Effects of Irregular Respiratory Motion on the Positioning Accuracy of Moving Target with Free Breathing Cone-Beam Computerized Tomography

For positioning a moving target, a maximum intensity projection (MIP) or average intensity projection (AIP) image derived from 4DCT is often used as the reference image which is matched to free breathing cone-beam CT (FBCBCT) before treatment. This method can be highly accurate if the respiratory motion of the patient is stable. However, a patient’s breathing pattern is often irregular. The purpose of this study is to investigate the effects of irregular respiration on positioning accuracy for a moving target aligned with FBCBCT. Nine patients’ respiratory motion curves were selected to drive a Quasar motion phantom with one embedded cubic and two spherical targets. A 4DCT of the phantom was acquired on a CT scanner (Philips Brilliance 16) equipped with a Varian RPM system. The phase binned 4DCT images and the corresponding MIP and AIP images were transferred into Eclipse for analysis. FBCBCTs of the phantom driven by the same respiratory curves were also acquired on a Varian TrueBeam and fused such that both CBCT and MIP/AIP images share the same target zero positions. The sphere and cube volumes and centroid differences (alignment error) determined by MIP, AIP and FBCBCT images were calculated, respectively. Compared to the volume determined by MIP, the volumes of the cube, large sphere, and small sphere in AIP and FBCBCT images were smaller. The alignment errors for the cube, large sphere and small sphere with center to center matches between MIP and FBCBCT were 2.5 ± 1.8 mm, 2.4 ± 2.1 mm, and 3.8 ± 2.8 mm, and the alignment errors between AIP and FBCBCT were 0.5 ± 1.1 mm, 0.3 ± 0.8 mm, and 1.8 ± 2.0 mm, respectively. AIP images appear to be superior reference images to MIP images. However, irregular respiratory pattern could compromise the positioning accuracy, especially for smaller targets.

Knowledge and Practices of Dentists, Oral and Maxillofacial Surgeons of Cone Beam Computed Tomography (CBCT) and the Dentascanner in a Low Income Country: Case of Togo

Background: In dental-maxillofacial imaging, 3D sectional imaging progressively replaces conventional 2D imaging in developed countries. They are based specially on Computed tomography (CT-Scan), with the Dentascan application and cone beam computed tomography (CBCT). In developing countries those technics are newly introduced. Aim: This study aimed at studying the knowledge and practices of dentist and oral and maxillofacial surgeons on sectional imaging such as Dentascan and Cone Beam Computed Tomography (CBCT). Materials and Methods: We conducted an anonymous survey among dentists and oral maxillofacial surgeons in Togo over one month. Results: The response rate was 78.79% (27/33). They were mainly male sex (sex ratio of 2.25 men for one woman). They were aged between 27 and 71 years old with an average of 49.69 years old. The majority (61.54%) had a professional experience over 20 years. The majority of respondents (65.38%) believed their level of knowledge about dental x-Ray was poor. Half of them (50%) confirmed that they had never asked for a Dentascan, and 15.38% asked from time to time for it and only two (7.69%) asked often for this test. 96.15% confirm they have no knowledge of the Dentascan. Regarding the CBCT, 84.62% didn’t ask for it because this technique did not exist in Togo before. 69.20% of respondents confessed to be interested in continuing training on sectional imaging. Conclusion: This study shows that sectional imaging is very little used by oral and dental practitioners in Togo because of the ignorance of the new techniques and the absence of the CBCT. It is therefore necessary to promote the teaching of the new technique of sectional imaging in the training syllabus of oral and dental specialists and to initiate continuing medical training.

Cone beam computed tomographic analyses of alveolar bone anatomy at the maxillary anterior region in Chinese adults

To provide an anatomical basis for clinical implant esthetics,we evaluated the morphology of the nasopalatine canal（NPC） and analyzed labial and interproximal bone anatomy at the maxillary anterior region.We sought to investigate the effect of maxillary protrusion and tooth labiolingual inclination on labial bone anatomy in Chinese adults.Three dimensional（3D） images were reconstructed using cone-beam computed tomography（CBCT） images from 80 Chinese subjects and by SimPlant 11.04.The dimensions of the NPC,the thickness and profile of the labial bone,the width and height of the interproximal bone,angle sella-nasion-subspinale（SNA） and angle upper central incisor-nasion,subspinale（U1-NA） were measured.The incisive foramen of the NPC was markedly wider than its nasal foramen.The dimension of its labial bone wall demonstrated an increasing width from the crestal to apical measurements.The labial bone at the maxillary anterior region was rather thin,especially at 3 mm below the cemento-enamel junction（CEJ） and the mid-root level;the profile of the labial bone was more curved at the central incisor,and the interproximal bone became wider and shorter posteriorly.There were significant relationships between maxillary protrusion and labial bone profile,tooth labiolingual inclination and labial bone thickness（P 〈 0.02）.To achieve optimal esthetic outcome of implant,bone augmentation is necessary at the maxillary anterior region.For immediate or early placement at the maxillary anterior region,the implant should be located palatally to reduce labial bone resorption and marginal recession;its apex should be angulated palatally to avoid labial perforation at the apical region.To protect the NPC,implants at the central incisor region should be placed away from NPC.

Application of cone beam computed tomography in facial imaging science

Facial imaging is used to study the facial shapeand its developmental changes over time.This isimportant to diagnose acquired malformations,to studynormal and abnormal growth and to differentiatebetween the results of treatment and normal growth,and to validate facial recognition.The two mainmethods to study and record facial imaging are bymeans of cephalometry and anthropometry[1].Cephalometrics is the scientific study of themeasurements of the

Comparison of bone alignment and fiducial marker alignment for online cone-beam computed tomography-guided radiation therapy for prostate cancer

Objective The aim of the study was to evaluate the coverage of the prostate when prostatic implanted fiducial markers are used to verify setup of the patients in comparison to the pelvic bones while using conebeam computed tomography(CBCT). Methods Seventeen patients with prostate cancer were included. For each patient, daily online CBCT was done. CT planning was matched with CBCT with the help of fiducial markers(3–5 markers) and another matching with done the help of pelvic bony landmarks. Registration of clinical target volume(CTV) 1 including prostate plus seminal vesicles and CTV2 including prostate only was done and were used to confirm the target volume during the process of matching. Delineation of the rectum on every CBCT was done. Two automatic margin representing planning target volume(PTV) were created. PTV1 was generated by adding 1 cm in all directions(PTV1a) and 0.7 cm in the posterior direction(PTV1b). PTV2 was generated by adding 0.5 cm in all directions(PTV2a) and 0.3 cm in the posterior direction(PTV2b). PTV1a was prescribed to receive 46 Gy in conventional fractionation with a boost dose of 30 Gy to PTV1b. The same dose was prescribed to PTV2a and PTV2b. Calculation of the percentage of intersection between CTV1and CTV2 created on CBCT with the original CTV scan was done. A comparison between the two CTVs(CTV1and CTV2) mean dose and the original delineated CTV was done. Then a comparison to the mean dose of the original CTV of PTV1a, PTV2a(CTV1a and CTV2a), and for PTV1b and PTV2b(CTV1b and CTV2b). Calculation of the mean rectal dose and also V60, V70 and V74 was done on the delineated rectum on every CBCT, and then a comparison to the planned original rectal dose. Results The created CTV1and CTV2 intersection percentage with the original CTV1and CTV2 significantly increased by 85%(range, 65%–95%, P < 0.05), when fiducial markers were used. The main difference of the received mean dose was significantly less in comparison to pelvic bone alignment(0.03% to 2% vs 0.03% to 11.6% for PTV1a, P < 0.006;0.01% to 1.8% vs 0.03% to 10.2% for PTV2a, P < 0.014;0.08 to 2.11 vs 0.04 to 11.29 for PTV1b, P < 0.015 and 0.01 to 1.79 vs 0.01 to 9.69 for PTV2b, P < 0.004). With the use of less PTV margins, significant decrease of the rectal mean dose, V60, V70 and V74 by P < 0.004, P < 0.004, P < 0.0005 and P < 0.009, respectively. Reduction of the CTV1a and CTV1b mean dose by 1.13% and 0.28% in comparison to the initial CTV1a and CTV2a.Conclusion A significant improvement of prostatic cancer patients alignment when fiducial markers are used, with more homogenous dose distribution, and with significant decrease in PTV margins. The delivered rectal dose is significantly less allowing prostate dose escalation.

A Pilot Survey of Odontomas for Size Constancy Using Cone-Beam Computed Tomography: Effect of Age, Sex, Lesion Location, and Histological Type: A Case Series

Objectives: Odontoma is the most common type of odontogenic tumors. Many studies have analyzed the statistical associations between odontoma location and patient age and sex, according to the histological tumor type. However, few studies have assessed odontoma morphological characteristics using cone-beam computed tomography (CBCT). We aimed to evaluate the association between odontoma location and size. Methods: We performed CBCT on patients with odontomas (19 patients;10 women, 9 men;average age, 12.6 [range, 6 - 34] years) according to the pathology type at a university hospital between April 2008 and February 2017. The locations of the lesions were noted, and their sizes were measured on CBCT images. Buccolingual, mesiodistal, and vertical diameters of the lesions were recorded on the same slice with the greatest diameters on axial, coronal, and sagittal CBCT images. Results: Altogether, 9 (47.4%) and 10 (52.6%) odontomas were located in the mandible and maxilla, respectively. There was no significant difference in the mesiodistal and vertical diameters on the CBCT image between the mandibular and maxillary groups when the odontoma size was compared with location (p < 0.05). However, the average diameters in only the buccolingual diameter were significantly greater in the maxilla. There were no significant differences between the two groups according to sex, age, or histological type. Conclusions: These data suggest that the sizes of odontomas in the maxilla are affected by bone expansion in the buccolingual direction, but they may be invariable in most settings. Three-dimensional assessment across the age groups suggests a lack of variation in size.

基于CBCT观察上颌阻生尖牙患者蝶鞍形态变异情况

目的 利用锥形束CT(cone-beam computed tomography,CBCT)探讨上颌尖牙阻生与蝶鞍形态变异的相关性,从三维方向上评价蝶鞍变异对上颌尖牙阻生的临床预判。方法 收集125例上颌阻生尖牙患者(研究组)和125例与之相匹配的尖牙正常萌出者(对照组)。将所有样本CBCT数据导入Dolphin软件,进行重建头颅侧位片和三维图像,记录观察各组蝶鞍桥接(Ⅰ、Ⅱ、Ⅲ型)的类型分布和发生情况。使用SPSS 25.0软件对各组结果进行统计学分析。结果 研究组蝶鞍桥接的发生率显著高于对照组(P=0.004),PIC(腭侧尖牙阻生)组蝶鞍桥接的发生率显著高于对照组(P=0.007),Ⅱ型和Ⅲ型蝶鞍桥接分布和对照组存在统计学差异(P=0.012)。而BIC(唇侧尖牙阻生)组和对照组蝶鞍桥接的发生情况无统计学差异。三维重建图像上各组间蝶鞍桥接发生率无统计学差异(P>0.05)。结论 上颌尖牙阻生与蝶鞍桥接的发生情况有相关性,但仅上颌尖牙腭侧阻生患者更易发生蝶鞍桥接,而上颌尖牙唇侧阻生患者蝶鞍桥接的发生情况无变化。

基于CBCT中牙髓和牙体体积的机器学习用于青少年儿童年龄推断

目的利用锥形束计算机体层成像(cone beam computed tomography,CBCT)影像中左上颌中切牙与左上颌尖牙的牙髓体积和牙体体积,采用逐步回归法和机器学习方法分别推断青少年儿童年龄,并对推断效果进行比较分析。方法收集498例上海市汉族青少年儿童口腔颌面CBCT影像,测量左上颌中切牙与尖牙的牙髓体积和牙体体积并加以运算,运用K-最近邻、岭回归和决策树3种机器学习算法以及逐步回归法建立4个年龄推断模型,计算并比较决定系数、平均误差、均方根误差、均方误差和平均绝对误差等指标。绘制相关性热图,对参数间的单调关系进行可视化分析。结果K-最近邻模型(R^(2)=0.779)和岭回归模型(R^(2)=0.729)相对于逐步回归法(R^(2)=0.617)表现更为优越,而决策树模型(R^(2)=0.494)的拟合效果较差。相关性热图显示,年龄和牙髓体积、牙髓与牙体硬组织的体积比以及牙髓与牙体的体积比之间呈单调负相关。结论牙髓体积及牙髓体积占比与年龄之间存在密切关系,采用基于CBCT的机器学习方法能够提供更为准确的年龄推断结果,为进一步开展基于CBCT的深度学习牙龄推断研究奠定基础。

骨性Ⅲ类错伴下颌偏斜成人下颌骨形态的CBCT研究

目的:用锥体束CT(CBCT)资料分析骨性Ⅲ类错伴下颌偏斜成人患者下颌骨的形态特征。方法:纳入骨性Ⅲ类错伴下颌偏斜的成人患者20例作为偏斜组,个别正常20例为正常组。进行CBCT扫描,用INVIVO 5软件对下颌骨进行三维重建,定位标记点,对测量值进行统计分析。结果:正常组两侧测量值无统计学差异(P>0.05)。偏斜组中偏斜侧下颌升支长度、体积、下颌骨总长度、体积、下颌体后半部分长度、髁突单位、下颌角与下颌体的单位长度均小于对侧(P<0.05),偏斜侧下颌角的角度大于对侧,其余结果无统计学差异(P>0.05)。偏斜组2侧各项的差值与正常组相比均有统计学意义(P<0.05),其余结果无统计学差异(P>0.05)。结论:骨性Ⅲ类错伴下颌偏斜侧的髁突与下颌升支小于对侧;下颌体的后部轻度不对称;下颌体前半部分两侧基本对称。

成人骨性Ⅲ类错牙合伴下颌偏斜患者下颌骨三维对称性的CBCT观察分析

目的:研究成人骨性Ⅲ类错伴下颌偏斜患者下颌骨的三维特征。方法:纳入正畸成人骨性Ⅲ类错患者62名,按照颏点的偏离程度分为颜面部不对称组30例和颜面部对称组32例,用锥形束CT(cone-beam computed tomography,CBCT)三维扫描获得颅面部DICOM数据,采用Dolphin 11.0对下颌骨进行三维重建,选择描述下颌骨骨性结构特征的13个点进行描记,对下颌骨37个变量进行分析统计。结果:颜面部不对称组偏斜侧髁突及下颌角点相对于偏斜对侧处于向后、向外、向上的位置,偏斜对侧有着更长的下颌体、下颌支、髁突和更大的下颌支倾斜度及髁突倾斜度。结论:髁突、下颌支、下颌体的不对称生长发育及下颌骨的旋转都是导致下颌偏斜的因素。

CBCT与螺旋CT对颞颌关节成像的比较

目的:通过锥体束CT(CBCT)与螺旋CT对颞颌关节成像的比较,探讨CBCT影像与螺旋CT对颞下颌关节成像大体解剖结构的一致性;通过比较分析研究CBCT在颞下颌关节检查成像中的临床诊断意义。方法:对1名成人通过严格的TMJ临床检查为健康关节志愿者在同一时间行CBCT与螺旋CT扫描,并进行分析。结果:CBCT与螺旋CT二者重建的解剖形态影像基本一致。受检者的影像均可较清晰再现颞下颌关节结构形态及相对位置关系。结论:比较证实CBCT能准确反映颞下颌关节解剖形态,具有广泛的临床应用前景。

54例正常人双侧颞下颌关节CBCT测量值分析

目的:探讨应用CBCT(cone-beam computed tomography)对成年人两侧颞下颌关节进行多项指标数据测量分析。方法:在TMJ成像与测量技术的基础上,筛选出正常成人54例,通过严格的TMJ临床检查确定为健康关节,利用Newtom 9000 CBCT对其ICP位颞下颌关节进行成像后测量分析。结果:在轴位测得髁状突水平角以及单侧髁状突距矢状中线的距离;平行于髁状突长轴的斜位,测髁状突长轴径,垂直角度,沿髁状突长轴顶内外极间任意角间隙宽度;垂直于髁状突长轴的斜位测量关节髁状突前中后任意角间隙宽度,关节凹深度和前斜面角度关节颈厚度;矢状位测关节髁状突前中后任意角间隙宽度,关节凹深度和前斜面角度关节颈厚度。结论:正常成人双侧髁状突位置及关节窝形态性别差异不明显,双髁状突位置及关节窝形态基本对称。

CBCT在诊治埋伏阻生牙中的应用

目的:探讨CBCT在埋伏阻生牙诊治中的应用。方法:对56例(37颗多生牙、41颗阻生牙)经全景片检查需进一步明确诊断的埋伏阻生牙,进行CBCT扫描,通过三维重建、矢状位、冠状位及轴位断层进行分析。结果:与全景片比较,CBCT能准确定位埋伏阻生牙的位置、生长方向、数量,准确率差异有统计学意义(P<0.05)。结论:CBCT可以更直观、准确地对埋伏阻生牙定位,特别是在上颌前牙区的临床诊治更有应用价值。

CBCT在牙齿纵裂中的临床诊断价值评价

目的:比较CBCT与X线根尖片在诊断牙齿纵裂准确度中的差异性,评价CBCT在牙齿纵裂中的临床诊断价值。方法:在病人知情同意下选取临床上怀疑有牙根纵裂的病人40例(40个牙),均拍摄X线根尖片并进行CBCT扫描。分别由2位专家采用单盲法对CBCT、根尖片影像进行诊断,比较两种影像学方法诊断牙齿纵裂中的真实性。结果:CBCT扫描诊断牙齿纵裂的敏感性Sen、粗符合率CA、约登指数γ、阴性预测值PV-分别为97.37%、97.50%、97.37%、66.67%,而X线根尖片则为73.68%、72.50%、23.68%、9.09%,在诊断牙齿纵裂方面,CBCT扫描与X线根尖片相比有更高的敏感性和准确度,差别具有统计学意义(P<0.05)。结论:与X线根尖片相比CBCT扫描对牙齿纵裂的诊断具有更高的准确度,有重要的临床应用价值。

下颌神经管在CBCT与曲面体层片上的一致性评价

目的:对比分析下颌神经管在CBCT与曲面体层片上可见性的一致性,探讨影响下颌神经管在图像上可见性的非病变因素。方法:选取2013年12月~2014年2月期间在华西口腔医院同时拍摄了CBCT与曲面体层片的患者92例,由2位放射科医师同时观察患者的CBCT片与曲面体层片。把CBCT及曲面体层片上的下颌神经管从颏孔至下颌升支前缘处平分为1、2、3三个区域,分为0、1、2、3四个等级的分对下颌神经管的可见性进行评分。结果:2位医师间的内部一致性检验符合标准。CBCT上,区域1平均得分为2.120,区域2为2.337,区域3为2.533;曲面体层片上,区域1平均得分为1.772,区域2为1.973,区域3为2.207。越往后区域可见性越高。结论:CBCT对下颌神经管的可见性显著高于曲面体层片,仅有1%的下颌神经管在曲面体层片上可见,在CBCT上不可见。下颌神经管的可见性与年龄呈相关性,年龄越大,可见性越低。

CBCT和根尖放射线片诊断根尖周炎的对比性研究

目的:比较应用CBCT和根尖放射线片对慢性根尖周炎的严重程度及病变范围进行评估的差异性,评价CBCT在慢性根尖周病变的诊断、治疗方案的确定及预后等方面的临床价值。方法:选取临床上有根尖周炎症状的53例患者(96颗牙),均拍摄根尖放射线片和CBCT,分别由2位专家采用单盲法进行放射线影像学诊断,比较两种影像学方法对根尖周炎的存在及病变范围评估的差异性。结果:根尖放射线片发现82.3%,CBCT发现100%的患牙存在根尖周病变。并且在两者都诊断出根尖炎时,CBCT的PAI值明显高于根尖片。结论:在诊断慢性根尖周炎方面,CBCT扫描与根尖放射线片相比具有更高的敏感性和精确度。和根尖放射线片比较,CBCT对临床上根尖周炎的诊断、严重程度及预后判断都更有优势,从而能够更好的指导临床治疗。

上颌四眼圈簧扩弓后对上颌牙齿及上颌骨变化影响的CBCT研究

目的:使用锥体束CT(CBCT)评估上颌四眼簧慢速扩弓后上颌牙齿及上颌骨宽度的变化。方法:选择13例需要综合性正畸治疗的患者(男5例,女8例),平均年龄(14.4±2.2)岁,使用上颌四眼圈簧扩弓。对患者扩弓前(T1)后(T2)的变化进行CBCT扫描,测量扩弓前后两侧尖牙、第一前磨牙、第二前磨牙和第一磨牙之间的牙冠和根尖之间的宽度,第一磨牙的倾斜度,基骨弓和腭中缝宽度的变化。应用SPSS 17.0软件对测量结果进行配对t检验。结果:四眼圈簧扩弓后牙弓变化明显。4对牙的牙间距分别增加了(2.47±1.05)mm、(2.97±1.90)mm、(2.79±1.21)mm、(3.15±1.15)mm,根尖距分别减小了(1.19±0.40)mm、(2.12±0.68)mm、(2.02±0.65)mm、(1.34±0.63)mm,左侧磨牙倾斜度减小了4.45°±2.86°,右侧磨牙倾斜度减小了4.02°±1.45°,基骨弓宽度增加了(2.37±0.96)mm,腭中缝宽度增加了(1.21±0.50)mm,差异均具有统计学意义(P<0.001)。结论:四眼圈簧扩弓器对上颌牙弓的扩弓主要通过牙齿倾斜移动完成,而非整体移动。

汉族人群腭大孔解剖位置及其与腭穹隆形态关系的CBCT研究

目的:研究汉族青年人群腭大孔解剖位置及其与腭穹窿形态的关系。方法:采用CBCT测量209名18~45岁汉族受试者腭大孔的相对位置及毗邻关系,并讨论腭穹窿形态对腭大孔位置的影响。结果:腭大孔在第三磨牙近中、腭侧和远中的分布率分别是17.22%、64.59%和18.18%。男性与女性腭大孔至腭中缝(GPF-MMS)的距离分别为(16.29±1.47)mm和(15.60±1.35)mm,腭大孔至牙槽嵴顶(GPF-AC)的距离为(14.02±2.69)mm和(12.29±2.41)mm。GPF-MMS的距离在腭高耸组中明显低于腭低平组;相反,GPF-AC的距离在腭高耸组中明显高于腭低平组。结论:汉族青年人群腭大孔的位置与患者腭穹隆形态和性别有关。

CBCT三维重建及X线片用于诊断口腔正畸患者埋伏牙的效果比较

目的 分析锥形束电子计算机断层扫描(CBCT)三维重建及X线片分别用于诊断口腔正畸患者埋伏牙的价值。方法 选取2018年10月至2020年10月在宝鸡市口腔医院接受影像学诊断的80例口腔正畸埋伏牙患者(共计122颗牙齿)作为研究对象,分别于治疗前后采用CBCT三维重建及X线片检查,以手术证实结果为金标准对埋伏牙分布情况进行分析,并采用Kappa检验分析CBCT及X线片在埋伏牙牙弓唇腭侧位置判断的灵敏度、特异度、准确率。结果 经手术结果证实,122颗埋伏牙主要分布于上颌前牙区、下颌前牙区,分别占其总数的48.36%、16.39%;多生牙主要分布于上颌,占埋伏牙总数的15.57%;经Kappa检验一致性分析显示,CBCT和X线对埋伏牙均具有较好的诊断效能,且CBCT评估埋伏牙在唇颊侧、舌腭侧、冠腭根唇侧、冠唇根腭侧的Kappa值均高于X线。结论 CBCT三维重建及X线片对口腔正畸患者埋伏牙的诊断有较高价值,但CBCT拥有较高的准确性,值得临床推广。

CBCT三维头影测量常用指标的初步探索

目的研究三维转化头颅侧位片(二维)头影测量与CBCT三维头影测量两种测量方法测得的部分常用指标的结果的相关性,初步探索CBCT三维头影测量的应用。方法选择100例符合纳入标准的错牙合畸形患者,对其进行三维转化头颅侧位片头影测量与CBCT三维头影测量,将两种方法的测量结果进行配对样本t检验和拟合优度检验,探讨两者之间的差异性和拟合程度。结果两种头影测量方法结果间的差异均有统计学意义(P<0.05),两种测量方法结果的拟合优度检验发现,7项指标拟合程度较高(0.8<R^(2)<1),1项(SN-MP)拟合程度中等(0.5<R^(2)<0.8),两种头影测量方法8项指标的结果间均存在相关性。结论使用CBCT三维定点方法测得的头影测量的部分常用指标的结果可以反映错牙合畸形患者牙颌面的形态,三维头影测量标准化定点和正常值数据库的建立有待进一步的研究和确立。