计算机辅助的牙槽骨密度定量测量系统准确性和灵敏度的研究

目的建立计算机辅助的牙槽骨密度定量测量系统,并通过样本测试检验系统的测量准确性及灵敏度,实现对牙槽骨中羟磷灰石（HP）含量的估测。方法在X线骨密度测量法基础上利用定位投照的直接数字化牙片,以铝梯为参照校正投照条件差异导致的影像灰度误差,辅以计算机技术建立牙槽骨密度定量测量系统。用该系统测量HP含量不同的19个样本的平均灰度值,根据已知的铝梯灰度和厚度推算这些灰度值对应的等效铝厚度和校正灰度。建立等效铝厚度、校正灰度与HP含量之间的一元线性回归方程,将等效铝厚度、校正灰度回代入方程计算出估测的HP含量;与HP的实际含量相比,计算估测的偏误率。随机选择2个样本重复测量10次,计算牙槽骨密度定量测量系统的测量误差范围,结合回归方程,计算该系统检测HP含量变化的灵敏度。结果等效铝厚度、校正灰度与HP含量之间有明显相关性;当测得的等效铝厚度大于0.67 mm或校正灰度大于41个灰阶时,对HP含量估测的偏误率在5%以下。用等效铝厚度进行估测时,HP含量的变化大于0.17 mg/mm2即可被有效检出;用校正灰度进行估测时,HP含量的变化大于0.18 mg/mm2即可被有效检出。结论本研究牙槽骨密度定量测量系统的准确性和灵敏度能够满足临床和科研的需要,可用于对牙槽骨密度的横向比较和纵向观察,有较广阔的应用空间。     

锥形束CT辅助诊断慢性牙周炎牙槽骨缺损的准确性研究

目的 评价锥形束CT在辅助诊断慢性牙周炎牙槽骨缺损中的准确性及其与根尖X线片、曲面体层X线片和临床检查结果的一致性,以期为锥形束CT在辅助诊断慢性牙周炎骨缺损中的应用提供依据.方法 采用单纯随机抽样法纳入2012年12月至2013年12月就诊于西安交通大学医学院附属口腔医院牙周黏膜科并确诊为慢性牙周炎的患者75例,分别进行锥形束CT、根尖X线片及曲面体层X线片检查,用华海MedViewer及EzlmPlant软件测量牙槽骨缺损的高度,同时行全口牙周探诊检查,确定附着丧失水平及釉质牙骨质界至牙槽嵴顶的距离,作为影像学检查结果的临床评判指标.对临床测量值及锥形束CT测量牙槽骨的缺损值行配对t检验,采用单因素方差分析评价4种方法检测近远中牙槽骨缺损的结果,以P＜0.05为差异有统计学意义.结果 共纳入1 494颗牙,8 964个位点,3种影像学方法中仅锥形束CT可以检测出唇(颊)或舌(腭)侧牙槽骨破坏;对近远中向牙槽骨缺损的测量结果显示,锥形束CT[近中:(5.5±0.4)mm,远中:(5.6±0.8)mm]与根尖X线片[近中:(5.1±0.6)mm,远中:(5.1±0.8)mm]、锥形束CT与全口曲面体层X线片[近中:(4.9±0.4)mm,远中:(4.9±0.8)mm]的测量结果相比差异均有统计学意义(P值均＜0.01),临床探诊[近中:(5.5±0.6)mm,远中:(5.5±0.6)mm]与根尖X线片及全口曲面体层X线片相比差异亦有统计学意义(P值均＜0.01),但临床探诊与锥形束CT的测量结果相比差异无统计学意义;锥形束CT与临床探诊对不同区域1 494颗牙齿牙槽骨缺损差异的检出情况一致,两种方法检测不同区域牙齿及1 494颗牙不同位点的牙槽骨缺损差异均无统计学意义(P值均＞0.05),两种方法不存在牙位及位点差异性.结论 锥形束CT与临床探诊在评价不同牙位及不同位点的牙槽骨缺损中一致性最高;锥形束CT在判断慢性牙周炎骨缺损方面与临床检查结果具有较高的一致性,优于根尖X线片和曲面体层X线片.     

CBCT在慢性牙周炎诊断中的应用

目的研究锥形束CT在慢性牙周炎诊断中的应用。方法拍摄30例慢性牙周炎患者锥形束CT片和曲面断层片,观察796颗牙近远中、及颊(唇)、舌侧牙槽骨吸收情况。并通过锥形束CT对其中60颗单根牙近、远中和颊(唇)、舌侧8个位点的牙槽骨吸收情况进行测量取均值,与曲面断层片测量得的近、远中牙槽骨吸收均值进行比较。结果锥形束CT片和曲面断层片均可明确显示近、远中牙槽骨吸收情况,两者之间比较差异无统计学意义(P>0.05)。锥形束CT测得牙齿近、远中牙槽骨吸收的均值与曲面断层片测得的均值比较,差异有统计学意义(P<0.05)。锥形束CT在判断颊(唇)、舌侧骨吸收及根分叉病变方面,明显优于曲面断层片。结论锥形束CT比曲面断层片对慢性牙周炎牙槽骨吸收的诊断更加准确。     

种植体周围炎治疗前后牙槽骨的锥形束CT评价

目的 应用锥形束CT评价种植体周围炎治疗前后牙槽骨状态.方法 选择行种植修复完成后并发种植体周围炎患者12例.于种植体周围炎常规治疗前后行锥形束CT检查,测量牙槽骨密度和牙槽骨高度,利用SPSS 16.0软件对所测数据进行t检验,分析牙槽骨高度与密度的改变,并分析观察者内部和观察者之间测量值的可信度.结果 种植体周围炎...     

上颌磨牙区种植体周围骨密度CT测量值与其稳定性的相关分析

目的:探讨基于锥形束CT (CBCT)的上颌磨牙种植体周围骨密度的CT测量灰度值,与牙种植术后稳定性(ISQ)之间的关系。方法:按条件筛选接受上颌磨牙区牙种植修复患者33例,术前通过预种植位置CBCT扫描,并利用CT重建软件模拟测量预种植体周围骨密度灰度值,以亨氏单位(Hounsfield units, HU)表示。随后根据软件模拟种植体方位制作种植导板,于相应预种植区植入ITI种植体48枚,并分别于术后即刻、术后3个月使用共振频率分析(resonance frequency analysis,RFA)仪器分别测量和记录种植体的稳定系数(implant stability quotient,ISQ)。运用SPSS软件对实验数据进行统计学分析。结果:33例患者上颌磨牙种植体周围骨密度灰度值均值为(439.8±101.7) HU;术后即刻ISQ均值为(58.6±7.6) HU,术后3个月ISQ均值为(66.1±7.7) HU,二者差异有统计学意义(P<0.01)。上颌磨牙种植体周围骨密度HU值分别与术后即刻稳定系数ISQ、3个月后稳定系数ISQ均呈正相关性,其中与前者呈弱相关(r=0.33),与后者呈强相关(r=0.63)。结论:在上颌磨牙区,根据种植区域骨密度的CT测量值,对该区域牙种植体预后判断具有一定的临床指导意义。     

不同分割阈值重建锥形束CT数字化牙模型的精度研究

目的: 比较不同分割阈值对锥形束CT（CBCT）重建数字化牙模型测量精度的影响。方法: 选取20例需拔除智牙患者的CBCT,应用Mimics软件,根据不同灰度值（grey value,GV）进行阈值分割后,重建三维数字化模型。所有患者均取硅橡胶印模,灌制石膏模型。分别测量数字化模型和石膏模型上、下颌全牙列牙的近远中径。采用SPSS 16.0软件包中的配对t 检验、散点图和组内相关系数（intraclass correlation coefficient,ICC）,评估不同分割阈值对重建的CBCT数字化模型测量精度的影响。结果: 不同分割阈值重建的CBCT数字化牙模型与石膏模型测量项目之间均数的差范围为-0.36~0.32 mm。以GV 1200、1400阈值分割后,重建的数字化模型测量值与石膏模型测量值无统计学差异（P>0.01）,其余阈值重建的数字化模型测量值与石膏模型有统计学差异（P<0.01）。CBCT重建数字化模型与石膏模型的测量值ICC均>0.95,其中,GV1200阈值重建的数字化模型ICC最高,为0.995。结论: 不同分割阈值对CBCT重建数字化牙模型的精度有一定影响,对不同结构的侧重也不同,临床上应加以选择调整。     

根管封闭剂和锥形束CT拍摄参数对牙根纵裂诊断的影响

目的 研究根管封闭剂和锥形束CT(CBCT)拍摄参数对牙根纵裂(vertical root fractures,VRF)诊断的影响。方法 收集人前磨牙40颗,去冠,随机均分为4组:iRoot SP、AH Plus、载银锌介孔钙硅纳米粒子(Ag-Zn-MCSNs)和对照组。根管充填后制备VRF模型,然后将牙根置入人上颌前磨牙牙槽窝内,拍摄CBCT,视野(field of view,FOV)和体素分别为:12 cm×8 cm、0.30 mm;12 cm×8 cm、0.15 mm;8 cm×8 cm、0.15 mm;8 cm×8 cm、0.30 mm。由2名观察者对CBCT图像进行判读。结果 各实验组之间的准确性均无统计学差异(P＞0.05)。医师正确诊断根纵裂的部位均是在轴面冠1/3区。结论 不同根管封闭剂和CBCT拍摄参数诊断VRF的准确性无显著影响,建议应用CBCT诊断根充牙齿的VRF时,在满足诊断需求的前提下,选择较小FOV及较大的体素,以尽量降低辐射剂量。     

锥形束CT数字化牙颌模型线性测量的可重复性及精确性研究

目的:本研究目的是探讨锥形束CT数字化牙颌模型线性测量的可重复性及精确性。方法:随机选取17名治疗前的正畸患者分别拍摄CBCT及制取印模。4名测量员分别对CBCT数字化牙颌模型和石膏牙颌模型进行36个指标的测定,每位测量员对每一个指标的测量重复10次。以石膏牙颌模型为标准,应用组内相关系数(ICC)及配对t检验评价CBCT数字化牙颌模型测量的可重复性及精确性。结果:CBCT数字化牙颌模型所有测量项目ICC均高于0.75。CBCT数字化牙颌模型与石膏牙颌模型测量项目之间,均数的差范围是-0.42~0.84mm,其中22项测量项目之间,均数的差异有统计学意义。结论:CBCT数字化牙颌模型测量的可重复性与石膏牙颌模型相当,但在本研究所设定的拍摄条件下,CBCT数字化牙颌模型的测量的精确性不如后者。     

两种影像学方法对颌骨后部牙槽骨高度测量结果的对比分析

目的:对比曲面体层片和锥形束CT在测量上、下颌后部可用牙槽骨高度上的差异,分析曲面体层片的误差,为临床提供参考。方法:以62例第一磨牙缺失病例为研究样本,包括28例下颌牙列缺损、22例上颌牙列缺损和12例双颌牙列缺损病例。所有病例均拍摄曲面体层片(放置5mm直径钢球)和锥形束CT。将曲面体层片数据导入图像处理软件,测量第一磨牙拟植入种植体部位(缺牙间隙的中点或者近中邻牙远中5mm位置)牙槽嵴顶至下齿槽神经管上缘或上颌窦底最低点的距离,以钢球直径计算放大率并得到校正后的可用牙槽骨高度。对于锥形束CT图像,则是在配套软件界面下,确定拟植入种植体的三维位置,并测量该位置到上述参考点的距离。两组测量结果均输入SPSS软件,以T检验分析两种测量方法的差异。结果:共测量下颌病例40例,曲面体层片和锥形束CT测量所得平均距离分别为(14.6±3.4)mm和(13.7±2.8)mm,差异有统计学意义(P<0.05)。上颌34例,曲面体层片和锥形束CT测量所得平均距离分别为(11.8±2.5)mm和(12.1±1.4)mm,差异无统计学意义。结论:通过对比,发现在对下颌可用牙槽骨高度进行测量时,曲面体层片存在高估可能,在临床中,应增加种植体与下齿槽神经管的安全距离。     

广东地区60名正常青年Monson球面半径的锥形束CT测量

目的应用锥形束CT测量分析广东地区正常青年Monson球面半径,探讨个性化测量Monson球面半径的方法,为口腔临床咬合重建提供参考。方法采用单纯随机抽样法从广州医科大学附属口腔医院体检人群中招募60名广东地区正常青年志愿者[男性30名,女性30名,年龄(22.1±2.0)岁(18~26岁)],于广州医科大学附属口腔医院放射科行锥形束CT扫描,对锥形束CT数据行三维重建,对重建后模型进行定点、描图和测量,采用单样本t检验比较男性和女性Monson球面半径的差异。结果60名正常青年Monson球面半径为(100.72±4.89)mm,男性和女性Monson球面半径分别为(103.48±4.19)和(97.97±3.93)mm,男女差异有统计学意义(P<0.01)。结论采用锥形束CT可准确测量Monson球面半径,结果可为平面重建提供参考。     

Conventional Multi‐Slice Computed Tomography (CT) and Cone‐Beam CT (CBCT) for Computer‐Assisted Implant Placement. Part I: Relationship of Radiographic Gray Density and Implant Stability

Purpose: The relationship of conventional multi‐slice computed tomography (CT)‐ and cone beam CT (CBCT)‐based gray density values and the primary stability parameters of implants that were placed by stereolithographic surgical guides were analyzed in this study. Materials and Methods: Eighteen edentulous jaws were randomly scanned by a CT (CT group) or a CBCT scanner (CBCT group) and radiographic gray density was measured from the planned implants. A total of 108 implants were placed, and primary stability parameters were measured by insertion torque value (ITV) and resonance frequency analysis (RFA). Radiographic and subjective bone quality classification (BQC) was also classified. Results were analyzed by correlation tests and multiple regressions (p < .05). Results: CBCT‐based gray density values (765 ± 97.32 voxel value) outside the implants were significantly higher than those of CT‐based values (668.4 ± 110 Hounsfield unit, p < .001). Significant relations were found among the gray density values outside the implants, ITV (adjusted r² = 0.6142, p = .001 and adjusted r² = 0.5166, p = .0021), and RFA (adjusted r² = 0.5642, p = .0017 and adjusted r² = 0.5423, p = .0031 for CT and CBCT groups, respectively). Data from radiographic and subjective BQC were also in agreement. Conclusions: Similar to the gray density values of CT, that of CBCT could also be predictive for the subjective BQC and primary implant stability. Results should be confirmed on different CBCT scanners.     

口腔常用修复材料的 CBCT 影像灰度值差异的探索

目的：探索口腔常用修复材料在 CBCT 影像中的灰度值的差异规律。方法：采用 CBCT 扫描36种口腔常用修复材料立方体,Mimics 软件读取断层影像灰度值的方法。结果：探索到了36种口腔常用修复材料在 CBCT 影像中灰度值间的差异规律,即灰度值不仅在不同类材料间有大的差异,在同类不同品型材料间亦有较大的差别。结论：口腔常用修复材料在 CBCT 影像中的灰度值差异规律,提供了建立三维数字模型时选取材料和材料组合的客观依据。     

The usefulness of cone-beam computed tomography gray values for alveolar bone linear measurements

Objectives:To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values.Materials and Methods:Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value–assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards).Results:The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017).Conclusions:These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.     

Reliability of voxel values from cone‐beam computed tomography for dental use in evaluating bone mineral density

Objectives: The aim of this study was to investigate whether it was possible to evaluate bone mineral density (BMD) using voxel values from cone‐beam CT (CBCT) for dental use. Materials and methods: A water phantom with an aluminum rod and sample tubes containing iodine solutions of various concentration was imaged by CBCT and multi‐slice CT (MSCT). Voxel values and CT numbers, respectively, of the samples were measured and their correlation was investigated. In addition, based on the CT numbers of a hydroxyapatite (HA) reference phantom, a conversion formula from voxel value to BMD was obtained. Results: There was a positive correlation between the voxel values of CBCT and the iodine concentration of the solutions, regardless of the X‐ray dose or the mean energy, although the voxel values had a slight tendency to be saturated at higher iodine concentrations. An excellent correlation between the voxel values and CT numbers was also observed. A regression analysis showed that nonlinear (linear‐quadratic model) regression was more appropriate than linear regression fitting for plotting these two values, although the latter might be usable for clinical applications. The conversion formula from the voxel value of CBCT to the equivalent BMD was as follows: y=?0.03669x²+3.602x?350.3 (x: voxel value, y: BMD mg/cm³ HA). Conclusions: This study revealed that there was a high correlation between the voxel values of CBCT and the CT numbers of MSCT. Although this was an in vitro study with assumed ideal conditions for measuring voxel values, there was a clear possibility for estimating CT numbers and BMD using the voxel values from the CBCT images, but the relationship was not entirely linear and should be examined further. To cite this article:
Nomura Y, Watanabe H, Honda E, Kurabayashi T. Reliability of voxel values from cone‐beam computed tomography for dental use in evaluating bone mineral density.
Clin Oral Impl Res. 21 , 2010; 558–562.
doi: 10.1111/j.1600‐0501.2009.01896.x     

Comparative study of the accuracy of CBCT implant site measurements using different software programs

PurposeTo measure and compare the accuracy of the linear dimensions of implant sites recorded from cone beam computed tomography (CBCT) images using Blue Sky Plan, coDiagnostiX, and RadiAnt.Materials and MethodsFive human dry skulls were imaged with a CBCT device then sectioned to obtain sample transverse cross-sections of the edentulous ridges, and the height and width of the ridge were measured with a digital caliper to provide the gold standard measurements. The CBCT datasets were exported in DICOM format and imported into the three test software programs which were used to obtain reformatted sectional images corresponding to the sample transverse cross-sections, and the height and width of the edentulous ridge was recorded using the linear measurement tool. Reliability of the measurements were measured using the intraclass correlation coefficient. One-sample t-test (test value: zero) was used to test the statistical significance of the mean of the absolute errors for each software program. Analysis of Variance with Repeated Measures was used to test the statistical significance of the difference between the means of the absolute errors obtained by the different software programs. Statistical significance was set at a p-value of 0.05.ResultsThe reliability of the gold standard and image measurements were excellent. All three software programs demonstrated a statistically significant mean absolute measurement error of between 0.43 and 0.56 mm (p-value < 0.01), but no significant difference in error values was found between any of the tested programs (p- value = 0.18).ConclusionsThere was no statistically significant difference in accuracy of linear CBCT measurements of implant sites recorded using Blue Sky Plan, coDiagnostiX, and RadiAnt.     

Bone quality assessment based on cone beam computed tomography imaging

Objectives: The aim of this in vitro study was to investigate the accuracy of fractal analysis and morphometry for bone quality assessment as measured with dual energy X-ray absorptiometry (DXA).
Material and methods: Nineteen mandibular bone samples were used for the creation of artificial bone lesions ( n =5) or decalcification ( n =12) to simulate osteoporosis; two samples were used as controls. Cone beam computed tomography (CBCT) and DXA scans were made before and after processing the samples. The image data obtained from the CBCT scans were used to calculate the mean fractal dimension (FD), bone area and density (morphometric analysis) of the samples. Bone mineral density (BMD) was obtained from the DXA scans and set as a reference value for bone quality. The correlation between BMD and FD and between BMD and morphometric results were calculated.
Results: A significant correlation between FD and BMD (ρ=+0.71 to +0.75; P <0.05) was observed. Bone area and BMD of the specimens (ρ=+0.69 to +0.85; P <0.05) were also significantly related, in contrast to the density analysis, for which no significant correlation to BMD was found.
Conclusions: The results of this study suggest that fractal analysis and bone area measurement have potential to evaluate bone quality on CBCT images, while density measurement does not seem to be valid.     

锥束CT数字化模型与石膏模型在牙颌测量中的对比研究

目的:确定利用锥束CT(CBCT)数字化牙颌模型测量得到的数据与石膏模型测量数据是否具有一致性。方法:对23例患者的锥束CT数字化模型和石膏模型进行配对研究。使用NNTViewer软件分析由NewTom VGi锥束CT扫描仪所形成的三维牙颌模型,同时制取超硬石膏模型。由测量人员分别对2种模型进行Little指数、前牙覆覆盖、Bolton指数、HOWES指数等线性数据重复测量,对比分析测量结果。结果:所有的测量数据呈正态分布。配对t检验表明用于测量上颌骨和下颌骨的牙性指标差异均无显著性。在上下颌骨骨性结构的测量中2种模型之间的差异具有统计学意义。结论:CBCT的数字模型和石膏模型在牙性线性测量具有一致性,在骨性结构测量数据相对石膏模型具有更好的可重复性与精确性。     

Influence of object location in cone beam computed tomography (NewTom 5G and 3D Accuitomo 170) on gray value measurements at an implant site

Objectives

The aim of this study was to determine the gray value variation at an implant site with different object location within the selected field of view (FOV) in two cone beam computed tomography (CBCT) scanners.

Methods

A 1-cm-thick section from the edentulous region of a dry human mandible was scanned by two CBCT scanners: 3D Accuitomo 170 (J. Morita, Kyoto, Japan) and NewTom 5G (QR Verona, Verona, Italy). Five FOVs were used with each CBCT scanner. Within each FOV, the specimen was located at different positions. The scans were converted to DICOM format. Data analysis was performed using 3Diagnosys (ver. 3.1, 3DIEMME, Cantu, Italy) and Geomagic software (Studio 2012, Morrisville, NC). On one of the scans, a probe designating the site for pre-operative implant placement was selected. The inserted virtual implant was transformed on the same region on each CBCT scan by a three-dimensional registration algorithm. The mean voxel gray value of the region around the probe was derived separately from all CBCT scans. The influence of object location within each FOV on variability of voxel gray values was assessed.

Results

In both CBCT systems, object location had a significant influence on gray value measurements (F _4,16 = 3.71, p = 0.0255 for Accuitomo and F _4,16 = 9.31, p = 0.0000 for NewTom).

Conclusions

Gray level values from CBCT images are influenced by object location within the FOV.