Mass point-spring model is one of the commonly used models in virtual surgery. However, its model parameters have no clear physical meaning, and it is hard to set the parameter conveniently. We, therefore, proposed a method based on genetic algorithm to determine the mass-spring model parameters. Computer-aided tomography (CAT) data were used to determine the mass value of the particle, and stiffness and damping coefficient were obtained by genetic algorithm. We used the difference between the reference deformation and virtual deformation as the fitness function to get the approximate optimal solution of the model parameters. Experimental results showed that this method could obtain an approximate optimal solution of spring parameters with lower cost, and could accurately reproduce the effect of the actual deformation model as well.
Algorithms ; Models, Theoretical ; Surgery, Computer-Assisted ; Tomography

A new diamond-based variable spring-mass model has been proposed in this study. It can realize the deformation simulation for different organs by changing the length of the springs, spring coefficient and initial angle. The virtual spring joined in the model is used to provide constraint and to avoid hyperelastic phenomenon when excessive force appears. It is also used for the calculation of force feedback in the deformation process. With the deformation force feedback algorithm, we calculated the deformation area of each layer through screening effective particles, and contacted the deformation area with the force. This simplified the force feedback algorithm of traditional spring-particle model. The deformation simulation was realized by the PHANTOM haptic interaction devices based on this model. The experimental results showed that the model had the advantage of simple structure and of being easy to implement. The deformation force feedback algorithm reduces the number of the deformation calculation, improves the real-time deformation and has a more realistic deformation effect.
Algorithms ; Computer Simulation ; Feedback ; Models, Biological

Objective To evaluate the clinical value of interventional therapy of patent ductus arteriosus(PDA).Methods A total of 941 patients(259 male and 682 female) with PDA admitted from March 1998 to August 2007,aged from 3 months to 74 years old(mean age 13.7?14.5 years old) were included in this study.The clinical characteristics and the outcomes of the therapy were retrospestively studied.Results These PDA types were classified according to Krichenko's classification by aortic angiography.Among all the patients,641 of then(68.1%) had type A PDA,11 patients(1.1%) had type B,202 patients(21.5%) had type C,8 patients(0.85%) had type D and 79 patients(8.4%) had type E PDA.The ranges for the minimun inner diameter of PDA was 1.2-1.5(4.6?2.9) mm,the inner diameter of aorta end was 2.0-32.7(11.1?5.7) mm,the length was 2-42.6(6.7?3.3) mm and the mean pulmonary arterial pressure was 9.7-106(34.7?19.4) mm Hg.Various occlusion devices were used to close the PDA including AGA mushroom occluder in 146 patients,AGA atrioseptal defect device in 2 patients,homemade PDA ductal occluders in 720 patients,homemade membranous ventricular septal defect device in 18 patients,homemade muscular ventricular septal defect device in 6 patients, eccentricity PDA devices in 18 patients and Germany pfm spring coil in 31 patients.Transcather closure was unsuccessful in 7 patietns and the success rate of operation was 99.3%(934/941).Conclusion Most patients can be cured by catheterization closure.To master procedural indication and accurate manipulation skill can reduce the procedural complications.The procedures should be handled carefully in infants or patients with pulmonary artery hypertension.The evaluation of pulmonary artery pressure is the key point prior to the interventional therapy.The experience on long-term efficacy of transcatheter PDA closure in patients complicated with pulmonary artery hypertension needs further exploration.

Objective:To observe influence of simvastatin on differentiation ,proliferation ,migration and adhesion of marrow-derived smooth muscle progenitor cells (SPCs) and screen coated eluting stent drugs of new generation . Methods :The mononuclear cells (MNCs) were isolated from rat marrow by density gradient centrifugation method , and then plated on fibronectin-coated culture dishes ,after culture 8d ,marrow-derived SPCs were identified by α-smooth muscle actin (α-SMA) immunofluorescent staining and counted under inverted fluorescence microscope .The MNCs and adhesion cells were treated with simvastatin (0.01~10 μmol/L) respectively for 8 d and 24h .SPCs pro-liferation ,migration and adhesion were observed by Tritium thymidine (3 H-TdR) intake method ,modified Boyden chamber assay and adhesion assay .Results:Compared with control group (no simvastatin intervention ) ,0.01μmol/L simvastatin significantly inhibited the MNCs differentiation towards SPCs [ (85 ± 4) vs .(79 ± 5)] ,proliferation [ (4070 ± 184) vs .(3833 ± 126)] ,migration [ (44 ± 3) vs .(39 ± 3)] and adhesion of SPCs [ (59 ± 5) vs .(52 ± 4)] , P<0.05 all ,and number of SPCs significantly reduced along with simvastatin concentration increased (P<0.01) . Conclusion:Simvastatin could inhibit the differentiation ,proliferation ,migration and adhesion of marrow-derived smooth muscle progenitor cells .

Objective to investigate the relationship between the size of ostium secondary atrial septal defect (ASD) and the pulmonary arterial pressure (PAP) in children less than 5 years of age. Methods During the period from April 2000 to January 2011, a total of 189 child patients less than 5 years of age with ostium secondary ASD were admitted to General Hospital of Shenyang Military Command. Under general anaesthesia with ketamine cardiac catheterization was performed, PAP was measured, and percutaneous occlusion of ASD was carried out in all patients. The clinical indexes, including sex, age, body height, body weight, body surface area, diameter of ASD defect, heart- to- thorax ratio, the systolic, diastolic and mean pressure of the pulmonary artery, etc. were determined. The patients were followed up for one year and postoperative cardiac ultrasonography was performed to check the results. The patients were divided into groups according to the defect size. Results The 189 patients consisted of 77 males and 112 females with a male-to-female ratio of 1 ∶ 1.5. The mean age was (4.1 ± 0.9) years old, ranging from 2 to 5 years old. The mean weight was (17.2 ± 3.6) kg, ranging from 10.0 to 30.0 kg. The mean height was (104.9 ± 9.2) cm, ranging from 77 to 135 cm. The mean body surface area (BSA) was (0.71 ± 0.10) m2, ranging from 0.46 to 1.02 m2. The mean size of ASD was (12.6 ± 4.8) mm, ranging from 5 to 29 mm. The mean size of ASD, which was modified by BSA, was (18.0 ± 7.0) mm/m2, ranging from 5.3 to 38.9 mm/m2. The mean systolic PAP was (41.1 ± 8.9) mmHg with a range of 15 - 67 mmHg. The mean diastolic PAP was (16.8 ± 6.5) mmHg with a range of 3 - 45 mmHg. The mean PAP was (24.9 ± 6.7) mmHg with a range of 12 - 48 mmHg. One hundred and fifty- nine patients (89.4%) had pulmonary arterial hypertension (PAH) which was determined by right heart catheterization, but no patient showed PAH when the pulmonary arterial pressure was measured by echocardiography before the procedure as well as 1, 3, 6, 12 months after the procedure. No definite correlation existed between the size of ASD and the pulmonary artery pressure (P > 0.05). Conclusion Pulmonary artery pressure measured by right heart catheterization has no definite correlation with the size of ASD in children less than 5 years of age. Pulmonary artery pressure obtained from right heart catheterization is higher than that determined by cardiac ultrasonography, which may be caused by the effect of ketamine when general anaesthesia is used in performing right heart catheterization.

Objective To evaluate clinical effectiveness of transcatheter closure of atrial septal defects ( ASD) with severe pulmonary arterial hyperyension ( sPAH) by fenestrated Amplatzer septal occluders ( ASO) . Methods From September 2002 to April 2013, 17 patients of ASD with sPAH received transcatheter ASD closure using fenestrated occluders. Aged from 18 - 72 years, the diameters of ASDs were 18 - 33 mm. The systolic pulmonary arterial hypertension measured by transthoracic echocardiogram were 80 - 112 (96. 9 ± 8. 9) mmHg. The follow-up study included electrocardiography, chest radiography and echocardiography. All the patients were followed up for 1. 5 - 12 ( mean 6. 4 ± 0. 7) years. Results Systolic pulmonary arterial pressure (sPAP) of 60 - 108 (88. 7 ± 11. 7) mmHg and mean pulmonary artery pressure ( mPAP) of 29. 3 - 60 (51. 0 ± 8. 1) mmHg were measured by cardiac catheterization before ASD closure. Qp/ Qs was 1. 50 - 2. 44 (1. 8 ± 0. 31) and the pulmonary vascular resistance was 3. 1 - 9. 7 (5. 6 ± 1. 5) wood units (wu) . Immediately after the implantation of fenestrated occluders, sPAP decreased to 56 - 99 (70 ± 11. 5) mmHg and mPAP to 27 - 51. 7 (41. 1 ± 7. 1) mmHg. On the 3 d, 3 m and 6 m follow-up exam, RVEDd decreased ( P ﹤ 0. 05), while LVEDd, LVEDV and LVEF increased significantly (P ﹤ 0. 05) . sPAP decreased significantly after transcatheter closure at 3 m and 6 m as compared to pre-closure levels (both P ﹤ 0. 05) . The mean sPAP in long term follow up was (60. 2 ± 13. 3) mmHg which had significant decrease compared to pre-closure level ( P ﹤ 0. 01), but no significant difference found when compared to 6 m follow up (P ﹥ 0. 05). Conclusions ASD closure with fenestrated ASO is a satisfactory approach for ASD with severe PAH.

Objective To investigate the risk factors and early diagnosis of the severe thrombocytopenia complicating transcatheter ccclusion of patent ductus arteriosus ( PDA ) . Methods Between February, 2011 and May, 2015, 80 patients with patent ductus arteriosus underwent percutaneous intervention occlusion were studied. Results Average age were ( 17. 5 ± 17. 1 ) years, 63 were females (78. 8%), mean weight were (35. 6 ± 20. 2)kg (from 6. 0 to 75. 0 kg), mean body surface area (BSA) were (1. 09 ±0. 44) m2(from 0. 32 to 1. 91 m2). A bolus of heparin calcium (80 U/kg) was administered by intravenous injection. The mean diameters of patent ductus arteriosus were 4 mm (from 2 to 18 mm), and the mean diameters of occluders were 12 mm (from 6 to 30 mm). 14 patients were found to have severe thrombocytopenia (PLT count﹤100 × 109/L). The reduction rate of platelet in 12 of 14 patients was more than 19%. The diameters of all occluders were equal to or more than 14 mm, the mean diameters of patent ductus arteriosus were 10 mm ( from 6 to 18 mm) and the mean diameters of occluders were 18 mm ( from 14 to 30 mm). All the 14 patients started to present progressive decrease in PLT count since the second day post procedure. Taking the selected occluder diameter greater than 14 mm as cut-off points in diagnosis of severe thrombocytopenia, the sensitivity was 100%, specificity was 68%, the positive predictive value was 40%, and the negative predictive value was 100%. Combined with the postprocedural second day complete blood count analysis and the platelet count decreased by 10% as cut-off points in diagnosis of severe thrombocytopenia patients, the sensitivity was 93%, specificity was 67%, the positive predictive value was 65%, the negative predictive value was 93% . If taking the platelet count decreased by 7% on second day as cut-off points in diagnosis of severe thrombocytopenia patients, the sensitivity was 100%, specificity was 57%, the positive predictive value was 61%, the negative predictive value was 100% . Logistic regression analysis discovered that risk factors of severe thrombocytopenia after PDA are procedural platelet count and occluder diameter. Conclusions The risk factors of severe thrombocytopenia complicating transcatheter ccclusion of patent ductus arteriosus were the procedural reduction of platelet count and big occluder diameter. Patients with PDA who were inplanted with occluders equal to or bigger than 14 mm should retest the numbers of platelet on the second day after procedure and retest on third day if the numbers reduce on the second day, which may help in the prediction of severe thrombocytopenia.

Objective: To study the expressions of endothelin-1 in primary cultured atrial myocyte model at early stages of atrial fibrillation by rapid pacing. Methods: The primary rat atrial myocytes were cultured, in which a rapid paced cell model was established. The polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were applied to detect the messenger ribonucleic acid (mRNA) expression and secretion of endothelin-1 on 3 h, 6 h, 12 h and 24 h after rapid pacing. Results: Compared with before pacing, there were continuous and significant increase in expression of ET-1mRNA [ (0.31±0.02) vs. (0.52±0.07), (0.62±0.09), (0.75±0.05) ] and secretion of endothelin-1 [ (3.4±0.8) ng/L vs. (6.0±1.4) ng/L, (8.3±1.5) ng/L, (11.2±2.1) ng/L] on 6 h, 12 h and 24 h after rapid pacing, P<0.01 all. Conclusion 　 Expressions of ET-1mRNA and secretion of endothelin-1 significantly increase depend on time in early rapid pacing atrial myocytes, indicating that endothelin-1 participates in atrial pathological remodeling during atrial fibrillation.

Objective To evaluate the clinical safety, efficacy and long-term outcome of transcatheter occlusion for ruptured aortic sinus of valsalva aneurysm (RASA) into the right atrium.Methods Between January 2006 and April 2013, fifteen patients [11 males and 4 females,aged from 21 to 48 years with an mean age of (35.50±8.79) years] with RASA ruptured into the right atrium were enrolled in this study.Domestic made patent ductus arteriosus (applied in six patients) or small waist double-disk ventricular septal defect (applied in nine patients) occluders were used for transcatheter closure.All the patients were followed up for any change in cardiac rhythm,and residual shunt,occluders morphology and possible valve regurgitation by echocardiography.Results All RASA were confirmed by aortography,including eleven cases with rupture of right coronary sinus of valsalva and four cases with rupture of the noncoronary sinus of valsalva shunting into the right atrium.NYHA function class was(2.56±0.63)before the occlusion.Cardiac catheterization showed mean pulmonary arterial pressure and Qp/Qs ratio were (25.38±8.21)mmHg (1 mmHg=0.133 kPa) and 1.34-2.81(1.93±0.39), respectively.Aortic angiography showed that the RSA was 4-10(6.42±1.92)mm at its narrowest end.There was no serious complication during the operation and all the patients had successful transcatheter closure without residual shunt.After transcatheter RASA occlusion, mean pulmonary artery pressure decreased to (16.1±5.3) mmHg (P<0.05).The diameter of right atrium,right ventricle, left atrium and pulmonary artery diameter and left ventricular end-diastolic dimension all showed significant decrease (P<0.01).All patients were followed up for 35-132(78.6±28.57)months.All patients presented with a NYHA function class Ⅰ to Ⅱ cardiac function in their last follow up which was significantly improved compare to pre-occlusion level (P<0.01).There were no infective endocarditis,device displacement and embolism,serious aortic regurgitation,myocardial ischemia,serious arrhythmia or death in any of the patients during follow up.Conclusions Transcatheter closure of Valsalva aneurysm ruptured into right atrium with the domestic made patient ductus arteriosus and small-waist ventricular septal defect occluder is safe and effective with a good long term prognosis.

Objective: To investigate the safety and efficacy of transcatheter closure of ruptured sinus of Valsava aneurysm(RSVA). Methods: A total of 33 RSVA patients underwent transcatheter closure from January 2006 to March 2017 in our hospital were included in this retrospective study. The RSVA was diagnosed by echocardiography.Different type of occluders were applied for transcatheter closure based on the aortography results. All the patients were followed up after the procedure. Results: The patients were (37.6±12.1) years old,and the male patients accounted for 78.8%(26 cases).RSVA from right coronary sinus was found in 25 patients,and draining chamber was right atrium in 13 cases, right ventricle in 12 cases. RSVA from noncoronary sinus was diagnosed in 8 patients,and the draining chamber was right atrium. Aortography defined the narrowest diameter at the rupture site was (6.4±1.7)mm. The ratio of Qp/Qs was 2.2±0.5,and the mean pressure of pulmonary artery was 24.0(21.2,33.7)mmHg(1 mmHg=0.133 kPa). One patient developed serious occluder related aortic regurgitation and underwent surgery, transcatheter closure was successfully performed in 32 patients. The success rate of transcatheter closure was 97.0%. Two types of device were used in the study including small-waist double-disk ventricular septal defect(VSD) occluders in 20 cases and patent ductus arteriosus(PDA) occluders in 12 cases. During a median follow-up of 73.5(28.3,89.5) months, there were no infective endocarditis, residual shunt, thrombosis, device displacement,serious aortic regurgitation, serious arrhythmia or death.At the last follow-up, the left atrial diameter((37.4±6.5) mm vs. (41.5±5.3)mm,P<0.01),right atrial diameter((42.4±3.0) mm vs. (48.5±6.0)mm,P<0.01), right ventricular diameter((22.2±3.8) mm vs. (27.7±7.2)mm,P<0.01) and left ventricular end-diastolic diameter((51.3±4.9) mm vs.(55.0±4.3)mm,P<0.01)measured by echocardiography were all smaller than pre-procedural level. Conclusion Transcatheter closure of RVSA is a safe and effective strategy and associated with a good long-term outcome.