鎝－99m放射藥劑對雙能量X光骨質密度偵測值的影響

The Impact of Tc-99m on the Detection of Bone Mineral Density by Dual Energy X-Ray Absorptiometry

蘇章松(Chang-Sung Su) ； 陳錦薰(Jiin-Shiun Chen) ； 崔志成(Chih-Cheng Tsui) ； 鄭如華(Ru-Hwa Cheng) ； 陳遠光(Yen-Kung Chen)

《中華放射線技術學雜誌》 32卷1期 (2008/06) Pp. 73-78

https://doi.org/10.30045/CJRT.200806.0010

摘要

骨質疏鬆症是最常見的骨骼疾病，臨床上要診斷骨質疏鬆症只有測骨質密度，大部份骨質密度檢查爲雙能量χ-ray吸收儀器，有些外在影響因素會干擾測量出來的數值，其中鎝－99m放射核種所射出的γ-ray對於雙能量χ-ray吸收的偵測器會有所影響。利用GE Lunar Prodigy骨質密度儀與專用校正金屬假體，四節不同密度椎骨，水域體積爲13 L放入0、2、5、10、20 mCi的不同活性之鎝－99m放射製藥，測量其密度共20次並紀錄L-1、L-2、L-3、L-4與L2~L4的測量值，骨質密度掃瞄完後，將其有放射活性的水域假體四組個別放置APEX Helix伽瑪閃爍攝影機掃瞄，記錄雙探頭伽瑪閃爍攝影機收集γ-ray計數率（K count/秒），設計以上實驗來探討核醫鎝－99m掃瞄製劑在不同活性下對於骨質密度量測的影響及造成之差異。實驗結果在放射劑量設定範圍在0 mCi至20 mCi，其骨質密度由0.12 %至-1.62 %變化，當放射活性越大與金屬假體密度越大時，對於雙能量χ-ray吸收儀器的偵測器影響機率也大幅增加，而間接影響骨質密度的下降。在核醫臨床掃瞄發現注射3分鐘與3小時後γ-ray平均速率數值與實驗組中2 mCi與5mCi的數值是相接近，間接獲得其骨質密度影響程度也只有下降0.4 %(0.005 g/平方公分)。最好的方法則需讓病患等待24小時（4 個半衰期）與多喝水，讓病患身上鎝－99m放射藥物活性減低，得到正確的骨質密度數值。

關鍵字

骨質疏鬆症 ； 骨質密度 ； 雙能量χ-ray吸收儀器 ； 鎝－99m

並列摘要

The diagnosis of osteoporosis, the most common bone diseases, depends on the detection of bone mineral density by dual energy χ-ray absorptiometry. However, factors such as radioisotope-emitted γ-ray may affect the measurements. Therefore, how the radioactivity (such as Tc-99m) may interfere with the measurement of bone mineral density is investigated in this study. Metallic phantoms are placed into a box containing 13 liters of water, with and without the addition of Tc-99m, and the density is measured for 20 times by dual energy χ-ray absorptiometry. In the group with Tc-99m addition, count rates of Tc-99m-emitted γ-ray are collected using APEX Helix gamma camera. Our results show when either the radioactivity of Tc-99m or the density of metallic phantom increases, the interference with dual energy χ-ray absorptiometry increases, which in turn cause the decrease of bone mineral density measurement. It is also deducible that when bone mineral density by dual energy χ-ray absorptiometry is performed from 3 minutes to 3 hours after the injection of Tc-99m in whole body bone scan, the result may falsely decrease 0.4% (0.005 g/cm^(2)). The measurement is better to be performed at least 24 hours (4 half-life of Tc-99m) after the nuclear medicine examinations with Tc-99m.

並列關鍵字

Osteoporosis ； Bone Mineral Density ； dual energy χ-ray absorptiometry ； Tc-99m