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This paper describes a new system to match the impedance automatically for a re-entrant resonant cavity applicator during brain tumor hyperthermia treatments non-invasively. We have already discussed the effectiveness of the heating method using a manual impedance matching controller with heating experiments of an agar phantom and computer simulations. With this heating method, to generate heating power in the cavity, it is necessary to match the impedance and to tune the resonant frequency. In the initial prototype heating system, both were manually adjusted. However, it was difficult to match the impedance and to tune the frequency especially using a high resonant frequency. To overcome this problem, we developed the automatic impedance matching system (AIMS). It is known that reflected power is generated when the impedance matching is not complete. In this system, to reduce the reflected power which is fed back to the computer, the stepping motor to turn the dial of the variable capacitors is controlled by developed software. To evaluate the developed AIMS, the heating experiments of the agar phantom, using several electromagnetic modes, were performed. The VSWRs are 1.05 and 1.01 using manual matching and AIMS, respectively. From these results, we found that the temperature rise in the agar phantom using AIMS was about 180% (with TM012-like mode) and about 110% (with TM010-like mode) more than using the manual type controller under the same heating condition. It was found that the proposed system was very effective for hyperthermia treatment using the resonant cavity applicator even when the resonant frequency was high.

This paper describes a new heating method used to expand the heating area of a needle applicator by using a needle applicator made of a shape memory alloy (SMA) for brain tumor hyperthermia treatment. The purpose of the study described here is to show the ability of the method to expand a defined heating region. One major disadvantage of RF interstitial hyperthermia treatment is that this heating method has a small heating area. To overcome this problem, a new type of needle made of a SMA was developed. The thermal properties of this proposed method, when applied to agar phantoms, were calculated with computer simulations and these properties were checked experimentally with the current physical version of the heating system. The calculated temperatures were in close agreement with the measured temperatures with an error of 10% or less. In both the numerical calculations and experimental results the proposed SMA needle heat treatment expanded the heating area to approximately 300% of that of a non-SMA needle heat treatment. These results suggest that the proposed heating method using the SMA needle applicator is capable of being used for invasive brain tumor hyperthermia treatments.

This paper describes the possibility of a new heating method with a needle applicator made of a shape memory alloy (SMA) to expand the heating area for interstitial brain tumor hyperthermia treatments. The purpose of the study described here is to show the capability of the method to expand a defined heating region with the developed three-dimensional (3-D) anatomical human head model using the finite element method (FEM). One major disadvantage of RF interstitial hyperthermia treatment is that this heating method has a small heating area. To overcome this problem, a new type of needle made of a SMA was developed. The specific absorption rate (SAR) distributions of this proposed method, when applied to the 3-D anatomical human head model reconstructed from two-dimensional (2-D) MRI and X-ray CT images, were calculated with computer simulations. The calculated SAR distributions showed no unexpected hot spots within the model. The heated area was localized around the tumor. These results suggest that the proposed heating method using the SMA needle applicator and the developed method for reconstructing a 3-D anatomical human head model are capable of being used for invasive brain tumor hyperthermia treatments.

我々はこの20年間における1施設での, 視床ならびに被殻部の悪性神経膠腫症例をステージ分類し, この部位における温熱治療症例の臨床的特徴について報告する. 対象は, 新潟大学において治療を受けた基底核部 (視床を含む) のグレード3および4の悪性グリオーマ43例である. 病期分類は, 視床並びに被殻部の腫瘍の大きさを基に行った. すなわち, ステージ1 (2cm未満), ステージ2 (2―4cm), ステージ3 (4cm以上) とし, 腫瘍が被殻や視床を超えて他部位へ進展しているものをステージ4, 脳室への進展例 (播種例) をステージ5として分類した. 当科における温熱治療は, 腫瘍内に電極を局所麻酔下に生検する際に同時に埋め込んでくるもので, 通常の外照射60Gyとともに週2回計3ないし4回の加温を行うものである. 化学療法はACNUまたはMCNUを温熱放射線治療中に静注もしくは動注しているが, 高齢者においては併用していない. その結果, ステージ4症例は全症例の30％を占め, ステージ5症例も含めると40％にもなった. 摘出術施行例は43例中14例で, 残りの29例は生検術症例である. そのうちの14例は生検術とともに温熱治療のための針電極を留置し, 放射線治療とともに温熱治療を行った. 平均生存期間は11ヶ月であった (視床部では17ヶ月, 被殻部で11ヶ月). 視床部の悪性グリオーマは被殻部の症例に比し, 若年である傾向が認められ, 予後も若干良好であった. 温熱症例の平均生存期間は22か月で, 非温熱治療, 生検術群の9ヶ月に比べ, 生存期間延長の傾向が認められた. 基底核部悪性グリオーマは深部であるため, 摘出術が可能であることが少なく予後不良であったが, 温熱治療により有効例も認められるようになっている.