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題 名 | 低能量X射線射質之研究=The Study of the Beam Quality of the Low Energy X-rays |
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作 者 | 涂振邦; 陳為立; 朱健豪; 黃文松; 林芳仁; 簡哲民; | 書刊名 | 中華放射線醫學雜誌 |
卷 期 | 29:4 2004.08[民93.08] |
頁 次 | 頁185-190 |
分類號 | 418.94 |
關鍵詞 | 劑量術; 半值層; 純鍺偵測器; 能譜; Dosimetry; HVL; Pure germanium detector; Spectra; |
語 文 | 中文(Chinese) |
中文摘要 | 使用Keithley 6517A電量計和核研所自製的原級自由空氣游離腔測量PANTAK校正用低能X光機產生之低能量X射線(10 kV, 25 kV, 30 kV, 50 kVa, 50 kVb之管球電壓)的第一及第二半值層(HVL),其第一HVL分別為0.038, 0.171, 0.242, 2.267, 1.013 mm Al,和國際度量衡局(BIPM)之差異在3%以內,符合在±5%國際標準誤差範圍內。由第一及第二半值層之結果可進而去算出均勻係數及有效能量。使用DSG Model NGP1000-16 之純鍺偵測器量測前述X射線能譜,經由下列四項之理論修正,而完成較符合真正X射線之能譜:(1)偵測器的本質偵測效率,(2)特性輻射k-X射線的逃逸,(3)光峰效率,(4)多頻道能譜儀之能量校正。10kV之能譜修正前後,皆無改變。25 kV、30kV、50kVa及50kVb之能譜在修正前後,有些許的改變。修正後,在低能量的部份,皆有往高能量的地方做一些偏移。25kV及30kV之能譜,皆有出現Ge之特性kα-X射線(9.9keV)及kβ-X射線(11.0keV)。50kVa及50kVb之能譜,因已加上附加濾片,所以把低能量的部分過濾掉,所以沒有出現Ge之特性k-X射線。在建立校正用低能X光機之HVL及正確X射線能譜之測量後,就可進行與BIPM低能量X射線射質的比對,進而建立我國低能量X射線劑量的國家標準。 |
英文摘要 | Keithley 6517A electron meter and free air ion chamber were used to measure the 1st and 2nd half-value-layer (HVL) of the PANTAK low energy x-ray machine which has 10 kV, 25 kV, 30 kV, 50 kVa and 50 kVb tube voltage. The result of the 1st HVL is 0.038, 0.171, 0.242, 2.265 and 1.013 mm Al. The difference of HVL compared with BIPM is less than 3%, which is in agreement with the ±5% deviation of the international standard. Through the above results we can calculate and derive the homogeneity coefficient and the effective energy. We also used Detector Systems GmbH (DSG) Model NGP 1000-16 pure germanium (Ge) detector to measure the spectra of this x-ray machine. Those spectra were modified by using 1. detection efficiency, 2. escape probabilities of the k x-rays, 3. photopeak efficiencies, and 4. energy calibration for multiple channel analyzers. The spectrum of 10 kV is not changed after the unfolding process, and a little change was noted in the 25 kV, 30 kV, 50 kVa and 50 kVb. Through the unfolding process the spectra shift to a higher energy direction in the low energy portion. The characteristic kx-ray (9.9keV) and kβx-ray (11.0keV) of Ge has displayed in the 25 kV and 30 kV spectra. It has not been shown in the 50 kVa and 50 kVb, because the additional filter had filtered off the portion of low energy x-ray. The beam quality of the low energy x-rays conforms to the international standard, and offers the calibration standard and quality comparison of international level, and may contribute to dose calibration standard of mammography. |
本系統中英文摘要資訊取自各篇刊載內容。