Int J Oral Maxillofac Implants. 2021 Mar-Apr;36(2):307-312. doi: 10.11607/jomi.8773.
To evaluate the influence of low-dose protocols, with different numbers of basis images, on the precision of linear bone measurements in CBCT images.
Five polyurethane mandibles, with different levels of bone resorption, were used in this in vitro study. To obtain the reference standard, landmarks were made in the mandibular superior and buccal cortices, and then a digital caliper was used to measure the bone height and thickness at these regions. CBCT images were obtained with the PaX-i3D (Vatech) unit set at 50 kV, 4 mA, 0.2-mm voxel size and 50 × 50-mm field of view. Keeping these parameters fixed, each mandible was scanned twice, with different protocols: Low dose (L) had an acquisition time of 24 seconds and 720 basis images, and ultralow dose (UL) had an acquisition time of 15 seconds and 450 basis images. Then, measurements of bone height and thickness were performed on the images, using the previously determined landmarks as reference. The obtained data were submitted to statistical analysis, with a significance level of .05. Analysis of variance, Student t test, and intraclass correlation coefficient were employed.
Regarding bone height, there were no significant differences between the measurements obtained with the L and UL protocols (P = .8648). Additionally, the L and UL protocols did not differ in relation to the reference standard (P = .8717 and P = .9928, respectively). Likewise, there were no significant differences between the measurements obtained with the L and UL protocols (P = .7969) for bone thickness, nor between these protocols and the gold standard (P = .7455).
Considering the great demand for precise measurements in implantology, protocols of low-dose radiation can be used without compromising clinical planning.
评估不同基图像数量的低剂量方案对 CBCT 图像中线性骨测量精度的影响。
本体外研究使用了五具具有不同程度骨质吸收的聚氨酯下颌骨。为了获得参考标准，在下颌骨的上皮质和颊皮质制作了标志点，然后使用数字卡尺测量这些区域的骨高度和厚度。使用 PaX-i3D（Vatech）单位以 50 kV、4 mA、0.2-mm 体素大小和 50×50-mm 视野获得 CBCT 图像。保持这些参数不变，每个下颌骨用两种不同的方案扫描两次：低剂量（L）的采集时间为 24 秒，有 720 个基图像；超低剂量（UL）的采集时间为 15 秒，有 450 个基图像。然后，使用之前确定的标志点作为参考，在图像上进行骨高度和厚度的测量。将获得的数据进行统计分析，显著性水平为.05。采用方差分析、学生 t 检验和组内相关系数进行分析。
在骨高度方面，L 和 UL 方案获得的测量值之间没有显著差异（P =.8648）。此外，L 和 UL 方案与参考标准之间也没有差异（分别为 P =.8717 和 P =.9928）。同样，L 和 UL 方案获得的骨厚度测量值之间没有显著差异（P =.7969），与金标准之间也没有差异（P =.7455）。
鉴于在种植体中对精确测量的巨大需求，可以使用低剂量辐射方案而不会影响临床规划。
