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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective To establish the three-dimensional (3D) finite element (FE) model of thoracolumbosacral T1-S spine based on the computed tomography (CT) images of patients with scoliosis and study its dynamic characteristics. Methods The established scoliotic model was validated by axial compression and shear loading, and the predicted responses were in good agreement with the experimental data. The modal and harmonic analyses were performed using the ABAQUS software, and during the harmonic analysis, the dynamic response of the model was collected at frequencies 5 Hz and 10 Hz. Results From the modal analysis, the first fourth-order modal was extracted. The first- and second-order resonant frequencies of the model were 1.097 Hz and 1.384 Hz, respectively, and the vibration mode was longitudinal bending and lateral bending, respectively. The distribution of the second- and third-order modal resonant frequencies were 5.688 Hz and 28.090 Hz, and the vibration mode was vertical vibration and twisting around the long axis, respectively. The peak amplitude in the harmonic analysis appeared near the modal frequencies, and the average amplitude of vertebral body of the lateral convex segment was larger than that of other segments of the scoliotic spine. Under the vibration frequencies of 5 Hz and 10 Hz, the stress inhomogeneously concentrated on the concave and convex sides of the segments of the vertebral deformity as well as on the intervertebral disc. Conclusions The segments of the spinal deformity in patients with scoliosis were the weak links of their spines and more vulnerable to damage in a vibrating environment. Patients with scoliosis should avoid a vibrating environment, particularly in a sensitive frequency range. The research outcomes provide methodological assistance and mechanical analysis references for the protection, rehabilitation treatment, and clinical pathological studies of patients with scoliosis.
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BACKGROUND: In the patients with congenital scoliosis, the spinal motor units exhibit developmental disorders and poor range of motion. It has been found that the compensation ability of coronal lumbosacral region (L4-S1) is associated with the occurrence of non-compensable trunk migration postoperatively.OBJECTIVE: To establish the three-dimensional finite element models of coronal lumbosacral region of normal and patients with congenital scoliosis and to compare the strain, displacement, stress and stiffness under different loading conditions among models.METHODS: One normal subject and two congenital scoliosis patients with different coronal lumbosacral region flexibility were selected, DICOM image datawere obtained by spiral CT scanning at the lumbosacral region, and then imported into MIMICS software, and a three-dimensional model was established according to the gray values of each tissue on CT,followed by simplified by GEOMAGIC, and finally imported into ABAQUS foftware to conduct a mechanic analysis under different loading conditions.RESULTS AND CONCLUSION: (1) Under different lateral forces, in the three models, the maximum stress mainly distributed on the frontal region of L4 cortical bone, and maximum displacement concentrated on L5. (2) There was no significant change in the stress distribution in the two scoliosis models, but the compensable model showed larger displacement change, and its stiffness was significantly less than that of the non-compensable model, indicating that the compensable model is easy to deform. (3) These findings suggest that three-dimensional finite element model is helpful to perform a biomechanical analysis for coronal lumbosacral region of congenital scoliosis, among which, a compensable model exhibits large displacement, suggesting a good flexibility.
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Objective To study the correlation between the deformation and displacement trend of the lumbosacral vertebra (L1-S1) for two typical scoliosis spines under vertical loads,so as to provide the mechanical basis of treatment and prevention of scoliosis in clinic.Methods The X-ray computed tomography (CT) images of two typical scoliosis spines (Lenke-4AN type and Lenke-5CN type) were converted into 3D models,and their finite element models were then established and verified.The internal stress distribution and displacement variation of the models were calculated by the finite element software;the correlation between the lumbosacral vertebral structure and displacement of the spine was analyzed.Results Under the same boundary conditions and load cases,the stress and displacement for two kinds of lumbosacral vertebral models showed different trends.Due to its leftleaning and forward convex bending deformation as well as the relatively large lordosis angle (60°) and smaller left-leaning angle (17.37°),the Lenke-4AN type lumbosacral spine produced slightly small forward convex displacement (8.18 mm) and relatively large left-leaning displacement (0.97 mm).The Lenke-5CN type lumbosacral spine showed left-leaning and forward convex bending deformation as well,with relatively large lordosis angle(59°) and left-leaning angle (26.97°),so it produced more severe left-leaning displacement (20.65 mm) andforward convex displacement (9.22 mm).Conclusions The deformation trend of lumbosacral vertebra is closelyrelated to its structural characteristics,and different scoliosis lumbosacral vertebral structures will cause the corre-sponding deformation trend.The research findings are important for the prevention and treatment of scoliosis.
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BACKGROUND: Inherent modal analysis and harmonic response analysis on the human normal lumbosacral vertebraehave been reported, but there is a lack of comparative research on their modal analysis results before and after pediclescrew fixation.OBJECTIVE: To explore the dynamic characteristics of human lumbosacral vertebrae using three-dimensional finiteelement method.METHODS: Finite element model of lumbosacral vertebrae (L1-S1) before and after pedicle screw fixation was developedand validated based on CT images, and the modal analysis and harmonic response analysis were then conducted.RESULTS AND CONCLUSION: (1) Representative nodes were selected at the spinous process segments of L1, L3 andL5, and numbered as A, B, and C, respectively. (2) The maximum displacement of each node in Y and Z directions oflumbosacral vertebral model after internal fixation was significantly decreased compared with those of the normallumbosacral vertebral model, suggesting that screw fixation system plays a protective role in lumbosacral vertebrae, andreduces its amplitude under external load, thus diminishing its sensitivity to external load. (3) The lumbosacral vertebralmodal analysis can provide basis for further study on dynamic analysis, and the parameters such as natural frequency,modal shape and vibration amplitude of the lumbar spine have been determined.
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Objective To evaluate the therapeutic effects of methamphetamine (MA) dependence and the repairment of DA neuronal function by SPECT corpus striatum DAT visual digital neural molecular imaging techniques.Methods 25 MA dependent patients (BPRS score ≥ 35) were treated by self-designed treatment program for more than 6 months.The clinical therapeutic effects were scored with reducing rate of BPRS.MA dependent patients were examined by SPECT corpus striatum DAT imaging before and after treatment,while healthy volunteers were examined only once.The SPECT corpus striatum DAT images were analyzed visually and quantitatively.Results The reducing rate of BPRS showed that the total effective rate was 80.0％.Visual analysis of SPECT corpus striatum DAT images showed that the distribution of DAT in the corpus striatum was regionally reduced or defected in various degrees before treatment,and was significantly increased after treatment.Quantitative analysis showed that the bilateral striatal V ((19.26 ± 2.85) cm3),m((20.22±2.99) g) and Ra(4.78±0.79) ％) of MA dependent patients were significantly lower compared with those of the healthy volunteers(respectively (35.39±4.42) cm3,(37.16±4.64) g and (7.93± 0.86) ％) (all P＜ 0.01) before treatment and were significantly improved (P＜ 0.01) after treatment (V:(22.80±4.28) cm3,m:(23.93± 4.49) g and Ra:(5.64 ± 0.99) ％) with a 76.0％ corpus striatum DAT improvement rate.However,the bilateral striatal V,m and Ra of MA dependent patients after treatment were still lower than those of the healthy volunteers (P＜0.01).There was no significant difference between the striatal DAT improvement rate and the BPRS reduction rate (P＞ 0.05).Conclusion SPECT corpus striatum DAT visual digital neural molecular imaging techniques are reliable in the evaluation of the treatment programs for MA dependence and the repair of DA neuronal function.
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Heavy-ions have the similar characteristic of depth-dose distribution with protons, but exhibit enhanced physical and radiobiological benefits. With increasing development in technical and clinical research, more facilities are being installed in the world. At the same time, many critical techniques of heavy-ion therapy facility were optimized and completed. This paper classified and reviewed the basic structure of heavy-ion system equipments, especially the accelerator, gantry, nozzle , TPS.
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Humanos , Institutos de Câncer , Radioterapia com Íons Pesados , Neoplasias , TerapêuticaRESUMO
Objective To investigate the application value of identification of the scalp surface locations of cerebral ischemia lesions before direct revascularization for moyamoya disease and to design surgical approaches according to this by using the fusion of single photon emission computed tomography ( SPECT) cerebral perfusion imaging with CT imaging. Methods The clinical data of 13 adult patients with ischemic-type moyamoya disease underwent superficial temporal artery-middle cerebral artery bypass surgery were analyzed retrospectively. SPECT cerebral perfusion imaging was fused with CT imaging of the same machine before procedure. The lesions of ischemia were located on the cortical surface. The surgical approaches were designed at the center of the ischemic lesions. The patients were followed up for 6 to 12 months after procedure. The improvement of clinical symptoms and cerebral perfusion of the patients were observed after operation. Results One patient had perioperative cerebral hyperperfusion syndrome,and the others did not have any perioperative complications. At one-month follow-up, the improvement of symptoms in 4 patients were excellent,in 5 were good,in 4 were fair,and none was poor. At 6 to 12 month follow-up,the improvement of symptoms in 9 patients were excellent,in 4 were good,and none was poor. The postoperative visual SPECT cerebral perfusion imaging analysis suggested that the cerebral perfusion was improved significantly as compared with before procedure in all patients. Quantitative analysis:There was significant difference in target ischemic lesions between preoperative Fb and postoperative Fb ([2. 13±1. 06]% vs. [4. 13±2. 09]%;P50%) , which indicated that the efficacy of the procedure was remarkable. The superficial temporal arteries fed to brain of the patients were observed after procedure by using the head CT angiography. The postoperative head MRI reexamination showed no new infarcts occurred at 6 months. Conclusion Combine SPECT cerebral perfusion imaging with CT imaging to design surgical approach for superficial temporal artery-middle cerebral artery bypass surgery may improve the efficacy and reduce the risks of operation.
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BACKGROUND: Long-term sustained release naltrexone has been reported in clinical application near one year that it can improve emotional state and relieve addiction; therefore, the effect of long-term sustained release naltrexone on memory restoration at neuropsychology level were explored. OBJECTIVE: To observe the effect of long-term sustained release naltrexone on memory ability of opioid addicts. DESIGN, TIME AND SETTING: A contrast observational study was performed at Drug Rehabilitation Centers of Wuhan, Changde, Zhengzhou, and Jiangyang between October and December 2006. Healthy controls were tested in Shenzhen Hospital of Peking University in October 2006. PARTICIPANTS: A total of 88 males with opioid addicts were divided into naltrexone group (n=35), compulsory detoxification group (n=26), and non-treatment group (n=27). Another 22 healthy subjects were considered as the controls. METHODS: At 6-12 months before testing, naltrexone (3.1 g) was subcutaneously implanted into bilateral abdominal wall in the naltrexone group; patients in the compulsory detoxification group underwent completely compulsory detoxification for 6 months, and the examination results, including diamorphine, methadone, and buprenorphine in urine, were negative on the immediately testing day. Event related potential and its wave form were recorded from the opioid addicts in the three groups and from healthy controls who finished semantic recognition between new and old words using portable-type event related potential working system. MAIN OUTCOME MEASURES: Correct rate and response time of semantic memory; latency and amplitude of language related potential-N400. RESULTS: ①There were significant differences in correct rate and response time between three expedmental groups and healthy control group (P ＜ 0.001 ); in addition, correct rate was significantly increased, and response time was significantly shortened in the naltrexone group compared to compulsory detoxification group and non-treatment group (P＜ 0.05). ② N400 latency in the three experimental groups was significantly longer than healthy control group (P ＜ 0.01), while N400 amplitude in the naltrexone group was increased, which was no significant difference compared to healthy control group (P> 0.05) but was significant difference compared to compulsory detoxification group and non-treatment group (P ＜ 0.01). CONCLUSION: Long-term sustained release naltrexone can effectively improve neural function and enhance semantic memory of the opioid addicts.
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Objective To study the effects of carvedilol on the stability of plasma catecholamine in patients with post-acute myocardial infarction during consecutive periods. Methods Thirty-slx patients selected with acute myocardial infarction were randomized to experimental group treated with the nonselective beta-blocker earvedilol( n=18) and control group treated with the selective beta-blocker metoprolol(=18) for 12-months follow-up. In the two groups,the concentrations of plasma norepinephrine and epinephrine were measured before the treatment and after 2 months,4 months,6 months,8 mouths,10 months and 12 months and new cardiac events were supervised. Results After the treatment, in each point of periods, experimental group showed lower concentrations of plasma norepinephrine and epinephrine statistically than control group(P<0.05) ,and a stable dynamic change during 12 months of treat-ment( P>0.05 ) ;the occurrence rate of new cardiac events was lower significantly in experimental group than in con-trol group(P<0.05). Conclusion Carvedilol can decrease the spillover of sympathetic nerve, control more stably cardiac sympathetic nerve activity and then decrease more sharply the occurrence rate of new cardiac events in pa-tients with acute myocardial infarction than metoprolol.
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Objective To investigate the effects and relations of carvedilol on heart rate turbulence and secretion of sympathetic nerve in patients with myocardial infarction. Methods Sixty-six patients selected with acute myocardial infarction were randomized to enroll into experimental group ( n = 33 ) treated with earvedilol and control group( n = 33 ) treated with metoprolol for 12 months follow-up treatment. The concenrrarions of plasma norepinephrine(NE) and epinephrine (E) and 24 hour Holter monitoring were messured respectively before the treatment ,after 6 months and 12 months; and new cardiac events were supervised for all cases. Quantification of heart rate turbulenee(HRT) were carried out by computer analyzing two factors: turbulence onset(TO) and turbulence slope(TS) from the data of 24 hour Holter monitoring. NE,E,TO,TS and the occurrence rate of new cardiac events were compared between two groups and in different times of treatment. The correlation between TO,TS and NE,E was analysed. Results Before the treatment, there was no significant differences between two groups to the comparisons of NE,E,TO and TS(P＞0.05). After treating 6 and 12 months, NE, E and TO of experimental group were all lower than control group's significantly, accordingly TS were all higher(P＜0.05). By comparing 3 times( before,after 6 and 12 months of treatment), NE, E and TO of two groups dropped, meanwhile TS rose; experimental group showed significant changes( P＜0.05 ), but control group showed no significant differences(P＞0.05 ). The occurrence rate of new cardiac events of experimental group was lower than control group's significantly (P＜0.05 ).There was significant correlation between NE, E and TO, TS (P＜0.05 ). Conclusion Carvedilol treatment can block the secretion of sympathetic nerve after myocardial infarction and prevent the occurrences of new cardiac events significantly; the changes of the secretion of sympathetic nerve can play an important role for heart rate turbulence (HRT) ,the changes of HRT would be hopeful to predict new cardiac events alter myocardial infarction.
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AIM To identify differentially expressed proteins in the plasma that may be used as biomarkers for heroin addiction through a two-dimensional (2-D)gel electrophoresis/mass spectrometry approach. METHODS Following removal of albumin and IgG,the plasma from 5 heroin abusers and 5 normal controls was separated by 2-D gel electrophoresis using immobi-lized pH gradients 4 -7 drystrip and PAGE. Gel ima-ges were analyzed using ImageMaster Elit 5.0. Differ-ential proteins were selected and analyzed through tan-dem mass spectrometry. RESULTS Average number for samples was 350±21 protein spots. In them there were 5 spots that differed by more than 1.5 fold be-tween the two groups obtained through image analysis.Through tandem mass spectrometry above spots were identified as fibrinogen γ (increased by 5 fold), hu-man α1-B-glycoprotein (decreased to 1/1.8 of control group), uncleaved α1-antitrypsin (increased by 2.5 fold), chain of transthyretin (decreased to 1/2 of con-trol group ) and ccruloplasmin (increased by 6.6 fold ). CONCLUSION There are differences between heroin abusers and normal controls in the blood plasma proteome. Some proteins may have a role in the damage to central nervous system through heroin abuse. Such proteins may provide novel biomarkers for diagnosis and therapeutic targeting, as well as clues forunderstanding the mechanism of heroin abuse.
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Objective To study the effects of low power laser irradiation in nasal cavity on cerebral blood flow and cerebral function in patients with brain infarction. Methods Thirty-nine patients with cerebral infarction were divided into a intravenous laser irradiation group and a laser irradiation in nasal cavity group. For the group of intravenous irradiation (ILIB group,18 cases), the patients lay on the bed with their heads fixed and were treated with intravenous laser irradiation for 30 min. Both before and after the therapy they received a SPECT cerebral perfusion imaging separately. For the group of laser irradiation in nasal cavity (LINC group,21 cases), the patients received laser irradiation in nasal cavity for 30 min and also SPECT cerebral perfusion imaging tests both before and after therapy. BFCR% model was used to quantify the blood flow of the focal and mirror regions. Results SPECT showed that there was significant improvement in perfusion of the entire brain and cerebral function in both ILIB and LINC groups after 30 minutes of treatment,each compared to those before treatment; the changes in the focal rCBF and cerebral function were much more obvious (P0.05). BFCR% in focal region was significantly higher than that in mirror region (P0.05). Conclusion Low power laser irradiation in nasal cavity can improve the focal rCBF and cerebral function of the patients with brain infarction, which is similar to that of the ILIB.