Department of General and Specialized Dentistry, Section Oral and Maxillofacial Radiology, Academic Center for Dentistry Amsterdam (ACTA), Gustav Mahlerlaan 3004, 1081 LA Amsterdam, the Netherlands.
Dentomaxillofac Radiol. 2013;42(3):79884780. doi: 10.1259/dmfr/79884780. Epub 2012 Aug 29.
The aim of this study was to determine the grey value variation at the implant site with different scan settings, including field of view (FOV), spatial resolution, number of projections, exposure time and dose selections in two cone beam CT (CBCT) systems and to compare the results with those obtained from a multislice CT system.
A partially edentulous human mandibular cadaver was scanned by three CT modalities: multislice CT (MSCT) (Philips, Best, the Netherlands), and two CBCT systems: (Accuitomo 170(®), Morita, Japan) and (NewTom 5G(®), QR, Verona, Italy). Using different scan settings 36 and 24 scans were obtained from the Accuitomo and the NewTom, respectively. The scans were converted to digital imaging and communications in medicine 3 format. The analysis of the data was performed using 3Diagnosys(®) software (v. 3.1, 3diemme, Cantù, Italy) and Geomagic studio(®) 2012 (Morrisville, NC). On the MSCT scan, one probe designating the site for pre-operative implant placement was inserted. The inserted probe on MSCT was transformed to the same region on each CBCT scan using a volume-based three-dimensional registration algorithm. The mean voxel grey value of the region around the probe was derived separately for each CBCT. The influence of scanning parameters on the measured mean voxel grey values was assessed.
Grey values in both CBCT systems significantly deviated from Hounsfield unit values measured with MSCT (p = 0.0001). In both CBCT systems, scan FOV and spatial resolution selections had a statistically significant influence on grey value measurements (p = 0.0001). The number of projections selection had a statistically significant influence in the Accuitomo system (p = 0.0001) while exposure time and dose selections had no statistically significant influence on grey value measurements in the NewTom (p = 0.43 and p = 0.37, respectively).
Grey-level values from CBCT images are influenced by device and scanning settings.
本研究旨在确定不同扫描设置（包括视野[FOV]、空间分辨率、投影数量、曝光时间和剂量选择）下种植体部位的灰度值变化，并将结果与多层 CT 系统（MSCT）的结果进行比较。
对一具下颌骨部分缺失的人体尸体进行三种 CT 模式扫描：MSCT（荷兰飞利浦 Best 公司）和两种 CBCT 系统：Accuitomo 170（®）（日本 Morita 公司）和 NewTom 5G（®）（意大利 Verona QR 公司）。Accuitomo 分别获得 36 次和 24 次扫描，NewTom 获得 24 次扫描。扫描结果转换为数字成像和通信 3 格式。使用 3Diagnosys（®）软件（v. 3.1，3diemme，Cantù，意大利）和 Geomagic studio（®）2012（美国北卡罗来纳州 Morrisville）对数据进行分析。在 MSCT 扫描中，插入一个指定术前种植体放置位置的探头。将 MSCT 上插入的探头通过基于体积的三维配准算法转换到每个 CBCT 扫描的相同区域。分别为每个 CBCT 计算探头周围区域的平均体素灰度值。评估扫描参数对测量平均体素灰度值的影响。
两种 CBCT 系统的灰度值均明显偏离 MSCT 测量的 Hounsfield 单位值（p=0.0001）。在两种 CBCT 系统中，扫描视野和空间分辨率选择对灰度值测量有统计学显著影响（p=0.0001）。Accuitomo 系统中，投影数量选择对灰度值测量有统计学显著影响（p=0.0001），而 NewTom 系统中，曝光时间和剂量选择对灰度值测量无统计学显著影响（p=0.43 和 p=0.37）。
CBCT 图像的灰度值受设备和扫描设置的影响。
