The Association between Lower Incisal Inclination and Morphology of the Supporting Alveolar Bone—A Cone-Beam CT Study

Aim To investigate the relationship between the positioning of the lower central incisor and physical morphology of the surrounding alveolar bone. Methodology Thirty-eight patients （18 males, 20 females）, with mean age of 13.4 years, were included in this study. As part of orthodontic treatment planning the patients were required to take dental Cone-beam CT （CBCT） covering the region of lower incisors, the sur- rounding alveolar bone and the mandibular symphysis. The cephalometric parameters were designed and measured to indicate the inclination of lower central incisor and physical morphology of the adjacent alveolar bone. Computer-aided descriptive statistical analysis was performed using SPSS 15.0 software package for Windows. A correlation analysis and a linear regression analysis between the incisor inclination and the alveolar bone morphology were performed. Results Significant positive correlations were found between the lower central incisor inclination and the morphological contour of the alveolar bone （P〈0.05）. The lower central incisor root apex was closer to the lingual alveolar crest when it was buccally inclined. Conclusion The morphology of the alveolar bone may be affected by incisal inclination.

利用Cone-Beam CT探讨支抗微螺钉周围骨密度与其稳定性的关系

目的:利用Cone-Beam CT测量支抗微螺钉周围骨密度值,探讨其与微螺钉稳定性的关系。方法:选取颌骨左右对称植入微螺钉后一侧松动而另一侧稳固的7名(共18枚微螺钉)正畸患者。拍摄CBCT,所得三维影像重建后用OnDemand 3DApplication软件对微螺钉骨内部分周围2mm范围内骨密度(以Hounsfield Unit表示)进行测量,自身对照比较分析双侧对称部位所植入微螺钉周围骨密度测量值间的差异。结果:松动微螺钉与稳定微螺钉骨内部分周围2mm范围内骨密度无统计学差异,两侧微螺钉钉尖部1/3、钉中部1/3及钉颈部1/3周围骨密度均无统计学差异。结论:微螺钉种植支抗的稳定性与其周围骨密度间未发现明显相关性。

Cone-beam CT技术及其在口腔正畸学中的应用进展

在正畸的诊断治疗过程中,Cone-beam CT已广泛应用于口腔界的各个领域,本文旨在对Cone-beamCT的原理、特点及其在口腔正畸领域中的应用进行综述,以期增加正畸医师对于Cone-beam CT的理解。

Slice-wise reconstruction for low-dose cone-beam CT using a deep residual convolutional neural network

Because of the growing concern over the radiation dose delivered to patients, X-ray cone-beam CT(CBCT) imaging of low dose is of great interest. It is difficult for traditional reconstruction methods such as Feldkamp to reduce noise and keep resolution at low doses. A typical method to solve this problem is using optimizationbased methods with careful modeling of physics and additional constraints. However, it is computationally expensive and very time-consuming to reach an optimal solution. Recently, some pioneering work applying deep neural networks had some success in characterizing and removing artifacts from a low-dose data set. In this study,we incorporate imaging physics for a cone-beam CT into a residual convolutional neural network and propose a new end-to-end deep learning-based method for slice-wise reconstruction. By transferring 3D projection to a 2D problem with a noise reduction property, we can not only obtain reconstructions of high image quality, but also lower the computational complexity. The proposed network is composed of three serially connected sub-networks: a cone-to-fan transformation sub-network, a 2D analytical inversion sub-network, and an image refinement sub-network. This provides a comprehensive solution for end-to-end reconstruction for CBCT. The advantages of our method are that the network can simplify a 3D reconstruction problem to a 2D slice-wise reconstruction problem and can complete reconstruction in an end-to-end manner with the system matrix integrated into the network design. Furthermore, reconstruction can be less computationally expensive and easily parallelizable compared with iterative reconstruction methods.

Clinically relevant human temporal bone measurements using novel high-resolution cone-beam CT

Objective: To test the feasibility of measuring fine temporal bone structures using a newly established cone-beam computed tomography(CBCT)system.Materials and methods: Six formalin-fixed human cadaver temporal bones were imaged using a high-resolution CBCT system that has 900 frames and copper t aluminum filtration. Fine temporal bone structures, including those of the facial nerve canal and vestibular structures, were identified and measured.Results: The fine structures of the middle ear, including the tympanic membrane, tendon of the tensor tympani, cochleariform process of the semicanal of the tensor tympani, pyramidal eminence, footplate of the stapes, full path of the facial nerve within the temporal bone, supralabyrinthine space, semicircular canals, pathway of the subarcuate canal, and full path of the vestibular aqueduct, were clearly demonstrated. The vestibular aqueduct has a midpoint width of 0.4 ± 0.0 mm and opercular width of 0.5 ± 0.1 mm(mean ± SD). The length of the internal acoustic meatus was 10.6 ± 1.2 mm(mean ± SD), and the diameter of the internal acoustic meatus was 3.7 ± 0.3 mm(mean ± SD).Conclusion: This novel high-resolution CBCT system has potentially broad applications in the diagnosis of inner ear disease and in monitoring associated pathological changes, surgical planning, navigation for the ear surgery, and temporal bone training.

Validation of a novel imaging approach using multi-slice CT and cone-beam CT to follow-up on condylar remodeling after bimaxillary surgery

The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography （MSCT） and postoperative cone-beam computed tomography （CBCT） images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients （11 female and 9 male） who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant （P〈O.05） mean bone volume decrease of 26.4%_ 11.4% （502.9 mm3＋ 268.1 mm3）. No significant effects of side, sex or age were found. Good to excellent （ICC〉 0.6） intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel （0.4 mm） for MSCT （0.3 mm __. 0.2 mm） and CBCT （0.4 mm _ 0.3 mm）, thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

Scatter correction method for cone-beam CT based on interlacing-slit scan

Cone-beam computed tornography （CBCT） has the notable features of high efficiency and high precision, and is widely used in areas such as medical imaging and industrial non-destructive testing. However, the presence of the ray scatter reduces the quality of CT images. By referencing the slit collimation approach, a scatter correction method for CBCT based on the interlacing-slit scan is proposed. Firstly, according to the characteristics of CBCT imaging, a scatter suppression plate with interlacing slits is designed and fabricated. Then the imaging of the scatter suppression plate is analyzed, and a scatter correction Calculation method for CBCT based on the image fusion is proposed, which can splice out a complete set of scatter suppression projection images according to the interlacing-slit projection images of the left and the right imaging regions in the scatter suppression plate, and simultaneously complete the scatter correction within the fiat panel detector （FPD）. Finally, the overall process of scatter suppression and correction is provided. The experimental results show that this method can significantly improve the clarity of the slice images and achieve a good scatter correction.

Multiple helical scans and the reconstruction of over FOV-sized objects in cone-beam CT

In cone-beam computed tomography （CBCT）, there are often cases where the size of the specimen is larger than the field of view （FOV） （referred to as over FOV-sized （OFS））. To acquire the complete projection data for OFS objects, some scan modes have been developed for long objects and short but over-wide objects. However, these modes still cannot meet the requirements for both longitudinally long and transversely wide objects. In this paper, we propose a multiple helical scan mode and a corresponding reconstruction algorithm for both longitudinally long and transversely wide objects. The simulation results show that our model can deal with the problem and that the results are acceptable, while the OFS object is twice as long compared with the FOV in the same latitude.

Iodized oil uptake assessment with cone-beam CT in chemoembolization of small hepatocellular carcinomas

AIM:To evaluate the utility of assessing iodized oil uptake with cone-beam computed tomography(CT)in transarterial chemoembolization(TACE)for small he-patocellular carcinoma(HCC).METHODS:Cone-beam CT provided by a biplane flat-panel detector angiography suite was performed on eighteen patients(sixteen men and two women;41-76 years;mean age,58.9 years)directly after TACE for small HCC(26 nodules under 30 mm;mean diam-eter,11.9 mm;range,5-28 mm).The pre-procedural locations of the tumors were evaluated using tripha-sic multi-detector row helical computed tomography(MDCT).The tumor locations on MDCT and the iodized oil uptake by the tumors were analyzed on cone-beam CT and on spot image directly after the procedures.RESULTS:All lesions on preprocedural MDCT were de-tected using iodized oil uptake in the lesions on cone-beam CT(sensitivity 100%,26/26).Spot image depictediodized oil uptake in 22 of the lesions(sensitivity 85%).The degree of iodized oil uptake was overestimated(9%,2/22)or underestimated(14%,3/22)on spot image in f ive nodules compared with that of cone-beam CT.CONCLUSION:Cone-beam CT is a useful and conve-nient tool for assessing the iodized oil uptake of small hepatic tumors(< 3 cm)directly after TACE.

An analytical simulation technique for cone-beam CT and pinhole SPECT

This study was aimed at developing an efficient simulation technique with an ordinary PC.The work involved derivation of mathematical operators,analytic phantom generations,and effective analytical projectors developing for cone-beam CT and pinhole SPECT imaging.The computer simulations based on the analytical projectors were developed by ray-tracing method for cone-beam CT and voxel-driven method for pinhole SPECT of degrading blurring.The 3D Shepp-Logan,Jaszczak and Defrise phantoms were used for simulation evaluations and image reconstructions.The reconstructed phantom images were of good accuracy with the phantoms.The results showed that the analytical simulation technique is an efficient tool for studying cone-beam CT and pinhole SPECT imaging.

Derivative-Hilbert-Backprojection based image reconstruction from truncated projections in helical cone-beam CT

In helical cone-beam computed tomography(CT), Feldkamp-Davis-Kress(FDK) based image reconstruction algorithms are by far the most popular. However, artifacts are commonly met in the presence of lateral projection truncation. The reason is that the ramp filter is global. To restrain the truncation artifacts, an approximate reconstruction formula is proposed based on the Derivative-Hilbert-Backprojection(DHB) framework. In the method, the first order derivative filter is followed by the Hilbert transform. Since the filtered projection values are almost zero by the first order derivative filter, the following Hilbert transform has little influence on the projection values, even though the projections are laterally truncated. The proposed method has two main advantages. First, it has comparable computational efficiency and image quality as well as the conventional helical FDK algorithm for non-truncated projections. The second advantage is that images can be reconstructed with acceptable quality and much lower computational cost in comparison to the Laplace operator based algorithm in cases with truncated projections. To point out the advantages of our method, simulations on the computer and real data experiments on our laboratory industrial cone-beam CT are conducted. The simulated and experimental results demonstrate that the method is feasible for image reconstruction in the case of projection truncation.

Delivered Dose Verification for Lung Cancer Stereotactic Body Radiotherapy Using Cone-Beam CT

Purpose: Verified the delivered dose distribution of lung cancer Stereotactic Body Radiotherapy (SBRT) using the cone-beam CT images. Methods: Twenty lung cancer patients who underwent SBRT with 100 CBCT images were enrolled in this study. Delivered dose distributions were recalculated on CBCT images with the deformed and non-deformed methods, respectively. The planned and delivered dose distributions were compared using the dose-volume histograms. Results: The delivered target coverage (V100) per patient inside target volume deviated on average were 0.83% ± 0.86% and 1.38% ± 1.40% for Pct vs. Pcbct and Pct vs. Pdcbct, respectively. The Conformity Index (CI) and Gradient Index (GI) showed a good agreement among the plans. For the critical organs, only minor differences were observed between the planned dose and the delivered dose. Conclusions: CBCT images were a useful tool for setup and dose delivery verification for lung cancer patients who underwent SBRT.

Three-dimensional weighting reconstruction algorithm for circular cone-beam CT under large scan angles

Improving imaging quality of cone-beam CT under large cone angle scan has been an important area of CT imaging research. Considering the idea of conjugate rays and making up missing data, we propose a three-dimensional(3D) weighting reconstruction algorithm for cone-beam CT. The 3D weighting function is added in the back-projection process to reduce the axial density drop and improve the accuracy of FDK algorithm. Having a simple structure, the algorithm can be implemented easily without rebinning the native cone-beam data into coneparallel beam data. Performance of the algorithm is evaluated using two computer simulations and a real industrial component, and the results show that the algorithm achieves better performance in reduction of axial intensity drop artifacts and has a wide range of application.

Method for Converting Cone-Beam CT Values into Hounsfield Units for Radiation Treatment Planning

Cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (EDs) necessary for dose calculation from CBCT images because of the effects of scatter contamination during CBCT image acquisition. This paper presents a mathematical method for converting the pixel values of CBCT images (CBCT values) into Hounsfield units (HUs) of radiation treatment simulation CT (simCT) images for use in radiation treatment planning. CBCT values are converted into HUs by matching the histograms of the CBCT values with the histograms of the HUs for each slice via linear scaling of the CBCT values. For prostate cancer and head-and-neck cancer patients, the EDs obtained from converted CBCT values (mCBCT values) show good agreement with the EDs obtained from HUs, within approximately 3.0%, and the dose calculated on the basis of CBCT images shows good agreement with the dose calculated on the basis of the simCT images, within approximately 2.0%. Because the CBCT values are converted for each slice, this conversion method can account for variation in the CBCT values associated with differences in body size, body shape, and inner tissue structures, as well as in longitudinally displaced positions from the isocenter, unlike conventional methods that use electron density phantoms. This method improves on conventional CBCT-ED conversion and shows considerable potential for improving the accuracy of radiation treatment planning using CBCT images.

基于Halcyon加速器百分百图像引导模式下盆腔肿瘤CTV-PTV边界外放的研究

目的探讨基于Halcyon加速器百分百图像引导模式下盆腔肿瘤临床靶区-计划靶区(Clinical Target Volume,CTV)-(Planning Target Volume,PTV)边界外放的摆位误差。方法选取2023年1—5月在Halcyon加速器上行调强放射治疗的19例盆腔肿瘤患者为研究对象,采集每个患者分次间、纠正后、分次内300套共900个锥形束CT图像,与计划CT进行配准融合,得到三维方向上的矢量误差,用X(左右)方向、Y(头脚)方向、Z(腹背)方向表示。计算摆位误差及分布趋势,并根据纠正后及分次内的摆位误差计算CTV-PTV的外放边界。结果X方向上,分次间、纠正后、分次内的摆位绝对误差分别为(2.07±1.82)、(0.19±0.19)、(0.30±0.28)mm;Y方向上,分次间、纠正后、分次内的摆位绝对误差分别为(3.87±2.67)、(0.23±0.31)、(0.27±0.23)mm;Z方向上,分次间、纠正后、分次内的摆位绝对误差分别为(0.72±0.83)、(0.20±0.22)、(0.30±0.27)mm,差异均有统计学意义(P<0.05)。纠正后和分次内X、Y、Z 3个方向分别有97%和96.33%的摆位误差在1 mm以内。CTV-PTV外放边界从6.36 mm缩小到1.06 mm。结论从摆位误差角度来看,基于Halcyon加速器百分百图像引导模式下的盆腔肿瘤治疗,根据纠正后和分次内的摆位误差计算CTV-PTV外放边界为1.1 mm。通过Halcyon加速器治疗盆腔肿瘤患者可降低摆位误差,提高患者靶区和危及器官的安全精度,缩小CTV-PTV边界外放值,减少正常组织的累及体积。

术中滑轨CT辅助在经皮骶髂关节螺钉治疗骨盆后环损伤中的应用

目的:比较术中滑轨CT联合C形臂X线机辅助与单纯使用C形臂X线机辅助透视下经皮骶髂关节螺钉治疗骨盆后环损伤临床疗效。方法:自2018年12月至2022年2月收治76例骨盆后环损伤患者,其中,C形臂联合滑轨CT辅助下行内固定治疗39例为CT组,男23例,女16例,年龄(44.98±7.33)岁;仅在C形臂透视下行内固定治疗37例为C形臂组,男24例,女13例,年龄(44.37±10.82)岁。合并有前环骨折患者42例,均采用经皮髂前下棘内置外固定架(internal fixation,INFIX)或耻骨上支螺钉固定骨盆前环。术后比较两组随访时间、置钉时间、并发症。比较两组Matta复位评价、Majeed疗效评价、CT分级及二次手术翻修率。结果:CT组置钉时间(32.63±7.33) min,短于C形臂组(52.95±10.64) min(t=-9.739,P<0.05)。CT组随访时间(11.97±1.86)个月,C形臂组(12.03±1.71)个月,两组比较差异无统计学意义(P>0.05)。两组术后并发症发生比较,差异无统计学意义(χ~2=0.159,P>0.05)。CT组Matta复位评价结果(Z=2.79,P<0.05)、Majeed疗效评价结果(Z=2.79,P<0.05)、CT分级(Z=2.83,P<0.05)均优于C形臂组。CT组二次手术翻修率低于C形臂组(χ~2=5.641,P<0.05)。结论:术中滑轨CT联合C形臂辅助下经皮骶髂关节螺钉置入手术与传统C形臂透视相比,具有手术时间短、准确度及安全性高、术后二次翻修率显著下降等特点,是重建骨盆骨折后环稳定性的有效方法之一。

CT血管成像对ACI患者颈动脉狭窄程度及侧支循环的价值研究

目的分析、探究CT血管成像技术在ACI患者颈动脉狭窄、侧支循环等病情诊断方面的成效。方法对我院2021.3-2022.3月期间收治的100例急性脑梗死(ACI)患者一般病理资料进行回顾性分析,以数字减影血管造影(DSA)结果为诊断金标准,对CT血管成像技术(CTA)的诊断价值进行分析,以临床出具的数字减影血管造影(DSA)结果为金标准,分析CT血管成像技术(CTA)在临床上的诊断价值,评估此技术在临床诊断中的效能。结果与临床金标准相比,CTA诊断技术具有较高的临床评估价值[Kappa>0.8~1.0,曲线下面积(AUC)>0.9,P<0.01];CTA诊断技术在评估颈动脉狭窄程度等方面与临床金标准具有一定的一致性[Kappa>0.6~0.8,曲线下面积(AUC)>0.7~0.9,P<0.01];而在评估侧支循环临床诊断中,CTA诊断技术与临床金标准具有一致性,具有较高的评估价值[Kappa>0.8~1.0,曲线下面积(AUC)>0.9,P<0.01]。结论以临床“金标准”的诊断结果为依据分析,CTA诊断技术能够对ACI患者出现病变的血管形态及侧支循环状态等进行全面的评估,CTA诊断结果可为治疗工作提供准确性相对较高且客观的医学依据,确实是评估ACI患者颈动脉狭窄程度、侧支循环状态的可靠办法;而与DSA技术相比,CTA与之具有较高的一致性,说明在病情发作早期为ACI患者实施CTA检查可获悉颈动脉的狭窄及侧支循环状态,有利于改善患者群体的预后。

D-CBCT在肺癌容积旋转调强计划精准治疗中的临床应用

目的探讨椎形束CT(D-CBCT)在肺癌容积旋转调强(VMAT)计划精准治疗中的临床应用。方法选取2019年10月~2022年10月在南通市第三人民医院放射治疗科就诊的100例肺癌患者。根据CBCT扫描模式不同,分为4D组(n=57)和3D组(n=43)。比较两组患者放疗摆位误差、内靶区(ITV)体积、靶区剂量、心脏受照剂量和肿瘤控制效果。结果在校正前后和治疗后,两组各摆位误差绝对值无统计学差异(P>0.05);4D组患者中下叶肿瘤ITV体积低于3D组(P<0.05);4D组的最大剂量(D_(max))、最小剂量(D_(min))和平均剂量(D_(mean))靶区剂量均高于3D组(P<0.05);4D组的V10、V20、V30及平均受量(D_(mean))等心脏受照剂量均低于3D组(P<0.05);4D组和3D组患者的客观有效率无明显差异(P>0.05)。结论可将D-CBCT应用于肺癌容积旋转调强计划精准治疗中,尤其采用4D-CBCT可更好提供靶区剂量,减少肺癌患者的中下叶肿瘤ITV体积和心脏受照剂量。

胸腹部平扫CT值用于机会性筛查骨质疏松的可行性

目的:基于定量CT(QCT)探讨胸部常规kVp平扫和腹部能谱GSI平扫下椎体CT值用于机会性筛查骨质疏松的可行性。方法:前瞻性收集接受胸腹部平扫的患者431例,胸部CT扫描采用常规120 kVp,腹部扫描采用能谱(GSI)模式。对胸腹部扫描重叠的T11~L1椎体进行分析。使用QCT骨密度测量工作站测得胸部常规120 kVp下T11~L1椎体的骨密度(BMD),同时分别测量胸部120 kVp与腹部GSI扫描70 keV单能量下T11~L1椎体的CT值。采用组内相关系数(ICC)评估数据测量的一致性,Spearman相关性检验分析椎体BMD值与CT值之间的相关性。不同椎体间CT值差异采用Friedman秩和检验。参考QCT诊断标准,将椎体分为骨质疏松、骨量减少和骨量正常组,采用Kruskal-Wallis比较三组间及组内CT值差异。组内120 kVp-CT值和GSI-CT值采用Wilcoxon秩和检验。以T11~L1椎体BMD均值行骨质状态判定,采用受试者操作特征(ROC)曲线分析椎体CT值评估骨质状态的诊断效能。结果:椎体BMD与120 kVp-CT值和GSI-CT值均呈正相关(r=0.976、0.963,P<0.001)。120 kVp和GSI下T11~L1椎体CT值依次为T11[144.00(72.00)、158.00(79.00)]、T12[137.00(67.00)、150.00(76.00)]、L1[128.00(67.00)、137.00(74.00)],不同椎体及椎体内差异均有统计学意义(P<0.001)。431例患者共1293个椎体,骨量正常组椎体496个、骨量减少组椎体415个、骨质疏松组椎体382个。120 kVp和GSI下骨量正常、骨量减少和骨质疏松组椎体CT值依次为[181.50(43.67)、199.65(48.57)]、[132.20(18.50)、144.00(23.00)]和[87.75(22.20)、93.30(27.20)],不同骨质状态组间椎体CT值差异有统计学意义(P<0.05),且各组组内椎体GSI-CT值均高于椎体120 kVp-CT值(P<0.05)。120 kVp-CT值与GSI-CT值诊断骨量减少的AUC分别为0.976、0.967,差异无统计学意义(P=0.0937);诊断骨质疏松的AUC均为1.000,差异无统计学意义(P=1.000)。结论:胸部常规120 kVp及腹部GSI平扫CT值均可用于机会性筛查骨质疏松,诊断效能良好。

颅脑CT灌注成像及磁共振成像在脑梗死患者中的应用

目的分析颅脑CT灌注成像及磁共振成像对脑梗死患者的诊断价值。方法选取2022-03—2023-05在江苏省中西医结合医院就诊的80例疑似脑梗死患者为研究对象,对比分析GE Revolution CT颅脑灌注成像、磁共振成像及联合检查的敏感性、特异性、准确性,制作3种影像学检查的受试者工作特征(ROC)曲线。结果根据患者病情和临床综合诊断确诊,80例疑似脑梗死患者中脑梗死阳性69例(86.25%),脑梗死阴性11例(13.75%)。3种影像学检查方法的灵敏度、准确率比较,从高到低依次为联合检查、GE Revolution CT颅脑灌注成像检查、磁共振成像检查,差异有统计学意义(P<0.05)。GE Revolution CT颅脑灌注成像检查、磁共振成像检查、联合检查诊断脑梗死的ROC曲线下面积(AUC)分别为0.8109、0.7688、0.8682。结论GE Revolution CT颅脑灌注成像与磁共振成像检查的联合应用,有利于提高脑梗死患者诊断的灵敏度、准确率及AUC水平。