Advertisement calls from species of the Limnonectes hascheanus-limborgi complex (Anura: Dicroglossidae) from Peninsular Malaysia.

Limnonectes hascheanus and Limnonectes limborgi are two very similar-looking and closely related species and are sometimes referred to as the Limnonectes hascheanus-limborgi complex (Inger & Stuart 2010). Inger & Stuart (2010) tackled the systematics of the complex and confirmed the status of L. limborgi as a distinct species and not a junior synonym to L. hascheanus by providing molecular data and morphological characters of its distinctiveness. The geographic ranges of the two species were also reported to be distinct where L. hascheanus is mainly restricted to the southern part of the Thai-Malay Peninsula while L. limborgi is distributed from southern Myanmar north into northern Thailand and Laos before curving around into central Laos, northeastern Thailand, Cambodia, and southern Vietnam (Inger & Stuart 2010).

Non-iatrogenic implantation of cutaneous metastasis from hepatocellular carcinoma.

PURPOSE: Cutaneous metastases as an extrahepatic metastasis from hepatomas (HCC) is extremely rare and always carry a poor prognosis and less survival time. Previously, there has been a limited number of literature that reported skin metastasis in a large number of cases, which has rarely been discussed in the empirical treatment and therapy of cutaneous metastasis, especially for non-iatrogenic implantation. It is necessary to discuss this kind of metastasis. PATIENTS AND METHODS: We summarize cases from our medical center from 2013 to 2021, there are 12 patients diagnosed with non-iatrogenic implantation of cutaneous metastasis after HCC. We conducted the investigation of the clinical prognosis, pathological characteristics, and treatment of those patients. RESULTS: All patients were male, the age ranged from 21 to 71 years old, the average size of primary HCC was over 5 cm, there was four patient's cutaneous metastasis from the skin of head (including scalp and occipital region), followed by right abdominal (2 patients), right chest wall (2 patients), back (2 patients), umbilical (1 patient), gluteal region (1 patient). The cutaneous metastases presented as solitary or multiple nodules, papules, and erythema without ulcers with sizes between 0.5 cm and 5 cm. 7 patients died after being diagnosed with cutaneous metastasis within 2-19 months. CONCLUSIONS: The rate of non-iatrogenic implantation cutaneous metastasis is low, but the prognosis is poor, combining with histopathological analysis and history of diseases can be helpful in diagnosis. For large HCC (> 5 cm), systematic treatment is recommended to prevent the occurrence of cutaneous metastasis and improve the prognosis after hepatectomy.

Single-center Experience in the Diagnosis and Treatment of Hepatic Perivascular Epithelioid Cell Neoplasm.

BACKGROUND AND AIMS: Perivascular epithelioid cell neoplasms (PEComas) are a rare type of mesenchymal neoplasm and their preoperative diagnosis is challenging. In this study, we summarized the experience from a single medical center to study the examinations, clinical presentations, and pathological and histological characteristics of PEComas in the liver in order to optimize overall understanding of the diagnosis and treatment of these neoplasms. METHODS: We conducted a retrospective analysis to investigate the clinical and pathological characteristics as well as imaging presentations of 75 patients diagnosed with hepatic PEComa in The First Affiliated Hospital of Zhejiang University between April 2010 and April 2020. RESULTS: Among the 75 patients, 52 were women, and the median age was 48 years. Most patients had no specific symptoms, and two were admitted to the hospital for a second time owing to relapse. All patients underwent surgical resection. Histologically, 38 patients had classical angiomyolipoma (AML) and 37 had epithelioid AML. The PEComas were accompanied by positive immunohistochemical expression of HMB45, Melan-A, and smooth muscle actin. Follow-up data were obtained from 47 of the total 75 patients, through October 2020. Two patients had metastasis after surgery. CONCLUSIONS: AML is the most common type of hepatic PEComa. There are no specific symptoms of hepatic PEComa, and serological examinations and imaging modalities for accurate preoperative diagnosis are lacking. Epithelioid AML should be considered a tumor of uncertain malignant potential; however, the prognosis of PEComa after resection is promising.

MiR-25 enhances autophagy and promotes sorafenib resistance of hepatocellular carcinoma via targeting FBXW7.

Sorafenib resistance is a major challenge in the treatment of patients with advanced hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) are a large family of non-coding RNA molecules, which is an important mechanism of drug resistance. We previously found that knockdown of miR-25 increased the sensitivity of TRAIL-induced apoptosis in liver cancer stem cells. We aimed to study the effects of miR-25 on sorafenib resistance of HCC and the underlying mechanisms. In the present study, we analyzed the expression of miR-25 between HCC and normal tissues and predicted miR-25 target genes through databases. After transfecting miR-25 mimics, inhibitor or FBXW7 Plasmid, CCK-8 and flow cytometry assay was performed to determine the sorafenib resistance. We performed LC3-dual-fluorescence assay and Western blotting to detect the autophagy levels. The expression of miR-25 was upregulated in human HCC tissues and was associated with tumor pathological grade, clinic staging, and lymphatic metastasis. MiR-25 enhanced sorafenib resistance of HCC cells and autophagy. FBXW7 is the direct target of miR-25. Overexpression of FBXW7 could reverse the increase of sorafenib resistance caused by miR-25 mimics. Our results suggested that miR-25 increased the sorafenib resistance of HCC via inducing autophagy. In addition, miR-25 decreases the expression of FBXW7 protein to regulate autophagy. Therefore, miR-25 may represent a novel therapeutic target for the treatment of HCC.

A Nomogram Estimation for the Risk of Microvascular Invasion in Hepatocellular Carcinoma Patients Meeting the Milan Criteria.

OBJECTIVE: We aimed to develop and validate a nomogram for preoperatively estimating the risk of microvascular invasion (MVI) in hepatocellular carcinoma (HCC) within the Milan criteria. METHODS: The clinical data of 312 HCC patients who underwent liver surgery at the xxx from Jan 2017 to Dec 2019 were retrospectively collected. Then, the study population was categorized into the training and validation group based on the date of surgery. To identify risk factors related to MVI, we conducted a series of logistic regression analyses. By combining these risk factors, a nomogram was then established. We further clarified the usability of our model through the area under the ROC curve (AUC), decision curve analysis (DCA), and calibration curve. RESULTS: Pathological examination revealed MVI in 108 patients with HCC (34.6%). Three independent predictors were identified: level of alpha-fetoprotein (AFP) exceeds 194 ng/mL (OR = 2.20, 95% CI: 1.13-4.31, p = 0.021), size of tumor (OR = 1.59; 95% CI: 1.18-2.12; P < 0.001) and number of tumors (OR = 3.37, 95% CI: 1.64-7.28, p < 0.001). A nomogram was subsequently built with an AUC of 0.73 and 0.74 respectively in the training cohort and validation cohort. The calibration curve showed a relatively high consistency between predicted probability and observed outcomes. Besides, the DCA revealed that the model was clinically beneficial for preoperatively predicting MVI in HCC. CONCLUSIONS: A model for evaluating the risk of MVI HCC patients was developed and validated. The model could provide clinicians with a relatively reliable basis for optimizing treatment decisions.

[Effect of acupuncture on pain-emotion related brain regions in patients with cervical spondylosis of cervical type: a fMRI study].

OBJECTIVE: To observe the changes of functional connectivity of brain pain-emotion regulation region in patients with cervical spondylosis of cervical type by functional magnetic resonance imaging (fMRI). METHODS: Thirty-two subjects were selected. Of them, 16 patients with cervical spondylosis of cervical type were divided into an observation group and 16 healthy subjects into a control group. The patients in the observation group were treated with acupuncture at Tianzhu (BL 10), Jingbailao (EX-HN 15), Jianzhongshu (SI 15) and ashi points for 30 min. The rest-state fMRI data was collected before and after acupuncture in the observation group. The subjects in the control group received no treatment, and the rest-state fMRI data was collected once. The visual analogue scale (VAS) score before and after treatment and the pain catastrophizing scale (PCS) score before treatment in the observation group were recorded. The resting-state brain functional imaging characteristics between the observation group and control group before treatment, between the observation group before and after treatment, were compared. Based on the brain functional connectivity of region of interest (ROI) the changes of functional connectivity in insula and ventral tegmental area (VTA) in emotional regulation brain region were observed, and the correlation between functional connectivity changes and VAS、PCS scores in patients of the observation group was analyzed. RESULTS: In the observation group, the VAS score was (1.94±1.12) after the treatment, which was lower than (5.62±1.20) before treatment (P<0.05). The PCS score before treatment was (19.18±8.42) in the observation group. Compared with the control group, the areas with increased functional connectivity with insula in the observation group before acupuncture included bilateral dorsolateral prefrontal lobe and right middle cingulate gyrus, and the areas with increased functional connectivity with VTA included right central posterior gyrus and right insula. In the observation group, the connectivity coefficient of left insula and left dorsolateral prefrontal lobe (r=0.438, P<0.05), the connectivity coefficient of right insula and right dorsolateral prefrontal lobe (r=0.483, P<0.05) were positively associated with the VAS score. In the observation group, the connectivity coefficient between the right insula and the right middle cingulate gyrus (r=-0.560, P<0.05), the connectivity coefficient between the right VTA and the right insula (r=-0.525, P<0.05) were negatively associated with the PCS score. After acupuncture, the areas with decreased functional connectivity with insula included bilateral posterior central gyrus, right anterior central gyrus, middle cingulate gyrus and left corpus callosum, while the bilateral suboccipital gyrus and left cerebellum showed increased functional connectivity with right insula. The areas with decreased functional connectivity with VTA included bilateral dorsomedial prefrontal cortex, left anterior cingulate gyrus, right middle temporal gyrus and left anterior cingulate gyrus. After acupuncture in the observation group, the functional connectivity of left VTA left dorsomedial prefrontal cortex and left anterior cingulate cortex (r=-0.548, P<0.05), the functional connectivity of right VTA-bilateral dorsomedial prefrontal cortex and left anterior cingulate cortex (r=-0.547, P<0.05) were negatively associated with the PCS score. CONCLUSION: Pain involves the formation and expression of "pain-emotion-cognition". Acupuncture can systematically regulate the brain functional connections between cognitive regions such as dorsal prefrontal lobe and anterior cingulate gyrus and emotional regions such as insula and VTA in patients with cervical spondylosis of cervical type, suggesting that acupuncture has a multi-dimensional and comprehensive regulation effect on pain.

Spatiotemporal patterns of anuran functional diversity in temperate montane forests.

Functional diversity is an integrative approach to better understand biodiversity across space and time. In the present study, we investigated the spatiotemporal patterns (i.e., elevation and season) and environmental determinants of anuran functional diversity on Tianping Mountain, northwest Hunan, China. Specifically, 10 transects were established from low (300 m a.s.l.) to high (1 492 m a.s.l.) elevations, and anuran communities were sampled in spring, early summer, midsummer, and autumn in 2017. Four functional diversity indices were computed for each transect in each season using ecomorphological functional traits. Our results demonstrated that these indices had contrasting responses to increasing elevations. However, they did not differ significantly among seasons in terms of temporal patterns. Interestingly, the unique spatiotemporal functional diversity patterns were impacted by distinct environmental variables, such as leaf litter cover, water temperature, number of trees, and water conductivity.

Multiple myeloma with CD138 changed from positive to negative: A case report.

BACKGROUND: Multiple myeloma (MM) is a common malignant disease of the blood system, caused by the neoplastic proliferation of plasma cells that accumulate in bone marrow (BM). Here, we report a case of MM patient with CD138 marker changed from positive to negative. METHODS: BM and peripheral blood samples from a 48-year-old patient with MM were examined and analyzed by conventional morphology, flow cytometry, and immunodetection. RESULTS: Imaging examination and clinical manifestations fulfilled criteria for MM. On the first hospitalization, flow cytometry showed that the cells were CD138+ /CD38+ /CD19- /CD56+ . However, on the fifth hospitalization, flow cytometry revealed that the cells were CD138- /CD38+ /CD19- /CD56+ . CONCLUSIONS: MM is diagnosed on imaging and clinical manifestations, immunophenotype of flow cytometry is also an important method of diagnosing MM. However, the discovery of atypical immunophenotypes cannot prevent the diagnosis of MM, even provide a clue of disease progression.

Spatial and temporal patterns of amphibian species richness on Tianping Mountain, Hunan Province, China.

Exploring species richness patterns across space and time can help in understanding species distribution and in formulating conservation strategies. Among taxa, amphibians are of utmost importance as they are highly sensitive to environmental changes due to their unique life histories (Zhong et al., 2018). Here, we investigated the spatial and temporal patterns of amphibian species richness on Tianping Mountain in China. Specifically, we established 10 transects at low to high elevations, and sampled amphibians in April, June, August, and October 2017. Our results demonstrated that amphibian species composition and richness varied significantly at both spatial and temporal scales and were associated with gradients of environmental change in microhabitats on Tianping Mountain.

AntagomiR-199a Enhances the Liver Protective Effect of Hypoxia-Preconditioned BM-MSCs in a Rat Model of Reduced-Size Liver Transplantation.

BACKGROUND: Reduced-size liver transplantation (LT) was invented to overcome the shortage of donor livers; however, it has proven to be more susceptible to ischemia-reperfusion injury. Bone marrow-derived mesenchymal stem cell infusion has been shown to be protective following LT. Optimization of MSC infusion has been performed, among which hypoxia preconditioning and miRNA modulation have shown promise. MiR-199a inhibition was reported to induce angioneogenesis; however, whether mir-199a inhibition enhances the protective effect of Bone marrow-derived mesenchymal stem cells in LT remains unknown. In this study, we combined antagomiR-199a with hypoxia-preconditioned MSC (H-MSC) infusion to discuss their effect and mechanism in a rat model of reduced-size LT. METHODS: A reduced-size LT model was constructed and H-MSCs were intraportally injected during operation. AgomiR-199a and antagomir-199a were injected through the caudal vein once a day after LT. The level of apoptosis and proinflammatory cytokines were measured. An anti-vascular endothelial growth factor (VEGF) antibody was injected to further explore the underlying mechanism. RESULTS: AntagomiR-199a plus H-MSC not only significantly decreased ALT and AST 72 h after LT but also ameliorated the level of apoptosis and inhibited inflammatory reactions. On the contrary, agomir-199a reduced the protective effect of the H-MSC infusion. In terms of mechanism, the liver protective effect of miR-199a inhibition was abolished by treatment with a VEGF-neutralizing antibody. CONCLUSIONS: AntagomiR-199a enhanced the protective effect of H-MSCs infusion via activation of the hypoxia induction factor 1α/VEGF axis.

A Survey on Intelligent Screening for Diabetic Retinopathy.

Diabetic retinopathy (DR) is one of the leading causes of vision loss and can be effectively avoided by screening, early diagnosis and treatment. In order to increase the universality and efficiency of DR screening, many efforts have been invested in developing intelligent screening, and there have been great advances. In this paper, we survey DR screening from four perspectives: 1) public color fundus image datasets of DR; 2) DR classification and related lesion-extraction approaches; 3) existing computer-aided systems for DR screening; and 4) existing issues, challenges, and research trends. Our goal is to provide insights for future research directions on DR intelligent screening.

Liver vessel segmentation and identification based on oriented flux symmetry and graph cuts.

BACKGROUND AND OBJECTIVE: Accurate segmentation of liver vessels from abdominal computer tomography angiography (CTA) volume is very important for liver-vessel analysis and living-related liver transplants. This paper presents a novel liver-vessel segmentation and identification method. METHODS: Firstly, an anisotropic diffusion filter is used to smooth noise while preserving vessel boundaries. Then, based on the gradient symmetry and antisymmetry pattern of vessel structures, optimal oriented flux (OOF) and oriented flux antisymmetry (OFA) measures are respectively applied to detect liver vessels and their boundaries, and further to slenderize vessels. Next, according to vessel geometrical structure, a centerline extraction measure based on height ridge traversal and leaf node line-growing (LNLG) is proposed for the extraction of liver-vessel centerlines, and an intensity model based on fast marching is integrated into graph cuts (GCs) for effective segmentation of liver vessels. Finally, a distance voting mechanism is applied to separate the hepatic vein and portal vein. RESULTS: The experiment results on abdominal CTA images show that the proposed method can effectively segment liver vessels, achieving an average accuracy, sensitivity, and specificity of 97.7%, 79.8%, and 98.6%, respectively, and has a good performance on thin-vessel extraction. CONCLUSIONS: The proposed method does not require manual selection of the centerlines and vessel seeds, and can effectively segment liver vessels and identify hepatic vein and portal vein.

Automatic liver segmentation from abdominal CT volumes using graph cuts and border marching.

BACKGROUND AND OBJECTIVE: Identifying liver regions from abdominal computed tomography (CT) volumes is an important task for computer-aided liver disease diagnosis and surgical planning. This paper presents a fully automatic method for liver segmentation from CT volumes based on graph cuts and border marching. METHODS: An initial slice is segmented by density peak clustering. Based on pixel- and patch-wise features, an intensity model and a PCA-based regional appearance model are developed to enhance the contrast between liver and background. Then, these models as well as the location constraint estimated iteratively are integrated into graph cuts in order to segment the liver in each slice automatically. Finally, a vessel compensation method based on the border marching is used to increase the segmentation accuracy. RESULTS: Experiments are conducted on a clinical data set we created and also on the MICCAI2007 Grand Challenge liver data. The results show that the proposed intensity, appearance models, and the location constraint are significantly effective for liver recognition, and the undersegmented vessels can be compensated by the border marching based method. The segmentation performances in terms of VOE, RVD, ASD, RMSD, and MSD as well as the average running time achieved by our method on the SLIVER07 public database are 5.8 ± 3.2%, -0.1 ± 4.1%, 1.0 ± 0.5mm, 2.0 ± 1.2mm, 21.2 ± 9.3mm, and 4.7 minutes, respectively, which are superior to those of existing methods. CONCLUSIONS: The proposed method does not require time-consuming training process and statistical model construction, and is capable of dealing with complicated shapes and intensity variations successfully.

Efficient liver segmentation in CT images based on graph cuts and bottleneck detection.

Liver segmentation from abdominal computed tomography (CT) volumes is extremely important for computer-aided liver disease diagnosis and surgical planning of liver transplantation. Due to ambiguous edges, tissue adhesion, and variation in liver intensity and shape across patients, accurate liver segmentation is a challenging task. In this paper, we present an efficient semi-automatic method using intensity, local context, and spatial correlation of adjacent slices for the segmentation of healthy liver regions in CT volumes. An intensity model is combined with a principal component analysis (PCA) based appearance model to exclude complex background and highlight liver region. They are then integrated with location information from neighboring slices into graph cuts to segment the liver in each slice automatically. Finally, a boundary refinement method based on bottleneck detection is used to increase the segmentation accuracy. Our method does not require heavy training process or statistical model construction, and is capable of dealing with complicated shape and intensity variations. We apply the proposed method on XHCSU14 and SLIVER07 databases, and evaluate it by MICCAI criteria and Dice similarity coefficient. Experimental results show our method outperforms several existing methods on liver segmentation.

Liver vessel segmentation based on extreme learning machine.

Liver-vessel segmentation plays an important role in vessel structure analysis for liver surgical planning. This paper presents a liver-vessel segmentation method based on extreme learning machine (ELM). Firstly, an anisotropic filter is used to remove noise while preserving vessel boundaries from the original computer tomography (CT) images. Then, based on the knowledge of prior shapes and geometrical structures, three classical vessel filters including Sato, Frangi and offset medialness filters together with the strain energy filter are used to extract vessel structure features. Finally, the ELM is applied to segment liver vessels from background voxels. Experimental results show that the proposed method can effectively segment liver vessels from abdominal CT images, and achieves good accuracy, sensitivity and specificity.

Investigation of miscellaneous hERG inhibition in large diverse compound collection using automated patch-clamp assay.

AIM: hERG potassium channels display miscellaneous interactions with diverse chemical scaffolds. In this study we assessed the hERG inhibition in a large compound library of diverse chemical entities and provided data for better understanding of the mechanisms underlying promiscuity of hERG inhibition. METHODS: Approximately 300 000 compounds contained in Molecular Library Small Molecular Repository (MLSMR) library were tested. Compound profiling was conducted on hERG-CHO cells using the automated patch-clamp platform-IonWorks Quattro(™). RESULTS: The compound library was tested at 1 and 10 µmol/L. IC50 values were predicted using a modified 4-parameter logistic model. Inhibitor hits were binned into three groups based on their potency: high (IC50<1 µmol/L), intermediate (1 µmol/L< IC50<10 µmol/L), and low (IC50>10 µmol/L) with hit rates of 1.64%, 9.17% and 16.63%, respectively. Six physiochemical properties of each compound were acquired and calculated using ACD software to evaluate the correlation between hERG inhibition and the properties: hERG inhibition was positively correlative to the physiochemical properties ALogP, molecular weight and RTB, and negatively correlative to TPSA. CONCLUSION: Based on a large diverse compound collection, this study provides experimental evidence to understand the promiscuity of hERG inhibition. This study further demonstrates that hERG liability compounds tend to be more hydrophobic, high-molecular, flexible and polarizable.

Automatic Tooth Segmentation of Dental Mesh Based on Harmonic Fields.

An important preprocess in computer-aided orthodontics is to segment teeth from the dental models accurately, which should involve manual interactions as few as possible. But fully automatic partition of all teeth is not a trivial task, since teeth occur in different shapes and their arrangements vary substantially from one individual to another. The difficulty is exacerbated when severe teeth malocclusion and crowding problems occur, which is a common occurrence in clinical cases. Most published methods in this area either are inaccurate or require lots of manual interactions. Motivated by the state-of-the-art general mesh segmentation methods that adopted the theory of harmonic field to detect partition boundaries, this paper proposes a novel, dental-targeted segmentation framework for dental meshes. With a specially designed weighting scheme and a strategy of a priori knowledge to guide the assignment of harmonic constraints, this method can identify teeth partition boundaries effectively. Extensive experiments and quantitative analysis demonstrate that the proposed method is able to partition high-quality teeth automatically with robustness and efficiency.

Interactive tooth partition of dental mesh base on tooth-target harmonic field.

The accurate tooth partition of dental mesh is a crucial step in computer-aided orthodontics. However, tooth boundary identification is not a trivial task for tooth partition, since different shapes and their arrangements vary substantially among common clinical cases. Though curvature field is traditionally used for identifying boundaries, it is normally not reliable enough. Other methods may improve the accuracy, but require intensive user interaction. Motivated by state-of-the-art general interactive mesh segmentation methods, this paper proposes a novel tooth-target partition framework that employs harmonic fields to partition teeth accurately and effectively. In addition, a refining strategy is introduced to successfully segment teeth from the complicated dental model with indistinctive tooth boundaries on its lingual side surface, addressing an issue that had not been solved properly before. To utilise high-level information provided by the user, smart and intuitive user interfaces are also proposed with minimum interaction. In fact, most published interactive methods specifically designed for tooth partition are lacking efficient user interfaces. Extensive experiments and quantitative analyses show that our tooth partition method outperforms the state-of-the-art approaches in terms of accuracy, robustness and efficiency.

[Twisting acupuncture and sham acupuncture at Taichong (LR 3) in patients with essential hyper- tension: an fMRI study].

OBJECTIVE: With functional magnetic resonance imaging (fMRI), cerebral function imaging of acupuncture and sham acupuncture at Taichong (LR 3) in patients with essential hypertension (EH) was observed to analyze central mechanism of Taichong (LR 3) to treat EH. METHODS: Eighteen EH patients were divided into a twisting acupuncture group (10 cases) and a sham acupuncture group (8 cases), which were treated with twisting manipulation and sham acu- puncture at right Taichong (LR 3), respectively. The treatments were both given with 30-second manipulation and 30- second interval for totally 5 min. During the acupuncture, fMRI was adopted to scan the cerebral function imaging of EH patients on resting state, and the acquired data were analyzed with SPM2 module in Matlab software. RESULTS: Acupunc- ture at Taichong (LR 3) in EH patients mainly increased opposite-side oxygen consumption, which generally activated left anterior cingulated gyrus (BA 32), left inferior parietal lobule (BA 40), left inferior temporal gyrus (BA 19), left middle temporal gyrus (BA 37) and right anterior central gyrus (BA 6). The activated areas were related to motor, vision and cognition of emotion. Stimulation region of sham acupuncture mainly included right anterior cingulated gyrus (BA 24), left inferior parietal lobule (BA 40) and left inferior frontal gyrus (BA 7). CONCLUSION: The central mechanism of Tai- chong (LR 3) on antihypertensive effect and symptom improvement is not in thalamus and medulla that are traditionally believed to control blood pressure. Taichong (LR 3) could activate anterior cingulated gyrus to regulate parasympathetic nerve and lower blood pressure, and through anterior cingulated gyrus, the connection with the surrounding areas is strengthened to improve the cognitive impairment caused by long-term hypertension.

Physical modeling with orthotropic material based on harmonic fields.

Although it is well known that human bone tissues have obvious orthotropic material properties, most works in the physical modeling field adopted oversimplified isotropic or approximated transversely isotropic elasticity due to the simplicity. This paper presents a convenient methodology based on harmonic fields, to construct volumetric finite element mesh integrated with complete orthotropic material. The basic idea is taking advantage of the fact that the longitudinal axis direction indicated by the shape configuration of most bone tissues is compatible with the trajectory of the maximum material stiffness. First, surface harmonic fields of the longitudinal axis direction for individual bone models were generated, whose scalar distribution pattern tends to conform very well to the object shape. The scalar iso-contours were extracted and sampled adaptively to construct volumetric meshes of high quality. Following, the surface harmonic fields were expanded over the whole volumetric domain to create longitudinal and radial volumetric harmonic fields, from which the gradient vector fields were calculated and employed as the orthotropic principal axes vector fields. Contrastive finite element analyses demonstrated that elastic orthotropy has significant effect on simulating stresses and strains, including the value as well as distribution pattern, which underlines the relevance of our orthotropic modeling scheme.