使用線對PMMA假體以田口方法優化腦部電腦斷層影像品質

許多年以來，事故傷害一直位居國人十大死因之中，其中又以交通事故占大多數。許多研究顯示，頭部創傷是交通事故致死的主要原因之一，而電腦斷層常是頭部創傷的第一線診斷，改善影像品質可增加影像診斷價值，有助於提升頭部創傷患者存活機率。本研究使用2組線對壓克力(PMMA)假體，以及多層固態水假體模擬成人頭部，評估腦部電腦斷層影像解析度，採用田口分析法執行造影參數的最佳化，選定Thickness、kVp、mAs、Filter及FOV做為控制因子，並依據L18直交表設計參數組合。使用128切電腦斷層儀進行造影，影像由3位臨床資深放射師進行評分，每張影像重複進行3次評分，共獲得324個評分。研究結果，最主要因子為kVp，S/N值變化量由29.21至33.75，且於變異數分析(analysis of variance, ANOVA)結果為顯著。最佳化參數為Thickness 2.5 mm、300 mAs、140 kVp、Sharp Type Filter及FOV 200 mm，較常規設定之S/N提高5.3% (p < 0.001)，有效劑量提升約0.5 mSv。調整造影參數時，應注意濾片與其他因子間的交互作用。最佳化參數得以顯著改善影像解析能力，雖額外增加劑量，但仍低於法規劑量限值，有助於頭部創傷患者之臨床診斷。

In recent years, accident injuries have been among the top ten leading causes of death in Taiwan, and traffic accidents are the most. Many studies indicate that head trauma is one of the main causes of death in traffic accidents. Computed tomography (CT) is often the front-line diagnosis of head trauma. Brain CT examinations increase the value of imaging diagnosis by improving imaging quality. They also can improve the survival probability of the injured person in the head trauma. Resolutions of imaging quality of brain CT were evaluated by two groups of lined polymethylmethacrylate (PMMA) phantoms and assembled with multiple layers of solid water plate to imitate the adult head. Contrast parameters were using optimized Taguchi method, five major factors, thickness, kVp, mAs, filter, and field of view (FOV). According to L18 orthogonal arrays were designed. Using the 128 slice CT, each combination of the CT scan protocol was repeated three times by three well-trained radiologists to ensure the reproducibility. There are totally 324 scores.Results show that the dominate factors of this study includes kVp, signal to noise ratio (S/N) changes from 29.21 to 33.75. Furthermore, S/N value was significantly remarked factor using analysis of variance (ANOVA). The optimal results are thickness 2.5 mm, 300 mAs, 140 kVp, sharp filter type and FOV 200 mm, S/N values were improved 5.3% (p<0.001) than routine settings. Effective doses arise approximately 0.5 mSv. When adjusting the contrast settings of imagine quality, we should pay more attentions to the cross interaction between filter type and other factors. The optimal results can significantly improve the imaging ability. Furthermore, the radiation dose is higher than routine setting, but is still lower than the dose limit of authority. This study is helpful to the clinical diagnosis of the injured person in the head trauma.