水等価ファントムの比較検討

概要

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In radiation therapy, the dose absorbed by the target tissue needs to be extremely accurate. In order to obtain the target absorbed dose, radiation dose measurements are performed using a phantom instead of the patient's body, because the target absorbed dose cannot be directly measured. Although water is the best human muscle equivalent phantom, it is not useful for this purpose. Therefore, water equivalent solid phantoms are usually used for the measurements. We compared the following water equivalent solid phantoms for water:Tough water phantom, 457 Solid water phantom, RW-3, Mix-DP, polystyrene resin, polyethylene resin, and acrylic resin. The measurements obtained were 1)ionization current in the phantoms as determined by ionization chamber, 2)tissue-maximum ratio, 3)transmission measurements in water with and without the phantoms, 4)Hounsfield units of the phantoms for uniformity of inside phantoms as determined by computed tomography, and 5)accuracy of the phantoms. Results showed the phantoms to be almost equivalent to water, except for the acrylic resin phantom. However, the phantoms had various characteristics that affected accuracy, and the phantoms underwent change with time. Measurement error was caused by the characteristics of the phantoms. Therefore, it is important to measure the calibration coefficient of phantoms for water, regardless of what is stated on paper.
公益社団法人日本放射線技術学会の論文
1998-06-20