Department of Oral and Maxillofacial Radiology, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Department of Dental and Maxillofacial Radiodiagnostics, Medical University of Lublin, Lublin, Poland.
Head Face Med. 2022 Jun 29;18(1):20. doi: 10.1186/s13005-022-00326-1.
Artifacts fault image quality but handling several factors can affect it. This study was conducted to investigate the effect of object size on artifacts in cone-beam computed tomography systems.
Five phantoms, each containing a titanium implant in a sheep bone block, were fabricated of various sizes ranging from XS to XL: The M phantom was the same size as the device's field of view (FOV). The L and XL phantoms were 20 and 40% larger than the FOV while the S and XS phantoms were 20 and 40% smaller than FOV, respectively. Ballistic gelatin was used to fill the phantoms. Phantoms were scanned by NewTom VGI and HDXWill Q-FACE. The mean and standard deviation (SD) of gray values in each 120 ROI was obtained by OnDemand software. The contrast to noise ratio (CNR) was also calculated.
The gray value in S and M phantoms were more homogenous. The lowest SD value (10.20) was found in S phantom. The highest value for SD (125.16) was observed in XL phantom. The lowest (4.47) and highest (9.92) CNR were obtained in XL and S phantoms, respectively. HDXWill Q-FACE recorded a higher SD and a lower CNR than NewTom VGI (P < 0.05).
Object dimensions of the FOV size or up to 20% smaller provided better image quality. Since the dimensions of soft tissue in most patients are larger than the selective FOV, it is recommended that in CBCT artifacts studies, an object with dimensions closer to the patient's dimensions be used to better relate the results with the clinical condition, because the sample dimensions affect the amount of artifacts.
伪影会影响图像质量，但可以通过处理多个因素来减少伪影。本研究旨在探讨体素大小对锥形束 CT 系统伪影的影响。
制作了五个包含钛植入物的羊骨块的体模，大小分别为 XS 到 XL：M 体模与设备视野（FOV）相同。L 和 XL 体模比 FOV 大 20%和 40%，而 S 和 XS 体模比 FOV 小 20%和 40%。使用弹道凝胶填充体模。体模由 NewTom VGI 和 HDXWill Q-FACE 进行扫描。通过 OnDemand 软件获得每个 120 ROI 的灰度值均值和标准差（SD）。还计算了对比噪声比（CNR）。
S 和 M 体模的灰度值更均匀。S 体模的 SD 值最低（10.20）。XL 体模的 SD 值最高（125.16）。XL 和 S 体模的 CNR 分别为最低（4.47）和最高（9.92）。HDXWill Q-FACE 记录的 SD 值较高，CNR 较低，与 NewTom VGI 相比差异有统计学意义（P<0.05）。
FOV 尺寸或小 20%以内的物体尺寸提供了更好的图像质量。由于大多数患者的软组织尺寸大于选择性 FOV，因此建议在 CBCT 伪影研究中使用更接近患者尺寸的物体，以便更好地将结果与临床情况联系起来，因为样本尺寸会影响伪影的数量。
