研究のタイプ: 医学／生物学の研究 (experimental study)

[2.45GHzマイクロ波ばく露時のウサギでの急性ドシメトリおよび熱ストレスの行動上の徴候の閾値推定] med./bio.

Acute dosimetry and estimation of threshold-inducing behavioral signs of thermal stress in rabbits at 2.45-GHz microwave exposure

著者: Hirata A, Kojima M, Kawai H, Yamashiro Y, Watanabe S, Sasaki H, Fujiwara O
掲載誌: IEEE Trans Biomed Eng 2010; 57 (5): 1234-1242
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この研究は、ウサギに2.45 GHz マイクロ波（MW）ばく露実験を行い、全身平均比吸収率（SAR）と直腸温上昇との関係を調べた。マイクロ波（MW）の人体ばく露に関する現在の国際ガイドラインおよび基準では、基本制限は全身平均SARに基づき設定されている。その根拠は、一定レベルを超える全身平均SARが動物に、熱ストレスによる行動的兆候を引き起こすことにある。しかし、全身平均SARと体温変化との関係は十分に調べられていない。そこで、MWによる熱ストレスで誘発される行動徴候の閾値を推定すること、またそのために、MWエネルギーによる高レベル熱負荷の急性ドシメトリーを行うことを研究の目的とした。約100 - 1000 W / m2の電力密度で、合計24回の測定を実施した。ウサギの数値ファントムでの電磁量–熱量ドシメトリーの計算コードを用いて、実験するばく露時間および入射電力密度を設定した。その結果、さまざまな全身平均SARおよびばく露時間のウサギにおいて、1 ℃の深部体温上昇が、MW誘発熱ストレス閾値レベルで生じる複雑な行動徴候の推定値であることが示された；ウサギのMW誘発性行動徴候に必要な全身平均SARは、2.45 GHz MWで約1.3W / kgと推定された、と報告している。

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研究目的（著者による）

To clarify the relationship between whole body average specific absorption rate (SAR) and the rectal temperature elevation in rabbits and to estimate the threshold for inducing a behavioral sign due to microwave provoked thermal stress.The main aim of the study also was to conduct acute dosimetry for high thermal loads due to microwave energy (the experimental conditions were determined with a computational code for electromagnetic-thermal dosimetry via a numeric rabbit phantom).

詳細情報

Rabbits were chosen because of their high susceptibility to heat stress, since they have few sweat glands, and experience difficulty in eliminating excess body heat.
The study was performed with 14 unanesthetized and 10 anesthetized rabbits.
In the current international guidelines for human exposure to microwaves, the limit value is determined by the whole body average SAR value. Although it is known that absorbed microwave energy causes the behavioral sign of thermal stress, the relationship of whole body average SAR with temperature/temperature elevation has not been sufficiently investigated.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 2.45 GHz
ばく露時間: until the core temperature of the rabbit reached 41.5 °C
  • 電力密度: 100 W/m² spatial average (incident power density)
  • 電力密度: 220 W/m² spatial average (incident power density)
  • SAR: 1.18 W/kg average over mass (whole body) (for an incident power density of 100 W/m²)
  • SAR: 1.3 W/kg average over mass (whole body) (SAR value that caused behavioral signs of stress)
ばく露2: 2.45 GHz
ばく露時間: until the core temperature of the rabbit reached 41.5 °C
  • 電力密度: 730 W/m² spatial average (incident power density)
  • 電力密度: 980 W/m² spatial average (incident power density)
  • SAR: 1.18 W/kg average over mass (whole body) (for an incident power density of 100 W/m²)
  • SAR: 1.3 W/kg average over mass (whole body) (SAR value that caused behavioral signs of stress)

General information

24 experiments were performed first on anesthetized (10) and then on unanesthetized (14) rabbits. The article does not say how many rabbits were exposed to the individual exposure conditions.

ばく露1

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic field
特性
  • far field
ばく露時間 until the core temperature of the rabbit reached 41.5 °C
ばく露装置
ばく露の発生源／構造
Distance between exposed object and exposure source 1 m
ばく露装置の詳細 rabbit placed in a 10 m x 8 m x 6.5 m anechoic chamber with the bottom of the chamber covered with absorber material; rabbit positioned so that it was irradiated from the lateral side
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 100 W/m² spatial average 計算値 - incident power density
電力密度 220 W/m² spatial average 計算値 - incident power density
SAR 1.18 W/kg average over mass 計算値 whole body for an incident power density of 100 W/m²
SAR 1.3 W/kg average over mass 計算値 whole body SAR value that caused behavioral signs of stress
測定および計算の詳細

SAR calculations were done with a FDTD program

ばく露2

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic field
特性
  • far field
ばく露時間 until the core temperature of the rabbit reached 41.5 °C
ばく露装置
ばく露の発生源／構造
Distance between exposed object and exposure source 1.2 m
ばく露装置の詳細 rabbit placed in a 10 m x 8 m x 6.5 m anechoic chamber with the bottom of the chamber covered with absorber material; rabbit positioned so that it was irradiated from the lateral side
パラメータ
測定量 値 種別 Method Mass 備考
電力密度 730 W/m² spatial average 計算値 - incident power density
電力密度 980 W/m² spatial average 計算値 - incident power density
SAR 1.18 W/kg average over mass 計算値 whole body for an incident power density of 100 W/m²
SAR 1.3 W/kg average over mass 計算値 whole body SAR value that caused behavioral signs of stress
測定および計算の詳細

SAR calculations were done with a FDTD program

Reference articles

  • Wake K et al. (2007): [眼の作用に関するインビボ研究のためｎ2.45 GHz局所ばく露装置の開発]
  • Hirata A et al. (2006): [2.45Hzマイクロ波にばく露されたウサギ眼球での麻酔効果と温度変化の計算による確認]
  • Spiegel RJ (1984): [電磁界にばく露されたヒトのエネルギー堆積と結果的熱応答の予測に用いる数的モデルの考察]

ばく露を受けた生物:

方法 影響評価項目／測定パラメータ／方法

研究対象とした生物試料:
調査の時期:
  • ばく露中
  • ばく露後

研究の主なアウトカム（著者による）

The data suggest that a core temperature elevation of 1°C is an estimate of the threshold inducing complex behavioral signs of microwave-induced thermal stress in rabbits for different whole body exposure average SAR values and exposure durations. The whole body exposure average SAR value required for microwave-induced behavioral signs in rabbits was estimated as approximately 1.3 W/kg for 2.45 GHz microwaves.

研究の種別:

研究助成

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