Radiation doses in extraoral bitewing radiography compared with intraoral bitewing and panoramic radiography.

OBJECTIVES: We compared the effective dose (E) and thyroid equivalent dose of 2 extraoral bitewing (EOBW) units and compared E with their respective panoramic (PAN) modes and with intraoral bitewing radiography (IOBW). STUDY DESIGN: Child and adult anthropomorphic phantoms with dosimeters were used to evaluate Orthophos SL, Rayscan α+, and 1 intraoral unit using rectangular and circular collimation. Extraoral bitewing thyroid equivalent dose was assessed without and with thyroid shielding. RESULTS: Child and adult E values of EOBW were lower with Orthophos (3.6 and 8.6 µSv) than with Rayscan (28.1 and 30.2 µSv). For IOBW, E was lower with rectangular vs circular collimation for child (7.0 vs 11.8 µSv) and adult (4.6 vs 14.2 µSv). E values of EOBW were lower than PAN for Orthophos. The IOBW E was lower than Rayscan EOBW for child (≤11.8 vs 28.1 µSv) and adult (≤14.2 vs 30.2 µSv). Adult E for rectangular IOBW (4.6 µSv) was lower than EOBW with Orthophos (8.6 µSv) and Rayscan (30.2 µSv). Thyroid shielding reduced EOBW thyroid equivalent dose with Rayscan in the adult from 190.7 to 89.0 µSv. CONCLUSION: Orthophos provides significantly lower EOBW E than Rayscan, thus EOBW recommendations must be unit specific. For children, Orthophos EOBW could be an alternative to IOBW, for which rectangular collimation is recommended. Thyroid shielding reduced adult Rayscan equivalent dose but added imaging artifacts.

Evaluation of deep learning for detecting intraosseous jaw lesions in cone-beam computed tomography volumes.

OBJECTIVE: The study aim was to develop and assess the performance of a deep learning (DL) algorithm in the detection of radiolucent intraosseous jaw lesions in cone-beam computed tomography (CBCT) volumes. STUDY DESIGN: A total of 290 CBCT volumes from more than 12 different scanners were acquired. Fields of view ranged from 6 × 6 × 6 cm to 18 × 18 × 16 cm. CBCT volumes contained either zero or at least one biopsy-confirmed intraosseous lesion. 80 volumes with no intraosseous lesions were included as controls and were not annotated. 210 volumes with intraosseous lesions were manually annotated using ITK-Snap 3.8.0. 150 volumes (10 control, 140 positive) were presented to the DL software for training. Validation was performed using 60 volumes (30 control, 30 positive). Testing was performed using the remaining 80 volumes (40 control, 40 positive). RESULTS: The DL algorithm obtained an adjusted sensitivity by case, specificity by case, positive predictive value by case, and negative predictive value by case of 0.975, 0.825, 0.848, and 0.971, respectively. CONCLUSIONS: A DL algorithm showed moderate success at lesion detection in their correct locations, as well as recognition of lesion shape and extent. This study demonstrated the potential of DL methods for intraosseous lesion detection in CBCT volumes.

The effect of a deep-learning tool on dentists' performances in detecting apical radiolucencies on periapical radiographs.

OBJECTIVES: To determine the efficacy of a deep-learning (DL) tool in assisting dentists in detecting apical radiolucencies on periapical radiographs. METHODS: Sixty-eight intraoral periapical radiographs with CBCT-proven presence or absence of apical radiolucencies were selected to serve as the testing subset. Eight readers examined the subset, denoted the positions of apical radiolucencies, and used a 5-point confidence scale to score each radiolucency. The same subset was assessed by readers under two conditions: with and without Denti.AI DL tool predictions. For the two sessions, the performance of the readers was compared. The comparison was performed with the alternate free response receiver operating characteristic (AFROC) methodology. RESULTS: Localization of lesion accuracy (AFROC-AUC), specificity and sensitivity (by lesion) detection demonstrated improvements in the DL aided session in comparison with the unaided reading session. Subgroup performance analysis revealed an increase in sensitivity for small radiolucencies and in radiolucencies located apical to endodontically treated teeth.. CONCLUSION: The study revealed that the DL technology (Denti.AI) enhances dental professionals' abilities to detect apical radiolucencies on intraoral radiographs. ADVANCES IN KNOWLEDGE: DL tools have the potential to improve diagnostic efficacy of dentists in identifying apical radiolucencies on periapical radiographs.

Extraoral bite-wing radiographs: A universally accepted paradox.

BACKGROUND: The development of specialized panoramic radiograph machine software has spawned the introduction of an innovative and promising dental radiographic examination type: extraoral bite-wings. But does this unconventional type of imaging belong in the bite-wing family? Is there any relationship at all to the conventional bite-wing radiograph? OBJECTIVES: The purpose of this article is not to make a case for the diagnostic effectiveness of one system over the other; this is best left to further clinical evaluation. Instead, the authors intend to provide an outline of a few key and distinguishing elements of the intraoral bite-wing radiographic examination followed by those of the extraoral panoramic substitute and draw attention to the importance of reimagining the increasingly universal naming convention of this novel radiographic examination, the paradoxical "extraoral bite-wing radiograph", based on the fundamental principles of each of these imaging systems. PRACTICAL IMPLICATIONS: The accuracy of clinical and technical terminology in oral radiography is of paramount importance to both the profession and patients, especially when considering emerging technologies.

Dental microfracture detection using wavelet features and machine learning.

Microfractures (cracks) are the third most common cause of tooth loss in industrialized countries. If they are not detected early, they continue to progress until the tooth is lost. Cone beam computed tomography (CBCT) has been used to detect microfractures, but has had very limited success. We propose an algorithm to detect cracked teeth that pairs high resolution (hr) CBCT scans with advanced image analysis and machine learning. First, microfractures were simulated in extracted human teeth (n=22). hr-CBCT and microCT scans of the fractured and control teeth (n=14) were obtained. Wavelet pyramid construction was used to generate a phase image of the Fourier transformed scan which were fed to a U-Net deep learning architecture that localizes the orientation and extent of the crack which yields slice-wise probability maps that indicate the presence of microfractures. We then examine the ratio of high-probability voxels to total tooth volume to determine the likelihood of cracks per tooth. In microCT and hr-CBCT scans, fractured teeth have higher numbers of such voxels compared to control teeth. The proposed analytical framework provides a novel way to quantify the structural breakdown of teeth, that was not possible before. Future work will expand our machine learning framework to 3D volumes, improve our feature extraction in hr-CBCT and clinically validate this model. Early detection of microfractures will lead to more appropriate treatment and longer tooth retention.

Bitewing radiography dosimetry of a stationary intraoral tomosynthesis imaging system.

OBJECTIVES: This study assessed effective doses (E) from conventional and stationary intraoral tomosynthesis (s-IOT) radiography for posterior bitewing (PBW) examinations and evaluated the effect of sensor attenuation. STUDY DESIGN: An adult human tissue-equivalent phantom and optically stimulated luminescent dosimeters were used. Series of 4 PBW radiographs were acquired with circular and rectangular collimation. s-IOT PBW radiographs were acquired with built-in rectangular collimation. Radiographs were acquired without and with a sensor in the beam path. RESULTS: E (in µSv) was 15.7 and 8.2 for conventional-circular, 4.6 and 1.1 for conventional-rectangular, and 11.9 and 5.9 for s-IOT in sensor-absent and sensor-present scenarios, respectively. For sensor-absent exposures, E for conventional-rectangular was 29.3% and E for s-IOT was 75.8% of the conventional-circular dose. With the sensor present, these values were 13.4% and 72.0%, respectively (P < .001). Sensor-present E was lower than sensor-absent E for all modalities (P < .001). Reductions in equivalent doses were similar to effective dose reductions. CONCLUSIONS: For PBW examinations, E for s-IOT was smaller than for conventional radiography with circular collimation, but larger than for conventional radiography with rectangular collimation. The presence of a sensor maintained these differences but reduced E for all modalities.

The role of stationary intraoral tomosynthesis in reducing proximal overlap in bitewing radiography.

OBJECTIVES: This study examined the utility of stationary intraoral tomosynthesis (s-IOT) in opening proximal contacts in bitewing radiography. METHODS: 11 DENTSPLY Rinn Dental X-ray Teaching and Training Replica mannequins (Model #546002, Elgin, Ill) were imaged with a prototype s-IOT device (Surround Medical Systems, Morrisville, NC) and standard bitewing (SBW) technique. Premolar and molar bitewings were acquired with each system. Image receptor holders were used to position receptors and aid in the alignment of the position indicating devices. An expert operator (having more than 5 years of experience in intraoral radiography) acquired the images with the s-IOT prototype and standard intraoral X-ray devices. Images were assessed to analyze percentage overlap of the proximal surfaces using the tools available in ImageJ (NIH, Bethesda Maryland). RESULTS: 253-paired surfaces were included in the analysis. The difference in overlap was statistically significant with standard bitewing (SBW) images resulting in a median overlap of 13%, a minimum of 0%, a maximum of 100% and an interquartile range of 40%. s-IOT resulted in a median overlap of 1%, a minimum of 0%, a maximum of 37% and an interquartile range of 0%. The s-IOT prototype substantially reduced proximal surface overlap compared to conventional bitewing radiography. CONCLUSIONS: The use of s-IOT reduced proximal contact overlap compared to standard bitewing radiography for an experienced radiographer. Stationary intraoral tomosynthesis may be a potential alternative to SBW radiography, reducing the number of retakes due to closed contacts.

Comparing the diagnostic efficacy of intraoral radiography and cone beam computed tomography volume registration in the detection of mandibular alveolar bone defects.

OBJECTIVES: The aim of this study was to (1) compare bone loss detection accuracy with intraoral radiography and registered cone beam computed tomography (CBCT); (2) assess repeatability with both modalities; (3) determine factors affecting defect detection; and (4) determine the effect of buccolingual bone thickness on defect detection. STUDY DESIGN: Six observers viewed intraoral radiographs and CBCT scans before and after the defect to determine defect presence and extent. Receiver operating characteristic (ROC), sensitivity, specificity, logistic regression, odds ratio, intraclass correlation coefficient, and weighted kappa were used. RESULTS: CBCT and intraoral radiography mean ROC area under the curve values were not statistically different (0.90 vs 0.81; P = .06). CBCT had higher sensitivity compared with intraoral radiography (0.85 vs 0.63; P = .01) but similar specificity (0.91 vs 0.84; P = .45). Bone thickness, imaging modality, and observer had significant effects on defect detection (P < .001). Odds ratios for CBCT vs intraoral radiography were 2.29 for diagnostic accuracy and 1.52 for buccolingual bone thickness. There was moderate interobserver agreement for detection of defects and substantial intraobserver agreement for measurement of extent. CONCLUSIONS: CBCT showed equivalent diagnostic efficacy and specificity for defect detection and higher sensitivity compared with intraoral radiography. CBCT increases the odds of accurate defect assessment more than 2-fold compared with intraoral radiography. The odds of bone loss detection increase by approximately 50% per millimeter of buccolingual alveolar bone loss.

Characterization and preliminary imaging evaluation of a clinical prototype stationary intraoral tomosynthesis system.

PURPOSE: Technological advancements in dental radiography have improved oral care on many fronts, yet diagnostic efficacy for some of the most common oral conditions, such as caries, dental cracks and fractures, and periodontal disease, remains relatively low. Driven by the clinical need for a better diagnostic yield for these and other dental conditions, we initiated the development of a stationary intraoral tomosynthesis (s-IOT) imaging system using carbon nanotube (CNT) x-ray source array technology. Here, we report the system characterization and preliminary imaging evaluation of a clinical prototype s-IOT system approved for human use. METHODS: The clinical prototype s-IOT system is comprised of a multibeam CNT x-ray source array, high voltage generator, control electronics, collimator cone, and dynamic digital intraoral detector. During a tomosynthesis scan, each x-ray source is operated sequentially at fixed, nominal tube current of 7 mA and user-specified pulse width. Images are acquired by a digital intraoral detector and the reconstruction algorithm generates slice information in real time for operator review. In this study, the s-IOT system was characterized for tube output, dosimetry, and spatial resolution. Manufacturer specifications were validated, such as tube current, kVp, and pulse width. Tube current was measured with an oscilloscope on the analog output of the anode power supply. Pulse width, kVp, and peak skin dose were measured with a dosimeter with ion chamber and high voltage accessory. In-plane spatial resolution was evaluated via measurement of MTF and imaging of a line pair phantom. Spatial resolution in the depth direction was evaluated via artifact spread measurement. The size of the collimated radiation field was evaluated for compliance with FDA regulations. A dental phantom and human specimens of varying pathologies were imaged on a clinical 2D intraoral imaging system as well as s-IOT for comparison and to explore potential clinical applications. RESULTS: The measured tube current, kVp, and pulse width values were within 3% of the set values. A cumulative peak skin dose of 1.12 mGy was measured for one complete tomosynthesis scan using a 50-ms pulse per projection view. Projection images and reconstruction slices revealed MTF values ranging from 8.1 to 9.3 cycles/mm. Line pair imaging verified this result. The radiation field was found to meet the FDA requirements for intraoral imaging devices. Tomosynthesis reconstruction slice images of the dental phantom and human specimens provided depth resolution, allowing visibility of anatomical features that cannot be seen in the 2D intraoral images. CONCLUSIONS: The clinical prototype s-IOT device was evaluated and found to meet all manufacturer specifications. Though the system capability is higher, initial investigations are targeting a low-dose range comparable to a single 2D radiograph. Preliminary studies indicated that s-IOT provides increased image quality and feature conspicuity at a dose comparable to a single 2D intraoral radiograph.

Digital Radiographic Image Processing and Analysis.

This article describes digital radiographic imaging and analysis from the basics of image capture to examples of some of the most advanced digital technologies currently available. The principles underlying the imaging technologies are described to provide a better understanding of their strengths and limitations.

Automatic quantification framework to detect cracks in teeth.

Studies show that cracked teeth are the third most common cause for tooth loss in industrialized countries. If detected early and accurately, patients can retain their teeth for a longer time. Most cracks are not detected early because of the discontinuous symptoms and lack of good diagnostic tools. Currently used imaging modalities like Cone Beam Computed Tomography (CBCT) and intraoral radiography often have low sensitivity and do not show cracks clearly. This paper introduces a novel method that can detect, quantify, and localize cracks automatically in high resolution CBCT (hr-CBCT) scans of teeth using steerable wavelets and learning methods. These initial results were created using hr-CBCT scans of a set of healthy teeth and of teeth with simulated longitudinal cracks. The cracks were simulated using multiple orientations. The crack detection was trained on the most significant wavelet coefficients at each scale using a bagged classifier of Support Vector Machines. Our results show high discriminative specificity and sensitivity of this method. The framework aims to be automatic, reproducible, and open-source. Future work will focus on the clinical validation of the proposed techniques on different types of cracks ex-vivo. We believe that this work will ultimately lead to improved tracking and detection of cracks allowing for longer lasting healthy teeth.

The effect of image enhancements and dual observers on proximal caries detection.

OBJECTIVES: The aim of this study was to determine if the use of certain image enhancements and dual observers had an effect on the detection of caries, dentin extension, and cavitation. STUDY DESIGN: Seven observers viewed unenhanced and enhanced images taken on photostimulable phosphor plates (PSP) and Schick 33 sensors and were asked to determine whether proximal caries lesions, dentin extension, and cavitation were present. Pairs of observers also evaluated the unenhanced PSP images and recorded their confidence. Micro-computed tomography was used as the gold standard. RESULTS: For caries lesion detection, PSP outperformed Schick sensors, although the differences are most likely not clinically significant. Observers (single and dual) and filters had no effect on any of the diagnostic tasks. Schick sensors and unfiltered images were more specific for dentin extension. CONCLUSIONS: Caries detection was statistically greater with the PSP plate, but both detectors allowed for high accuracy. Expensive software or time-consuming consultations did not improve outcomes.

Cone-beam Computed Tomography Uses in Clinical Endodontics: Observer Variability in Detecting Periapical Lesions.

INTRODUCTION: The accurate interpretation of a cone-beam computed tomographic (CBCT) volume is critical in identifying the presence of disease correctly and consistently. The aim of this clinical study was to determine the effect of experience level on the detection of periapical lesions in CBCT volumes. METHODS: CBCT volumes of 22 maxillary molars were interpreted by 3 endodontic faculty, 3 endodontic residents, and 3 dental students. These groups were compared with the consensus opinion of 2 experienced oral and maxillofacial radiologists. The observers determined the presence or absence of apical radiolucencies for each root using a 5-point Likert scale. RESULTS: Compared with the radiologists, the average weighted kappa value for endodontic faculty was 0.49, for endodontic residents it was 0.35 and for dental students it was 0.32. Intrarater reliability for each group showed endodontic faculty having the highest average weighted kappa value of 0.68 followed by endodontic residents (0.48) and dental students (0.28). CONCLUSIONS: Clinicians' experience level appears to be correlated with their ability to correctly diagnose periapical disease in CBCT volumes. In addition, experience leads to better inter-rater reliability. In neither of these 2 categories was agreement found to be excellent, suggesting that more can be done to improve the CBCT interpretation skills of clinicians at various levels of experience.

Ex vivo evaluation of new 2D and 3D dental radiographic technology for detecting caries.

OBJECTIVES: Proximal dental caries remains a prevalent disease with only modest detection rates by current diagnostic systems. Many new systems are available without controlled validation of diagnostic efficacy. The objective of this study was to evaluate the diagnostic efficacy of three potentially promising new imaging systems. METHODS: This study evaluated the caries detection efficacy of Schick 33 (Sirona Dental, Salzburg, Austria) intraoral digital detector images employing an advanced sharpening filter, Planmeca ProMax(®) (Planmeca Inc., Helsinki, Finland) extraoral "panoramic bitewing" images and Sirona Orthophos XG3D (Sirona Dental) CBCT images with advanced artefact reduction. Conventional photostimulable phosphor images served as the control modality. An ex vivo study design using extracted human teeth, ten expert observers and micro-CT ground truth was employed. RESULTS: Receiver operating characteristic analysis indicated similar diagnostic efficacy of all systems (ANOVA p > 0.05). The sensitivity of the Schick 33 images (0.48) was significantly lower than the other modalities (0.53-0.62). The specificity of the Planmeca images (0.86) was significantly lower than Schick 33 (0.96) and XG3D (0.97). The XG3D showed significantly better cavitation detection sensitivity (0.62) than the other modalities (0.48-0.57). CONCLUSIONS: The Schick 33 images demonstrated reduced caries sensitivity, whereas the Planmeca panoramic bitewing images demonstrated reduced specificity. XG3D with artefact reduction demonstrated elevated sensitivity and specificity for caries detection, improved depth accuracy and substantially improved cavitation detection. Care must be taken to recognize potential false-positive caries lesions with Planmeca panoramic bitewing images. Use of CBCT for caries detection must be carefully balanced with the presence of metal artefacts, time commitment, financial cost and radiation dose.

Guide to Digital Radiographic Imaging.

This is a resource for clinicians who are considering purchasing a digital imaging system or those already using one who want to optimize its use. It covers selected topics in digital imaging fundamentals, detector technology, image processing and quality assurance. Through a critical appraisal of the strengths and limitations of digital imaging components, the goal of this guide is to contribute to the appropriate use of these systems to maximize the health benefit for patients.