質子射束在放射腫瘤的臨床應用正以可觀的速率增加，雖然有許多實驗研究，但是對於臨床質子射束放射治療應該用何種相對生物效應值（relative biological effectiveness，RBE）才是最為正確的，仍然極不確定。因此，本文將闡述關於臨床應用上質子RBE值的問題，即RBE隨著布拉格尖峰散佈（spread out Bragg-peak，SOBP）深度的變化、RBE與細胞和組織的輻射傷害參數（α／β值）影響。國外的研究團隊Raju和Robertson等人在哈佛粒子迴旋加速器設備用160MeV的SOBP質子束進行相關的研究，Gueulette等人則以85MeV質子觀察RBE與SOBP隨著深度的影響變化，此部份在本文亦將進行探討。目前的分析限制質子初始能量約70～200MeV（2～10cm的SOBP）。因RBE值大多隨著能量範圍200－300KVp的X射線的過濾而變化，故相對於仟伏特X射線的RBE值計算即不被包括在內。迄今各種活體和離體的研究、實驗數據都一致證實，在高原入口處的平均RBE值近乎於1.1，隨著SOBP深度的增加，此值可增加至大於1.2。這些觀察適用於初始能量為70～200MeV，約為2～10cm的SOBP以及劑量接近2Gy的射束，但是RBE數值增加或降低的程度，還是由細胞或組織的α／β值和分次治療劑量所影響。

The clinical application of proton beam in radiation oncology keeps increasing, although there are many related experiments, it's still not sure which RBE value of proton therapy is correct. Therefore, this article will mention about RBE value of proton beam in clinical application which is the RBE value changes with the SOBP and the influence of cell α/β value. This article will also mention that the research of SOBP of 160MeV proton beam with Harvard cyclotron equipment as well as the research of RBE value and SOBP of 85MeV proton beam. Current constraints of analyzing SOBP in proton beam energy are 70 to 200MeV ( 2 to 10cm SOBP ), because RBE value changes with the filtration of 200 to 300 KVp X-ray, so the several thousand volt is excluded. The in-vivo and in-vitro experimental data all verify that the average RBE value at the plateau entrance is approximately 1.1, even can reach 1.2 increasing with the depth of SOBP. These phenomena apply to 70 to 200MeV, which is 2 to 10 cm SOBP and the beam approaches to 2 Gy. However, the level of RBE value increasing or decreasing is affected by α/β value of cell as well as fraction dose.