Dublin Dental University Hospital, Trinity College Dublin, Dublin, Ireland.
Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
Dentomaxillofac Radiol. 2020 Oct 1;49(7):20200072. doi: 10.1259/dmfr.20200072. Epub 2020 Jun 22.
To identify a dose as low as diagnostically acceptable and a threshold level of image quality for cone beam CT (CBCT) imaging root canals, using maxillary first molar (M1M) second mesiobuccal (MB2) canals of varying complexity for two CBCT scanners.
Dose-area product (DAP) and contrast-to-noise ratio (CNR) were measured for two scanners at a range of exposure parameters. Subjective-image-quality assessment at the same exposures was performed for three M1Ms of varying MB2 complexity, positioned in an anthropomorphic phantom. Nine raters (three endodontists, three dental radiologists and three junior staff) assessed canal visibility, using a 5-point confidence scale rating.
Identification of simple-moderate MB2 canal complexity was achieved at a range of protocols, with DAP values of ≥209.3 and ≥203.2 mGy cm² and CNRs of 3 and 7.6 for Promax3D and Accuitomo-F170 respectively. For complex canal anatomy, target subjective image quality was not achieved, even at the highest DAP values for both scanners. Junior staff classified significantly more images as undiagnostic compared with senior staff ( = 0.043).
In this first study to address optimisation of CBCT imaging of root canal anatomy, a similar threshold dose for both scanners was identified for M1Ms with simple-moderate MB2 canal complexity. Increasing dose to enhance visualisation of more complex canal anatomy was ineffective. Selection of standard protocols (while avoiding lower kV/mA protocols) instead of high-resolution scans was a practical means of reducing patient dose. CNR is not a transferable measure of image quality.
使用两种锥形束 CT（CBCT）扫描仪，对上颌第一磨牙（M1M）第二近中颊（MB2）管的不同复杂性，确定一个可接受的诊断剂量和图像质量阈值。
在一系列曝光参数下，测量两种扫描仪的剂量面积乘积（DAP）和对比噪声比（CNR）。对三个具有不同 MB2 复杂性的 M1M 在仿体中进行相同曝光的主观图像质量评估，由九名评估者（三名牙髓病学家、三名牙科放射学家和三名初级工作人员）使用 5 分置信度评分评估根管可视性。
在一系列方案中，可以识别出简单到中度的 MB2 管复杂性，其 DAP 值分别为≥209.3 和≥203.2 mGy cm²，Promax3D 和 Accuitomo-F170 的 CNR 值分别为 3 和 7.6。对于复杂的管腔解剖结构，即使在两种扫描仪的最高 DAP 值下，也无法达到目标的主观图像质量。初级工作人员比高级工作人员（ = 0.043）分类出更多的不可诊断图像。
在这项首次针对根管解剖结构的 CBCT 成像优化的研究中，对上颌第一磨牙具有简单到中度 MB2 管腔复杂性的两种扫描仪确定了相似的阈值剂量。增加剂量以增强对更复杂的管腔解剖结构的可视化效果是无效的。选择标准方案（避免低千伏/毫安方案）而不是高分辨率扫描是降低患者剂量的一种实用方法。CNR 不是图像质量的可转移度量。
