Radiological Technology Diagnostic Imaging Center, Nagoya Daini Red Cross Hospital, Myoken-cho 2-9, 466-8650 Nagoya, Aichi, Japan.
Phys Med. 2012 Jan;28(1):71-5. doi: 10.1016/j.ejmp.2011.01.001. Epub 2011 Feb 9.
A method for determining half value layers (HVLs) of inverter-type X-ray equipment using a computed radiography (CR) systems was developed. This method is similar to the traditional method, where the air kerma (K) is measured using an ionization based dosimeter and increasing aluminum (Al) absorber thickness, but utilized an imaging plate (IP) and the sensitivity index (S number) of the CR system as the dosimeter and the dosimeter reading, respectively. The IP and the S number were calibrated using an ionization chamber having traceability to the National Standard Ionization Chamber. A modified version of the S number definition equation K=a × S(-b) was used to translate the S number to K values for X-ray beams produced using tube voltages ranging from 50 to 120 kV and additional Al filtration up to 2.5mm. The coefficient 'a' varied depending on the beam quality, while the coefficient 'b' showed a constant value of 0.991. The HVLs in the range from 1.8 to 5.5mm Al that were obtained with this method were in good agreement with those obtained with the traditional method, as uncertainties were between -7 and 4%. This method can be used to determine the HVLs of inverter-type X-ray equipment within an acceptable accuracy.
开发了一种使用计算机射线照相 (CR) 系统来确定逆变式 X 射线设备的半值层 (HVL) 的方法。该方法类似于传统方法，其中使用基于电离的剂量计测量空气比释动能 (K)，并增加铝 (Al) 吸收体厚度，但利用成像板 (IP) 和 CR 系统的灵敏度指数 (S 数) 作为剂量计和剂量计读数。使用可追溯到国家标准电离室的电离室对 IP 和 S 数进行校准。使用经过修正的 S 数定义方程 K=a×S(-b) 将 S 数转换为管电压范围为 50 至 120 kV 并附加 2.5mm 额外 Al 过滤的 X 射线束的 K 值。系数 'a' 取决于束质，而系数 'b' 显示出 0.991 的恒定值。使用该方法获得的 1.8 至 5.5mm Al 范围内的 HVLs 与传统方法获得的 HVLs 非常吻合，不确定度在 -7 至 4% 之间。该方法可用于以可接受的精度确定逆变式 X 射线设备的 HVLs。
