Arterial embolization hyperthermia: hepatic iron particle distribution and its potential determination by magnetic resonance imaging

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Abstract
Arterial embolization hyperthermia (AEH) consists of arterially embolizing liver tumours with ferromagnetic particles that generate hysteretic heating on exposure to an alternating magnetic field. A critical component of AEH is the concentration and distribution of ferromagnetic particles in the normal hepatic parenchyma (NHP), as well as in the tumour tissue. If the distribution of particles in NHP is heterogeneous, with areas of high concentration, then unwanted areas of necrosis may result during AEH. Using an in vivo rabbit liver tumour model, this study showed that hepatic arterial infusion of ferromagnetic particles does indeed result in a heterogeneous distribution of iron in NHP. The radiological technique of magnetic resonance imaging (MRI) was then evaluated as a potential tool for non-invasively and prospectively determining the concentration and distribution of particles within the hepatic tumour and NHP following hepatic arterial infusion. A preliminary in vitro experiment showed that although the concentration of iron within the tumour tissue (1.92–3.50 mg of iron per gram of tissue) was too great to measure, MRI was able to accurately determine the lower iron concentration (0.10–0.53 mg of iron per gram of tissue) in NHP. Further work is needed to evaluate MRI under in vivo conditions. If successful, MRI could become an important component of an emerging novel treatment for advanced hepatic malignancies.