Jiro Arakawa

SAR analysis of the improved resonant cavity applicator with electrical shield and water bolus for deep tumors by a 3-D FEM

This paper discusses the improvements of the re-entrant resonant cavity applicator, such as an electromagnetic shield and a water bolus for concentrating heating energy on deep tumors in an abdominal region of the human body. From our previous study, it was found that the proposed heating system using the resonant cavity applicator, was effective for heating brain tumors and also for heating other small objects. However, when heating the abdomen with the developed applicator, undesirable areas such as the neck, arm, hip and breast were heated. Therefore, we have improved the resonant cavity applicator to overcome these problems. First, a cylindrical shield made of an aluminum alloy was installed inside the cavity. It was designed to protect non-tumorous areas from concentrated electromagnetic fields. Second, in order to concentrate heating energy on deep tumors inside the human body, a water bolus was installed around the body. Third, the length of the lower inner electrode was changed to control the heating area. In this study, to evaluate the effectiveness of the proposed methods, specific absorption rate (SAR) distributions were calculated by FEM with the 3-D anatomical human body model reconstructed from MRI images. From these results, it was confirmed that the improved heating system was effective to non-invasively heat abdominal deep tumors.

SAR analysis of resonant cavity applicator using dielectric bolus with anatomical human model by finite element method

In this study, we propose a new heating method using a resonant cavity applicator to control the heated area using a dielectric bolus. The dielectric bolus is filled with a dielectric material such as water and is attached to a human head inside the cavity. In this paper, first, the proposed heating method using the dielectric bolus was described. Second, a 3-D anatomical human head model, which was constructed from 2-D MRI and X-ray CT images, was presented. Finally, from the results of specific absorption rate (SAR) distributions using 3-D FEM, it was shown that the heated area inside a human brain could be controlled by changing the electromagnetic field distribution. From these results, it was found that the proposed method for controlling the heated area was useful for effective hyperthermia treatments.

SAR analysis of the improved resonant cavity applicator by a 3-D FEM

This paper discusses the improvement of the reentrant resonant cavity applicator, such as an electromagnetic shield and water bolus for concentrating heating energy on deep tumors in an abdominal region of a human body.

Heating Properties of Resonant Cavity Applicator using Dielectric Bolus with Anatomical Human Head Model

In this paper, we propose a new heating control method of resonant cavity applicator using a dielectric bolus. The dielectric bolus is filled with dielectric such as water and is attached to a human head inside the cavity.

Experimental study of resonant cavity applicator with cooling effect of blood perfusion

We have proposed a non-invasive heating method using the resonant cavity applicator system for deep-seated brain tumors. In this study, the heating properties of a resonant cavity applicator using an agar phantom with the cooling effect of blood perfusion are described. Blood perfusion is an important factor to control the temperature distribution during hyperthermia treatments. The purpose of this study is to demonstrate the cooling effect around blood vessels with the resonant cavity applicator. First, we proposed a simple model made of an agar with a blood vessel. One tube made of Teflon material assumed to be blood vessel with water circulating through it was placed inside the agar phantom. Second, we heated the simple model using the developed resonant cavity applicator. From these heating results, it was found that cooling effects of blood perfusion appear within the heated area approximately 2 cm away from blood vessels.

New heating system using resonant cavity applicator with electrical shield for rheumatoid arthritis

This paper discusses the improvement of the reentrant resonant cavity applicator with an electromagnetic shield for concentrating heating energy in deep regions inside a human knee. Thermotherapy is widely used for musculoskeletal disorders as a physical therapy in clinical settings. Hot packs, paraffin baths, ultra-short waves and microwaves are generally used as well as therapeutic exercises for joint diseases such as osteoarthritis (OA) and rheumatoid arthritis. However, all of them have advantages and disadvantages, and a successful heating method for deep tissue has not yet been realized. In this paper, first, the heating method with the resonant cavity applicator is presented. Second, the proposed method of reconstructing the 3-D anatomical human FEM model to calculate temperature distributions is described. Third, the results of temperature distributions are discussed. Finally, the results of the temperature distributions for the resonant cavity applicator is compared with the temperature distribution for microwave diathermy. As the penetration depth of microwave diathermy used in the clinic is less than approximately 20 mm, it is not easy to heat the joint cavity. However, the proposed heating method with the resonant cavity applicator can be expected to heat the joint cavity.

Heating control method of resonant cavity applicator for non-invasive hyperthermia treatment

This paper describes a heating control method of the resonant cavity applicator for brain tumor hyperthermia treatment. In this study, we proposed several heating control method. In the first method, the diameters of the inner electrodes are changed. In addition, the position of the phantom between the inner electrodes was changed. In the second method, the dielectric bolus was used. The bolus is attached to the human head and is filled with dielectric materials, such as pure water, saline and so on. By changing the dielectric properties inside the bolus, heated region can be controlled. From these results, it was confirmed that proposed methods are useful for treating brain tumors.

Temperature estimation of hyperthermia treatment with blood perfusion inside blood vessels

In this paper, the heating properties of a resonant cavity applicator for heating brain tumors, calculated by a finite element method (FEM) with blood perfusion are described. We have already proposed the resonant cavity applicator system for treating brain tumors. We checked the effectiveness of the applicator using a prototype heating system with an agar phantom First, we construct a simple model with blood vessels for calculating temperature distributions using the FEM. In the simple model, a single thick blood vessel branches into two narrow blood vessels. Second, calculated temperature distributions are presented by solving the heat-flow equation. Also, comparisons of the temperature distributions when changing the flow conditions are discussed. Here, two resonant frequency patterns are used. From these results, it was found that the cooling effects of blood perfusion appear in the heated area approximately 2 cm away from the blood vessels.