-1.6%. the value of the rva measured by immunohistochemical staining was equal to 3.9+/-2.2%.
Conclusions:
After administration of an uspio blood-pool agent (t(2) relaxivity > 100 mm(-1) s(-1)), the blood water protons become mri invisible, and pixel-by-pixel bv map can be obtained by subtracting the calculated post-uspio density map from the pre-uspio density map. the value of absolute bv obtained with this novel mr approach is in good agreement with the value of the relative vascular measured by immunohistochemical staining.