Hepatic clearance of arterially infused ferromagnetic particles

Objective : Arterial embolization hyperthermia (AEH) consists of arterially embolizing tumours with ferromagnetic particles that generate hysteretic heating on exposure to an alternating magnetic field. It was the objective of this study to determine if such particles are cleared from the liver. Method : A lobe of normal liver in three pigs was arterially embolized with 300 mg of gamma-Fe2O3 particles (150 nm) suspended in lipiodol. The same liver lobe of three other pigs was embolized with 300 mg of ferromagnetic polymer matrix-encapsulated microspheres (32 mum) suspended in 1% tween-water. Samples of liver and blood were obtained before infusion, and at 60 min and 28 days after arterial infusion. At 28 days, samples of lung and other abdominal viscera were also obtained. The tissue samples were chemically analysed for iron content, and submitted to histopathological examination. Results : There was no significant reduction in the hepatic iron concentration in either treatment group 28 days after infusion. Both types of particles illicited an immunogenic response and were extensively phagocytosed in the liver. The particle/lipiodol suspension caused extensive necrosis of liver, while the microsphere/tween-water suspension was well tolerated. Small amounts of both types of ferromagnetic particles embolized in the lungs, but there was no evidence of embolization into other organs. There were no haematological or biochemical changes and all subjects experienced uneventful 28-day survivals. Conclusion : This study has shown that, although arterially infused ferromagnetic particles were extensively phagocytosed, there was no significant hepatic clearance 28 days after infusion. It also determined that the suspension of 150 nm ferromagnetic particles in lipiodol was too vaso-occlusive for use in hepatic tissue. However, the suspension of 32 mum microspheres containing ferromagnetic particles in tween-water was safe and well tolerated.