Figure 6.

Statistical comparisons between intracellular, extracellular, and vascular compartments across RG2, U87, and U251 tumors with ²³Na-MRSI and ¹H-DCE-MRI. (a) Relation between ∫Na⁺_b, ∫Na⁺_e and ∫Na⁺_i across tumor and healthy tissues. For the RG2 and U87 tumors, the ∫Na⁺_b values were significantly higher than normal tissue (p < 0.005, #). Also for these tumors, the ∫Na⁺_e values were significantly lower than normal tissue (p < 0.05, *). The mean values for the U251 tumor roughly followed the same trend but were not significant. Furthermore, there was no significant difference between ∫Na⁺_i values in tumor and normal tissues for any of the three tumor types. (b) Relations between tumor and normal tissues for ∆Na⁺_end and ∆Na⁺_mem for the three tumor types. Tumor ∆Na⁺_end values were significantly larger than normal values (p < 0.005, #), which were non-positive (data not shown). Moreover, ∆Na⁺_end in RG2 and U87 tumors was significantly greater than in the U251 tumor (p < 0.05, *), indicative of vascular differences between the tumor types. ∆Na⁺_mem values were, on average, weaker in tumor compared to normal tissue, but significant only in RG2 and U87 tumors (p < 0.05, *). Based on Figs. 5 and S5, it is clear that the relation between ∆Na⁺_end and ∆Na⁺_mem is negative. (c) ¹H-DCE-MRI data for the volume transfer coefficient (K^trans) and plasma volume fraction (v_p) values, which are known to reveal information regarding vascular structure and function. K^trans follows the same patterns as ∫Na⁺_b and ∆Na⁺_end across tumor types. K^trans (p < 0.005, #) and v_p (p < 0.05, *) were both significantly larger in RG2 and U87 tumors, compared to U251. See Figure S6 for the plasma flow rate (F_p) and the extracellular volume fraction (v_e) ¹H-DCE-MRI parameters for each tumor type. See Figure S7 for exemplary maps of ¹H-DCE-MRI parameters for individual animals from each tumor type.