Airflow effect on microwave ablation in lung model

Pulmonary microwave ablation has been trailed and became dramatically recognized as an alternative surgical method for lung cancer treatment due to its minimal invasive technique and destroyable only a small part of malignant tissue. Even though, lung is realized as a porous tissue in which filled of humid air and a capillary network that rather difficult to control an ablation region, then a prediction of lung destructive region by using MWA simulation seem to be a reliable investigation and numerical tool for supporting this medical maneuver. In this paper, we propose a simulation of microwave thermal ablation for lung cancer treatment in a simple lung model. Microwave applicator was designed as an opened-tip coaxial antenna of 2.45 GHz at 10 Watts. To study an effect of air flow in pulmonary bronchus, a small tube with air flow was also placed close to the microwave applicator then a temperature distribution and coagulation volume at 60 °c were analyzed. The in silico results show a predictable ablation shape which affected by a convection heat transfer of a humid air. However, before a real ablation with swine tissue, an amount of pulmonary blood flow in small blood vessel should be also included in the next investigation inorder to obtain more reasonable results.

I. Introduction

One of a hazard malignant tissue which mostly found in an elderly people around the world is a pulmonary or lung cancer. People who having a tobacco smoking in his/her medical record for a long time are realized as a high incident rate group to face with the lung cancer. In spite of this cancer is classified as an avoidable cancer but a number of patient from this disease is surprisingly never decrease and becomes an one of a main cause of death over the world. Even though, a standard gold of a general lung cancer treatment is known as an open lung surgery. However this medical maneuver must be performed as a big operation, patient always suffer after surgery and often take risk during the operation which depending on a size and position of that cancer [1]. Within the last decade thermal ablation by using an electromaonetic wave energy both in radio frequency (RFA) and microwave frequency (MWA) are become popular and realized as an another alternative standard technique in cancer treatment [2]. By this technique, an electromagnetic wave applicator is inserted into a cancerous target region under an ultrasound imaging guidance then output power is emitted from the applicator resulting a thermal heat propagation from a bioheat effect phenomenon due to an electric field interaction in living tissue. The well-known advantage of this technique especially the microwave ablation is a minimal invasive operation, less pain and less recovery time. However to enhance and support this medical procedure, some research has been proposed by using FEM simulation to investigate a predictable ablation result in term of a destruction or coagulation shape and temperature distribution pattern. This also includes a design of microwave applicator probe, a treatment protocol and a cancerous tissue model of various living organ especially for a complicate organ structure like lung which is composed of a hundred million of alveolar air sac, a network of capillary and blood vessel. With respect to an initial-boundary condition, a material property, multiphysics module selection and suitable post-processing this numerical simulation mostly provide a reasonable and predictable result. This can be always applied as a guideline before perform a real operation.