The study effects of the material of buildup cap to the measured value of output factor
10.3969/j.issn.1005-202X.2001.01.001
- VernacularTitle:平衡帽材料对准直器散射因子测量值的影响探讨
- Author:
Zhen TANG
;
Qingsong TU
;
Zhongyu LIU
- Publication Type:Journal Article
- From:
Chinese Journal of Medical Physics
2001;18(1):1,4-
- CountryChina
- Language:Chinese
-
Abstract:
To study the effects of the material of a buildup cap to the determined value of Output FactorSc．Material and MethodsUsing two buildup caps made of plastic A－150 and copper respectively．The ionizing values of ionization chamber were measured with Farmer 2570 electrometer in the fields of all kinds of sizes respectively and calibrated to reference field．Two groups of values of Sc were obtained and compared． Results The ionizing values measured with the buildup cap of copper is evidently larger than with the buildup cap of plastic A－150 and the maximum is 14％ but the difference between two groups of the values of Sc is not much evident and all is in the range of 1％． Conclusions Though the material of high density is not equivalent with airthe effects of that to the measured value of Sc is less．So using the buildup cap made of the material of high density for the measurement of Sc is also a quite good method specially in the fields of the small sizes．
