建立技術師之平均雙能量X光骨質密度吸收測量儀之精密度研究

雙能量X光骨質密度(bone mineral density, BMD)的檢測結果與技術師有關。骨質密度吸收測量儀的精密度檢測(precision assessment)目的在檢測技術師以相同的技術對患者重覆多次的骨密掃瞄之後，產生相同測量結果的能力。唯一能夠提供臨床醫師說明患者的骨質密度變化是有意義的方法，就是病患的骨質密度值必須大於技術師最小顯著變化值(Least significant change; LSC)。每位技術師都必須建立自己的最小顯著變化值。若執行骨質密度測量工作超過一人時，則必須將每位技術師的最小顯著變化值相加取平均值。本研究目的在建立3位技術師在腰椎骨質密度掃描上造成的平均最小顯著變化值。實驗對象為45位平均年齡為39.6±3.8歲（介於34-47歲）身體健康、腰椎解剖結構正常、無懷孕、且無服用影響骨骼代謝藥物的自願女性受測者。45位受測者平均身高為158.1±4.8公分(mean±SD)，體重為56.5±8.4公斤，身體質量指數(body mass index; BMI)為22.6±3.5。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)為0.394%。選擇正面腰椎(PAL umbar spine)掃描模式，每位放射技術師的精密度誤差值(precision error, PE)及最小顯著變化值(LSC)的建立是以雙能量X光骨質密度吸收測量儀(dual energy X-ray absorptiometry; Hologic QDR 4500)對15位自願者進行3次腰椎掃描，因此，本次實驗3位技術師共掃描過45位自願者，總共135次的腰椎掃描。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。參與每位放射技術師的精密度檢測的所有受測者的腰椎掃瞄，都在同一天內完成。3位技術師的精密度誤差值(PE)及最小顯著變化值(LSC)在一個月內完成。3位技術師的平均第一腰椎至第四腰椎(L1-L4)的精密度誤差值(PE)為0.009g/平方公分。為達到95%信賴度，將精密度誤差值乘上2.77倍，得到平均最小顯著變化值(LSC)為0.024g/平方公分。本次實驗，3位技術師的腰椎掃描的精密度誤差值(PE)，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0.020g/平方公分）。骨質密度測量儀的品質保證不但需要規律的掃描假體校正儀器，以及考慮病患本身有關的因素，如：假影，解剖結構退化，移動性及配合程度以外，另外也要訓練多位技術師在進行骨質密度測量時，對病人的擺位及結果分析上的一致性。多位放射技術師都遵循相同的擺位及分析標準實屬不易，這是一次由3位技術師建立出他們在進行腰椎骨質密度測量時，所造成的平均最小顯著變化值(LSC)的成功經驗。

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；多位放射技術師

並列摘要

The result of DXA bone density measurement is related to the technologist. Short-term in-vivo precision assessment measures technologist's ability to reproduce technical factors from one scan to next on same patient. The only one way that a physician can know that a real biologic change has occurred is to know if the least significant change (LSC) of the technique has been exceeded. Each technologist should establish their own LSC value. In the case of multiple technologists performing densitometry studies, the values for the precision studies form individual technologists be averaged to determine the precision for the facility. This study was performed to establish the average LSC value of lumbar spine bone mineral density measurements by 3 densitometry technologists. A total of 45 healthy female subjects who ranged from 34 to 47 years old (mean = 39.6±3.8) with normal anatomy, no pregnancy and without taking any medicine which could influence bone metabolism. 45 healthy volunteers' mean height was 158.1±4.8 cm (mean±SD), mean weight was 56.5±8.4 kg and mean body mass index (BMI) was 22.6±3.5. The percent coefficient of variation (% CV) of daily quality assurance was 0.394%. Choosing PA spine scan mode, precision error (group root-mean-square average standard deviation of the error; in g/cm^2) and LSC of each technologist were determined in 15 healthy volunteers scanned 3 times each at the lumbar spine (15 patient×3 scans/patient=45 scans/technologist×3 technologists=135 scans) on Hologic QDR 4500 scanner, with repositioning after each scan. All patients' L-spine scans for each technologist were done on same day. All precision error and LSC data derived from 3 technologists done within 1 month. The average precision error (RMS SD) in BMD for L1-L4 by 3 technologists was 0.009 g/cm^2. An average calculate LSC for the group at the 95% confidence interval was 0.024 g/cm^2 (= 0.009 g/cm^2×2.77). Precision overall is excellent and these results are consistent with International Society for Clinical Densitometry (ISCD) recommendations (the RMS SD less than 0.020 g/cm^2 for spine). As well as the regular scanning of phantoms to check system calibration and patient related factors (artifact, anatomy deformities, patients' movements, and patient cooperation), the other major quality assurance issue is the training of staff performing bone densitometry investigations to ensure consistency in patient positioning and scan analysis. It is difficult to follow the same positioning and analysis standard for multiple technologists. This study was a very successful experience about establishing an average LSC value created by multiple technologists.

並列關鍵字

DXA ； precision ； spine ； LSC ； multiple technologists

國際替代計量

建立技術師之平均雙能量X光骨質密度吸收測量儀之精密度研究

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