RBE - Reverse Beam Emission

Abbreviation for relative biological effectiveness. Also known as relative biological effectiveness. The radiation dose (unit: rad) required to absorb a certain biological effect varies depending on the type and energy of radiation. This relative dose ratio is often determined by comparing it with 250 kV X-rays. In other words, RBE = (absorbed dose required for 250 kV X-rays to produce a certain biological effect) / (absorbed dose required for the other radiation to produce the same effect). RBE is roughly set at 1 for X-rays, gamma rays, and electron beams, 2.5 for thermal neutrons, 10 for fast neutrons, protons, and alpha particles, and 20 for accelerated heavy ions, but generally it is influenced by complex factors such as the type and energy of radiation, dose rate, properties of organs and tissues, and the time of cell division. The product of absorbed dose and RBE is called the RBE dose, and is expressed in units of rem. From the standpoint of radiation protection, RBE is called the radiation quality factor, and the unit of the product with the absorbed dose is also rem, but in this case it is called the dose equivalent. [See other terms] Radiation weighting factor

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

relative biological effectivenessの略称．生物学的効果比ともいう．一定の生物学的効果を生じるまでに吸収する放射線の線量(単位 rad)は，放射線の種類やエネルギーによって異なる．この相対的な線量の比をいい，250 kV のX線との比較によって定める場合が多い．すなわち，RBE＝(250 kV のX線が一定の生物学的効果を生じるのに要する吸収線量)/(比較しようとするほかの放射線が同じ効果を生じるのに要する吸収線量)．RBEのおよその目安として，X線，γ線，電子線は1，熱中性子は2.5，速中性子，陽子，α粒子は10，加速された重イオンは20の値がとられているが，一般には，放射線の種類，エネルギーのほか，線量率，器官や組織の性質，細胞分裂の時期など，複雑な要因が関係してくる．吸収線量とRBEの積をRBE線量といい，レム(rem)単位で表す．なお，放射線保護の立場からは，RBEは線質係数(quality factor)といい，吸収線量との積の単位は同じくレムであるが，この場合は線量当量(dose equivalent)という．[別用語参照]放射線荷重係数

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