An experimental review with preliminary "ex vivo" analysis of tumor thermal ablation mediated by magnetic nanoparticles using multiparametric MRI- A study at a tertiary hospital in South India

ABSTRACT: Purpose: This study evaluates the efficacy of tumor thermal ablation mediated by magnetic nanoparticles using multiparametric MRI in an experimental rat model of colorectal liver metastases, aiming to quantify thermal increases and assess tissue effects. Materials and Methods: Eighteen male WAG/RijCrl rats underwent tumor induction via subcapsular injection of syngeneic colon adenocarcinoma cells. Magnetic fluid, comprising 25nm Fe₃O₄ nanoparticles suspended in Clinoleic® 20%, was infused intratumorally under ultrasound guidance in ten rats with confirmed tumors. MRI studies assessed infusion accuracy. Ex vivo livers were subjected to radiofrequency (RF) fields (12.5–16KA/m, 250–699KHz) for thermal induction, with temperature monitored in tumor tissue and immersion media (saline or distilled water). Histological analysis used hematoxylin-eosin and Perls blue staining to evaluate thermal lesions and iron deposits. Results: Tumors (33–480 mm³) were successfully infused with 3.5–5.5 mg of nanoparticles. Thermal induction in saline-immersed livers showed significant temperature increases proportional to RF frequency and nanoparticle dose, while distilled water immersion limited heating to tumor tissue. No thermal lesions were observed histologically, but iron deposits and necrotic pathways from injections were noted. Conclusion: Ultrasound-guided nanoparticle infusion effectively localized magnetic particles within tumors. RF-induced thermal increases were observed, influenced by immersion media and nanoparticle concentration. Further studies are needed to optimize thermal ablation for tissue necrosis and evaluate adjacent tissue effects. Keywords: magnetic nanoparticles, thermal ablation, colorectal liver metastases, multiparametric MRI, radiofrequency.