CONFORMAL RF ABLATION TO REDUCE “DEAD REGION” WITH ADJUVANT INJECTION OF MAGNETIC MICRO/NANO PARTICLES: FEASIBILITY STUDY

摘要

Radiofrequency (RF) ablation is a minimally invasive technique for tumor treatment. Intended benefits of oncological RF ablation include the availability of tumor treatment in nonsurgical candidate, minimal risk to patient, reduced morbidity and shorter recovery period compared with those after conventional surgery, and the potential for treatment on an outpatient basis. RF ablation, by producing heat energy that raises the temperature of the target tissue to a degree sufficient to cause thermally mediated coagulation necrosis, has been shown to be remarkably effective for thermal ablation of small tumors. Although RF hyperthermia has been successful in ablating small tumors, further optimization of the ablation technique is required to induce the larger volumes of coagulation that are necessary to treat larger tumors. In addition, due to the extremely irregular shape of tumor in clinics, the conventional RF ablation technique is hard to produce a conformal lesion to exactly enwrap the tumor as could as possible. This may lead to “dead region” within the area between RF probes and thus a failed treatment. To obtain a conformal treatment of complex tumor, strategies to flexibly control the size and shape of the ablated zone are desired.It is well known that for a given total RF power output, the power deposition at each point in space is strongly dependent on the local electrical conductivity. Along this direction, it has been demonstrated that altering electrical conductivity of tissue through saline injection prior to or during RF ablation can increase RF tissue coagulation volume [1]. In our recent work,it was further suggested that magnetic microano particles with high electrical conductivity can also be used as effective adjuvants to enhance the efficacy of RF ablation [2].Consequently, it is possible to adjust RF tissue heating and coagulation area by introducing materials with high electrical conductivity into the tissues before or during RF application,and thus to obtain conformal treatment of tumor.Based on the above consideration, the feasibility of conformal RF ablation with adjuvant injection of magnetic microano particles is demonstrated through numerical simulation in this study. It is indicated that alteration of tissue conductivity can be flexibly used to enable desired energy deposition in biological tissues, and thus conveniently controlling the size and shape of RF induced coagulation in tissues by injecting microano particles with specific volume and concentration distributions. The results suggest that the present method will likely be used as an adjuvant therapy of RF ablation to achieve clinical benefit.