Department of Diagnostic and Interventional Radiology, University Hospital Frankfurt, Frankfurt, Germany.
Department of Diagnostic and Interventional Radiology, University Hospital Frankfurt, Frankfurt, Germany.
Eur J Radiol. 2019 Jul;116:68-75. doi: 10.1016/j.ejrad.2019.04.005. Epub 2019 Apr 22.
To investigate and optimize the impact of different exposure parameters on image quality and radiation dose for a latest generation orthopedic cone-beam CT system.
110 consecutive scans of the same cadaver forearm were performed before and after the insertion of a distal radius plate on the palmar radius to achieve highest intra-individual comparability. All scans were conducted on a latest generation cone-beam CT scanner (Carestream OnSight 3D Extremity System, Carestream Health, Rochester, NY, USA). Extremity imaging was performed using different combinations of tube voltage (kV) and tube current - exposure time product (mAs). Radiation dose (DLP and CTDI) was recorded to widely varying combinations. Subjective and objective image quality analysis included a blinded evaluation by five different readers independently using 5-point-Likert scales.
Highest radiation dose was achieved using the manufacturers' suggested standard protocol (90-kV and 5.0 mAs with DLP of 111.91 mGycm and CTDI of 4.49 mGy), while 70-kV and 2.0 mAs provided the most dose reduction with DLP of 20.34 mGycm and CTDI of 0.79 mGy. Regarding subjective image quality, higher tube voltage improved depiction of cortical bone (p ≤ 0.038) and cancellous bone (p ≤ 0.001) as well as overall image quality (p ≤ 0.027). Changes of the tube current - exposure time product did not show significant alterations of image quality (p ≥ 0.063). After plate insertion, only the subjective overall image quality showed reduced subjective perception (p < 0.001). Between the different scan protocols, no relevant changes were observed in the objective image quality analysis (SNR: p ≥ 0.125; CNR: p ≥ 0.086). However, presence of osteosynthesis significantly lowered the mean SNR and CNR (p < 0.001).
Even with lowest exposure settings, orthopedic extremity CBCT revealed good overall image quality. The best result regarding subjective image quality was achieved with 85-kV / 4.7 mAs with a dose reduction of 18,9% compared to the manufacturer's recommended protocol (90-kV and 5.0 mAs).
研究并优化不同曝光参数对最新一代骨科锥形束 CT 系统图像质量和辐射剂量的影响。
在掌骨桡侧插入桡骨远端板前后，对 110 例同一 cadaver 前臂进行连续扫描，以实现个体内的最佳可比性。所有扫描均在最新一代锥形束 CT 扫描仪（Carestream OnSight 3D 四肢系统，Carestream Health，罗彻斯特，NY，美国）上进行。使用不同的管电压（kV）和管电流-曝光时间乘积（mAs）组合进行四肢成像。记录辐射剂量（DLP 和 CTDI），以广泛变化的组合。主观和客观的图像质量分析包括由 5 位不同的读者进行的盲法评估，使用 5 分李克特量表进行评估。
使用制造商推荐的标准方案（90kV 和 5.0mAs，DLP 为 111.91mGycm，CTDI 为 4.49mGy）可获得最高的辐射剂量，而 70kV 和 2.0mAs 可将剂量降低最多，DLP 为 20.34mGycm，CTDI 为 0.79mGy。关于主观图像质量，较高的管电压可改善皮质骨（p≤0.038）和松质骨（p≤0.001）以及整体图像质量的显示（p≤0.027）。管电流-曝光时间乘积的变化并未显示图像质量的显著改变（p≥0.063）。在插入钢板后，只有主观整体图像质量的主观感知降低（p<0.001）。在不同的扫描方案之间，客观图像质量分析未见明显变化（SNR：p≥0.125；CNR：p≥0.086）。然而，存在骨合成术显著降低了平均 SNR 和 CNR（p<0.001）。
即使使用最低的曝光设置，骨科四肢 CBCT 也能获得良好的整体图像质量。主观图像质量的最佳结果是在 85kV/4.7mAs 下获得的，与制造商推荐的方案（90kV 和 5.0mAs）相比，剂量降低了 18.9%。
