Dynamic contrast‐enhanced magnetic resonance imaging of human melanoma xenografts with necrotic regions

Abstract

Purpose To investigate whether high-resolution images of necrotic regions in tumors can be derived from gadopentetate dimeglumine (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) series. Materials and Methods E-13 human melanoma xenografts were used as preclinical models of human cancer. DCE-MRI was performed at a voxel size of 0.23 × 0.47 × 2.0 mm³ with the use of spoiled gradient recalled sequences. Tumor images of E · F (E is the initial extraction fraction of Gd-DTPA and F is blood perfusion) and λ (the partition coefficient of Gd-DTPA, which is proportional to extracellular volume fraction) were produced by subjecting DCE-MRI series to Kety analysis, and these images were compared with histological preparations from the imaged slices. Results Strong correlations were found between fraction of necrotic tissue and fraction of voxels with λ > λ_L for λ_L values of 0.4 to 0.6. Binary λ images differentiating between λ values > λ_L and λ values < λ_L were found to mirror necrotic regions well in tumors with large necroses. However, necrotic foci that were small compared with the voxel size were not detectable. Conclusion Clinically relevant images of necrotic tumor regions can be obtained for E-13 melanomas by subjecting Gd-DTPA-based DCE-MRI series to Kety analysis. J. Magn. Reson. Imaging 2007;26:133–143.