PRACTICAL METHODS OF ELECTRON DEPTH-DOSE MEASUREMENT COMPARED TO USE OF THE NACP DESIGN CHAMBER IN WATER
PRACTICAL METHODS OF ELECTRON DEPTH-DOSE MEASUREMENT COMPARED TO USE OF THE NACP DESIGN CHAMBER IN WATER
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DOI：
10.1118/1.595986
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发表时间：
1987-11-01
期刊：
影响因子：
3.8
通讯作者：
JOST, RJ
中科院分区：
文献类型：
--
作者：
TENHAKEN, RK;FRAASS, BA;JOST, RJ
使用两个不同的小体积顶针电离室和p型硅二极管在水体模中以及两个平行板电离室、热释光剂量计和射线照相胶片在流行的透明聚苯乙烯体模中进行中心轴相对剂量与深度的测量。将获得的值与使用平面平行电离室进行的水体模中的类似测量结果进行比较，该电离室由北欧临床物理学家协会（NACP）设计并优化用于电子束。NACP腔室预期对电子注量的干扰最小，并且最不容易出现测量点不确定性。它在水幻影中的使用非常接近最近的国际协议的精神。获得了由两种不同加速器产生的箔散射电子束的数据，场尺寸从6 cm × 6 cm到25 cm × 25 cm，能量从6到20 MeV。为每种测量器械定义了易于识别的有效测量点，并对原始数据进行了标准校正，以获得深度-剂量曲线。通过比较50%剂量的深度和实际范围，定量分析了各种技术与NACP水标准之间的一致程度。所有的方法都被发现产生合理的结果时，仔细实施，小于1毫米的平均差异是很容易实现的。发现使用p型硅二极管探测器进行测量特别有用，因为它们是点状的，并且从所有实际考虑来看都直接表示相对剂量，因此需要很少或不需要对原始读数进行校正。
Central axis relative dose versus depth measurements were performed using two different small volume thimble ionization chambers and ap‐type silicon diode in a water phantom and with two parallel‐plate ionization chambers, thermoluminescent dosimeters, and radiographic film in a popular clear polystyrene phantom. Values obtained were compared to the results of similar measurements in a water phantom performed with a plane‐parallel ionization chamber designed and optimized for use in electron beams by the Nordic Association of Clinical Physicists (NACP). The NACP chamber is expected to minimally perturb the electron fluence and be least prone to point of measurement uncertainties. Its use in a water phantom closely approximates the spirit of recent international protocols. Data were obtained for the foil scattered electron beams generated by two different accelerators for field sizes from 6 cm × 6 cm to 25 cm × 25 cm and energies between 6 and 20 MeV. Easily identifiable effective points of measurements were defined for each measurement device and standard corrections were applied to the raw data to obtain depth‐dose curves. The degree of agreement between the various techniques and the NACP‐water standard was quantitatively analyzed through comparison of the resulting depths of 50% dose and practical range. All methods were found to yield reasonable results when carefully implemented, with average differences of less than 1 mm being easily achievable. Measurements withp‐type silicon diode detectors were found to be particularly useful, as they are pointlike and appear from all practical considerations to directly represent relative dose, thus requiring little or no correction to raw readings.