Measurement accuracy of reconstructed 2-D images obtained by multi-slice helical computed tomography

The present dental reconstructed computed tomography (CT) images consist of continuously piled-up axial CT images that are perpendicular to the axial CT plane. In the mandibular posterior region, the angles of designed implants frequently differ from the angles perpendicular to the axial CT plane and the measurement of mandibular height is inaccurate. This study was performed to clarify the measurement accuracy of double-oblique reconstructed images in multi-slice helical CT, using dried mandibles. The mandibular height was measured from the alveolar crest immediately below the aluminum tube to the superior border of the mandibular canal using the double-oblique reconstructed images and the micro-CT average images of three semi-lateral dried mandibles. The mean of the differences between the double-oblique reconstructed images with a table pitch of 1.5 in a helical scan and the micro-CT average images was 0.31 mm. It is concluded that the accuracy of the double-oblique reconstructed image measurements with helical scan is high. So this double-oblique program can be applied to the imaging diagnosis in dental implant treatment.     

Measurement of mandibles with microfocus x-ray computerized tomography and compact computerized tomography for dental use

PURPOSE: The trabecular bone patterns in jaws and tooth structure were analyzed using microfocus x-ray computerized tomography (micro-CT), and the usefulness of this method was reported. This study was performed to clarify the accuracy of micro-CT and to determine whether micro-CT could replace bone slice segments as a means for assessment of the accuracy of medical radiography units. In addition, the accuracy of compact CT for dental use (compact CT) was evaluated using the same method. MATERIALS AND METHODS: Three dried hemimandibles were used in this study. Images of mandibular interdental alveolar bone in the premolar and molar regions were obtained using micro-CT and compact CT. Measurement of the mandibular shape at 6 sites using micro-CT images and at 4 sites using compact CT images was performed, and then the values of the micro-CT and compact CT were compared with those of bone slice segments. RESULTS: The accuracy of mandibular measurement and the ratios of agreement for micro-CT were significantly higher than those for compact CT. Moreover, the coefficient of correlation of the rate of trabecular bone between compact CT images and bone slice segment images was 0.916. DISCUSSION: The significant difference in mandibular measurement between micro-CT and compact CT was considered to be related to pixel size. CONCLUSION: Micro-CT can replace bone slice segments for assessment of the accuracy of medical radiography units. In addition, compact CT can be used for imaging diagnosis in dental implant treatment. It is suggested that the ratio of trabecular bone could be used to evaluate the bone density.     

Accuracy of mandibular cross-sectional imaging with tuned- aperture computed tomography (TACT), iteratively reconstructed TACT, and multidirectional, linear, and transverse panoramic tomography

OBJECTIVE: This study was designed to compare 5 modalities with respect to accuracy in mandibular cross-sectional imaging. The modalities tested were tuned-aperture computed tomography (TACT), iteratively reconstructed TACT, multidirectional tomography, linear tomography, and transverse panoramic tomography. STUDY DESIGN: Twenty sites were selected from 3 dry human mandibles, and cross-sectional views were imaged through use of each of the 5 modalities. A quantitative analysis included measurements of 2 linear distances; a qualitative study included image evaluation by 6 observers. A nested mixed analysis of variance model was used to control for mandibles and locations within mandibles for the quantitative analysis; the Cochran-Mantel-Haenszel test was used for the qualitative analysis. RESULTS: There was a significant difference in measurement error for maximum height but not for width. There was also a significant difference in qualitative image evaluation results. CONCLUSIONS: Of the 5 modalities tested, the narrow-layer multidirectional tomographic technique produced the greatest diagnostic accuracy and quality in cross-sectional imaging. The transverse panoramic tomographic technique produced the least diagnostic accuracy and quality. Linear tomography, TACT, and iteratively reconstructed TACT were intermediate in accuracy and quality.     

Accuracy in measurement of distance using limited cone-beam computerized tomography

PURPOSE: The purpose of this study was to evaluate the accuracy of measurement of distance on the images produced by limited cone-beam computerized tomography (CT). MATERIALS AND METHODS: Five cadaver mandibles were examined by spiral computerized tomography (SCT) and limited cone-beam computerized tomography (LCBCT). The vertical distance from a reference point to the alveolar ridge was measured by caliper on the sliced mandible, and measurement error on the CT images was calculated in percentages based on the actual values and the measurement values obtained from the CT images. RESULTS: Measurement error was determined to range from 0 to 1.11 mm (0% to 6.9%) on SCT and from 0.01 to 0.65 mm (0.1% to 5.2%) on LCBCT, with measurement errors of 2.2% and 1.4%, respectively (P < .0001). DISCUSSION: This study suggests that distance can be measured accurately using LCBCT. The size of the rectangular solid images obtained using LCBCT (30 mm wide and 42.7 mm long) is thought to be adequate for observation of mandibular bony structure and for preoperative assessment before dental implant placement. CONCLUSION: In this experiment on cadaver mandibles, LCBCT was shown to be a useful tool for preoperative evaluation in dental surgery because the relatively small field size of its images limits the patient's exposure to radiation.     

Accuracy of magnetic resonance imaging compared with computed tomography for implant planning

Aim: The objective of this study was to evaluate the reliability of magnetic resonance imaging (MRI) compared with computed tomography (CT) for dental implant planning in respect to bone measurements. Methods: Five dry mandibles were submitted to MRI and CT examinations. Each mandible had three specific sites identified with markers, in a total of 15 sites to be studied. The images provided by the MRI and CT examinations were delivered to four specialists in Oral and Maxillofacial Radiology to measure the bone height at the specific sites. Subsequently, the bone height of the dry mandibles was directly measured in the determined sites. The measurements obtained by the specialists in MRI and CT images were compared with the measurements obtained directly from the dry mandibles using the ANOVA test with a 0.05 significance level. Results: The differences between the measurements obtained directly from the dry mandibles and the measurements from the MRI exams varied from 0.13 to 1.67 mm, with 10 sites being overestimated in MRI exams and five sites being underestimated. The differences between the measurements from the dry mandibles and CT exams varied from 0.02 to 1.25 mm, with nine sites being overestimated in CT exams and six sites being underestimated. The differences between the measurements from the MRI and CT exams varied from 0.03 to 1.00 mm, with nine sites giving higher values in MRI exams and six sites giving higher values in CT exams. There were no statistically significant differences between the three grous of measurements (P=0.98). Conclusion: The MRI, when compared with CT, shown to be reliable in respect to bone measurements for dental implant planning.     

Accuracy of computerized tomography for the evaluation of mandibular sites prior to implant placement

The objective of the present study was to observe the effect of positioning of the mandible on the accuracy of cross-sectional images obtained by reformatting computerized tomographic (CT) scans. An additional aim was to evaluate the ability of a software program (DentalVox, Era Scientific) to reconstruct these measurements on the reformatted images, regardless of the positioning of the mandible, accurately and without distortion. The test was carried out by examining a partially edentulous dry human mandible with an acrylic radiologic template. Through the use of an acrylic glass support, the mandible was positioned at angles of 0, 10, 15, 20, and 30 degrees relative to the scanning gantry, and a series of CT scans was performed that provided five sets of axial images. Each set of original axial images was reformatted by the DentalVox software, used first in its basic function, which is typical of all software for axial CT measurement (control group), and again in its function of site-specific multiplanar reconstruction (test group). The results showed that the position of the mandible in relation to the CT gantry can influence the precision of the linear measurements. The error ranged from 2% to 51%. The DentalVox software allowed the reconstruction of cross-sectional images with very little distortion regardless of the mandibular position.     

Linear measurement accuracy of CBCT panoramic reconstructions: experimental study with dry human mandibles

Introduction

Studies on software accuracy of reformatted panoramic computed tomography (CT) images are scarce.

Objectives

The aim of this study was to evaluate the software accuracy of reformatted panoramic views from cone-beam computed tomography (CBCT).

Methods

Ten dry mandibles were scanned using CBCT with different voxel sizes. Following the reconstruction of panoramic views with three different software, horizontal and vertical linear measurements were performed using the electronic rules of each software. Measurements of the corresponding dry mandibles were taken with a digital caliper and defined as the gold standard.

Results

There were no statistically significant differences in linear distances among the dry mandibles and reformatted panoramic CT views. The relative error ranged from 1.3 to 8.0%, depending on the software and voxel size.

Conclusions

The linear measurements on reformatted panoramic views are reliable.

     

Radiation absorbed from dental implant radiography: a comparison of linear tomography, CT scan, and panoramic and intra-oral techniques

Absorbed radiation dose in bone marrow, thyroid, salivary gland, eye, and skin entrance was determined by placement of lithium fluoride thermoluminescent dosimeters (TLD's) at selected anatomical sites within and on a human-like x-ray phantom. The phantom was exposed to radiation from linear tomographic and computer-assisted tomographic (CT) simulated dental implant radiographic examinations. The mean dose was determined for each anatomical site. Resulting dose measurements from linear tomography and computer-assisted tomography are compared with reported panoramic and intra-oral doses. CT examination delivered the greatest dose, while linear tomography was generally lowest. Panoramic and intra-oral doses were similar to those of linear tomography.     

Quality of preimplant low-dose tomography

OBJECTIVES: The aim of this study was to test the influence of radiation dose on image quality in mandibular preimplant computed tomographic examinations and to compare the quality of computed and conventional spiral tomographic images. STUDY DESIGN: Cross-sectional images were obtained on 17 patients with conventional spiral tomography (Scanora technique) and reformatted computed tomography at 40 and 80 mAs. Observers graded the acceptability of images for implant planning and traced the contour of the mandibular body and canal. RESULTS: Conventional spiral tomographic images scored significantly higher than computed tomographic images whereas mean score differences between computed tomographic techniques were not statistically significant. Anatomic structures, in particular the mandibular canal, were more frequently untraceable in high-dose than in low-dose computed tomography but always traceable in conventional tomograms. CONCLUSION: Conventional spiral tomograms were subjectively preferred over computed tomographic images. For mandibular implant planning, computed tomography examinations can be performed with lower-than-standard mAs. Quantum noise seems to contribute to the visibility of anatomic structures in reformatted computed tomographic images.     

Accuracy of linear vs spiral tomography: Alveolar crest to sinus/nasal floor height

AIM: To determine the accuracy of tomography in the linear measurement of alveolar bone at maxillary sinus/nose location. METHODS: Two dry skulls each marked with 10 pairs of guttaperchas placed on buccal and lingual sides of the maxillary ridge were used in this in vitro study. The distance between the alveolar crest and the sinus/nasal floor was measured on tomographic views, prepared by linear and spiral techniques. The ridges were then sectioned so that each section would include one pair of buccal and lingual guttaperchas. The actual distances directly measured on the sections were compared to those of the equivalent tomographic sections (the magnification co-efficient was applied). Paired t-test was used to statistically analyze the data. RESULTS: The measurement error with the application of linear tomography and spiral tomography was shown to be 0.455 ± 0.838 mm (P = 0.029) and 0.17 ± 0.78 mm (P = 0.347), respectively. There was a statistically significant difference between the liner tomography values and actual values (P = 0.029). This difference was representative of underestimation. McNamara’s test was used to assess the ± 1 mm error; 73.7% of the linear values and 84.2% of the spiral values were within the ± 1 mm error limit. McNamara’s test did not show any significant differences between the 2 methods in this regard (P = 0.625). The linear values were significantly different to the actual values (P = 0.029) but not to the spiral values (P = 0.185). CONCLUSION: Spiral tomography has enough accuracy for the measurement of alveolar ridge height. Although linear tomography somewhat underestimates the actual values it provides satisfactory accuracy.     

The role of objective plane angulation on the mandibular image using cross-sectional tomography

Cross-sectional jaw images in the buccolingual direction obtained by conventional or computerized tomography are used in the image diagnosis of dental implant treatment. This study was performed to clarify the subjective image quality of the mandibular depiction by shifting the angles of the tomographic objective plane. A panoramic machine with a linear tomographic function was used to obtain cross-sectional tomographic images on bilateral first molar regions of 10 dried human mandibles. The angles of tomographic objective planes were shifted horizontally within a range of +/- 20 degrees at intervals of 5 degrees from the tomographic objective plane, which was automatically determined. The image qualities of 4 anatomical structures-alveolar crest, buccal and lingual cortical bone, and mandibular canal-were subjectively scored on a 5-point scale method. As a result, the permitted tomographic objective angles were from -1.7 degrees to 2.5 degrees, a range of 4.2 degrees for all 4 anatomical structures. When this result was compared with a previous geometric result, the permitted range of the angles was quite narrow. The tomographic objective angles should be manually set in accordance with an optimal tomographic plane for individual patients by using the positioning technique in linear tomography.     

Radiologic measurements of the mandible: a comparison between CT-reformatted and conventional tomographic images

This study was carried out to compare the accuracy of determination of the mandibular contour and the position of the mandibular canal in cadaver mandibles by the multiplanar reconstruction method (MPR-CT), which has recently come to be used widely for preoperative examinations, with those by tomographic techniques and to evaluate the usefulness of MPR-CT. Using three imaging systems, i.e. Quantum CT scanner, Scanora, and OP-100, a total of 6 sites were scanned in the molar regions of 3 cadaver mandibles. The images obtained were measured twice each by 4 radiologists. The anatomic structures measured were the height and thickness of the mandible, distance from the alveolar crest to the mandibular canal, and distance from the buccal cortical bone to the mandibular canal. After scanning, the scanned areas of the mandibles were sliced at a thickness of 2 mm, and soft X-ray images of these slices were obtained. The values of the above 4 anatomic structures obtained by measurements in the soft X-ray radiograms using digital-display calipers were regarded as true values. When compared with the true values, the errors in the distance from the alveolar crest to the mandibular canal were within 1 mm (+/- 1 mm) in 93.7% of the measurements by Direct-CT, 89.6% of the measurements by MPR-CT, 87.5% of the measurements by Scanora, and 47.9% of the measurements by OP-100, and the accuracy of the 4 methods ranked in the order of Direct-CT, MPR-CT, Scanora, and OP-100. A similar tendency was observed in the measurements of other anatomic structures, and statistically significant differences were observed among the methods. Thus, MPR-CT allows more accurate measurements than by the other 2 tomographic techniques,and to be useful as a preoperative examination for implant surgery.     

锥形束CT用于评价离体牙槽骨高度准确性的研究

目的评价锥形束CT（CBCT）图像测量离体牙槽骨高度的准确性和可重复性,为其应用于牙周病的临床诊断和预后评价提供理论依据。方法使用CBCT对8具干燥下颌骨进行扫描,在图像上重复测量236个人工选择标志点处牙槽嵴顶至釉牙骨质界的距离;同时使用游标卡尺直接测量以上标志点处牙槽嵴顶至釉牙骨质界的距离。应用SPSS 13.0软件对所得数据进行统计学分析。结果CBCT图像对牙槽嵴顶至釉牙骨质界距离的重复测量结果间差异无统计学意义（P>0.05）;CBCT图像与游标卡尺对牙槽嵴顶至釉牙骨质界距离的测量结果间差异也无统计学意义（P>0.05）。结论CBCT图像可清晰显示牙与牙槽骨之间的空间解剖关系,其对牙槽骨高度体外测量的结果具有准确性和可重复性。     

Assessment of three-dimensional X-ray images: reconstruction from conventional tomograms, compact computerized tomography images, and multislice helical computerized tomography images

Three-dimensional X-ray images (3D images) were used for imaging diagnosis in the oral and maxillofacial region. These images could be fundamentally reconstructed from various tomograms, though clinical 3D images were mainly reconstructed from computerized tomography (CT) images. In this investigation, 3D images were reconstructed from conventional tomograms with a panoramic unit, compact CT images, and multislice helical CT images, and the usefulness of each system was subjectively assessed for dental implant treatment. Three hemilateral dried human mandibles were used and were examined by linear tomography with a panoramic unit, compact CT, and multislice helical CT, and 3D images were reconstructed by using the rendering software for each system. The 3D images were visually evaluated on a 5-point scale covering the alveolar ridge, buccal and lingual bone surface, mental foramen, and tooth sockets. As a result, 3D images reconstructed from conventional tomograms with the panoramic unit were assessed as fair to unsure, compact CT 3D images were assessed as unsure to good, and multislice helical CT 3D images were assessed as good to excellent. It was concluded that compact CT 3D images and multislice helical CT 3D images were useful in dental implant treatment.     

Effect of mandibular positioning on preimplant site measurement of the mandible in reformatted CT

The purpose of this study was to evaluate the effect of mandibular positioning on measurement of the reformatted cross-sectional image of the mandible in computed tomography (CT) according to the area on the mandible. Five dried mandibles, partially edentulous in the premolar and molar areas, were selected. The inferior border of the mandible was placed at 0-, 5-, 10-, 15-, and 20-degree angles to the CT scanning plane, and CTs were taken. The marked area of the reformatted cross-sectional image taken at each angle was found, and the distance from the most superior border of the mandibular canal to the alveolar crest was measured. As the angle between the CT scanning plane and mandibular plane increased, the distance from the most superior border of the mandibular canal to the alveolar crest also increased. The degree of increase was more pronounced in the posterior portion of the mandible than in the anterior portion of the mandible. As mandibular positional change in the CT gantry can affect the vertical measurement of the reformatted cross-sectional image, a correct guiding plane is necessary to accurately position the jaw to the CT scanning plane.     

Intra- and inter-observer variability and accuracy in the determination of linear and angular measurements in computed tomography. An in vitro and in situ study of human mandibles

The observer variability and accuracy of linear and angular computed tomography (CT) software measurements in the transaxial plane were investigated for the temporomandibular joint with the General Electric 8800 CT/N Scanner. A dried and measured human mandible was embedded in plastic and scanned in vitro. Sixteen observers participated in the study. The following measurements were tested: inter- and extra-condylar distances, transverse condylar dimension, condylar angulation, and the plastic base of the specimen. Three frozen cadaveric heads were similarly scanned and measured in situ. Intra- and inter-observer variabilities were lowest for the specimen base and highest for condylar angulation. Neuroradiologists had the lowest variability as a group, and radiology residents and paramedical personnel had the highest, but the differences were small. No significant difference was found between CT and macroscopic measurement of the mandible. In situ measurement by CT of condyles with structural changes in the transaxial plane was, however, subject to substantial error. It was concluded that transaxial linear measurements of the condylar processes free of significant structural changes had an error and an accuracy well within acceptable limits. The error for angular measurements was significantly greater than the error for linear measurements.     

Dimensional accuracy of a binder jet model produced from computerized tomography data for dental implants

A full-scale model produced by multislice helical computerized tomography (CT) was made by using the binder jet method and applied for presurgical diagnosis, surgical simulation, and the production of surgical templates for dental implant treatment. In this study, accuracy of the full-scale model with plaster powder was assessed by shifting the binary threshold values. A step phantom was made from bone-equivalent material. When it was placed in water, the CT imaging was performed with a multislice helical CT unit. Three-dimensional (3-D) images were reconstructed by 3-D visualization software. Using 4 different threshold values, full-scale models were produced by a binder jet method with plaster powder. All sides of the full-scale models were directly measured, and their values were compared with that of the step phantom. The mean difference was approximately 0.1 mm in the axial plane when the setting was 0.75 for the threshold. In total, the mean difference was approximately 0.2 mm when the setting was 0.50 for the threshold. It is suggested this full-scale model could be applied for presurgical diagnosis, surgical simulation, and the production of surgical templates in dental implant treatment.     

Digital volume tomography in the diagnosis of periodontal defects: an in vitro study on native pig and human mandibles

BACKGROUND: The aim of this study of native pig and human mandibles was to investigate the accuracy and quality of the representation of periodontal defects by intraoral radiography (IR), panoramic radiography (PR), computed tomography (CT), and digital volume tomography (DVT) in comparison with histologic specimens. METHODS: Following the standardized preparation of periodontal defects (14 dehiscences, fenestrations, 2- to 3-walled intrabony defects, respectively; Class I, II, and III furcation involvement) in six pig and seven human mandibles, IR, PR, CT, and DVT were performed. The histologic specimens were produced by cutting blocks with the individual defects out of the mandibles, embedding them in acrylic, and producing sagittal and axial microsections. The intrabony defects were measured using appropriate software on the digitized IR and PR images programs. The histologic sections were measured by reflecting stereomicroscopy. The statistical comparison between the measurements of the radiographic images and those of the histologic specimens was performed with Pearson's correlation coefficient. The quality of the radiographic images was determined through the subjective perception and detectability of the intrabony defects by five independent observers. RESULTS: All intrabony defects could be measured in three planes in the CT and DVT scans. Comparison with the histologic specimens yielded a mean deviation of 0.16 +/- 0.10 mm for the CT scans and 0.19 +/- 0.11 mm for the DVT scans. On the IR and PR images, the defects could be detected only in the mesio-distal and craniocaudal planes. In comparison with the histologic specimens, the IR images revealed a mean deviation of 0.33 +/- 0.18 mm and the PR images a mean deviation of 1.07 +/- 0.62 mm. The quality rating of the radiographic images was highest for the DVT scans. CONCLUSIONS: Overall, the CT and DVT scans displayed only a slight deviation in the extent of the periodontal defects in comparison with the histologic specimens. Both radiographic imaging techniques permitted imaging of anatomic osseous structures in three planes, true to scale, and without overlay or distortion. The DVT scans showed the best imaging quality.     

Precision,reproducibility, and accuracy of bone crest level measurements of CBCT cross sections using different resolutions

Objective:To evaluate the precision, reproducibility, and accuracy of alveolar crest level measurements on CBCT images obtained with different voxel sizes.Materials and Methods:CBCT exams were made of 12 dried human mandibles with voxel dimensions of 0.2, 0.3, and 0.4 mm. Bone crest level was measured directly on the mandibles with a digital caliper and on CBCT images. Images were measured twice by two examiners. Intra- and interexaminer precision and reproducibility were assessed using paired and t-tests, respectively. Accuracy was evaluated using t-tests.Results:Precision and reproducibility of bone crest level tomographic measurements was good for all voxel sizes evaluated. The images with 0.2-mm voxel size showed a decreased number of intraexaminer errors. A high accuracy for measurements of bone crest level was observed for all CBCT definitions, except for the mandibular incisors using the 0.4-mm voxel size.Conclusions:Precision and reproducibility of alveolar bone level measurements were good for various voxel sizes. CBCT images demonstrated good accuracy for 0.2-mm and 0.3-mm voxel sizes. The mandibular incisor region needs better resolution than that provided by 0.4-mm voxel size for bone crest level measurements.     

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.