Parsi Masoumeh, Sohrabi Mehdi, Mianji Fereidoun, Paydar Reza
Health Physics and Dosimetry Research Laboratory, Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran.
Health Physics and Dosimetry Research Laboratory, Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran.
Phys Med. 2017 Jun;38:88-92. doi: 10.1016/j.ejmp.2017.05.054. Epub 2017 May 17.
A new quality-control-based (QC-based) method is introduced to obtain correction factors to be applied to displayed patient dose indices (CTDI and DLP) on CT scanner consoles to verify improvement of dose surveys for diagnostic reference levels (DRLs) determination.
An available data-base of QC documents and reports of 57 CT scanners in Tehran, Iran was used to estimate CTDI, DLP and relevant correction factors for three CT examination types including head, chest and abdomen/pelvis. The correction factor is the ratio of QC-based estimated dose to displayed dose. A dose survey was performed by applying on-site "data collection method" and correction factors obtained in order to select CT scanners in three modes for determination of CT DRLs by inclusion of: (a) all CT scanners before displayed dose indices were corrected (57), (b) only CT scanners calibrated by QC experts (41) and (c) all CT scanners after displayed dose indices were corrected (57).
For the 41 CT scanners, correction factors of three examination types obtained in this study are within the acceptance tolerance of IAEA HHS-19. The correction factors range from 0.45 to 1.7 (average of 3 examinations) which is due to the change in the calibrated value of CTDI over extended time. The DRL differences in three modes are within ±1.0% for CTDI and ±12.4% for DLP.
The "QC-based correction method" applied to mode (c) has improved the DRLs obtained by other two modes. This method is a strong alternative to "direct dose measurement" with simplicity and cost effectiveness.
引入一种基于质量控制（QC）的新方法来获取校正因子，以应用于CT扫描仪操作台上显示的患者剂量指标（CTDI和DLP），从而验证用于确定诊断参考水平（DRL）的剂量调查的改进情况。
利用伊朗德黑兰57台CT扫描仪的QC文件和报告的可用数据库，估计包括头部、胸部和腹部/骨盆在内的三种CT检查类型的CTDI、DLP及相关校正因子。校正因子是基于QC估计的剂量与显示剂量的比值。通过应用现场“数据收集方法”和获得的校正因子进行剂量调查，以便在三种模式下选择CT扫描仪来确定CT DRL，包括：（a）在显示剂量指标校正之前的所有CT扫描仪（57台），（b）仅由QC专家校准的CT扫描仪（41台），以及（c）在显示剂量指标校正之后的所有CT扫描仪（57台）。
对于41台CT扫描仪，本研究获得的三种检查类型的校正因子在国际原子能机构HHS-19的接受公差范围内。校正因子范围为0.45至1.7（3次检查的平均值），这是由于CTDI校准值在较长时间内发生了变化。三种模式下CTDI的DRL差异在±1.0%以内，DLP的DRL差异在±12.4%以内。
应用于模式（c）的“基于QC的校正方法”改进了通过其他两种模式获得的DRL。该方法是“直接剂量测量”的有力替代方法，具有简单性和成本效益。
