Schulz R J, Weinhous M S
Med Phys. 1985 Mar-Apr;12(2):166-8. doi: 10.1118/1.595758.
In the recently published AAPM protocol for the dosimetry of high-energy photons and electrons, the response of an ionization chamber is defined as the dose to the gas in the chamber per unit electrometer reading, Ngas. Using a graphite calorimeter, Ngas has been determined for a Farmer-type ionization chamber using 4- and 25-MV x rays. The procedure was to measure the dose to graphite using the calorimeter, and then obtain the response of the chamber at the same depth in a graphite phantom. Equation (9) of the AAPM protocol was then used to calculate Ngas. The values of Ngas determined with the calorimeter are within 1% of Ngas calculated according to the AAPM protocol, using the 60Co exposure-calibration factor.
在最近发表的美国医学物理师协会（AAPM）关于高能光子和电子剂量测定的协议中，电离室的响应被定义为电离室中气体的剂量与每单位静电计读数Ngas之比。使用石墨量热计，已针对使用4兆伏和25兆伏X射线的 Farmer 型电离室确定了Ngas。具体步骤是使用量热计测量石墨的剂量，然后在石墨模体的相同深度处获取电离室的响应。然后使用AAPM协议的方程（9）来计算Ngas。用量热计确定的Ngas值与根据AAPM协议使用钴 - 60曝光校准因子计算得出的Ngas值相差在1%以内。
