Gray Value Measurements Research Articles

Deep learning to assess bone quality from panoramic radiographs: the feasibility of clinical application through comparison with an implant surgeon and cone-beam computed tomography.

Bone quality is one of the most important clinical factors for the primary stability and successful osseointegration of dental implants. This preliminary pilot study aimed to evaluate the clinical applicability of deep learning (DL) for assessing bone quality using panoramic (PA) radiographs compared with an implant surgeon's subjective tactile sense and cone-beam computed tomography (CBCT) values. In total, PA images of 2,270 edentulous sites for implant placement were selected, and the corresponding CBCT relative gray value measurements and bone quality classification were performed using 3-dimensional dental image analysis software. Based on the pre-trained and fine-tuned ResNet-50 architecture, the bone quality classification of PA images was classified into 4 levels, from D1 to D4, and Spearman correlation analyses were performed with the implant surgeon's tactile sense and CBCT values. The classification accuracy of DL was evaluated using a test dataset comprising 454 cropped PA images, and it achieved an area under the receiving characteristic curve of 0.762 (95% confidence interval [CI], 0.714-0.810). Spearman correlation analysis of bone quality showed significant positive correlations with the CBCT classification (r=0.702; 95% CI, 0.651-0.747; P<0.001) and the surgeon's tactile sense (r=0.658; 95% CI, 0.600-0.708, P<0.001) versus the DL classification. DL classification using PA images showed a significant and consistent correlation with CBCT classification and the surgeon's tactile sense in classifying the bone quality at the implant placement site. Further research based on high-quality quantitative datasets is essential to increase the reliability and validity of this method for actual clinical applications.

Can we use X-ray CT to generate 3D penetration resistance data?

Noninvasive imaging of soils with X-ray CT has proven to be a useful method to assess soil structure from a pore space perspective. In contrast, methods like cone penetration tests reflect soil structure from the perspective of the soil matrix as assessed by its mechanical strength. Because both the gray value (GV) obtained with X-ray CT and the penetration resistance (PR) obtained with a cone penetration test depend on soil density there should be a relationship between the two. To the best of our knowledge, no studies attempted so far to investigate the nature of the PR ∼ GV relationship and to understand how well PR and GV are correlated. We aimed at bridging that gap and carried out a combined analysis of local GV and PR with undisturbed soil cores sampled in two soil textures, i.e., loam and sand. To carry out the GV measurements, we developed a new approach which considers an adaptive volume of the zone of influence of the penetrometer tip as a function of soil density. For sand and when looking at samples individually, the correlation between PR and GV was best when the soil microscale heterogeneity was high, i.e., when dense and loose zones of soil were present on the course of the penetrometer tip. For loam, the correlation between PR and GV was not dependent on soil heterogeneity. When looking at the whole dataset, the agreement between PR and GV was better in loam than in sand, with a distance correlation metric of 0.66 for loam and 0.34 for sand, respectively. For loam, the relationship PR ∼ GV had a trend which was similar to that of a hyperbola, i.e., with escalating PR values in a narrow GV range. For sand, no particular model could be recognized. In order to provide a proof-of-concept on how to generate 3D PR maps, the co-located measurements of GV and PR were used to establish an empirical relationship and X-ray CT was used to extrapolate it in 3D. This was carried out with the loam dataset by fitting a hyperbolic function to the PR ∼ GV data pairs. This model was then used to convert GVs into PR values, at a spatial resolution equal to that of the shaft diameter of the penetrometer tip we have used. Notwithstanding the fact that the suggested approach is dependent on numerous experimental conditions and edaphic factors, we advocate for the use of 3D PR maps. These maps could be used in root-soil interactions research, for which the study and breeding of cultivars that could show plastic response in their root systems under mechanical stress is becoming more and more important. This is particularly relevant in the context of mechanized modern agriculture.

Correlation of powder degradation, energy absorption and gas pore formation in laser-based powder bed fusion process of AlSi10Mg0.4

Gas pore formation observed during laser-based powder bed fusion is yet not fully understood. This study is a comprehensive investigation of the mechanisms of hydrogen pore formation in the powder bed fusion process of AlSi10Mg0.4 via laser beam. The influence of varying process parameters such as hatch distance, layer thickness and build plate temperature as well as the impact of virgin and long-term reused powder on part porosity and melt pool characteristics is investigated in detail. A novel, very efficient method to characterize powder aging by the correlation of powder gray value measurements with the oxygen content is presented. The relation between powder aging and the change of the absorption coefficient reveals the origin of gas formation as being intimately related to the energy input. Vacuum heat treatment of as-built parts indicates the potential of hydrogen removal in a postprocessing step with the prospect of welding additively manufactured aluminum parts.

Comparison of Trabecular Bone in Impacted and Normal Erupted Unilateral Maxillary Canine Teeth Using Cone-Beam Computed Tomography in Patients Scheduled for Orthodontic Treatment at the Universitas Airlangga Dental and Oral Hospital

Background. Cone-beam computed tomography is being utilized in more clinical contexts and determining bone density with this method is becoming more important. Dentists, particularly dentomaxillofacial radiologists, orthodontists, and oral surgeons, must have a solid understanding of gray value. The gray values acquired from conebeam computed tomography images are used to assess dental implant bone density, diagnose dental ankylosis, and diagnose and differentiate pathological lesions. Objective. To determine the difference in the gray value of the trabecular bone in the impacted and normal erupted maxillary canine teeth using cone computed tomography. Methods. We retrospectively evaluated the cone-beam computed tomography images of patients scheduled for orthodontic treatment at the Universitas Airlangga Dental and Oral Hospital. On cross-sectional cone-beam computed tomography images, the region of interest determination of 5 mm2 in the area was placed in the trabecular bone and the gray value measurements were collected using Digital Imaging and Communications in Medicine (OnDemand3D™) dental software. The images were categorized by type of impacted canine teeth after assessing the gray values of all the teeth. Using images on the mesial, distal, buccal, and palatal areas, gray values of impacted and non-impacted teeth were compared. We used the SPSS 24 software. Results. From a total of 13 patient radiographs, we found types I (6/13), II (6/13), and VII (1/13). The mean pixel values of impacted maxillary unilateral canine teeth were 1972.92 (mesial), 2016.55 (distal), 1990.66 (buccal), and 1904.39 (palatal). The mean pixel values of normal erupted maxillary canines were 1754.93 (mesial), 1710.53 (distal), 1852.94 (buccal), and 1674.49 (palatal). There were significant differences between impacted and normal erupted maxillary canines: mesial (P = 0.018), distal (P = 0.000), buccal (P = 0.003), and palatal (P = 0.036). Conclusion. There were statistically significant differences between affected and unaffected gray values in the canines in FOV size 51 × 55 mm. However, no statistically significant differences were found in the gray values in trabecular bone of unilateral maxillary impacted canines and normal erupted canines on the mesial, distal, buccal, and palatal sides.

Gray value measurement for the evaluation of local alveolar bone density around impacted maxillary canine teeth using cone beam computed tomography.

Background To investigate whether any relationship between local alveolar bone density and maxillary canine impaction using gray values from cone beam computed tomography.Material and Methods The cone beam computed tomography images of 151 patients were retrospectively evaluated. Maxillary canine was defined as an impacted tooth when root formation was complete and the patient’s age older than 13 or the other side of the maxillary canine has completely erupted. Similarly, complete eruption was defined as the tooth in its expected occlusion and position. Using the cone beam computed tomography software, the region of interest which was 5 mm2 in area, was placed in the trabecular bone on cross sectional cone beam computed tomography images and the gray value measurements were recorded. After measuring the gray values of all the teeth, the images were grouped according to the field of view size. Comparison of the gray values of impacted and non-impacted teeth was made between images with the same field of view size.Results A total of 151 patients, 101 (66.9%) female and 50 (33.1%) male, were included in the study. The mean age of the patients was 24.94 ±13.9. In images with a 40X40 field of view, the gray values of the impacted canine teeth were higher than the gray values of the non-impacted ones and statistically significant difference was found between them (p=0.003). However no statistically significant difference was found between the gray values of impacted and non-impacted canine teeth in 60x60 and 100x50 field of view (p=0.197, p=0.170, respectively).Conclusions We suggest using the smallest field of view size when evaluating bone density using gray values from cone beam computed tomography images and we support the idea that the local increased bone density may influence on impaction. Key words:Cone-beam computed tomography, tooth, impacted, bone density, maxilla, image processing, computer-assisted.

Impact of the endocannabinoid system on murine cranial and alveolar bone phenotype

PurposeThe endocannabionoid signaling system has been demonstrated to be present in the skeleton, with involvement in the regulation of skeletal homeostasis. However, investigations substantiating these findings in cranial and alveolar bones are missing to date. The aim of our study was to investigate a potential impact of the endocannabinoid system on cranial and alveolar bone structures and phenotypes. Basic proceduresCB1-/-, CB2-/- and WT mice (n = 5) were scanned via μCT. Reconstructed datasets were processed for analyses. Cranial cephalometric measurements were performed with OnyxCeph3TMsoftware. Alveolar bone densities were determined via mean grey value measurements with Mimics research 18.0. Alveolar bone heights around teeth in upper and lower jaws were morphometrically analyzed. Alveolar osteoclasts were quantified via TRAP staining of paraffin-embedded histologies. Bone-marrow derived macrophages isolated from murine hind legs were analyzed for CD40 and MMR expression via flow cytometry. Main findingsCB2-/- mice exhibited significantly higher bone densities with mean grey values of 138.3 ± 22.6 compared to 121.9 ± 9.3 for WT for upper jaws, and 134.6 ± 22.9 compared to 116.1 ± 12.9 for WT 134.6 ± 22.9. Concurrently, CB2 receptor knockout entailed reduced alveolar bone heights of about 50% compared to WT mice. Antigen-presenting cell marker expression of MMR was significantly diminished in bone-marrow derived macrophages of CB2-/- mice. Cranium dimensions as much as alveolar osteoclasts were unaffected by receptor knockouts.CB1 receptor knockout did not involve statistically significant alterations in the parameters investigated compared to WT mice. Principal conclusionsThe endoncannabinoid system, and particularly CB2 receptor strongly affects murine alveolar bone phenotypes. These observations suggest CB2 as promising target in the modulation of oral bone phenotypes, probably by impact on bone dynamics via osteal immune cells.

Qualitative and Quantitative Assessment of Alveolar Bone Destruction in Adult Rats Using CBCT.

Cone-beam computed tomography (CBCT) has strong potential to be utilized in various aspects of veterinary dentistry. Using ex vivo rat maxillary bone and teeth, the purpose of this study was to compare gray value, surface area, and volumetric measurements of teeth with and without experimental periodontitis by CBCT. Periodontitis was induced in 36 molar teeth, while 36 teeth with a healthy periodontium served as control. Images of each specimen along with teeth were obtained using CBCT. The following measurements for each tooth with periodontitis (n = 36) were recorded: gray value measurement, width, height, depth, surface area, and volume of the alveolar bone loss. For the control group (n = 36), gray value measurement, surface area, and volume of the alveolar bone were recorded. All measurements were repeated after 3 weeks. As the gold standard, the rat maxillas were decalcified and paraffin-embedded for further immunocytochemical study. One-way analysis of variance (ANOVA) was used. Significance level was set at P < .05. Correlation values for gray value, width, height, depth, surface area, and volume measurements were 0.983, 0.966, 0.962, 0.880, 0.998, and 0.999, respectively, for the first and second measurements. One way ANOVA showed statistically significant differences between teeth with and without alveolar bone destruction conducted for gray value, surface area, and volume measurements (P = .000). Mean gray value, surface area, and volume measurements decreased 56.46%, 81.89%, and 78.56%, respectively, for teeth with alveolar bone destruction in comparison to healthy teeth. Cone-beam computed tomography provided useful qualitative and quantitative information regarding induced periodontitis in the rat maxilla.

Detecting bone changes along dental implants, after immediate or delayed loading, using digital subtraction on cropped panoramic radiographs. A prospective clinical trial with minimum 3-year follow up

Aim The aim of this study was to assess bone changes along implants after immediate or delayed loading, using subtractions of digital images originated from cropped panoramic radiographs and visual evaluation. Materials and methods Eleven patients received 4 Ankylos implants interforaminal in the mandible. In 7 patients the implants were loaded immediately and 4 followed delayed loading. All patients were restored with a telescopic overdenture with Syncone abutments. From each patient 3 panoramic radiographs (PRs) were obtained: upon delivery of the restoration (T1), 6 months later (T2) and after 3 years (T3). 33 implants were finally selected. The radiographs were analyzed using the Emago® Software. The grey scale values were measured either manually (Stage A) or automatically (Stage B) in six areas (neck, middle and apex; both mesially and distally) along the implants’ sides to evaluate the bone density during clinical function. Images were also visually evaluated by five observers to detect bone changes at the cervical implant area. Results Strong positive correlation between the two stages (A and B) was found in all 3 examinations (Pearson’s r 0.84-0.98). The t-test showed no statistically significant differences in grey level values between immediate and delayed loading (p<0.05) and no statistically significant changes in the visual evaluation among implants undergoing either immediately or delayed loading (p<0.05). Conclusions Emago® is a valuable method for bone level assessment around implants’ neck. The grey value measurements of the bone adjacent to the implants that have been loaded either immediately or delayed do not significantly differ after 3 years of fuction. The visual assessment of the PRs images supports these findings.

Quantitative Features of the Choriocapillaris in Healthy Individuals Using Swept-Source Optical Coherence Tomography Angiography.

To quantify vessel density (VD) and grey value (GV) as a measure of flow in the choriocapillaris (CC) in healthy subjects with optical coherence tomography angiography (OCTA). In this prospective, noncomparative case series, 3 mm × 3 mm OCTA images of 36 eyes of 22 healthy individuals were obtained using a swept-source instrument. VD and GV levels were calculated on CC en face slabs in the central 1-mm (subfoveal field) and surrounding 2.5-mm parafoveal ring. VD was calculated as a ratio of vessel area over nonvessel area following image binarization. GV was computed as the mean, un-normalized greyscale intensity value for all pixels in the region of interest. For each eye, the procedure was repeated 1 minute to 2 minutes later and intersession repeatability was analyzed. The choroidal thickness (CT) was automatically measured in the subfoveal and parafoveal regions and compared to VD and GV values. The VD ratio and GV was lower in the subfoveal field than in the parafoveal four sectors. The intersession intraclass correlation coefficients were high for both VD and GV measurements. There was no correlation observed between CT and VD or GV. Quantitative metrics can be obtained from CC OCTA en face images. These values show moderate to good intersession repeatability. These normative data may be of value as a reference of comparison in future studies of eyes with disease. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:623-631.].

Quinolinic acid-immunoreactivity in the naïve mouse brain

Quinolinic acid (QUIN) has been suggested to be involved in infections, inflammatory neurological disorders and in the development of psychiatric disorders. In this view, several studies have been performed to investigate QUIN localization in the brain and its neurotoxic effects. However, evidence is lacking regarding QUIN in healthy, control conditions. The aim of this study was to investigate the region-specific distribution and pattern of QUIN expression in the naïve mouse brain. In addition, possible sex differences in QUIN-immunoreactivity and its link with affect-related behavioural observations were assessed.For this purpose, naïve mice were subjected to the forced swim test (FST) and 20min open field (OF) testing to measure affect-related behaviour. Afterwards, brains were assessed for QUIN-immunoreactivity. QUIN-immunoreactivity was particularly observed in the cingulate cortex (CC), highlighting clearly delineated cells, and the thalamic reticular nucleus (TRN), showing a more diffuse staining pattern. Subsequently, QUIN-positive cells in the CC were counted, while QUIN-immunoreactivity in the TRN was examined using gray value measurements. No significant differences between sexes were observed for the number of QUIN-positive cells in the CC, neither in levels of QUIN-immunoreactivity in the TRN. A direct correlation was found between QUIN-positive cells in the CC and QUIN-immunoreactivity in the TRN. Moreover, in male mice, a very strong correlation (rsp=.943; p<.01) between QUIN-immunoreactivity at the level of the TRN and motor activity in the OF was observed. Thus, our results suggest that QUIN – detected in the CC and the TRN – may play a role in regulating motor activity in normal conditions.

Assessment of metal artefact reduction around dental titanium implants in cone beam CT.

The aim of this study was to investigate if the metal artefact reduction (MAR) tool used in the software of the ORTHOPANTOMOGRAPH(®) OP300 (Instrumentarium Dental, Tuusula, Finland) can improve the gray value levels in post-operative implant scans. 20 potential implant sites were selected from 5 edentulous human dry mandibles. Each mandible was scanned by a CBCT scanner, and images were produced under three different conditions: implant sites drilled but no implants inserted, implants inserted without application of MAR and implants inserted with application of MAR. Using Geomagic(®) Studio 2012 (Geomagic, Morrisville, NC) and 3Diagnosys(®) v. 5.3.1 (3Diemme(®) SRL, Cantù, Italy) software, three scans of each mandible were superimposed. The mean gray value of identical regions of bone around the implants was derived for each condition. The differences between gray value measurements at implant sites derived from different conditions were assessed. A significant difference was found between mean gray values from the scans with no implants inserted and with implants inserted (with and without MAR) (p = 0.012). No significant difference was revealed for gray values measured from scans with and without MAR (p = 0.975). The MAR tool in the software of the ORTHOPANTOMOGRAPH OP300 CBCT scanner does not significantly correct the voxel gray values affected by the metal artefact in the vicinity of an implant in human dry mandibles.

Influence of object location in cone beam computed tomography (NewTom 5G and 3D Accuitomo 170) on gray value measurements at an implant site

Objectives The aim of this study was to determine the gray value variation at an implant site with different object location within the selected field of view (FOV) in two cone beam computed tomography (CBCT) scanners.

Influence of cone beam CT scanning parameters on grey value measurements at an implant site

The aim of this study was to determine the grey value variation at the implant site with different scan settings, including field of view (FOV), spatial resolution, number of projections, exposure time and dose selections in two cone beam CT (CBCT) systems and to compare the results with those obtained from a multislice CT system. A partially edentulous human mandibular cadaver was scanned by three CT modalities: multislice CT (MSCT) (Philips, Best, the Netherlands), and two CBCT systems: (Accuitomo 170(®), Morita, Japan) and (NewTom 5G(®), QR, Verona, Italy). Using different scan settings 36 and 24 scans were obtained from the Accuitomo and the NewTom, respectively. The scans were converted to digital imaging and communications in medicine 3 format. The analysis of the data was performed using 3Diagnosys(®) software (v. 3.1, 3diemme, Cantù, Italy) and Geomagic studio(®) 2012 (Morrisville, NC). On the MSCT scan, one probe designating the site for pre-operative implant placement was inserted. The inserted probe on MSCT was transformed to the same region on each CBCT scan using a volume-based three-dimensional registration algorithm. The mean voxel grey value of the region around the probe was derived separately for each CBCT. The influence of scanning parameters on the measured mean voxel grey values was assessed. Grey values in both CBCT systems significantly deviated from Hounsfield unit values measured with MSCT (p = 0.0001). In both CBCT systems, scan FOV and spatial resolution selections had a statistically significant influence on grey value measurements (p = 0.0001). The number of projections selection had a statistically significant influence in the Accuitomo system (p = 0.0001) while exposure time and dose selections had no statistically significant influence on grey value measurements in the NewTom (p = 0.43 and p = 0.37, respectively). Grey-level values from CBCT images are influenced by device and scanning settings.

In vivostudy of pixel grey-measurement in digital subtraction radiography for monitoring caries remineralization

The aim of this study was to evaluate the performance of a quantitative method, based on pixel grey value measurements, for monitoring caries remineralization. Proximal radiographs of 11 patients (61 enamel caries lesions) were taken both before and after a 2 month remineralization protocol. Radiographs were digitized and for each area a follow-up image was subtracted from a baseline image. A quantitative analysis was undertaken using ImageTool software (University of Texas Health Science Center, San Antonio, TX). For each caries lesion diagnosed, a mean pixel value was obtained in digital subtraction radiographs (SR) using a scale ranging from 0-255 grey values. To identify caries status after the remineralization protocol, a subjective analysis of SR was undertaken by 6 radiologists who graded the lesions as demineralized (n = 10), unchanged (n = 34) or remineralized (n = 17). There was a statistically significant difference between the mean pixel values for demineralized (112.1+/-14.4), unchanged (127.3+/-12.3) and remineralized (137.5+/-13.8) lesions. It was concluded that the status of proximal caries lesions after remineralization therapy can be assessed by pixel grey measurements in SR and may constitute a suitable complementary method for monitoring the results of remineralization protocol in clinical practice.

A combined behavioral and morphological study on the effects of fetal asphyxia on the nigrostriatal dopaminergic system in adult rats

Fetal asphyxic insults in the brain are known to be associated with developmental neurological problems like neuromotor disorders. However, little is known about the long-term consequences of fetal asphyxia (FA). For that reason, the present study investigated the long-term effects of FA on motor behavior and dopaminergic circuitry. FA was induced at embryonic day 17 by 75-minute clamping of the uterine circulation. SHAM animals underwent the same procedure except for the clamping. This was followed by full-term vaginal delivery of animals in all groups (FA, SHAM and untreated controls). At 6 months, basal and amphetamine-induced locomotor activity was measured during open field testing. Brain sections were stained for tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP). TH-positive cells and GFAP-positive cells in substantia nigra pars compacta (SN C) and striatum were counted using design-based stereology. Moreover, TH-immunoreactivity in the striatum was assessed by grey value measurements. Behavioral analysis demonstrated that SHAM and FA showed less basal and amphetamine-induced activity than controls. Histochemically, FA decreased the number of TH-positive neurons in the SN C and lowered TH-positive in the striatum. Furthermore, more GFAP-positive cells were found in the SN C and striatum in FA than in either control and SHAM groups. Additionally, FA animals showed ventriculomegaly associated with smaller white matter as well as grey matter volumes. The data show that FA was associated with deficits in both dopamine-related motor behavior and biochemistry. These alterations were associated with nigrostriatal astrogliosis. The present study demonstrates the sensitivity of the dopaminergic system towards FA.

Differential Diagnosis of Large Periapical Lesions Using Cone-Beam Computed Tomography Measurements and Biopsy

This study compared the differential diagnosis of large periapical lesions (granuloma versus cyst) to traditional biopsy using Cone Beam Computed Tomography (CBCT), the NewTom 3G. Large lesions were scanned and a preoperative diagnosis based on gray value measurements of the imaged lesion area was made. After surgery a biopsy report was obtained and compared to the CBCT diagnosis. In 13 out of 17 cases, the diagnosis coincided. In 4 out of 17 cases, the CBCT read cyst with the oral pathologist’s diagnosis being granuloma. Thus, the CBCT may provide a more accurate diagnosis than biopsy and histology providing a diagnosis without invasive surgery and/or waiting a year to see if nonsurgical therapy is effective.