The Combination of IVIM-DWI and BOLD-fMRI to Evaluate the Early Efficacy of Photodynamic Microenvironment-Modulating Therapy in Nasopharyngeal Carcinoma.
BACKGROUND Photodynamic microenvironment-modulating therapy (PMMT) represents a promising strategy for nasopharyngeal carcinoma (NPC). However, early assessment of therapeutic response remains challenging. PURPOSE To evaluate whether intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and blood oxygen level-dependent functional MRI (BOLD-fMRI) can noninvasively detect early responses to PMMT in an NPC xenograft model. STUDY TYPE Experimental, animal model. ANIMAL MODEL Subcutaneous 5-8F NPC xenograft model (110 female BALB/c nude mice). FIELD STRENGTH/SEQUENCE 3.0 T, T2WI FSE sequence, IVIM-DWI single-shot echo-planar imaging sequence, and BOLD-fMRI SPGR sequence. ASSESSMENT Following tumor establishment, mice were randomly assigned to five treatment groups: PBS, NH2-MIL-101(Fe), PPa@NH2-MIL-101(Fe) + near-infrared (P@MIL+NIR), Doxy@NH2-MIL-101(Fe) (D@MIL), and PPa + Doxy@NH2-MIL-101(Fe) + NIR (PD@MIL+NIR). IVIM-DWI (D and f) and BOLD-fMRI (R2*) were acquired before and after treatment to assess changes in tumor microstructure, perfusion, and oxygenation. The proliferation, apoptosis, angiogenesis, and hypoxia of NPC tumor were evaluated by Ki-67 immunofluorescence staining, TUNEL immunofluorescence staining, VEGF immunohistochemical staining, and HIF-1α immunohistochemical staining. STATISTICAL TESTS One-way ANOVA, the intraclass correlation coefficient (ICC), Pearson's correlation analysis, and the Least Significant Difference (LSD) test for post hoc pairwise comparisons, p value < 0.05 was considered significant. RESULTS Good and excellent agreements between two evaluators can be seen (The range of ICCs was from 0.864 to 0.985). In P@MIL+NIR, D@MIL, and PD@MIL+NIR groups, D and f values initially decreased and then increased, while R2* values peaked at 0.5 h (63.20 ± 2.57, 61.62 ± 0.98, and 67.38 ± 1.37) and gradually declined. D, f, and R2* values were significantly correlated with the histological staining results. DATA CONCLUSION The combination of IVIM-DWI and BOLD-fMRI could be used in monitoring the early therapeutic responses to PD@MIL-based PMMT in NPC. EVIDENCE LEVEL 1. TECHNICAL EFFICACY Stage 1.