Intravoxel Incoherent Motion Diffusion-weighted MR Imaging for Monitoring the Therapeutic Efficacy of Interventional Photothermal Therapy with Nanoparticles in Rabbit VX2 Tumors

introductionIn this study, we evaluated the efficacy of transcatheter intra-arterial infusion of lecithin-modified Bi-Ln nanoparticles (Bi-Ln NPs) combined with interventional photothermal therapy (IPTT) using a rabbit VX2 tumor model, employing intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) for assessment.

methodsThirty-two rabbit liver VX2 tumor models were established, and transcatheter intra-arterial infusion of Bi-Ln NPs was performed using superselective intubation under digital subtraction angiography (DSA) guidance. IPTT was then carried out by inserting a near-infrared (NIR) optical fiber into the rabbit VX2 tumors under real-time ultrasound guidance. Magnetic resonance imaging (MRI) was performed one day before treatment and seven days after treatment to evaluate therapeutic efficacy, using T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), gadolinium-enhanced T1WI, and IVIM-DWI. After treatment, gross and histopathological examinations were conducted to categorize liver tumors into viable tumor, inflammatory reaction, and necrotic regions. IVIM-derived parameters were calculated and compared across these regions. Additionally, immunohistochemical analysis was performed to further assess treatment efficacy.

resultsThe tumor-bearing rabbits exhibited significant therapeutic effects, as shown by comparative analysis of MRI images and parameters before and after treatment. Both the mean apparent diffusion coefficient (ADC) and diffusion coefficient (D) increased significantly after treatment (P = 0.008 and P = 0.034, respectively). Pathological analysis also revealed an elevated apoptosis rate of tumor cells, with a mean of 43.26 ± 12.26%. Across the different lesion regions, the ADC and D values were significantly lower in the viable tumor region than in the inflammatory reaction region (both P < 0.001). However, the D* values in the viable tumor region did not differ significantly from those in the inflammatory reaction region. Additionally, the ADC, D, and f values were significantly reduced in the necrotic region compared with the inflammatory reaction region (P = 0.003, <0.001, and <0.001, respectively). In the receiver operating characteristic (ROC) analysis, the diffusion coefficient (D) demonstrated the highest area under the curve for distinguishing between the inflammatory reaction and viable tumor regions. DISCUSSION: IVIM-DWI demonstrates strong potential for detecting early tumor responses to therapeutic interventions and for differentiating tissue types following treatment. The parameters derived from this technique may provide preliminary insight into therapy-induced physiological changes.

conclusionThe combination of transcatheter intra-arterial infusion and IPTT represents a promising strategy for effective tumor eradication, thereby improving therapeutic outcomes. IVIM-DWI offers a quantitative tool for monitoring early treatment responses in hepatic tumors and distinguishing between different tissue types after therapy.