锥形束CT扫描时间对阻生第三磨牙临床诊断及空间分辨率的影响

胡随馨; 徐晨; 师占平; 徐萍; 田瑜; 王家柱; 王懿; 张海钟

doi:10.3969/j.issn.2095-5227.2021.04.008

锥形束CT扫描时间对阻生第三磨牙临床诊断及空间分辨率的影响

Associations between cone-beam CT scanning time with the clinical diagnosis and spatial resolution of impacted third molars

摘要

摘要:
背景锥形束CT(cone-beam CT，CBCT)在临床诊断中的广泛应用给口腔科医生和患者带来了极大便利，但相比传统X线检查，其累积辐射量增加，引起了科研工作者的高度重视。
目的研究CBCT扫描时间对阻生第三磨牙临床诊断及空间分辨率的影响。
方法收集2020年12月因阻生齿拔除需求来解放军总医院第一医学中心就诊的22～36岁患者30例，采用NewTom 5G的18 s eco(扫描时间2.4 s)、24 s Enhanced(标准模式，扫描时间4.8 s)两种模式拍摄CBCT，以右侧下颌第三磨牙(48)距下颌神经管最近的牙根根尖与下牙槽神经管的垂直距离(n=30)及右侧上颌第三磨牙(18)距上颌窦窦底最近的牙根根尖与上颌窦底的垂直距离(n=20)为测量指标，比较两种模式的准确性、患者所受辐射剂量及空间分辨率。另采用CatPhan 600模体的CTP528模块，仅改变扫描时间，测量NewTom 5G的空间分辨率及模体所受辐射量。
结果两种模式右侧下颌第三磨牙距下颌神经管最近的牙根根尖与下牙槽神经管的垂直距离(P=0.738)及两组右侧上颌第三磨牙距离上颌窦窦底最近的牙根根尖距上颌窦底的垂直距离(P=0.260)差异均无统计学意义。18 s eco模式的辐射量(DLP_1，CTDIvol₁)是24 s Enhanced模式(DLP₂，CTDIvol₂)的一半DLP₁ vs DLP₂：(24.78±4.86) mGy·cm vs (50.34±10.08) mGy·cm；CTDIvol₁ vs CTDIvol₂：(2.75±0.54) mGy vs (5.56±1.16) mGy。P均＜0.001。
结论 18 s eco模式和24 s Enhanced模式均能满足临床诊断需求，前者辐射量约为后者的一半，在不影响临床诊断的前提下对于阻生第三磨牙可使用18 s eco模式拍摄CBCT，以减少扫描时间及患者所受辐射量。

Abstract:
Background The wide application of cone-beam CT (CBCT) in clinical diagnosis has brought great convenience to dental doctors and patients, and compared with traditional X-ray films, the increase in cumulative radiation dose has attracted the attention of researchers.
Objective To investigate the effect of different CBCT scanning times on the clinical diagnosis and spatial resolution of impacted third molars.
Methods A total of 30 patients, aged 22-36 years, admitted to our hospital in December 2020 for the removal of impacted teeth were enrolled. NewTom 5G was used for CBCT in two modes, i.e., 18 s eco (scanning time: 2.4 s) and 24 s Enhanced (standard mode; scanning time: 4.8 s), and the two modes were compared in terms of accuracy, radiation dose, and spatial resolution based on the measurement standard of the vertical distance between the nearest root apex of the right mandibular third molar (48) to the mandibular nerve canal and the inferior alveolar nerve canal (n=30) and the vertical distance between the nearest root apex of the right maxillary third molar (18) to the bottom of the maxillary sinus and the bottom of the maxillary sinus (n=20). By changing the scanning time, the CTP528 module of CatPhan 600 phantom was used to measure the spatial resolution of NewTom 5G and the radiation dose received by the module.
Results There were no significant differences between the two modes in the vertical distance between the nearest root apex of the right mandibular third molar to the mandibular nerve canal and the inferior alveolar nerve canal (D1 and D2) (P=0.738) and the vertical distance between the nearest root apex of the right maxillary third molar to the bottom of the maxillary sinus and the bottom of the maxillary sinus (D3 and D4) (P=0.260). The radiation dose of 24 s Enhanced (DLP₂, CTDIvol₂) was twice of 18 s eco (DLP₁, CTDIvol₁)(DLP₁ vs DLP₂: 24.78 ± 4.86 mGy·cm vs 50.34 ± 10.08 mGy·cm; CTDIvol₁ vs CTDIvol₂: 2.75 ± 0.54 mGy vs 5.56 ± 1.16 mGy; P＜0.001, respectively).
Conclusion Both the 18 s eco mode and the 24 s Enhanced standard mode can meet the requirements of clinical diagnosis, and the radiation dose of the former is about half of that of the later. The 18 s eco mode can be used in CBCT to help accurate diagnosing impacted third molars, so as to reduce scanning time and radiation exposure to patients.

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