Computational evaluation of effectiveness for intratumoral injection strategies in magnetic nanoparticle assisted thermotherapy

Purpose: To investigate, evaluate, and compare the effectiveness of intratumoral magnetic nanoparticle (MNP) injection strategies (single-site and multi-site injection). The comparison is done with respect to a hypothetical case of uniform MNP distribution within tumor volume. Methods: The injection strategies have been modeled in a three-dimensional tumor surrounded by healthy tissues while considering Gaussian spatial distribution of MNPs. In single-site injection strategy, the MNPs are injected at tumor centre, while in multi-site injection strategy the tumor is compartmentalized and injected at 9 sites (8 sites in compartments and one at tumor centre). The temperature field is computed in tissues during and after the thermo-therapy, by solving Pennes' Bio-heat model, using finite volume method. From temperature field, effectiveness of each injection strategy is quantified in terms of thermal dosimetry, i.e. Arrhenius thermal damage and CEM 43 in tissues. The analysis has been done with two MNP injection doses (4 mg and 5 mg of MNPs/cm(3) of tumor). Results: Temperature in multi-site injection strategy is more homogenous in comparison to single-site injection strategy. With injection dose of 5 mg of MNPs/cm(3) of tumor, multi-site injection strategy thermally affects greater tumor volume than single-site injection strategy (17% in thermal damage, and 14 % in CEM 43). Multi-site injection strategy with 4 mg of MNPs/cm(3) of tumor, produces almost equivalent thermal damage to tumor volume as single-site injection strategy with 5 mg of MNPs/cm(3) of tumor. The thermal damage produced by multi-site injection strategy is very close to the damage in uniform MNP distribution. However, increased MNP spread in multi-site injection strategy affects greater healthy tissue volume. Conclusion: Multi-site injection strategy performs better than single-site injection strategy. However, selection of injection site number, location, and amount of MNPs to be injected at each injection site plays a key role in optimization of this thermotherapy. (C) 2019 Elsevier Ltd. All rights reserved.