雙能量X光骨質密度吸收測量儀精密度檢測的重要性

Importance of Precision Assessment in Dual-Energy X-ray Absorptiometry

張賴昇平(Sheng-Pin Changlai) ； 華亦熙(Yi-Shi Hwua) ； 蔡松樹(Song-Su Tsai)

《中華放射線技術學雜誌》 32卷1期 (2008/06) Pp. 47-55

https://doi.org/10.30045/CJRT.200806.0007

摘要

骨質密度(bone mineral density, BMD)的檢測結果與放射師有關，骨質密度吸收測量儀的精密度檢測(precision assessment, PE)可以檢定一位放射師對同一病人在不同時間骨質密度檢測結果，得到良好再現性的能力。精密度檢測中的精密度誤差值(precision error; PE)更可提供醫師在臨床診斷病患多次BMD掃描結果之間的變動，是否具有生物意義的判斷指標。因此，本研究目的在爲一台雙能量X光骨質密度吸收測量儀實施精密度檢測，並建立施測步驟及操作人員的精密度誤差值。實驗對象爲15位年齡21.3-37.3歲（平均年齡28.4±5.3歲）身體健康、沒有懷孕、腰椎解剖結構正常、且無服用影響骨骼代謝藥物的女性自願受測者。以雙能量X光骨質密度吸收測量儀(dual energy X-ray absorptiometry, DXA)進行3次腰椎掃描。選擇正面腰椎(AP Lumbar spine)掃描模式，受測者每做完一次掃描，必須下檢查台，再上檢查台，重新擺位及測量。15位受測者腰椎的掃描都在同一天內完成。將15位受測者3次腰椎掃描骨密度值，代入國際臨床骨密學會(ISCD)所建立的全世界公認的精密度計算式裡，分別計算出精密度誤差值(PE)及最小顯著變化值(least significant change, LSC)。15位受測者平均身高爲158.6±4.9公分(mean±SD)，體重爲57.2±8.3公斤，身體質量指數(body mass index, BMI)爲22.7±2.9，15位受測者腰椎(L1-L4)總共45次掃描的平均骨質密度值爲1.225±0.114 g/平方公分。實驗當天骨質密度吸收測量儀的每日校準變異係數百分比(percent coefficient of variation, %CV)爲0.08%。15位受測者3次腰椎掃描骨密度值經”ISCD Precision Calculating Tool”公式，計算得到第一腰椎至第四腰椎(L1-L4)的精密度誤差值(PE)爲0.005g/平方公分。爲達到95%信賴度，將精密度誤差值乘上2.77倍，最後得到最小顯著變化值(LSC)爲0.014g/平方公分。本次放射師的腰椎掃描的精密度誤差值，完全符合國際臨床骨密學會的建議標準（腰椎的PE值應小於0.02g/平方公分）。骨質密度吸收測量儀的精密度檢測結果與骨質密度測量儀的品保，放射師的操作技巧，以及病人在掃描時的配合程度有關。

關鍵字

雙能量X光骨質密度吸收測量儀 ； 精密度檢測 ； 腰椎 ； 最小顯著變化值

並列摘要

Bone mineral density (BMD) results are technologist dependent. Short-term in-vivo precision study measures technologist's ability to reproduce technical factors from one scan to next on same patient. The precision error (PE) determines how much change in BMD must be seen between measurements before is can be considered a true biological change. Interpreting physician will be use precision error when comparing baseline and follow-up scans. This study was performed to determine the precision of lumbar spine bone mineral density measurements by a new dual-energy X-ray absorptiometry (GE Lunar Prodigy Advance, Madison, Wisconsin). Precision (group root-mean-square average standard deviation of the error; in g/cm^(2)) and least significant change (LSC) were determined in 15 healthy volunteers (mean aged 28.4 years of age) with normal anatomy, no pregnancy and without taking any medicine was scanned 3 times each at the lumbar spine, with repositioning after each scan. Their mean height was 158.6±4.9 cm, mean weight was 57.2±8.3 kg and mean body mass index (BMI) was 22.7±2.9. Each patient was done on same day. The percent coefficient of variation (%CV) of daily quality assurance was 0.08%. Precision error (RMSSD) in BMD for lumbar spine (L1-L4) scans was 0.005 g/cm^(2). This result was consistent with International Society for Clinical Densitometry (ISCD) recommendations (the RMS SD less than 0.02 g/cm^(2) for lumbar spine). Calculate LSC for the group at the 95% confidence interval was 0.014 g/cm^(2). The results of precision assessment were related to multiple causes such as the quality assurance of PXA, technologist's skill, and cooperation of patient during scan.

並列關鍵字

DXA ； precision assessment ； lumbar ； least significant change