Evaluation of bone changes in the temporomandibular joint using cone beam CT

Objective

The aim of this study was to assess bone changes and mobility in temporomandibular joints (TMJs) using cone beam CT (CBCT) in a population sample in Recife, PE, Brazil.

Methods

The TMJ images of patients treated by a radiologist at a private dental radiology service over a period of 1 year were retrieved from the computer database and assessed using a computer with a 21-inch monitor and the iCAT Cone Beam 3D Dental Imaging System Workstation program (Imaging Sciences International, Hatfield, PA). The Pearson χ² test was used to analyse the differences in percentage of bone changes among the categories of mobility (p ≤ 0.05). The McNemar test was used to compare the presence of bone changes in TMJs on the right and left sides (p ≤ 0.05).

Results

An adjusted logistic regression model was used to assess the effect of age and gender on the occurrence of bone changes (p ≤ 0.05). Bone changes were present in 227 (71%) patients. Age group and gender showed a statistically significant association with presence of bone changes (p ≤ 0.05). There was no significant difference between the right and left sides (p = 0.556) and in condylar mobility (p = 0.925) with regard to the presence of degenerative bone changes.

Conclusions

There is a high prevalence of degenerative bone alteration in TMJs, which is more frequent in women and mostly located in the condyle. The prevalence of degenerative bone changes increases with age. There is no correlation between condylar mobility and the presence of degenerative bony changes in TMJs.     

Evaluation of juxta-apical radiolucency in cone beam CT images

Objectives:

The aim of this study was to analyse the position and relationship of juxta-apical radiolucency (JAR) to the mandibular canal and buccal and/or lingual cortical plates using cone beam CT (CBCT).

Methods:

A retrospective study was carried out to analyse the JAR on CBCT for 27 patients. These findings were compared with 27 age- and sex-matched patients without the presence of JAR, which acted as the control group. The CBCT images were analysed according to a checklist, to evaluate the position of the JAR and its relationship to the mandibular canal. Then, any thinning or perforation of either the buccal or lingual cortical plate due to JAR was noted, and a classification to quantify the thinning of cortical plates was proposed. The findings in the two groups were analysed using a paired comparison by McNemar test.

Results:

A statistical increased thinning of cortical plates was seen in the JAR group compared with the control group, and most of the cases were in the J3 group. None of the patients in either the JAR or the control group showed perforation of the buccal and/or lingual cortical plate on CBCT images.

Conclusions:

A classification to quantify the thinning of cortical plates was proposed, which may be used for objective evaluation of the thinning of the cortical plates in future studies. The present study gives an insight into the relationship of the juxta-apical area with the mandibular canal and cortical plates in the mandible using CBCT.     

Topical contrast agents to improve soft-tissue contrast in the upper airway using cone beam CT: a pilot study

The purpose of this study is to explore the topical use of radiographic contrast agents to enhance soft-tissue contrast on cone beam CT (CBCT) images. Different barium sulphate concentrations were first tested using an airway phantom. Different methods of barium sulphate application (nasal drops, syringe, spray and sinus wash) were then tested on four volunteers, and nebulized iodine was tested in one volunteer. CBCT images were performed and then assessed subjectively by two examiners for contrast agent uniformity and lack of streak artefact. 25.0% barium sulphate presented adequate viscosity and radiodensity. Barium sulphate administered via nasal drops and sprays showed non-uniform collection at the nostrils, along the inferior and/or middle nasal meatuses and posterior nasal choana. The syringe and sinus wash showed similar results with larger volumes collecting in the naso-oropharynx. Nebulized iodine failed to distribute into the nasal cavity and scarcely collected at the nostrils. All methods of nasal application failed to adequately reach or uniformly coat the nasal cavity beyond the inferior nasal meatuses. The key factors to consider for optimum topical radiographic contrast in the nasal airway are particle size, flow velocity and radio-opacity.     

Evaluation of a cone beam CT artefact reduction algorithm

Objectives

An algorithm and software to reduce metal artefact has been developed recently and is available in the Picasso Master 3D® (VATECH, Hwaseong, Republic of Korea), which under visual assessment produces better quality images than were obtainable previously. The objective of this in vitro study was to investigate whether the metal artefact reduction (MAR) algorithm of the Picasso Master 3D machine reduced the incidence of metal artefacts and increased the contrast-to-noise ratio (CNR) while maintaining the same gray value when there was no metallic body present within the scanned volume.

Methods

20 scans with a range of 50–90 kVp were acquired, of which 10 had a metallic bead inserted within a phantom. The images obtained were analysed using public domain software (ImageJ; NIH Image, Bethesda, MD). Area histograms were used to evaluate the mean gray level variation of the epoxy resin-based substitute (ERBS) block and a control area. The CNR was calculated.

Results

The MAR algorithm increased the CNR when the metallic bead was present; it enhanced the ERBS gray level independently of the presence of the metallic bead. The image quality also improved as peak tube potential was increased.

Conclusion

Improved quality of images and regaining of the control gray values of a phantom were achieved when the MAR algorithm was used in the presence of a metallic bead.     

Radiological examination of the articular eminence morphology using cone beam CT

Objective

The purpose of the present study was to investigate the articular eminence inclination and height according to age and gender in patients with temporomandibular joint (TMJ) dysfunction and healthy controls using cone beam CT (CBCT).

Methods

The measurements were performed on CBCT records of 52 TMJ dysfunction patients (11 males and 41 females) and 41 control patients (17 males and 24 females). The eminence inclination and height were measured on the CBCT images.

Results

The eminence inclination and height values were higher in males than in females in both TMJ dysfunction patient and control groups; however, these differences were not statistically significant (p>0.05). While no statistically significant differences were found in the eminence inclination and height values between the age groups (p>0.05) in the TMJ dysfunction patient group, there were statistically significant differences in the control group. The eminence inclination was highest between the ages of 21 and 30 years and showed a decrease after the age of 30 years. Additionally, the eminence inclinations of the control patients were statistically higher than those of the TMJ dysfunction patients.

Conclusion

There were no statistically significant differences in eminence inclination and height according to gender. The eminence inclination reaches its highest value between the ages of 21 and 30 years and shows a decrease after the age of 31 years in healthy patients. The eminence inclination was steeper in healthy control patients than in patients with TMJ dysfunction.     

Image quality assessment of three cone beam CT machines using the SEDENTEXCT CT phantom

Objectives:

The SEDENTEXCT Project proposed quality assurance (QA) methods and introduced a QA image quality phantom. A new prototype was recently introduced that may be improved according to previous reports. The purpose of this study is to evaluate image quality in various protocols of three cone beam CT (CBCT) machines using the proposed QA phantom.

Methods:

Using three CBCT machines, nine image quality parameters, including image homogeneity (noise), uniformity, geometrical distortion, pixel intensity value, contrast resolution, spatial resolution [line pair (LP) chart, point spread function (PSF) and modulation transfer function (MTF)] and metal artefacts, were evaluated using a QA phantom proposed by SEDENTEXCT. Exposure parameters, slice thickness and field of view position changed variously, and the number of total protocols was 22.

Results:

Many protocols showed a uniform gray value distribution except in the minimum slice thickness image acquired using 3D Accuitomo 80 (Morita, Kyoto, Japan) and Veraviewepocs 3Df (Morita). Noise levels differed among the protocols. There was no geometric distortion, and the pixel intensity values were correlated with the CT value. Low contrast resolution differed among the protocols, but high contrast resolution performed well in all. Many protocols showed that the maximum line pair was larger than 1 LP mm⁻¹ but smaller than 3 LP mm⁻¹. PSF and MTF did not correlate well with the pixel size. The measured metal artefact areas varied for each device.

Conclusions:

We studied the image quality of three CBCT machines using the SEDENTEXCT phantom. Image quality varied with exposure protocols and machines.     

X-CT设备低对比度分辨力检测方法研究与分析

目的：检测X—CT设备低对比度分辨力，评价X—CT系统在低对比度条件下区分目标物的能力。方法：利用Catphan体模的CTP515模决进行测试，同样扫描条件重复三次，得到CT设备在低对比度条件下可分辨目标物的最小直径。结果：1％、0．5％和0。3％对比度条件下，A设备三次重复扫描得到的结果分别为(2、4和5mm)、(2、3和3mm)、(2、3和5mm)，螺旋扫描结果为(2、5和6mm)；B设备三次重复扫描得到的结果分别为(3、5和7mm)、(2、6和8mm)、(2、4和6mm)。针对多种对比度检测结果，利用Excel绘制低对比度分辨力变化曲线。结论：利用多种对比度条件评价低对比度分辨力使评价更客观全面。利用低对比度分辨力变化曲线图可对体模不能提供的其他对比度条件下的低对比度分辨力进行估计，而且简单易行。     

Detection of cavitated approximal surfaces using cone beam CT and intraoral receptors

Objectives

The aim of this study was to compare cone beam CT (CBCT) in a small field of view (FOV) with a solid-state sensor and a photostimulable phosphor plate system for detection of cavitated approximal surfaces.

Methods

257 non-filled approximal surfaces from human permanent premolars and molars were recorded by two intraoral digital receptors, a storage phosphor plate (Digora Optime, Soredex) and a solid-state CMOS sensor (Digora Toto, Soredex), and scanned in a cone beam CT unit (3D Accuitomo FPD80, Morita) with a FOV of 4 cm and a voxel size of 0.08 mm. Image sections were carried out in the axial and mesiodistal tooth planes. Six observers recorded surface cavitation in all images. Validation of the true absence or presence of surface cavitation was performed by inspecting the surfaces under strong light with the naked eye. Differences in sensitivity, specificity and agreement were estimated by analysing the binary data in a generalized linear model using an identity link function.

Results

: A significantly higher sensitivity was obtained by all observers with CBCT (p < 0.001), which was not compromised by a lower specificity. Therefore, a significantly higher overall agreement was obtained with CBCT (p < 0.001). There were no significant differences between the Digora Optime phosphor plate system and the Digora Toto CMOS sensor for any parameter.

Conclusions

CBCT was much more accurate in the detection of surface cavitation in approximal surfaces than intraoral receptors. The differences are interpreted as clinically significant. A CBCT examination performed for other reasons should also be assessed for approximal surface cavities in teeth without restorations.     

Detection of periodontal bone loss using cone beam CT and intraoral radiography

Objective

The aim of this study was to compare periapical radiographs with cone beam CT (CBCT) imaging in detecting and localizing alveolar bone loss by comparing linear measurements of the height, depth and width of the defects and identifying combined bone defects in tomographic images.

Methods

The images were selected from a secondary database containing images of patients referred for periodontal evaluation. The sample consisted of 51 sites showing both horizontal and vertical bone loss, assessed by 3 trained examiners.

Results

The results showed that there were no statistically significant differences between the imaging methods in terms of identification of the pattern of bone loss. However, there were differences between the two methods when the distance between the cemento-enamel junction (CEJ) and the alveolar crest (AC) was measured. When the distance between the CEJ and the deepest point and width of the defect were measured, the methods showed no statistically significant difference. In this study, 30.8% of the 39 teeth evaluated had combined bone defects.

Conclusions

The two methods differ when detecting the height of the alveolar bone crest but present similar views of the depth and width of bone defects. CBCT was the only method that allowed for an analysis of the buccal and lingual/palatal surfaces and an improved visualization of the morphology of the defect.     

The influence of exposure parameters on jawbone model accuracy using cone beam CT and multislice CT

Objective

The main purpose of this study was to investigate the influence of exposure parameters on jawbone model accuracy when using cone beam CT (CBCT) and multislice CT (MSCT).

Methods

A lower and an upper edentulous human cadaver jaw were scanned using micro-CT (Skyscan 1173 high energy spiral scan micro-CT; Skyscan NV, Kontich, Belgium) at 35 μm to serve as true reference. The in vitro samples were exposed using six CBCT units and one MSCT system. CBCT exposure protocols were chosen according to clinically available settings. The variables were kilovoltage, milliamperage, voxel size and/or scan time. Image segmentation was based on local thresholds using profile lines. The resulting jawbone segmentations were registered with the reference and image processing was done to internally fill the segmentations. A point-based distance calculation was performed between the three-dimensional objects and reference scans and deviation percentages were calculated for 2 mm, 1 mm and 0.5 mm intervals.

Results

All points of the MSCT surface models lay within a 1 mm deviation range and 98.5% within 0.5 mm compared with micro-CT. For the different CBCT systems, accuracy came close to MSCT with mean percentages of 98.9% within 1 mm deviation and 92.8% within 0.5 mm. A difference of approximately 1% between lower and upper jaws could be perceived. For the specific CBCT exposure protocols, only scan time and voxel size revealed certain significant differences.

Conclusion

Jawbone model accuracy using CBCT was comparable with MSCT. The surface models of the upper jaws deviated slightly more than those for lower jaws. CBCT exposure settings had a limited influence on accuracy with scan time and voxel size as the main factors.     

Reproducibility and accuracy of measuring unerupted teeth using limited cone beam X-ray CT

OBJECTIVE: The purpose of this investigation was to determine the reproducibility among observers and accuracy of the measurement of the tooth crown width of unerupted teeth using limited area cone beam X-ray CT. METHODS: 3DX multi-image micro-CT (3DX, Morita Co., Kyoto, Japan) images of impacted supernumerary teeth in the median maxillary region taken prior to extraction were used for the samples. The width of the tooth on the 3DX image was measured five times by five individual observers. Significant differences in values among the observers in the measurement were determined by one-way analysis of variance for examining reproducibility. The measurement results of the ten samples on 3DX images were compared with the laboratory measurements using a three-dimensional co-ordinate measuring apparatus, using the Wilcoxon signed-rank sum test. RESULTS: There was no significant difference among the observers in the measurement (P>0.05). The measurement results shown on 3DX images were significantly larger than those of the laboratory measurements (P<0.05). The mean difference was +0.088 mm. CONCLUSIONS: 3DX has high reproducibility for measuring the tooth crown width of unerupted teeth. While 3DX measurement values were larger than the laboratory measurements, the difference is clinically insignificant.     

Deriving Hounsfield units using grey levels in cone beam CT: a clinical application

Objective

To present a clinical study demonstrating a method to derive Hounsfield units from grey levels in cone beam CT (CBCT).

Methods

An acrylic intraoral reference object with aluminium, outer bone equivalent material (cortical bone), inner bone equivalent material (trabecular bone), polymethlymethacrylate and water equivalent material was used. Patients were asked if they would be willing to have an acrylic bite plate with the reference object placed in their mouth during a routine CBCT scan. There were 31 scans taken on the Asahi Alphard 3030 (Belmont Takara, Kyoto, Japan) and 30 scans taken on the Planmeca ProMax 3D (Planmeca, Helsinki, Finland) CBCT. Linear regression between the grey levels of the reference materials and their linear attenuation coefficients was performed for various photon energies. The energy with the highest regression coefficient was chosen as the effective energy. The attenuation coefficients for the five materials at the effective energy were scaled as Hounsfield units using the standard Hounsfield units equation and compared to those derived from the measured grey levels of the materials using the regression equation.

Results

In general, there was a satisfactory linear relation between the grey levels and the attenuation coefficients. This made it possible to calculate Hounsfield units from the measured grey levels. Uncertainty in determining effective energies resulted in unrealistic effective energies and significant variability of calculated CT numbers. Linear regression from grey levels directly to Hounsfield units at specified energies resulted in greater consistency.

Conclusions

The clinical application of a method for deriving Hounsfield units from grey levels in CBCT was demonstrated.     

Effective dose from cone beam CT examinations in dentistry

Cone beam CT (CBCT) is becoming an increasingly utilized imaging modality for dental examinations in the UK. Previous studies have presented little information on patient dose for the range of fields of view (FOVs) that can be utilized. The purpose of the study was therefore to calculate the effective dose delivered to the patient during a selection of CBCT examinations performed in dentistry. In particular, the i-CAT CBCT scanner was investigated for several imaging protocols commonly used in clinical practice. A Rando phantom containing thermoluminescent dosemeters was scanned. Using both the 1990 and recently approved 2007 International Commission on Radiological Protection recommended tissue weighting factors, effective doses were calculated. The doses (E(1990), E(2007)) were: full FOV head (92.8 microSv, 206.2 microSv); 13 cm scan of the jaws (39.5 microSv, 133.9 microSv); 6 cm high-resolution mandible (47.2 microSv, 188.5 microSv); 6 cm high-resolution maxilla (18.5 microSv, 93.3 microSv); 6 cm standard mandible (23.9 microSv, 96.2 microSv); and 6 cm standard maxilla (9.7 microSv, 58.9 microSv). The doses from CBCT are low compared with conventional CT but significantly higher than conventional dental radiography techniques.     

Intracranial physiological calcifications evaluated with cone beam CT

Objectives

The purpose of this study was to evaluate cone beam CT (CBCT) scans for the presence of physiological and pathological intracranial calcifications.

Methods

CBCT scans from male and female patients that met our ascertainment criteria were evaluated retrospectively (n = 500) for the presence of either physiological or pathological intracranial calcifications.

Results

Out of the 500 patients evaluated, 176 had evidence of intracranial physiological calcification (35.2% prevalence), and none had evidence of pathological calcification. There was a 3:2 male-to-female ratio and no ethnic predilection; the ages of affected patients ranged from 13 years to 82 years with a mean age of 52 years. The majority of calcifications appeared in the pineal/habenular region (80%), with some also appearing in the choroid plexus region bilaterally (12%), and a smaller subset appearing in the petroclinoid ligament region bilaterally (8%).

Conclusions

Intracranial physiological calcifications can be a common finding on CBCT scans, whereas pathological intracranial calcifications are rare.     

Three-dimensional segmentation of the upper airway using cone beam CT: a systematic review

The objectives of this study were to systematically review the literature for studies that used cone beam CT (CBCT) to automatically or semi-automatically model the upper airway (including the pharyngeal, nasal and paranasal airways), and to assess their validity and reliability. Several electronic databases (MEDLINE®, MEDLINE In-Process & Other Non-Indexed Citations, all evidence-based medicine reviews including the Cochrane database, and Scopus) were searched. Abstracts that appeared to meet the initial selection criteria were selected by consensus. The original articles were then retrieved and their references were searched manually for potentially suitable articles that were missed during the electronic search. Final articles that met all the selection criteria were evaluated using a customized evaluation checklist. 16 articles were finally selected. From these, five scored more than 50% based on their methodology. Although eight articles reported the reliability of the airway model generated, only three used intraclass correlation (ICC). Two articles tested the accuracy/validity of airway models against the gold standard, manual segmentation, using volumetric measurements; however, neither used ICC. Only three articles properly tested the reliability of the three-dimensional (3D) upper airway model generated from CBCT and only one article had sufficiently sound methodology to test the airway model''s accuracy/validity. The literature lacks proper scientific justification of a solid and optimized CBCT protocol for airway imaging. Owing to the limited number of adequate studies, it is difficult to generate a strong conclusion regarding the current validity and reliability of CBCT-generated 3D models.     

Comparison of conventional and cone beam CT synthesized cephalograms

OBJECTIVES: To compare cephalometric measurements from synthesized cone beam CT (CBCT) lateral cephalograms using orthogonal and perspective projections with those from conventional cephalometric radiographs and dry skulls. METHODS: Ten skulls were imaged using CBCT and conventional cephalometry. CBCT volume data were exported in DICOM format and imported in Dolphin 3D (pre-release version). Orthogonal and perspective lateral cephalometric radiographs were created from 3D virtual models. Nine linear and five angular measurements were made in Dolphin at three different times. Three calliper measures of midsagittal landmarks were made directly onto skulls. Perspective and conventional image measurements were corrected for known magnification. Reproducibility of measurements was assessed using multivariate analysis of variance (MANOVA). Linear and angular measurements were compared between image modalities by measurement using a repeated measures MANOVA model. Differences and absolute value of differences between image measurements and skull measurements were assessed using analysis of variance (ANOVA). RESULTS: Measurements were not different between the imaging modalities (P>0.05), except for the mandibular unit length (P=0.01). Linear midsagittal measurements were significantly greater than skull measurements for perspective CBCT and significantly less than skull measurements for conventional images (P=0.003). Precision of orthogonal CBCT midsagittal linear measurements was significantly better than the other modalities (P=0.007). Orthogonal CBCT projections provided more accurate midsagittal skull measurements than perspective CBCT or conventional cephalometric radiographs. CONCLUSIONS: CBCT can reproduce conventional cephalometric geometry with similar precision and accuracy. Orthogonal CBCT projections provided greater accuracy of measurement for midsagittal plane dimensions than perspective CBCT or conventional cephalometric images.     

Accuracy of linear intraoral measurements using cone beam CT and multidetector CT: a tale of two CTs

Objectives

The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT.

Methods

Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated.

Results

Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (−1.35 mm; 1.82 mm) than in CBCT (−0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (−0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%).

Conclusions

CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.     

Feasibility of low dose contrast material administration in CT coronary angiography using 320-detector CT scanner

目的:探讨单次心跳内采集数据320排CT冠状动脉成像时低对比剂用量的可行性.方法:将131例行冠状动脉CTA检查的病例分为3组,A组对比剂剂量为0.8ml/kg,注射流率4.5ml/s;B组对比剂剂量0.7ml/kg,注射流率5.0ml/s;C组对比剂剂量0.6ml/kg,注射流率5.5ml/s.所有病例心率均＜70次/分,单心跳采集心脏数据.分别在主肺动脉干、升主动脉、右冠状动脉和左冠状动脉主干内选择相同的兴趣区测量其CT值,采用单因素方差分析比较3组病例动脉强化程度的差异.结果:C组主肺动脉干CT值为(185.40±46.74)HU,强化程度最低,与A组和B组[分别为(225.77±79.69)和(216.79±51.06)HU]间差异有统计学意义(P＜0.05);各组之间升主动脉、右冠状动脉和左冠状动脉主干强化程度差异无统计学意义(P＞0.05).结论:320排CT冠状动脉成像能显著降低单心跳扫描患者对比别用量,并保证冠状动脉足够程度的强化.