Adaptive multi-resolution hash-encoding framework for INR-based dental CBCT reconstruction with truncated FOV.

To provide an indication-based and scanner-specific radiation dose and risk guide for paediatric patients undergoing dental and maxillofacial cone beam computed tomography (CBCT) examinations. Five commercially available scanners were simulated in EGSnrc Monte Carlo (MC) code. Dedicated, in-house built, head and neck voxel models, each consisting of 22 segmented organs, were used in the study. Organ doses and life attributable risk (LAR) for cancer incidence were assessed for males and females, aged 5 to 14years old, for every clinically available protocol: central upper and lower incisors, upper and lower premolars, upper and lower jaws, cleft palate, temporal bone, sinus, dentomaxillofacial complex, and face and skull imaging. Dose results were normalised to the x-ray tube load (mAs) and logarithmic curves were fit to organ dose and risk versus age data. Females demonstrated higher LAR values in all cases. A well-established dose decreasing pattern with increasing age-at-exposure was observed. Central upper incisor protocols were those with the lowest risk, contrary to skull protocols which provided the highest LAR values. Salivary glands and oral mucosa were the highest irradiated organs in all cases, followed by extrathoracic tissue (ET) in protocols where the entire nasal cavity was inside the primary field. The dose to thyroid was considerably high for younger patients. This work provides an extensive dose assessment guide for 5 dental CBCTs, enabling detailed dose assessment for every paediatric patient. • Radiation dose concerns due to the growing use of paediatric dental and maxillofacial CBCT underline the need for justification that should in part be based on radiation exposure in radiology. • Patient-specific dose calculations based on Monte Carlo simulations and head-neck paediatric voxel models overcome the limitations of conventional thermoluminescent dosimeter (TLD) dosimetry and provide proper guidance for justification of CBCT exposures. • Monte Carlo simulations with head-neck models reveal an organ dose and radiation risk decreasing pattern with increasing age at exposure, and with decreasing size of the scanning volume of interest (field of view).

To date there is a lack of published information on appropriate methods to determine patient doses from dental cone-beam computed tomography (CBCT) equipment. The goal of this study is to apply and extend the methods recommended in the American Association of Physicists in Medicine (AAPM) Report 111 for CBCT equipment to characterize dose and effective dose for a range of dental imaging equipment. A protocol derived from the one proposed by Dixon et al (2010 Technical Report 111, American Association of Physicist in Medicine, MD, USA), was applied to dose measurements of multi-slice CT, dental CBCT (small and large fields of view (FOV)) and a dental panoramic system. The computed tomography dose index protocol was also performed on the MSCT to compare both methods. The dose distributions in a cylindrical polymethyl methacrylate phantom were characterized using a thimble ionization chamber and Gafchromic™ film (beam profiles). Gafchromic™ films were used to measure the dose distribution in an anthropomorphic phantom. A method was proposed to extend dose estimates to planes superior and inferior to the central plane. The dose normalized to 100 mAs measured in the center of the phantom for the large FOV dental CBCT (11.4 mGy/100 mAs) is two times lower than that of MSCT (20.7 mGy/100 mAs) for the same FOV, but approximately 15 times higher than for a panoramic system (0.6 mGy/100 mAs). The effective dose per scan (in clinical conditions) found for the dental CBCT are 167.60 ± 3.62, 61.30 ± 3.88 and 92.86 ± 7.76 mSv for the Kodak 9000 (fixed scan length of 3.7 cm), and the iCAT Next Generation for 6 cm and 13 cm scan lengths respectively. The method to extend the dose estimates from the central slice to superior and inferior slices indicates a good agreement between theory and measurement. The Gafchromic™ films provided useful beam profile data and 2D distributions of dose in phantom.

Adaptive typhoon cloud image enhancement using genetic algorithm and non-linear gain operation in undecimated wavelet domain

The gray values accuracy of dental cone‐beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone‐beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis‐free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis‐free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1–9 were below 12% and gray value differences for ROIs 13–18 away from prostheses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant‐supported titanium prosthesis, and between 46% and 59% for regions between double implant‐supported, nickel‐chromium alloys (Ni‐Cr) prostheses. Quantification of the effect of prostheses and scanning parameters on dental CBCT gray values was assessed.PACS numbers: 87.59.bd, 87.57Q

Objective. Cone beam computed tomography (CBCT) has been wildly used in clinical treatment of dental diseases. However, patients often have metallic implants in mouth, which will lead to severe metal artifacts in the reconstructed images. To reduce metal artifacts in dental CBCT images, which have a larger amount of data and a limited field of view compared to computed tomography images, a new dental CBCT metal artifact reduction method based on a projection correction and a convolutional neural network (CNN) based image post-processing model is proposed in this paper. Approach. The proposed method consists of three stages: (1) volume reconstruction and metal segmentation in the image domain, using the forward projection to get the metal masks in the projection domain; (2) linear interpolation in the projection domain and reconstruction to build a linear interpolation (LI) corrected volume; (3) take the LI corrected volume as prior and perform the prior based beam hardening correction in the projection domain, and (4) combine the constructed projection corrected volume and LI-volume slice-by-slice in the image domain by two concatenated U-Net based models (CNN1 and CNN2). Simulated and clinical dental CBCT cases are used to evaluate the proposed method. The normalized root means square difference (NRMSD) and the structural similarity index (SSIM) are used for the quantitative evaluation of the method. Main results. The proposed method outperforms the frequency domain fusion method (FS-MAR) and a state-of-art CNN based method on the simulated dataset and yields the best NRMSD and SSIM of 4.0196 and 0.9924, respectively. Visual results on both simulated and clinical images also illustrate that the proposed method can effectively reduce metal artifacts. Significance. This study demonstrated that the proposed dual-domain processing framework is suitable for metal artifact reduction in dental CBCT images.

Letters to the Editor.

We aimed to assess the diagnostic accuracy of different cone beam CTs (CBCTs) and the influence of field of view (FOV) in diagnosing simulated periapical lesions. 6 formalin-fixed lateral mandibular specimens from pigs were used for creating 20 standardized periapical bone defects. 18 roots were selected for the control group. Three CBCT devices [Accuitomo 3D® (Morita, Kyoto, Japan), NewTom 3G (Quantitative Radiology, Verona, Italy) and Scanora® (Soredex, Tuusula, Finland)] and three FOVs (NewTom 3G® FOV 6, 9 and 12 inches) were used to scan the mandible. Five observers assessed the images, using a five-point probability scale for the presence of lesions. Specificity, sensitivity and areas under the receiver operating characteristic (ROC) curves were calculated. Sensitivity ranged from 72% to 80%. Specificity ranged from 60% to 77%. A difference in scoring between Scanora and the other two devices existed only in the control group. ROC analysis for different FOVs showed a decreased sensitivity with an increasing FOV, but this difference was not significant. the control group, there was a difference between the CBCT devices regarding their specificity. FOV size did not show any difference in diagnostic performance. In cases in which conventional radiographic methods in combination with clinical evaluation are not sufficient, CBCT may be the method of choice to assess periapical pathology. CBCT examinations should be complementary to a clinical examination and FOV adaptation can be utilized to keep the dose to the patient as low as possible.

The quality of dental pulp cone beam computed tomography (CBCT) images significantly impacts the accuracy of disease diagnosis. However, existing CBCT images often suffer from deficiencies such as artifacts, noise, resolution limitations and data processing issues, which frequently lead to misdiagnoses and missed diagnoses. This study aims to construct a highly accurate dental pulp CBCT image segmentation model based on the pulse-coupled neural network (PCNN) approach. By optimizing the PCNN model, this work sought to enhance the segmentation accuracy of dental pulp CBCT images and to evaluate the clinical efficacy of dental pulp revascularization surgery through quantitative analysis of the CBCT images, thereby improving the diagnostic accuracy of imaging data and the reliability of treatment outcome assessments. To achieve this, a cross-entropy thresholding method was introduced to optimize the PCNN model, establishing the Otsu-PCNN model for CBCT pulp segmentation. The model performance was evaluated using accuracy, sensitivity, positive predictive value (PPV) and the area under the receiver operating characteristic curve (ROC). The study involved 43 patients with pulp diseases who underwent dental pulp revascularization, with follow-ups conducted preoperatively and at 3, 6, 9, 12 and 18 months postoperatively. Changes in root image area (RIA), tooth root length (TRL) and apical diameter (AHd) were recorded, along with the classification of root development types. The results showed that the sensitivity and PPV of the Otsu-PCNN model were significantly higher than those of the optimized PCNN model ([Formula: see text]). The detection time for the Otsu-PCNN model was 13.80 s, with an ROC area of 0.93. The overall effective treatment rate for all patients was 100%. RIA, TRL and AHd increased from 30.55%, 2.58% and 19.95% at 3 months postoperatively to 84.85%, 25.18% and 51.62% at 18 months, respectively. Of the roots examined, 22 (48.84%) exhibited Type I root development. This study demonstrates that the optimization of the PCNN model significantly enhances the segmentation accuracy of dental pulp CBCT images, and that dental pulp revascularization surgery can effectively improve root development, yielding significant results in the treatment of pulp diseases.

Cone beam CT (CBCT) has been widely accepted as an imaging tool for a variety of dental and nondental applications. Although dental CBCT has evolved considerably in the last decade, there is still a lot of room for optimization of this modality at different levels. In this perspective, an overview is given of various hardware and software innovations that could be implemented in CBCT imaging in the foreseeable future. Some have already been applied to clinical practice but require further validation; others are being commonly applied by other imaging modalities and could be adapted for use in dental CBCT. The overview covers the x-ray tube, adaptive exposure techniques, beam and rotation geometry, detector technology and reconstruction algorithms. Furthermore, the combination of CBCT with optical imaging is discussed, the possibility of using these devices for nondental applications is evaluated, and the potential use of phase-contrast tomography is discussed.

In cone-beam computed tomography (CBCT), reconstructed images are inherently degraded, restricting its image performance, due mainly to imperfections in the imaging process resulting from detector resolution, noise, X-ray tube's focal spot, and reconstruction procedure as well. Thus, the recovery of CBCT images from their degraded version is essential for improving image quality. In this study, we investigated a compressed-sensing (CS)-based blind deconvolution method to solve the blurring problem in CBCT where both the image to be recovered and the blur kernel (or point-spread function) of the imaging system are simultaneously recursively identified. We implemented the proposed algorithm and performed a systematic simulation and experiment to demonstrate the feasibility of using the algorithm for image deblurring in dental CBCT. In the experiment, we used a commercially available dental CBCT system that consisted of an X-ray tube, which was operated at 90kVp and 5mA, and a CMOS flat-panel detector with a 200-μm pixel size. The image characteristics were quantitatively investigated in terms of the image intensity, the root-mean-square error, the contrast-to-noise ratio, and the noise power spectrum. The results indicate that our proposed method effectively reduced the image blur in dental CBCT, excluding repetitious measurement of the system's blur kernel.

Cone-beam computed tomography (CBCT) provides high-quality, three-dimensional imaging of the maxillofacial region. However, its use in pediatric patients remains controversial due to radiation dose concerns and the sensitivity of immature anatomical structures to radiation damage. This study aims to determine the prevalence and indications of dental CBCT usage in children. All CBCT images of pediatric patients under 15 years old, obtained from 2018 to 2025 at a university hospital, were retrospectively reviewed. Demographic data, indications for CBCT, imaging field of view (FOV), and average kVp and mA values were evaluated. Descriptive statistics and Chi-square tests were used for data analysis. A total of 266 CBCT images from children aged 5-14 years (mean age 11.06; 128 females, 138 males) were included. The prevalence of CBCT among all pediatric patients in this age group was found to be 2.1%. Of the CBCT scans, 175 were for the pathologies from maxilla, 88 from the mandible, and 3 involving both jaws. Imaging was most commonly performed in the anterior (incisor) region for both sexes, with a statistically significant higher rate in males (p<0.001). Surgical indications accounted for 81.6% of cases, while orthodontic indications comprised 18.4%. The most common reasons for CBCT imaging were impacted teeth (29.3%), pathological lesions (21.4%), supernumerary teeth (17.3%), and mesiodens (15.8%). The most frequently used FOV was 15x12 cm. The prevalence of CBCT use in pediatric patients is low and is primarily preferred before surgical interventions for impacted teeth and cyst/tumor-like lesions.

The recent use of cone beam computed tomography (CBCT) in the field of dentistry to obtain 3-dimensional (3D) images has enabled more effective examination and diagnosis in endodontic treatment. Such information has also been reported to be of benefit in surgical endodontic treatment such as intentional replantation. Here, we report a case of intentional replantation with the assistance of CBCT in which a good therapeutic outcome was achieved. The patient was a 30-year-old woman who visited our hospital with the chief complaint of spontaneous pain in the right maxillary first molar. Dental radiographs revealed a radiolucent area in the apical portion of the distal root, and a radiopaque area thought to be a broken shard from a small surgical instrument measuring approximately 1.5 mm in length. The shard was located outside the distal apical foramen. Based on these findings, the diagnosis was acute suppurative apical periodontitis of the right maxillary first molar. Infected root canal therapy was subsequently commenced. The patient's symptoms showed no improvement, however, and the pain persisted. Therefore, dental CBCT was performed to obtain 3D images, which confirmed a radiopaque area thought to be a broken shard from a small surgical instrument located outside the apical foramen of the distal root and facing in a direction that made it impossible to remove from the root canal. Because the patient's symptoms had shown no improvement and a foreign body was observed outside the apical foramen, intentional replantation combined with root resection was performed with informed consent. At a 1-year follow-up visit, progress was good, and there were no reported symptoms or signs. When reaching a diagnosis is difficult based on clinical findings and dental radiographs alone, the 3D images provided by CBCT offer a means of securing a more reliable diagnosis, allowing planning of treatment to be more effective.

Panoramic and intraoral radiographs are the basic imaging modalities used in dentistry. Often they are the only imaging techniques required for delineation of dental anatomy or pathology. Panoramic radiography produces a single image of the maxilla, mandible, teeth, temporomandibular joints and maxillary sinuses. During the exposure the x-ray source and detector rotate synchronously around the patient producing a curved surface tomography. It can be supplemented with intraoral radiographs. However, these techniques give only a two-dimensional view of complicated three-dimensional (3D) structures. As in the other fields of imaging also dentomaxillofacial imaging has moved towards 3D imaging. Since the late 1990s cone beam computed tomography (CBCT) devices have been designed specifically for dentomaxillofacial imaging, allowing accurate 3D imaging of hard tissues with a lower radiation dose, lower cost and easier availability for dentists when compared with multislice CT. Panoramic and intraoral radiographies are still the basic imaging methods in dentistry. CBCT should be used in more demanding cases. In this review the anatomy with the panoramic view will be presented as well as the benefits of the CBCT technique in comparison to the panoramic technique with some examples. Also the basics as well as common errors and pitfalls of these techniques will be discussed. Teaching Points • Panoramic and intraoral radiographs are the basic imaging methods in dentomaxillofacial radiology.• CBCT imaging allows accurate 3D imaging of hard tissues.• CBCT offers lower costs and a smaller size and radiation dose compared with MSCT.• The disadvantages of CBCT imaging are poor soft tissue contrast and artefacts.• The Sedentexct project has developed evidence-based guidelines on the use of CBCT in dentistry.

Background: Several factors must be considered when selecting the appropriate field of view (FOV) and voxel size for good image quality on Cone Beam Computed-Tomography (CBCT). The purpose of this study is to determine the factors that must be considered in selecting the appropriate FOV and voxel size to achieve good image quality according to the purpose of the examination. Method: Articles in Q1 and Q2 journals published within the period from January 2016 to September 2021 were searched from Scopus and PubMed online using the keywords field of view/FOV in CBCT, voxel size in CBCT, and FOV and voxel size in CBCT. On the basis of the article selection criteria, 13 journals were included in the study. Also included in the study were several types of three-dimensional (3D) CBCT machines: Planmeca ProMax® 3D ProFaceTM, i-Cat Cone Beam 3D, Picasso Trio CBCT: Carestream unit® CS 9300 CBCT, and Accuitomo F17D 3D CBCT. Result: It is generally recommended that a 0.2 mm voxel size be used to detect periodontal disease, secondary caries, fractures, external resorption, and endodontic complications. Meanwhile, for root fractures with an intracanal metallic post and an anatomic isthmus in the root canal, a 0.1 mm voxel size is recommended to be used, and for evaluating the implant, 0.3 mm and 0.4 mm voxel sizes are recommended. Conclusion: It was found in the review that most of the selected studies recommended using the smallest FOV available in the CBCT unit to detect pathological conditions and important anatomical structures.

Purpose: To reduce imaging radiation dose to the patient in cone-beam CT (CBCT) for image-guided radiation therapy via intensity-weighted region-of-interest (IWROI) imaging with a half-fan geometry. Methods: An intensity-weighting (IW) filter made of copper was mounted on the X-ray tube unit of the on-board imager (OBI) for CBCT data acquisition. Since a half-fan full-scan mode is the choice of scanning for most treatment sites including the chest and the abdomen due to its enlarged field-of-view (FOV), the half-fan scan mode has been used in this study. Accordingly, the IW filter was placed asymmetrically to cover outer part of the FOV. As a result, the region corresponding to the outer FOV was illuminated by the filtered beam during the scan. By sacrificing the image quality of the outer ROI-region, one can reduce the overall imaging radiation dose to the patient dramatically. A humanoid abdomen phantom was used for the IWROI imaging experiment. Both the Feldkamp-Davis-Kress (FDK) and the chord- based backprojection-filtration (BPF) algorithms were used for image reconstruction, and the results were compared. Correction of image artifacts caused by the edge of filter and the heterogeneity in beam-quality was also made. Results: FDK algorithm produced images with artifacts when truncated data were used, whereas the BPF algorithm was capable of reconstructing exact ROI images without truncation artifacts from the truncated cone-beam data. Dosimetric measurements are in progress to assess quantitative evaluation of imaging dose reduction. In addition, a feasibility study of image registration using the ROI images obtained by the proposed method is also going to be presented. Conclusions: The proposed half-fan-based IWROI imaging technique can be a valuable option for CBCT in IGRT applications, considering the substantial radiation dose imposed by the repeated use of conventional CBCT.