Background There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose, a quantity with direct correlations to biologic risk from dental x-ray exposures. Objective The purpose of this study was to measure doses and to calculate the effective doses (E) resulting from exposure parameters that are used for stationary intraoral tomosynthesis (s-IOT) and conventional imaging for adult posterior bitewing examinations of the dentition. Additionally, this study sought to evaluate the effect of sensor attenuation on patient dose. Materials and Methods To meet these aims, a human tissue equivalent adult phantom and optically stimulated luminescent (Landauer, Inc., Glenwood, IL) dosimeters were used to measure dose produced during simulated posterior bitewing examinations (n = 4). Optically stimulated luminescent dosimeters were used to measure x-ray dose at 24 head and neck tissue/organ sites of interest. Dosimetry was acquired by using a tissue equivalent phantom simulating the anatomy of an average adult male (AtomMax Model 711 HN,CIRS Inc., Norfolk, VA). Exposure parameters used were 70 kV/7 mA (0.7 mAs) and 0.12 mAs for s-IOT and conventional (KaVo FOCUS, Charlotte, NC), respectively. Analysis of variance (ANOVA) and Tukey’s HSD (“honest significant difference”) statistics on dose were utilized to demonstrate significant data relationships. Results Tabled 1 Effective dose by modality (μSv) Modality Dose (μSv) Rectangular Conventional with Sensor 1.1 Rectangular Conventional without sensor 4.6 s-IOT with sensor 5.9 s-IOT without sensor 11.9 Circular Conventional with sensor 8.2 Circular Conventional without sensor 15.7 Open table in a new tab Sensor-present doses were significantly lower than sensor-absent for all modalities (P = .0001). Significant differences in E were found for all modality combinations with the exception of s-IOT sensor-present modalities vs conventional rectangular sensor-absent modalities (P = .0482). Discussion Unadjusted s-IOT dose was 26% less than conventional-circular exposures and 61% greater than conventional-rectangular for sensor-absent exposures. Unadjusted sensor-present s-IOT dose was 28% less than conventional-circular exposures and 81% greater than conventional-rectangular exposures. Despite a 4-fold increase in mAs for s-IOT imaging compared with conventional imaging, E from s-IOT imaging was at least 26% less than the current most commonly implemented bitewing technique, conventional-circular, while providing substantially greater diagnostic yield in the form of 3-dimensional (3-D) information. There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose, a quantity with direct correlations to biologic risk from dental x-ray exposures. The purpose of this study was to measure doses and to calculate the effective doses (E) resulting from exposure parameters that are used for stationary intraoral tomosynthesis (s-IOT) and conventional imaging for adult posterior bitewing examinations of the dentition. Additionally, this study sought to evaluate the effect of sensor attenuation on patient dose. To meet these aims, a human tissue equivalent adult phantom and optically stimulated luminescent (Landauer, Inc., Glenwood, IL) dosimeters were used to measure dose produced during simulated posterior bitewing examinations (n = 4). Optically stimulated luminescent dosimeters were used to measure x-ray dose at 24 head and neck tissue/organ sites of interest. Dosimetry was acquired by using a tissue equivalent phantom simulating the anatomy of an average adult male (AtomMax Model 711 HN,CIRS Inc., Norfolk, VA). Exposure parameters used were 70 kV/7 mA (0.7 mAs) and 0.12 mAs for s-IOT and conventional (KaVo FOCUS, Charlotte, NC), respectively. Analysis of variance (ANOVA) and Tukey’s HSD (“honest significant difference”) statistics on dose were utilized to demonstrate significant data relationships. Sensor-present doses were significantly lower than sensor-absent for all modalities (P = .0001). Significant differences in E were found for all modality combinations with the exception of s-IOT sensor-present modalities vs conventional rectangular sensor-absent modalities (P = .0482). Unadjusted s-IOT dose was 26% less than conventional-circular exposures and 61% greater than conventional-rectangular for sensor-absent exposures. Unadjusted sensor-present s-IOT dose was 28% less than conventional-circular exposures and 81% greater than conventional-rectangular exposures. Despite a 4-fold increase in mAs for s-IOT imaging compared with conventional imaging, E from s-IOT imaging was at least 26% less than the current most commonly implemented bitewing technique, conventional-circular, while providing substantially greater diagnostic yield in the form of 3-dimensional (3-D) information.

Background There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose (E), a quantity with direct correlations to biologic risk from dental x-ray exposures. Objectives The purpose of this study was to measure doses and calculate (E) from adult full-mouth examinations (FMXs) by using handheld and conventional wall-mounted x-ray sources with both circular and rectangular collimation (RC). Materials and Methods A human tissue-equivalent phantom and optically stimulated luminescent dosimeters were used to measure dose from simulated FMXs (n = 18) at 24 head/neck tissue sites. The parameters were 70 kV/7 mA (0.84 mAs and 1.34 mAs) for Conventional Circular and RC handheld device; 60 kV/2.5 mA (2.16 mAs) for NOMAD Circular and RC handheld device; and 60 kV/2.0 mA (1.98 mAs) for Xray2 Go Circular (XTG) handheld device. Analysis of variance (ANOVA) and Tukey’s HSD (“honest significant difference”) statistics demonstrated significant relationships. Results The FMX E (µSv) values were: NOMAD RC (6.9); XTG (16.7); NOMAD Circular (17.4); and Conventional Circular (26.3). For circular techniques, the handheld device E was significantly lower than the conventional unit for both devices (P < .0001). With RC, E was significantly lower than all circular techniques (P < .0001). Significant differences in E were found for all modality combinations except NOMAD Circular and XTG (P = .8329). Operator groin exposure was significantly higher (60%–90%) than thyroid, chest, and trigger hand exposures, which were indistinguishable from ambient background levels, for all handheld modalities (P < .0001). Discussion Handheld device E was at least 34% less than conventional circular and as much as 74% less with the use of RC. Operator exposure to the groin can increase significantly from overangulating the handheld sources; however, the addition of RC can reduce this exposure by as much as 76%. There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose (E), a quantity with direct correlations to biologic risk from dental x-ray exposures. The purpose of this study was to measure doses and calculate (E) from adult full-mouth examinations (FMXs) by using handheld and conventional wall-mounted x-ray sources with both circular and rectangular collimation (RC). A human tissue-equivalent phantom and optically stimulated luminescent dosimeters were used to measure dose from simulated FMXs (n = 18) at 24 head/neck tissue sites. The parameters were 70 kV/7 mA (0.84 mAs and 1.34 mAs) for Conventional Circular and RC handheld device; 60 kV/2.5 mA (2.16 mAs) for NOMAD Circular and RC handheld device; and 60 kV/2.0 mA (1.98 mAs) for Xray2 Go Circular (XTG) handheld device. Analysis of variance (ANOVA) and Tukey’s HSD (“honest significant difference”) statistics demonstrated significant relationships. The FMX E (µSv) values were: NOMAD RC (6.9); XTG (16.7); NOMAD Circular (17.4); and Conventional Circular (26.3). For circular techniques, the handheld device E was significantly lower than the conventional unit for both devices (P < .0001). With RC, E was significantly lower than all circular techniques (P < .0001). Significant differences in E were found for all modality combinations except NOMAD Circular and XTG (P = .8329). Operator groin exposure was significantly higher (60%–90%) than thyroid, chest, and trigger hand exposures, which were indistinguishable from ambient background levels, for all handheld modalities (P < .0001). Handheld device E was at least 34% less than conventional circular and as much as 74% less with the use of RC. Operator exposure to the groin can increase significantly from overangulating the handheld sources; however, the addition of RC can reduce this exposure by as much as 76%.

Background The first generation stationary intraoral tomosynthesis (sIOT) device, developed at University of North Carolina (UNC), provides 3-D information in intraoral imaging with a speed and dose comparable with those of traditional intraoral radiography. Initial research shows promise in several diagnostic tasks, including caries and fracture detection. However, the original iterative reconstruction produces artifacts adjacent to metal restorations. Two new iterative reconstructions with metal artifact reduction (MAR1 and MAR2) have been developed. MAR1 segments the metal out before reconstruction and adds it back after reconstruction. MAR2 minimizes the artifact amplified at each iteration by dividing the projected error by the number of slices. Objective(s) The aim of this study was to compare the effectiveness of metal artifact reduction in tomosynthesis. Study Design Pilot samples of 2 extracted premolars with amalgam restorations were imaged by using the sIOT system. Reconstructions were generated using the original, MAR1, and MAR2 algorithms. Using line density plots, artifact pixel intensity and artifact width were measured for the original, MAR1, and MAR2 algorithms. Results The difference between average dentin pixel intensity and artifact pixel intensity for sample 1 was 8016, –5781, and 759 for the original, MAR1, and MAR2 reconstructions, respectively. Artifact width was 2.61 mm, 0.82 mm, and 1.38 mm, respectively. For sample 2, the difference in intensity was 8248, –5399, and 93, respectively. Artifact width was 1.71 mm, 1.06 mm, and 0.81 mm, respectively. Discussion/Conclusions MAR1 and MAR2 reduced the intensity of the artifacts; however, reduction by MAR2 was more pronounced. MAR1 produced radiopaque artifacts, whereas MAR2 produced radiolucent artifacts. MAR1 and MAR2 reduced the width of the artifacts, but the extent was reversed between the samples. The results support the value of MAR for tomosynthesis and suggests that MAR2 may be more effective. Continued development of artifact reduction techniques is needed with a more in-depth study using a larger sample size. The first generation stationary intraoral tomosynthesis (sIOT) device, developed at University of North Carolina (UNC), provides 3-D information in intraoral imaging with a speed and dose comparable with those of traditional intraoral radiography. Initial research shows promise in several diagnostic tasks, including caries and fracture detection. However, the original iterative reconstruction produces artifacts adjacent to metal restorations. Two new iterative reconstructions with metal artifact reduction (MAR1 and MAR2) have been developed. MAR1 segments the metal out before reconstruction and adds it back after reconstruction. MAR2 minimizes the artifact amplified at each iteration by dividing the projected error by the number of slices. The aim of this study was to compare the effectiveness of metal artifact reduction in tomosynthesis. Pilot samples of 2 extracted premolars with amalgam restorations were imaged by using the sIOT system. Reconstructions were generated using the original, MAR1, and MAR2 algorithms. Using line density plots, artifact pixel intensity and artifact width were measured for the original, MAR1, and MAR2 algorithms. The difference between average dentin pixel intensity and artifact pixel intensity for sample 1 was 8016, –5781, and 759 for the original, MAR1, and MAR2 reconstructions, respectively. Artifact width was 2.61 mm, 0.82 mm, and 1.38 mm, respectively. For sample 2, the difference in intensity was 8248, –5399, and 93, respectively. Artifact width was 1.71 mm, 1.06 mm, and 0.81 mm, respectively. MAR1 and MAR2 reduced the intensity of the artifacts; however, reduction by MAR2 was more pronounced. MAR1 produced radiopaque artifacts, whereas MAR2 produced radiolucent artifacts. MAR1 and MAR2 reduced the width of the artifacts, but the extent was reversed between the samples. The results support the value of MAR for tomosynthesis and suggests that MAR2 may be more effective. Continued development of artifact reduction techniques is needed with a more in-depth study using a larger sample size.

AIM:To determine whether a CBCT volume can aid in the location of MB2 canals in maxillary molars.METHODOLOGY:This prospective clinical study involved 50 patients that needed RCT on a maxillary molar. The teeth where the MB2 was located upon access with the dental operating microscope received routine root canal treatment, and teeth where MB2 was not located had a CBCT volume made after instrumenting the located canals. At the second appointment, the clinician used the aid of the CBCT volume and troughing to attempt to locate MB2.RESULTS:The clinicians located MB2 upon initial access in 70% (n = 35) of teeth. In the remaining 15 teeth, CBCT and troughing located MB2 53% of the time in that group (8/15 teeth). Overall, MB2 was located in 86% of the 50 first and second maxillary molars (maxillary first molars 90% and maxillary second molars 73%). A total of 15 CBCT volumes were made, and of these teeth, 33% of MB2 canals (5/15 teeth) were visualized on the CBCT volume.CONCLUSIONS:This prospective clinical study showed that the effectiveness of using CBCT to locate additional MB2 canals in maxillary molars appears limited. The use of the dental operating microscope in conjunction with selective troughing and CBCT imaging allowed clinicians to locate 90% (maxillary first molars) and 73% (maxillary second molars) of MB2 canals.

Objectives: The aim of this study was to compare two methods of measuring mandibular asymmetry. The first method uses mirroring of the mandible in the midsagittal plane; the second uses mirroring of the mandible and registration on the cranial base. Methods: Surface models were constructed from cone beam CT (CBCT) scans of 50 patients with asymmetry. For the first approach, a midsagittal plane was defined for each patient as the plane passing through nasion, anterior nasal spine and basion. Mirrors for both halves of the mandible were created. The second approach consisted of mirroring the image volume by flipping the left and right sides and then registering the mirrored image onto the cranial base using a mutual information maximization method. Surface distances between hemimandibles and mirrors were calculated for nine regions. Results: There was no statistically significant difference between the mean surface distance measurements obtained with the two approaches and when comparing both halves in most areas. Conclusion: Both mirroring techniques provided similar quantification of mandibular asymmetry in this cohort.

Objectives: The purpose of this study was to determine if lateral half-skull cephalometric images and multiplanar reconstruction (MPR) images derived from cone-beam computed tomography (CBCT) image volumes provide more precise identification of landmarks than conventional cephalometric radiographs.

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.

The feasibility of local computed tomography (LCT) for the detection of longitudinal fractures was previously demonstrated. The mean Az value computed from receiver operating characteristic (ROC) curves was 0.91. To achieve this high level of accuracy, 180 basis projections were used to generate the image volume. It was recognized that future clinical application of this modality would require a significant reduction in dose. One approach to achieving a lower dose is to reduce the number of basis projections.

The two-dimensional nature of conventional intraoral radiography is a potentially limiting factor for the detection of interproximal caries. Changes in the projection geometry and superimposition of tooth structures have a marked impact on the radiographic appearance of a caries lesion. The development of Local CT (LCT) offers a new way to visualize caries lesions without the traditional constraints. LCT provides high resolution 3D images with a limited field of view.

Systematic prospective observational studies have led to significant progress in the application of orthognathic surgery to treat dentofacial deformity. Remodeling of the mandibular condyles, a potential factor in postsurgical stability, has not been adequately evaluated previously. The development of cone-beam CT (CBCT) scanners has made it feasible to follow changes of the condyles and relate them to treatment outcomes. In order to assess condylar changes in 3 dimensions using CBCT, new measurement procedures have been developed based on previous work by Harris et al.1Harris M.D. Van Sickels J.E. Alder M. Factors influencing condylar position after the bilateral sagittal split osteotomy fixed with bicortical screws.J Oral Maxillofac Surg. 1999; 57: 650-654Google Scholar To develop quantitative measurement techniques assessing 3D condylar position, orientation, and morphology using CBCT. Subjects were scanned presurgically and 3 times postsurgically with the NewTom QR-DVT 9000 (QR-NIM, Verona, Italy). Initial data of the first 15 subjects of an expected total sample of 100 subjects were collected. Preliminary measurements were limited to (1) condylar angulation and (2) mediolateral distance between the condyle and the midsagittal plane (MSP). Presurgical and 4-6 weeks postsurgical scans were evaluated. Six patients had maxillary surgery only and served as controls. Nine patients had 2-jaw surgeries. For each condyle, a set of axial slices encompassing the medial and lateral poles were transferred to ImageJ (NIH, Bethesda, Md). From the image stack a maximum-intensity image was created. After outlining the outer contour of the condyle, the angle of the major axis of a best-fit ellipse was calculated. The average of 3 consecutive measurements with a maximum separation of 1 degree was recorded. MSP was defined as the line dividing the clivus and the base of the vomer in equal halves. The condylar angles were calculated with respect to MSP. The median of the change in condylar angulation in the control group was 0.9 degrees (IQR = 1.2) and in the 2-jaw surgery group 3.3 degrees (IQR = 2.2) (Mann-Whitney P < .05). The change in distance between the condyle and MSP was 0.3 mm (IQR = 0.2) and 0.6 mm (IQR = 0.8), respectively (Mann-Whitney P > .05). These limited preliminary data suggest that CBCT measurements of condylar angulation and mediolateral position are sufficiently robust, allowing meaningful comparisons of groups. Subject recruitment, data collection, and registration of 3D models are ongoing.

Letter to the EditorResolution of digitized intraoral dental filmsJohn B Ludlow and André MolJohn B LudlowDepartment of Diagnostic Sciences and General Dentistry University of North Carolina School of Dentistry Chapel Hill, NC 27599-7450 USASearch for more papers by this author and André MolDepartment of Diagnostic Sciences and General Dentistry University of North Carolina School of Dentistry Chapel Hill, NC 27599-7450 USASearch for more papers by this authorPublished Online:28 Jan 2014https://doi.org/10.1259/dmfr/36572583SectionsPDF/EPUBFull Text ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About"Resolution of digitized intraoral dental films." Dentomaxillofacial Radiology, 33(3), p. 208 References 1. Künzel A, Scherkowski D, Willers R, Becker J. Visually detectable resolution of intraoral dental films. Dentomaxillofac Radiol 2003; 32: 385–389. Link ISI, Google Scholar2. Curry TS, Dowdey JE, Murry RC. Christiansen's physics of diagnostic radiology (4th edn). Philadelphia, PA: Lea & Febiger, 1990, pp 232. Google Scholar Previous article Next article FiguresReferencesRelatedDetails Volume 33, Issue 3May 2004Pages: 141-209 British Institute of Radiology History Published onlineJanuary 28,2014 Metrics Download PDF

OBJECTIVE:To compare films from three speed groups for the detection of approximal caries.STUDY DESIGN:Insight, Ektaspeed Plus and Ultra-speed (Eastman-Kodak, Rochester, NY, USA) radiographs of the proximal surfaces of 40 extracted posterior teeth were evaluated by six observers. The presence or absence of caries was scored using a 5-point confidence scale. The actual status of each surface was determined from histology of ground sections. Observer responses were evaluated using ROC analysis and areas under the ROC curves (A(Z)) assessed using ANOVA.RESULTS:Ultra-speed film had a mean A(Z) of 0.88, Ektaspeed Plus 0.85, and Insight 0.84. These differences were not statistically significant (P=0.5). Differences between observers were also not statistically significant (P=0.42).CONCLUSIONS:The performance of the new F-speed film was not statistically different from E or D speed for caries detection. This film shows promise as a means of reducing patient dose while maintaining diagnostic quality.

OBJECTIVE:A high-resolution charge-coupled device was used to compare the diagnostic performances obtained with Trophy's new RVGui sensor and Kodak Ektaspeed Plus film with respect to caries detection.STUDY DESIGN:Three acquisition modes of the Trophy RVGui sensor were compared with Kodak Ektaspeed Plus film. Images of the proximal surfaces of 40 extracted posterior teeth were evaluated by 6 observers. The presence or absence of caries was scored by means of a 5-point confidence scale. The actual caries status of each surface was determined through ground-section histology. Responses were evaluated by means of receiver operating characteristic analysis. Areas under receiver operating characteristic curves (A(Z)) were assessed through analysis of variance.RESULTS:The mean A(Z) scores were 0.85 for film, 0.84 for the high-resolution caries mode, and 0.82 for both the low resolution caries mode and the high-resolution periodontal mode. These differences were not statistically significant (P =.70). The differences among observers also were not statistically significant (P =.23).CONCLUSION:The performance of the RVGui sensor in high- and low-resolution modes for proximal caries detection is comparable to that of Ektaspeed Plus film.

Objective. This study compares the physical characteristics of the RVG UI sensor (RVG) with Ektaspeed Plus film. Study Design. Dose-response curves were generated for film and for each of 6 available RVG modes. An aluminum step-wedge was used to evaluate exposure latitude. Spatial resolution was assessed by using a line-pair test tool. Latitude and resolution were assessed by observers for both modalities. The RVG was further characterized by its modulation transfer function. Results. Exposure latitude was equal for film and RVG in the periodontal mode. Other gray scale modes demonstrated much lower latitude. The average maximum resolution was 15.3 line-pairs per millimeter (lp/mm) for RVG in high-resolution mode, 10.5 lp/mm for RVG in low-resolution mode, and 20 lp/mm for film (P <.0001). Modulation transfer function measurements supported the subjective assessments. Conclusions. In periodontal mode, the RVG UI sensor demonstrates exposure latitude similar to that of Ektaspeed Plus film. Film images exhibit significantly higher spatial resolution than the RVG images acquired in high-resolution mode. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:109-19)

Digital image processing has seen a wide variety of applications in dental radiography. Examples of operations from any of the fundamental classes can be found in the literature, and the increasing role of digital technology in dental imaging will promote new developments and clinical applications. Further progress is not limited by a lack of available image processing tools; rather, improvement of our understanding of the various components of diagnostic imaging will facilitate the meaningful use of new imaging technologies in dentistry. Image processing cannot be separated from other aspects of the diagnostic imaging chain. Its diagnostic value fundamentally depends on image acquisition as well as on aspects of vision and cognition. If used properly, image processing can help to improve diagnostic outcomes and provide insight into other aspects of the imaging process that may be limiting the diagnostic yield. Although novelty is still a powerful force driving some scientific endeavors, advances in dental imaging will be based on the purposeful, goal-oriented development and application of new technology. Specifications for useful image processing operations need to be defined with the diagnostic problem in mind as well as the final outcome for the patient.

An algorithm was designed to automatically obtain information on the orientation of roots in dental radiographs aimed at localizing the periapical region. A curve was approximated mathematically by a cubic polynomial to intersect the boundary of the root at its apex. The performance was judged by comparing the location of this intersection with the actual location of the apex as determined by five expert observers. In an experiment with 262 roots of the eight tooth groups, the distance between these two points was less than 1 mm in 67.9% of all cases and less than 2 mm in 88.2%. The performance of the procedure appeared to depend on the tooth group (p < 0.01). The location of the intersection was reproducible within 1 mm in 86.4% of all cases. The reproducibility was, however, not equal for all tooth groups (p < 0.01). The experts were more consistent in localizing the apex than the system was (p < 0.01), although this difference was not confirmed for four of the tooth groups (p > 0.57), and was marginal for two others (0.01 < p < 0.02). It is concluded that the algorithm is promising in its capacity to track a majority of roots down to their apex. It could therefore add important knowledge to imaging procedures aimed at the digital analysis of the periapical region.

Trabecular pattern, the radiographic projection of trabecular bone, is a repeated structure that appears in a dental radiograph. Texture analysis, the computer image analysis of repeated patterns, is a technique that can be used to automate the diagnosis of periapical lesions with the detection of the absence of the texture that corresponds to the trabecular bone. The purpose of this study was to determine whether it is feasible to use texture analysis to identify the presence of the trabecular pattern in radiographs and to detect a periapical bone lesion based on a local absence of this pattern. Thirty-two mandibular periapical films, 16 with and 16 without periapical lesions, were used in this study. Texture analysis was carried out on the digital images of these radiographs. In the 16 films with lesions, they were all correctly identified, and no lesions were found in the 16 films without lesions. This result is based on the a priori knowledge of the user about the localization of the disease. Locating periapical regions without user interaction is a goal for future research.

An image analysis system was developed for the computer-aided diagnosis of periapical bone lesions in dental radiographs. The system was designed to (1) identify the periapical region, (2) determine the presence of a periapical lesion and (3) estimate the size of the lesion in cases when a lesion had been found. To initiate the procedure, an observer indicates an arbitrary point on the root in a digitized radiograph. From this initial point, the location of the radiographic projection of the apex of the root is automatically computed. Next, the trabecular bone pattern is detected through texture analysis. A local absence of the trabecular bone pattern in the periapical region is marked as a periapical bone lesion. When a lesion has been identified, its size is estimated based on local edge properties. Observer interaction is only allowed to adjust the result of the apex localization procedure if the apex has not correctly been localized. In an experiment with randomly selected radiographs of 111 mandibular roots, the performance of the system was tested against the consensual diagnosis of four expert observers. The sensitivity of the system to identify a lesion was 83.3%, the specificity 75.6% and the diagnostic accuracy 80.2%. The correlation between the size of the lesions as estimated by the system and by the observers was 0.67 (P < 0.01). When the procedure was repeated, the percentage of correctly reproduced lesion sizes by the system was 92.8%. The determination of the presence of a lesion was reproducible in 98.2% of all the cases.