數位X射線影像設備之調制轉換函數測定

Modulation Transfer Function Determination of Digital X-ray Imaging Devices

施彥豪(Yen-Hao Shih) ； 朱健豪(Chien-Hau Chu) ； 陳宗麟(Zong-Lin Chen) ； 黃科志(Ker-Jer Huang)

《台灣應用輻射與同位素雜誌》 8卷4期 (2012/12) Pp. 401-410

https://doi.org/10.29832/TJARI.201212.0001

摘要

核能研究所國家游離輻射標準實驗室建立一套，可對數位輻射成像系統的影像進行評估之技術及方法，目的為計算影像之調控轉換函數（modulation transfer function，MTF）。在環境建置部分，依循IEC 61267的內容，建立射質及半值層，影像分析部分包含國際上較為認可的兩種方法，即IEC 62220-1建議的刀口法和國際上普遍使用的狹縫法，對數位輻射成像系統之影像進行評估及計算，並研究刀口法及狹縫法影像分析之差異，以了解影像的客觀評估方法。實驗結果成功建立RQR及RQA射質，並成功利用刀口法及狹縫法取得數位輻射成像系統之調控轉換函數。刀口法部分觀察可發現較小的角度評估而得的調控轉換函數表現較佳，因小角度的採樣間距較小，較易採樣到線擴散函數曲線的峰值。本方法可供後續研究做為參考，作為計算噪聲功率譜（noise power spectra，NPS）、量子偵檢效率（detective quantum efficiency，DQE）的必要參數。

關鍵字

調控轉換函數 ； 刀口法 ； 狹縫法

並列摘要

In order to evaluate the image quality of the digital imaging devices, National Radiation Standard Laboratory of Institute of Nuclear Energy Research set up a program to determine the modulation transfer function (MTF) of the digital imaging devices. The beam quality and half-value layers of the X-ray irradiator were constructed by following IEC 61267. Knife-edge and slit testing methods were used in our experiments. The knife-edge testing method is recommended by IEC 6220-1 and the slit testing method is common used internationally. The differences of these two methods were also analysis. The radiation quality of RQR and RQA were constructed successfully. The MTF of the digital imaging device were determined by knife-edge testing method and slit testing method. From the knife-edge testing results, we found that MTF will be better at small angle. The sampling distance is smaller at the small angle test, so the critical point of the line spread function is much easier to be found. The results of these experiments could be used in determining the noise power spectra (NPS) and detective quantum efficiency (DQE).

並列關鍵字

Modulation Transfer Function ； MTF ； Knife-Edge Testing Method ； Slit Testing Method