探討自動曝露控制技術應用於模擬不同肥胖病人腰椎假體之適當性

自動曝露控制(automatic exposure control; AEC)已在影像診斷部門使用多年，被設計成不論身體區域、解剖結構厚度或使用不同的X光管電壓時，能使影像維持足夠的影像品質(image quality)，目前各主要儀器製造商皆有提供AEC，幫助醫事放射師執行X光攝影時，給予病人適當客觀的曝露條件。本研究探討AEC應用於肥胖病人腰椎攝影時，AEC是否能維持穩定之曝露因子(exposure factor)輸出，以及AEC應用於肥胖病人腰椎攝影之最適化使用建議。本研究使用Philips Diagnost TH X光機、Hologic DPA/QDR-1 Anthropomorphic Spine Phantom(以下簡稱腰椎假體)與自製之水假體(以下簡稱水假體)，得到85kVp、90kVp、96kVp與102kVp管電壓條件下以各種厚度水假體進行照射以產生曝露因子數值並計算標準差，之後選取曝露因子平均值超過20mAs之條件，以其對應之管電壓和水假體厚度進行編組。將腰椎假體置入水假體，以各編組條件進行AEC攝影並儲存影像作為對照組。根據對照組影像條件，手動調整較低且接近AEC建議之曝露因子條件，再進行攝影並儲存影像作為實驗組。請兩名醫事放射師作為受試對象，於雙螢幕工作站隨機顯示實驗組與對照組之腰椎影像，評估影像能否能區分優劣，若能區分優劣，指出較佳影像。記錄數據後執行Cohen's kappa一致性分析。依據研究結果AEC適合應用在管電壓102kVp、水假體厚度36cm以上病人之腰椎攝影。

關鍵字

自動曝露控制；肥胖病人；腰椎攝影；最適化

並列摘要

Instrument manufacturers provide Automatic Exposure Control (AEC) to help radiographers give appropriate objective exposure conditions when performing radiography. AEC has been used in imaging diagnost departments for many years and was designed to maintain image quality at a sufficient level regardless of body area, anatomical thickness, or the use of different X-ray tube voltages. This study investigated whether AEC can maintain a stable exposure factor output and optimization when using AEC in lumbar radiography of obese patients. Using the Philips Diagnost TH X-ray machine, the Hologic DPA/QDR-1 Anthropomorphic Spine Phantom and the selfmade water phantom, the exposure factor values generated with various thicknesses of water prosthesis at 85kVp, 90kVp, 96kVp, and 102kVp tube voltages were calculated. The standard deviation discusses the stability of AEC when used in obese patients. From the above records, the conditions for the average exposure factor exceeding 20 mAs were found and grouped with their corresponding tube voltage and water phantom thickness. The lumbar vertebral phantom was placed in the center of the water phantom, AEC radiography was performed with the conditions of each group and the images were stored as a control group. According to the image conditions of the control group, manually adjust the exposure conditions that are lower and close to the AEC recommendation, and then take a radiography and store the image as an experimental group. Two radiographers were asked to randomly display the lumbar vertebrae images of the experimental and control group on a dual screen workstation to assess whether the images could be distinguished from each other. If it was possible to distinguish, indicate which image was better. Perform Cohen's kappa consistency analysis after recording the data. The results suggest that AEC is suitable for lumbar radiography with a tube voltage of 102 kVp and a water phantom thickness of 36 cm or more, which means very obese patients.

並列關鍵字

automatic exposure control ； obese patient ； optimization ； lumbar radiography

國際替代計量

探討自動曝露控制技術應用於模擬不同肥胖病人腰椎假體之適當性

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