Trabecular bone structural parameters evaluated using dental cone-beam computed tomography: cellular synthetic bones

Comparison of periapical radiography, panoramic radiography, and CBCT in the evaluation of trabecular bone structure using fractal analysis

OBJECTIVES

The aim of this study is to compare imaging techniques to evaluate trabecular bone structure using Fractal Analysis (FA).

METHODS

Fifteen sheep hemimandibles were used for this study. Digital images were obtained using periapical radiography, panoramic radiography, and cone-beam computed tomography (CBCT). CBCT imaging was performed in standard (STD) and high-resolution (HR) modes. FA was conducted using ImageJ 1.3 software with the box-counting method on the images. The fractal dimension (FD) values were analyzed by the statistical software Jamovi 1.6.23. Statistical significance was accepted as p < 0.05.

RESULTS

The highest mean FD value was the FD on digital periapical radiographs (PaFD) (1.28 ± 0.04), and the lowest mean FD value was the FD on standard resolution cone-beam computed tomography images (STD-CBCTFD) (1.12 ± 0.10). Although there was no statistically significant difference between the PaFD and the FD on digital panoramic radiographs (PanFD) (p = 0.485), the PaFD was found to be significantly higher than STD-CBCTFD (p < 0.001), and the FD on high-resolution cone-beam computed tomography images (HR-CBCTFD) (p = 0.007). The PanFD was found to be significantly higher than the STD-CBCTFD (p = 0.004).

CONCLUSION

According to our results, in the evaluation of trabecular bone structure using FA, periapical radiographs and panoramic radiographs have similar image quality for assessment of the FD. On the other hand, CBCT results did not correlate with results from any of the other techniques in this study.

Effect of trabecular architectures on the mechanical response in osteoporotic and healthy human bone

Research at the mesoscale bone trabeculae arrangement yields intriguing results that, due to their clinical resolution, can be applied in clinical field, contributing significantly to the diagnosis of bone-related diseases. While the literature offers quantitative morphometric parameters for a thorough characterization of the mesoscale bone network, there is a gap in understanding relationships among them, particularly in the context of various bone pathologies. This research aims to bridge these gaps by offering a quantitative evaluation of the interplay among morphometric parameters and mechanical response at mesoscale in osteoporotic and non-osteoporotic bones. Bone mechanical response, dependent on trabecular arrangement, is defined by apparent stiffness, computationally calculated using the Gibson-Ashby model. Key findings indicate that: (i) in addition to bone density, measured using X-ray absorptiometry, trabecular connectivity density, trabecular spacing and degree of anisotropy are crucial parameters for characterize osteoporosis state; (ii) apparent stiffness values exhibit strong correlations with bone density and connectivity density; (iii) connectivity density and degree of anisotropy result the best predictors of mechanical response. Despite the inherent heterogeneity in bone structure, suggesting the potential benefit of a larger sample size in the future, this approach presents a valuable method to enhance discrimination between osteoporotic and non-osteoporotic samples.

Analysis of Bone Density and Bone Morphometry by Periapical Radiographs in Dental Implant Osseointegration Process

Objective. This research aimed to analyze the differences in bone density and bone morphometry by periapical implant radiography in the dental implant osseointegration stages. Methods. This experimental research uses 12 periapical radiographs of tibial bones from a New Zealand white rabbit (Oryctolagus cuniculus). The analysis was performed on day 3, 14, and 28 of the osseointegration stages with density, trabecular thickness (Tb.Th.), trabecular separation (Tb.Sp.), and trabecular number (Tb.N.) as parameters. The implant used is a titanium alloy and coated by SA (sunblasted with alumina acid) of 4 mm in diameter and 7 mm in length. The radiographic assessment of the osseointegration process is obtained with the region of interest (ROI) segmentation results. Additionally, each ROI was analyzed for bone density and morphometry using the open-source ImageJ software with the BoneJ plugin. The significant difference was evaluated by analysis of variance (F-test) with $p<0.05$ and nonparametric Kruskal–Wallis test with $p<0.05$ . Results. Analysis of the osseointegration images of dental implants at day 3, 14, and 28 with the periapical X-ray modality shows significant differences ( $p<0.05$ ) in the parameters measuring density and trabecular thickness (Tb.Th.). In the variables of trabecular separation (Tb.Sp.) and number (Tb.N.) ( $p>0.05$ ), there is no significant difference. Conclusion. Based on the results, density and trabecular thickness (Tb.Th.) showed a significant difference between healing times. However, trabecular separation (Tb.Sp.) and trabecular number (Tb.N.) showed no difference in healing time.

On the need of a scale-dependent material characterization to describe the mechanical behavior of 3D printed Ti6Al4V custom prostheses using finite element models

Additive manufacturing is widely used in the orthopaedic industry for the high freedom and flexibility in the design and production of personalized custom implants made of Ti6Al4V. Within this context, finite element modeling of 3D printed prostheses is a robust tool both to guide the design phase and to support clinical evaluations, possibly virtually describing the in-vivo behavior of the implant. Given realistic scenarios, a suitable description of the overall implant's mechanical behavior is unavoidable. Considering typical custom prostheses' designs (i.e. acetabular and hemipelvis implants), complex designs involving solid and/or trabeculated parts, and material distribution at different scales hinder a high-fidelity modeling of the prostheses. Moreover, uncertainties in the production and in the material characterization of small parts approaching the accuracy limit of the additive manufacturing technology still exist. While recent works suggest that the mechanical properties of thin 3D-printed parts may be peculiarly affected by specific processing parameters (i.e. powder grain size, printing orientation, samples' thickness) as compared to conventional Ti6Al4V alloy, the current numerical models make gross simplifications in describing the complex material behavior of each part at different scales. The present study focuses on two patient-specific acetabular and hemipelvis prostheses, with the aim of experimentally characterizing and numerically describing the dependency of the mechanical behavior of 3D printed parts on their peculiar scale, therefore, overcoming one major limitation of current numerical models. Coupling experimental activities with finite element analyses, the authors initially characterized 3D printed Ti6Al4V dog-bone samples at different scales, representative of the main material components of the investigated prostheses. Afterwards, the authors implemented the characterized material behaviors into finite element models to compare the implications of adopting scale-dependent vs. conventional scaleindependent approaches in predicting the experimental mechanical behavior of the prostheses in terms of their overall stiffness and the local strain distribution. The material characterization results highlighted the need for a scale-dependent reduction of the elastic modulus for thin samples compared to the conventional Ti6Al4V, which is fundamental to properly describe the overall stiffness and local strain distribution on the prostheses. The presented works demonstrate how an appropriate material characterization and a scale-dependent material description is needed to develop reliable FE models of 3D printed implants characterized by a complex material distribution at different scales.

Guided cortical and cancellous bone formation using a minimally invasive technique of BMSC- and BMP-2-laden visible light-cured carboxymethyl chitosan hydrogels

A cavity defect inside the bone is formed by deformed cancellous bone from the fixation of the cortical bone, and consequently, abnormal bone healing occurs. Therefore, repairing cancellous bone defects is a remarkable topic in orthopedic surgery. In this study, we prepared bone marrow-derived stem cell (BMSC)-laden and bone morphogenetic protein-2 (BMP-2)-laden visible light-cured carboxymethyl chitosan (CMCS) hydrogels for cortical and cancellous bone healing. Proton nuclear magnetic resonance (¹H NMR) analysis confirmed the methacrylation of CMCS (CMCSMA), resulting in 55 % of substitution. The higher concentration of CMCSMA hydrogel resulted in the lower swelling ratio, the larger viscosity, the slower degradation behavior, and the stronger compressive strength. The 5 w/v% hydrogel exhibited a controlled BMP-2 release for 14 days, while the 7 and 10 w/v% hydrogels displayed a controlled BMP-2 release for 28 days. Results of in vitro cytotoxicity and cell proliferation assays revealed the biocompatibility of the samples. In vivo animal tests demonstrated that BMSC- and BMP-2-laden 7 w/v% CMCSMA (CMCSMA+Cell+BMP-2) improved bone formation in the defected cortical and cancellous bones of the femur, as analyzed by micro-computed tomography (micro-CT) and histological evaluations. Consequently, we suggested that CMCSMA+Cell+BMP-2 can be a valuable scaffold for restoring cortical and cancellous bone defects.

Influence of Voxel Size on Evaluation of Trabecular Bone Microstructure on Human Mandibles: A CBCT study

Purpose: This study aims to assess the effect of voxel size on trabecular microstructural evaluation onhuman cadaver mandiblesusing cone beam computed tomography (CBCT) images. Methods: Twenty two Volumes of Interest were obtained from to human cadaver mandibles which were scanned in three different voxel sizes using CBCT. Scanning performed in 0.125 mm (Group 1), 0.2 mm (Group 2) and 0.3 mm (Group 3) voxel sizes. Regions of interest are calculated in both mandibles for both voxel sizes which are adjusted from apical third of all interdental alveolar trabecular bone from anterior and posterior mandible. Trabecular thickness (Tb. Th); trabecular separation (Tb. Sp); Bone Volume/Total Volume (BV/TV) values were obtained using plug in BoneJ of the software ImageJ. The results were evaluated statistically in software IBM SPSS Statistics 21. Results: Trabecular thickness and trabecular separation showed significant difference between first and the third and the second and the third groups (p=0.000), while first and second group did not. BV/TV values showed no significant difference between whole groups. Conclusion: Beside microstructural analysis is not their first purpose CBCT images carry knowledge about trabecular bone microstructure could be a valuable bone quality assessment tool. High correlation between values with 0.125 mm and 0.2 mm and low correlation between values with 0.125 mm and 0.3 mm voxel sizes suggest that; this knowledge is clinically more valuable when voxel size is 0.2 mm or thinner.

A Comparative Study of Multidetector Computed Tomography, Cone Beam Computed Tomography, and Computed Microtomography on Trabecular Bone Structures in the Human Mandible: An Ex Vivo Study

OBJECTIVE

The aim of this study was to evaluate the accuracy of multislice computed tomography (MSCT) and cone beam computed tomography (CBCT) scanners in the assessment of trabecular bone microarchitecture by radiomorphometric analysis.

METHODS

Eight dry human hemimandibles were selected and scanned by 4- and 128-MSCT, CBCT with different voxel sizes, and a computed microtomography (micro-CT). The images were spatially aligned, the axial slices were segmented using CTAn software (Skyscan, Konitch, Belgium), and 10 bone morphometric parameters were quantified. The micro-CT images were the criterion standard.

RESULTS

The results show the superiority of CBCT images with 0.2-mm voxel size and 128-MSCT.

CONCLUSIONS

We can conclude that the CBCT scanner with 0.2-mm voxel size and 128-MSCT had better performance on reproducibility of the distribution and organization of trabecular bone and marrow spaces evaluated in this study.

Characterization of Ultralow Density Cellular Solids: Lessons from 30 years of Bone Biomechanics Research

Advances in additive manufacturing techniques have enabled the development of micro-architectured materials displaying a combination of low-density and lightweight structures with high specific strength and toughness. The mechanical performance of micro-architectured materials can be assessed using standard techniques; however, when studying low- and ultralow density micro-architectured materials, standard characterization techniques can be subject to experimental artifacts. Additionally, quantitative assessment and comparisons of microarchitectures with distinct lattice patterns is not always straightforward. Cancellous bone is a natural, ultralow density (porosity often exceeding 90%), irregular, cellular solid that has been thoroughly characterized in terms of micro-architecture and mechanical performance over the past 30 years. However, most the literature on cancellous bone mechanical properties and micro-structure-function relationships is in the medical literature and is not immediately accessible to materials designers. Here we provide a brief review of state-of-the-art approaches for characterizing the micro-architecture and mechanical performance of ultralow density cancellous bone, including methods of addressing experimental artifacts during mechanical characterization of ultralow density cellular solids, methods of quantifying microarchitecture, and currently understood structure-function relationships.

Quantitative analysis of metal artefacts of dental implant in CBCT image by correlation analysis to micro-CT: A microstructural study

OBJECTIVES

Quantification of dental implant metal artefacts in CBCT images using correlation analysis of trabecular microstructural parameters from CBCT and micro-CT, and analysis of the effect of varying the angular position of the subject.

METHODS

Polyurethane synthetic bone blocks were first scanned without implants by micro-CT and CBCT. Two dental implants were then placed parallel in the bone blocks and these specimens were scanned by CBCT with different alpha angles. Three volumes of interest (VOI) were set for further analysis. Six microstructural parameters were measured: trabecular thickness (Tb_Th), trabecular spacing (Th_Sp), bone volume per total volume (BV/TV), bone surface per total volume (BS/TV), connectivity density (CD) andfractal dimension (FD). Micro-CT measurements were used as a gold standard for CBCT. Spearman correlation coefficients for each microstructural parameter from CBCT and micro-CT were calculated and compared using Steiger's Z test.

RESULTS

Without the implants, in VOI₁, the Spearman correlation coefficients of Tb_Th, Tb_Sp, BV/TV, BS/TV, CD and FD were 0.599, 0.76, 0.552, 0.566, 0.664 and 0.607, respectively. With the implants, the correlation coefficients decreased sharply in VOI₁. As the alpha angle increased from zero to 90°, the correlation coefficients increased and became significant. Similar results appeared in VOI₂. In contrast, in VOI₃, the correlation coefficient decreased as the alpha angle increased.

CONCLUSIONS

Metal artefacts were successfully quantified using microstructural parameters in terms of the image quality of the CBCT. Changes in alpha angle affected the quality of the CBCT image.

Cone beam computed tomography findings in the temporomandibular joints of chronic qat chewers: Radiographic bone density and trabecular microstructural analyses

OBJECTIVES

This cross-sectional comparative study investigated the effects of qat chewing habit on the radiographic bone density (RBD) and trabecular microstructure of temporomandibular joint condyles using cone beam computed tomography (CBCT).

STUDY DESIGN

In total, 85 systemically healthy Yemeni males were included and divided into qat chewers (QCs; n = 41); and non-qat chewers (NQCs; n = 44). The participants responded to a structured questionnaire and underwent standardized clinical examination and CBCT scanning of the temporomandibular joint. Measurements of RBD and trabecular microstructure (trabecular thickness, trabecular separation, bone volume fraction, and fractal dimension) were performed. Statistical significance was established at P ≤ .05.

RESULTS

No statistically significant differences were found between QCs and NQCs in RBD or trabecular microstructure. The mean standard deviations and maximum values of trabecular separation on the nonchewing side for QCs were significantly lower compared to the corresponding values for NQCs (0.60 and 2.68 for QCs vs 0.72 and 3.05 for NQCs; P = .025 and .05, respectively). A comparison between chewing and nonchewing sides in QCs revealed no significant differences.

CONCLUSIONS

Qat chewing habit induces insignificant changes in condylar RBD and trabecular microstructure as detected by CBCT. Further studies using advanced radiographic techniques are warranted.

Effect of Scanning Resolution on the Prediction of Trabecular Bone Microarchitectures Using Dental Cone Beam Computed Tomography

Assessing bone quality and quantity at the location of dental implants before dental implantation is crucial. In recent years, dental cone-beam computed tomography (dental CBCT) has often been used to assess bone quality and quantity prior to dental implant. However, the effect of scanning resolution on the prediction of trabecular bone microarchitectural parameters (TBMPs) remains unclear. The objective of this study was to examine how dental CBCT with various scanning resolution differs with regard to predicting TBMPs. This study used micro-computed tomography (micro-CT) with 18 μm resolution and dental CBCT with 100 μm and 150 μm resolutions on 28 fresh bovine vertebrae cancellous bone specimens. Subsequently, all images were input into the ImageJ software to measure four TBMPs: bone volume total volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp). One-way analysis of variance and Tukey’s test were subsequently used to assess the differences between three scanning modes for the four TBMPs. In addition, correlations between measurement results obtained from micro-CT and dental CBCT with two resolutions were measured. The experimental results indicated that significant differences in four TBMPs were observed between micro-CT and dental CBCT (p < 0.05). The correlation coefficients between BV/TV, Tb.N, and Tb.Sp obtained from micro-CT and from dental CBCT with 100 μm resolution (0.840, 0.739, and 0.820, respectively) were greater than the correlation coefficients between BV/TV, Tb.N, and Tb.Sp obtained from micro-CT and from dental CBCT with 150 μm resolution (0.758, 0.367, and 0.724, respectively). The experimental results revealed that the TBMPs measured with dental CBCT with two resolutions differed from ideal values, but a higher resolution could provide more accurate prediction results, particularly for BV/TV, Tb.N, and Tb.Sp.

Improving the prediction of the trabecular bone microarchitectural parameters using dental cone-beam computed tomography

Background

In this study, we explored how various preprocessing approaches can be employed to enhance the capability of dental CBCT to accurately estimate trabecular bone microarchitectural parameters.

Methods

In total, 30 bovine vertebrae cancellous bone specimens were used for in study. Voxel resolution 18-μm micro-computed tomography (micro-CT) and 100-μm dental CBCT were used to scan each specimen. Micro-CT images were used to calculate trabecular bone microarchitectural parameters; the results were set as the gold standard. Subsequently, before the dental CBCT images were converted into binary images to calculate trabecular bone microarchitectural parameters, three preprocessing approaches were used to process the dental CBCT images. For Group 1, no preprocessing approach was applied. For Group 2, images were sharpened and despeckable noises were removed. For Group 3, the function of local thresholding was added to Group 2 to form Group 3. For Group 4, the air pixels was removed from Group 3 to form Group 4. Subsequently, all images were imported into a software package to estimate trabecular bone microarchitectural parameters (bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular number (TbN), and trabecular separation (TbSp)). Finally, a paired t-test and a Pearson correlation test were performed to compare the capability of micro-CT with the capability of dental CBCT for estimating trabecular bone microarchitectural parameters.

Results

Regardless of whether dental CBCT images underwent image preprocessing (Groups 1 to 4), the four trabecular bone microarchitectural parameters measured using dental CBCT images were significantly different from those measured using micro-CT images. However, after three image preprocessing approaches were applied to the dental CBCT images (Group 4), the BV/TV obtained using dental CBCT was highly positively correlated with that obtained using micro-CT (r = 0.87, p < 0.001); the correlation coefficient was greater than that of Group 1 (r = −0.15, p = 0.412), Group 2 (r = 0.16, p = 0.386), and Group 3 (r = 0.47, p = 0.006). After dental CBCT images underwent image preprocessing, the efficacy of using dental CBCT for estimating TbN and TbSp was enhanced.

Conclusions

Image preprocessing approaches can be used to enhance the efficacy of using dental CBCT for predicting trabecular bone microarchitectural parameters.

Evaluation of trabecular pattern of mandible using fractal dimension, bone area fraction, and gray scale value: comparison of cone-beam computed tomography and panoramic radiography

OBJECTIVE

This study was performed to compare the fractal dimension (FD), bone area fraction (BAF), and gray scale value (GSV) on digital panoramic radiography (DPR) and cross-sectional cone-beam computed tomography (CBCT) using image analysis and to determine whether a relationship exists among parameters associated with bone quality.

METHODS

Thirty edentulous human hemimandibles were scanned by DPR and CBCT. Ninety regions of interest (ROIs) were evaluated on DPR and CBCT images to calculate the FD and BAF. The GSV of the ROI on CBCT was also calculated.

RESULTS

Statistically significant differences were observed in the FD values of the ROIs between DPR and CBCT (p = 0.002) and in the BAF values of ROIs between DPR and CBCT (p = 0.017). The Spearman's correlation test revealed a statistically significant high correlation between the FD and BAF values of the ROIs on DPR and between the FD and BAF values of the ROIs on CBCT (p < 0.01). No significant correlations were observed between the GSVs of ROIs on CBCT and the FD values of ROIs on DPR, the BAF values of ROIs on DPR, the FD values of ROIs on CBCT, and the BAF values of ROIs on CBCT (p > 0.05).

CONCLUSIONS

The GSV did not support the FD and BAF. Additionally, DPR and CBCT did not have similar image quality for assessing the FD, BAF, and GSV. In evaluating the trabecular structure, the use of panoramic radiographs should be continued because the image resolution of CBCT is lower and its generalized dose is higher than that of panoramic radiography. These results may serve as a reference for clinical practitioners using dental CBCT to analyze the trabecular structures of alveolar bones.

Quantification of Volumetric Bone Mineral Density of Proximal Femurs Using a Two-Compartment Model and Computed Tomography Images

Objectives

Dual-energy X-ray absorptiometry (DXA) is frequently used to measure the areal bone mineral density (aBMD) in clinical practice. However, DXA measurements are affected by the bone thickness and the body size and are unable to indicate nonosseous areas within the trabecular bone. This study aims to quantify the volumetric bone mineral density (vBMD) using computed tomography (CT) images and the two-compartment model (TCM) methods.

Methods

The TCM method was proposed and validated by dipotassium phosphate (K₂HPO₄) phantoms and a standard forearm phantom. 28 cases with DXA scans and pelvic CT scans acquired within six months were retrospectively collected. The vBMD calculated by TCM was compared with the aBMD obtained from DXA.

Results

For the K₂HPO₄ phantoms with vBMD ranging from 0.135 to 0.467 g/cm³, the average difference between the real and calculated vBMD was 0.009 g/cm³ and the maximum difference was 0.019 g/cm³. For the standard forearm phantom with vBMD of 0.194, 0.103, and 0.054 g/cm³, the average differences between the real and calculated vBMD were 0.017, 0.014, and 0.011 g/cm³. In the clinical CT image validation, a good linear relationship between vBMD and aBMD was observed with the Pearson correlation coefficient of 0.920 (p < 0.01).

Conclusions

The proposed TCM method in combination with the homemade cortical bone equivalent phantom provides accurate quantification and spatial distribution of bone mineral content.

Individual construction of freeform-fabricated polycaprolactone scaffolds for osteogenesis

The construction of engineered bone mostly focuses on simulating the extracellular matrix (ECM) for proper biological activity. However, the complexity of architecture and the variability of the mechanical properties of natural bones are related to individual differences in age, nutritional state, mechanical loading and disease status. Defect substitutions should be normed with the host natural bone, balancing architectural and mechanical adaption, as well as biological activity. Using a freeform fabrication (FFF) method, we prepared polycaprolactone (PCL) scaffolds with different architectures. With simulation of structural and mechanical parameters of rabbit femur cancellous bone, individual defect substitution with the characteristics of the rabbit femur was obtained with high porosity and connectivity. Biological adaption

Accuracy of biomarkers obtained from cone beam computed tomography in assessing the internal trabecular structure of the mandibular condyle

OBJECTIVE

The aim of this study was to validate the ability of cone beam computed tomography (CBCT) to measure condylar internal trabecular bone structure and bone texture parameters accurately.

STUDY DESIGN

Sixteen resected condyles of individuals undergoing temporomandibular joint replacement were collected and used as samples. These condyles were then radiographically imaged by using clinically oriented dental CBCT and research oriented micro-computed tomography (micro-CT). The CBCT scans were then compared with the gold standard micro-CT scans in terms of 21 bone imaging parameters. Descriptive histologic investigation of the specimens was also performed.

RESULTS

Significant correlations were found for several imaging parameters between the CBCT and micro-CT images, including trabecular thickness (r = 0.92), trabecular separation (r = 0.78), bone volume (r = 0.90), bone surface area (r = 0.79), and degree of anisotropy measurements (r = 0.77).

CONCLUSIONS

Measurements of trabecular thickness, trabecular separation, bone volume, bone surface area, and degree of anisotropy obtained from high-resolution dental CBCT images may be suitable bone imaging biomarkers that can be utilized clinically and in future research.

High-resolution-cone beam tomography analysis of bone microarchitecture in patients with acromegaly and radiological vertebral fractures

Vertebral fractures are an emerging complication of acromegaly but their prediction is still difficult occurring even in patients with normal bone mineral density. In this study we evaluated the ability of high-resolution cone-beam computed tomography to provide information on skeletal abnormalities associated with vertebral fractures in acromegaly. 40 patients (24 females, 16 males; median age 57 years, range 25-72) and 21 healthy volunteers (10 females, 11 males; median age 60 years, range: 25-68) were evaluated for trabecular (bone volume/trabecular volume ratio, mean trabecular separation, and mean trabecular thickness) and cortical (thickness and porosity) parameters at distal radius using a high-resolution cone-beam computed tomography system. All acromegaly patients were evaluated for morphometric vertebral fractures and for mineral bone density by dual-energy X-ray absorptiometry at lumbar spine, total hip, femoral neck, and distal radius. Acromegaly patients with vertebral fractures (15 cases) had significantly (p < 0.05) lower bone volume/trabecular volume ratio, greater mean trabecular separation, and higher cortical porosity vs. nonfractured patients, without statistically significant differences in mean trabecular thickness and cortical thickness. Fractured and nonfractured acromegaly patients did not have significant differences in bone density at either skeletal site. Patients with acromegaly showed lower bone volume/trabecular volume ratio (p = 0.003) and mean trabecular thickness (p < 0.001) and greater mean trabecular separation (p = 0.02) as compared to control subjects, without significant differences in cortical thickness and porosity. This study shows for the first time that abnormalities of bone microstructure are associated with radiological vertebral fractures in acromegaly. High-resolution cone-beam computed tomography at the distal radius may be useful to evaluate and predict the effects of acromegaly on bone microstructure.

The relationship between dental implant stability and trabecular bone structure using cone-beam computed tomography

Purpose

The objective of this study was to investigate the relationships between primary implant stability as measured by impact response frequency and the structural parameters of trabecular bone using cone-beam computed tomography(CBCT), excluding the effect of cortical bone thickness.

Methods

We measured the impact response of a dental implant placed into swine bone specimens composed of only trabecular bone without the cortical bone layer using an inductive sensor. The peak frequency of the impact response spectrum was determined as an implant stability criterion (SPF). The 3D microstructural parameters were calculated from CT images of the bone specimens obtained using both micro-CT and CBCT.

Results

SPF had significant positive correlations with trabecular bone structural parameters (BV/TV, BV, BS, BSD, Tb.Th, Tb.N, FD, and BS/BV) (P<0.01) while SPF demonstrated significant negative correlations with other microstructural parameters (Tb.Sp, Tb.Pf, and SMI) using micro-CT and CBCT (P<0.01).

Conclusions

There was an increase in implant stability prediction by combining BV/TV and SMI in the stepwise forward regression analysis. Bone with high volume density and low surface density shows high implant stability. Well-connected thick bone with small marrow spaces also shows high implant stability. The combination of bone density and architectural parameters measured using CBCT can predict the implant stability more accurately than the density alone in clinical diagnoses.

Fibroblast Growth Factor-23, Sclerostin, and Bone Microarchitecture in Patients With Osteoporotic Fractures of the Proximal Femur: A Cross-sectional Study

This cross-sectional observational cohort study was designed to simultaneously investigate bone microarchitecture and serum markers of bone metabolism in elderly osteoporotic patients experiencing a trochanteric or femoral neck fracture. Special emphasis was put on renal function, sclerostin and fibroblast growth factor-23 (FGF-23). Eighty-two patients (median age: 84 years; 49 trochanteric fractures) scheduled for emergency surgery due to an osteoporotic fracture participated. Bone specimens for ex vivo microcomputed X-ray tomography were sampled during surgery. Blood samples for laboratory workup were collected before surgery (t0) and 1 day afterward (t1). Fifty-eight patients consented to dual-energy X-ray absorptiometry scanning of the lumbar spine and/or contralateral femoral neck after recovery during the in-patient stay. Samples were grouped according to the site of fracture. Regression coefficients were controlled for age and/or estimated glomerular filtration rate (eGFR), if appropriate. Patients experiencing a femoral neck fracture presented with better preserved renal function (eGFR) and lower C-terminal fragment of fibroblast growth factor-23 (cFGF-23) concentrations compared to those with trochanteric fractures. By contrast, serum sclerostin was similar at both time points and did not differ between groups. Age-adjusted correlation analysis revealed negative associations between eGFR and cFGF-23 determined at t1 (R=-0.34; p<0.05) as well as between eGFR and sclerostin levels at t0 (R=-0.45; p<0.05) in patients with trochanteric and femoral neck fractures, respectively. Our study provides evidence that not only an age-related decline of renal function but also the type of skeletal injury may contribute to the circulating concentrations of cFGF-23.

Improving the Evaluation of Alveolar Bone Grafts with Cone Beam Computerized Tomography

Objective

Cone Beam computed tomography (CBCT) is used increasingly as a replacement for periapical x-rays when evaluating alveolar bone grafting. The manufacturer's standard settings for dental imaging may not, however, represent the optimal settings for evaluating postoperative alveolar bone grafts. We examined the influence of exposure parameters on CBCT image quality to optimize the quality of CBCT images while reducing the radiation dose to the minimum level necessary to obtain adequate images.

Methods

A defect was created in a cadaver head to simulate an alveolar cleft, and the area was filled with a synthetic material to simulate an alveolar bone graft. Serial CBCT scans were acquired, systematically varying tube voltage and tube current settings from 72 to 96kV and 3 to 12mA. Region of interest analysis was undertaken, and image quality was evaluated by comparing the ratios of native alveolar bone to soft tissue and the ratios of synthetic bone graft to soft tissue and by assessing image noise.

Results

Twenty-one CBCT data sets were obtained. Reducing tube voltage (kV) resulted in increased contrast ratio between bone and soft tissue and between synthetic bone graft and soft tissue, with maximal contrast at values of 76 kV/11 mA, 72 kV/12 mA, and 72 kV/11 mA. Of these, the setting with lowest image noise was 76 kV/11 mA. This setting also resulted in a radiation dose of less than half of the manufacturer's recommended settings for the same scan volume.

Conclusions

There is potential to improve CBCT image quality significantly while dramatically reducing the radiation dose during postoperative examinations for alveolar bone grafting in patients with cleft lip and palate.

Comparison of mandibular bone microarchitecture between micro-CT and CBCT images

OBJECTIVES

To compare microarchitecture parameters of bone samples scanned using micro-CT (µCT) to those obtained by using CBCT.

METHODS

A bone biopsy trephine bur (3 × 10 mm) was used to remove 20 cylindrical bone samples from 20 dry hemimandibles. Samples were scanned using µCT (µCT 35; SCANCO Medical, Brüttisellen, Switzerland) with a voxel size of 20 µm and CBCT (3D Accuitomo 170; J. Morita, Kyoto, Japan) with a voxel size of 80 µm. All corresponding sample scans were aligned and cropped. Image analysis was carried out using BoneJ, including the following parameters: skeleton analysis, bone surface per total volume (BS/TV), bone volume per total volume (BV/TV), connectivity density, anisotropy, trabecular thickness and spacing, structure model index, plateness and fractal dimension. Pearson and Spearman correlation coefficients (R) were calculated. CBCT values were then calibrated using the slope of the linear fit with the µCT values. The mean error after calibration was calculated and normalized to the standard deviation of the µCT values.

RESULTS

R-values ranged between 0.05 (plateness) and 0.83 (BS/TV). Correlation was significant for both Spearman and Pearson's R for 8 out of 16 parameters. After calibration, the smallest normalized error was found for BV/TV (0.48). For other parameters, the error range was 0.58-2.10.

CONCLUSIONS

Despite the overall correlation, this study demonstrates the uncertainty associated with using bone microarchitecture parameters on CBCT images. Although clinically relevant parameter ranges are not available, the errors found in this study may be too high for some parameters to be considered for clinical application.

Trabecular bone histomorphometric measurements and contrast-to-noise ratio in CBCT

OBJECTIVES

The aim of this study was to evaluate how imaging parameters at clinical dental CBCT affect the accuracy in quantifying trabecular bone structures, contrast-to-noise ratio (CNR) and radiation dose.

METHODS

15 radius samples were examined using CBCT (Accuitomo FPD; J. Morita Mfg., Kyoto, Japan). Nine imaging protocols were used, differing in current, voltage, rotation degree, voxel size, imaging area and rotation time. Radiation doses were measured using a kerma area product-meter. After segmentation, six bone structure parameters and CNRs were quantified. Micro-CT (μCT) images with an isotropic resolution of 20 μm were used as a gold standard.

RESULTS

Structure parameters obtained by CBCT were strongly correlated to those by μCT, with correlation coefficients >0.90 for all studied parameters. Bone volume and trabecular thickness were not affected by changes in imaging parameters. Increased tube current from 5 to 8 mA, decreased isotropic voxel size from 125 to 80 μm and decreased rotation angle from 360° to 180° affected correlations for trabecular termini negatively. Decreasing rotation degree also weakened correlations for trabecular separation and trabecular number at 80 μm voxel size. Changes in the rotation degree and tube current affected CNR significantly. The radiation dose varied between 269 and 1153 mGy cm(2).

CONCLUSIONS

Trabecular bone structure can be accurately quantified by clinical dental CBCT in vitro, and the obtained structure parameters are strongly related to those obtained by μCT. A fair CNR and strong correlations can be obtained with a low radiation dose, indicating the possibility for monitoring trabecular bone structure also in vivo.