Isocentric fixed angle irradiation-based DRR: a novel approach to enhance x-ray and CT image registration.

Objective.Digitally reconstructed radiography (DRR) plays an important role in the registration of intraoperative x-ray and preoperative CT images. However, existing DRR algorithms often neglect the critical isocentric fixed angle irradiation (IFAI) principle in C-arm imaging, resulting in inaccurate simulation of x-ray images. This limitation degrades registration algorithms relying on DRR image libraries or employing DRR images (DRRs) to train neural network models. To address this issue, we propose a novel IFAI-based DRR method that accurately captures the true projection transformation during x-ray imaging of the human body.Approach.By strictly adhering to the IFAI principle and utilizing known parameters from intraoperative x-ray images paired with CT scans, our method successfully simulates the real projection transformation and generates DRRs that closely resemble actual x-ray images.Main result.Experimental results validate the effectiveness of our IFAI-based DRR method by successfully registering intraoperative x-ray images with preoperative CT images from multiple patients who underwent thoracic endovascular aortic procedures.Significance. The proposed IFAI-based DRR method enhances the quality of DRR images, significantly accelerates the construction of DRR image libraries, and thereby improves the performance of x-ray and CT image registration. Additionally, the method has the generality of registering CT and x-ray images generated by large C-arm devices.

A study of balloon type on calcified coronary lesion predilation: A finite element analysis.

Calcified coronary lesions have been one of the more difficult types of lesion for interventional treatment, and angioplasty is required to break the calcification before stent implantation so that the stent can expand smoothly, however, it remains unclear which type of angioplasty is optimal for different calcified lesions. In this study, a finite element approach was used to model normal balloons, cutting balloons, and AngioSculpt balloons. In addition, calcified lesions of different degrees, thicknesses, and lengths were modeled according to Intravascular ultrasound (IVUS) calcification grade. The above three balloons were used to pretreat calcified lesions, and the brittle fracture module for calcification was used to detect fracture success, to facilitate virtual stent implantation after predilation. The simulation results showed that with a thickness of less than 0.3 mm, balloons were unable to deal with calcified plaques in lesions of less than 120°, for 180° calcified lesions the cutting balloon fractured the calcified material at 1.2 MPa, the AngioSculpt balloon produced multiple fractures at 0.8 MPa for 270° calcified plaques, but was unable to fracture calcified lesions with a thickness of 0.4 mm. Based on these results, we conclude that the length of the lesion did not affect calcification fracture, while the thickness of the lesion did. In calcified lesions of approximately 180°, the cutting balloon showed the best predilation results, while the AngioSculpt balloon was optimal for 270°. In annular calcification, all three balloons were unable to fracture the lesion.

Influence of different postballoon expansion procedures: A finite element analysis.

BACKGROUND: Postballoon expansion is considered as an appropriate procedure for adequate stent expansion for coronary bifurcation lesions. Two postballoon expansion procedures are currently recommended: proximal optimization technique (POT)/side/POT and POT/kiss/POT. However, the effects of the two postballoon expansion treatments are different. There is a lack of biomechanical study to quantify the difference. PURPOSE: It is recognized that biomechanical factors influence the occurrence of Major Cardiovascular Adverse Events (MACE), which includes recurrent angina pectoris, acute myocardial infarction and coronary heart disease death. The current paper evaluated the two postexpansion strategies and quantified biomechanical parameters to provide a basis for clinical decisions. METHODS: Based on the CT angiography (CTA) data of a patient diagnosed with coronary bifurcation lesions, a personalized coronary bifurcation lesion model was constructed, and the surgical procedure after two expansions was simulated. The POT/side/POT and POT/kiss/POT expansion procedures were analyzed from the perspective of biomechanics through finite element analysis. The biomechanics factors, including the percentage of stent malapposition and stent occlusion at the side branch (SB) opening, the stent ellipse index of proximal main vessel (PMV) segment, the minimum lumen area of the stent vessel segment and the stress distribution of the vessel wall, were used to quantify clinician concerns about factors affecting patient outcomes. The factors include stent adhesion, SB open stent occlusion, poor stent deformation, patency effect of vessel stenosis, and vessel wall damage. RESULTS: Both postexpansion procedures were successfully simulated. The malapposition rate during POT/side/POT was larger (1.2% vs. 0.42%) and stent occlusion at the SB opening from the cross-section perpendicular to the SB opening after the POT/side/POT procedure was 0.20%, compared with 0.00% after POT/kiss/POT. POT/kiss/POT produced a larger PMV segment stent ellipse index. Minimum lumen area after POT/side/POT was 5.6 mm2 and after POT/kiss/POT 5.9 mm2 . POT/kiss/POT produces an effect of greater vascular stress than POT/side/POT. CONCLUSION: Numerical simulations provide a quantitative analysis to inform clinicians of the differences between preoperative planning and surgical procedures. Biomechanical analysis of the differences between the two postexpansion strategies found that the POT/kiss/POT procedure resulted in better stent fit, less occlusion of the SB open stent and better vascular patency but also resulted in poor stent deformation and caused greater vessel wall stress. The current study informs rationales for clinical understanding of postexpansion strategies.

Influence of balloon location during proximal optimization technique (POT): A finite element analysis.

Proximal Optimization Technique (POT)is a post-expansion technique that must be completed after single-stent implantation for the coronary bifurcation. The optimal location for the distal balloon shoulder during POT remains debatable. In the present study, the finite element method is applied to simulate POT after single-stent implantation in the coronary bifurcation. Three different balloon locations based on the distal shoulder relative to the carina cut plane were analyzed: 1) "proximal":1mm before carina cut plane; 2) "standard": at the carina cut plane; and 3) "distal": 1 mm after the carina cut plane. The computational results showed differences in stent, vessel morphology, and vessel wall stress due to the different balloon locations. However, when distal balloon shoulder was located between two adjacent stent rings, it formed the distal cell of the stent, the best stent apposition, least stent structs obstruction at SB ostial. Moreover, best opening effect of distal cell of the stent can be achieved, with the least damage to the vessel wall.

Preclinical Study of Anticoagulation Regimens in Sheep After Implantation of CH-VAD Blood Pump.

Effective anticoagulation regimens are needed to reduce risks of thrombosis and bleeding in animal models of ventricular assist device to verify its hemocompatibility, biologic safety and reliability. This study is to develop a validated anticoagulation procedure for a sheep model to test the newly developed CH-VAD. CH-VAD models were established in six healthy sheep by constructing blood bypass of left ventricle → ventricular assist device → descending aorta. Heparin infusion was used during operation and in the prior 4 days to maintain activated clotting time 1.5-2.0 times the baseline. From the third day, proper dosage of warfarin was used orally to maintain international normalized ratio values within the range of 1.2-2.0. After termination, we examined whether there was thrombosis in the blood pump, grafts, and anastomotic stoma. Macroscopic and histopathologic examinations were performed in major organs to check for congestion and infarction. Bleeding complications were not found in any animals throughout the experiments. Activated clotting time values were 326 ± 33 s intraoperatively and 157 ± 28 s in the prior 4 days postoperatively. Activated partial thromboplastin time values increased slowly and reached the lower limit of the target range on the fourth day. Only in one of six cases was thrombus or fibrosis tissue found in the blood flow channel of the pump. Pathologic analysis showed no thrombosis, necrosis and microembolus in end-stage organs. Under the anticoagulation regimens, coagulation system could be well controlled to avoid thrombosis and bleeding complications in sheep models for CH-VAD.

Quantitative Evaluation of Coronary Plaque Progression by Computed Tomographic Angiography.

Understanding plaque formation in patients at risk for coronary artery disease-the leading cause of morbidity and death in the world-enables physicians to better determine whether and how to treat these individuals. We used computed tomographic angiography to quantitatively evaluate the progression of nonculprit coronary plaques along the full length of the right coronary artery in 21 patients with acute coronary syndrome. Each right coronary artery was analyzed in sequential, 3-mm-long segments, and the minimum luminal area, plaque burden, and plaque volume within each segment were evaluated at baseline and at 12-month follow-up. Serial remodeling of the right coronary artery was also evaluated. In total, 625 arterial segments were analyzed. At 12-month follow-up, the plaque burden had increased slightly by 0.34% (interquartile range [IQR], -4.32% to 6.35%; P=0.02), and the plaque volume was not significantly changed (0.33 mm3; IQR, -3.05 to 3.54; P=0.213). The minimum luminal area decreased 0.05 mm2 (IQR, -1.33 to 0.87 mm2; P=0.012), and this was accompanied by vessel reduction, as evidenced by negative remodeling in 43% of the 625 segments. We conclude that serial computed tomographic angiography can be used to quantitatively evaluate the morphologic progression of coronary plaques.

Prediction of coronary plaque progression using biomechanical factors and vascular characteristics based on computed tomography angiography.

OBJECTIVES: Coronary atherosclerotic plaques progress in a highly individual manner. Accurately predicting plaque progression will promote clinical management of atherosclerosis. The purpose of this study was to investigate the role of local biomechanics factors and vascular characteristics in coronary plaque progression and arterial remodeling. METHODS: Computed tomography angiography-based three-dimensional reconstruction of the native right coronary artery was performed in vivo in twelve patients with acute coronary syndrome at baseline and 12-month follow-up. The reconstructed arteries were divided into sequential 3-mm-long segments. Wall shear stress (WSS) and von Mises stress (VMS) were computed in all segments at baseline by applying fluid-structure interaction simulations. RESULTS: In total, 365 segments 3-mm long were analyzed. The decrease in minimal lumen area was independently predicted by low baseline VMS (-0.73 ± 0.13 mm2), increase in plaque burden was independently predicted by small minimal lumen area and low baseline WSS (6.28 ± 0.96%), and decrease in plaque volume was independently predicted by low baseline VMS (-0.99 ± 0.49 mm3). Negative remodeling was more likely to occur in low- (55%) and moderate-VMS (40%) segments, but expansive remodeling was more likely to occur in high-VMS (44%) segments. CONCLUSIONS: Local von Mises stress, wall shear stress, minimal lumen area, and plaque burden provide independent and additive prediction in identifying coronary plaque progression and arterial remodeling.

An automatic and accurate registration method for electro-anatomical map and CT surface.

BACKGROUND: Electro-anatomical maps (EAM) and CT surface registration are widely used for catheter navigation in atrial fibrillation ablations. However, few studies have investigated the registration algorithm. Moreover, some of them are semiautomatic, so that physicians must be proficient; some are inaccurate for catheter navigation. A both automatic and accurate registration method is needed. METHOD: A Hausdorff distance based approach (HD) was proposed for EAM/CT registration. First, using principal axes based registration, EAM/CT pairs were coarsely aligned. Then, using Hausdorff distance as the fine objective function, EAM/CT pairs were finely aligned. RESULTS: Six real EAM/CT pairs were collected from five patients and 38 simulated pairs were generated. Each pair was aligned using Carto-Merge, a stochastic approach (SA) and HD. Considering the balance of operability, accuracy and robustness, HD obtained the best EAM/CT registration results among the three approaches. CONCLUSION: Experiments validate that the proposed method registers EAM and CT surface both automatically and accurately.

Initial In Vivo Evaluation of a Novel Left Ventricular Assist Device.

The aim of the study was to use the ovine model to evaluate the hemocompatibility and end-organ effects of a newly developed magnetic suspension centrifugal left ventricular assist device (LVAD) by CH Biomedical Inc., Jiangsu, China. The LVADs were implanted in 6 healthy sheep, where inflow was inserted into the left ventricular apex and outflow was anastomosed to the descending aorta. All sheep received anticoagulation and antiaggregation therapy during the study. Hematologic and biochemical tests were performed to evaluate anemia, hepatorenal function, and the extent of hemolysis. The experiments lasted for up to 30 days on the beating hearts. All sheep were humanely killed at the termination of the experiments, and the end-organs were examined macroscopically and histopathologically. Autopsy was performed in all animals and there was no thrombus formation observed inside the pump. The pump's inflow and outflow conduits were also free of thrombus. Hematologic and biochemical test results were within normal limits during the study period. Postmortem examination of the explanted organs revealed no evidence of ischemia or infarction. Based on the in vivo study, this LVAD is suitable for implantation and can provide efficient support with good biocompatibility. The encouraging results in this study suggest that it is feasible to evaluate the device's long-term durability and stability.

In vivo evaluation of an implantable magnetic suspending left ventricular assist device.

PURPOSE: The CH-VAD is an implantable, fully magnetically suspended ventricular assist device developed by the China Heart Biomedical Corporation (Suzhou, China) for full cardiac support. This study was performed to evaluate the reliability, hemocompatibility and end-organ effects of CH-VAD in a 35-day animal model trial. METHODS: The pump was implanted in 6 sheep. The pump inflow was inserted into the left ventricle and the outflow graft was anastomosed to the descending aorta. Data on pump function and the health condition of the animals, including hematologic and biochemical tests, were collected during the study period. When each study was determined to termination, the sheep were humanely euthanized and the end organs were examined macroscopically and histopathologically. Hemolysis was evaluated based on the amount of free hemoglobin in the plasma. RESULTS: Except for one device that stopped operation on postoperative day 25 because of thrombus formation, the devices functioned normally until the scheduled termination. Gross examination of the pump interiors, inflow and outflow, and of the arterial anastomosis sites showed no significant abnormalities. Hematologic and biochemical test results were within normal limits during the study period. Macroscopic and histopathologic examinations of the explanted organs revealed no evidence of ischemia or infarction associated with the device implantation, except for small foci of infarction in the kidneys of two sheep. The free hemoglobin level in plasma peaked at 9.5 mg/dl on postoperative day 5. CONCLUSIONS: The CH-VAD system demonstrated promising reliability and blood-handling characteristics without obvious damage to end organs during a 35-day implantation in sheep.

Three new species of the tribe Meconematini (Orthoptera: Tettigoniidae) from Taiwan.

The paper reported three new species from Taiwan, i.e. Xizicus (Eoxizicus) taiwanensis sp. nov., Xizicus (Axizicus) falcata sp. nov. and Decma (Decma) brachyptera sp. nov., supplied the descriptions and illustrations. 

Development and evaluation of a computerized Mandarin speech test system in China.

OBJECTIVES: This study reports the development and evaluation of a Computerized Mandarin Speech Test System (CMSTS). METHODS: Taking into account the rules for developing speech materials and the unique linguistic characteristics of Mandarin, we designed and digitally recorded a set of materials comprised of seven lists of monosyllabic words, nine lists of disyllabic words, and fifteen lists of sentences with a high degree of subject familiarity. The CMSTS was developed with Visual Studio 2008, Access 2003 and DirectX 9. The system included five functions: listener management, a speech test, list management, data management, and system settings. We used the system to measure the speech recognition threshold (SRT) of 76 participants with normal hearing (age range: 20-28 years), and measured performance-intensity functions (PI) for all stimuli. RESULTS: The SRT results were in accord with pure-tone results obtained by pure-tone audiometry. In a speech recognition score (SRS) test, changing the presentation level had the strongest effect on sentence recognition, followed by the presence of disyllabic words. Monosyllabic words were least affected by changes in presentation level. The slopes of the linear portion of the PI using the system were in accord with the findings of previous studies using audiometers and CDs with similar materials. CONCLUSION: The CMSTS has sufficient sensitivity, and can facilitate the wider use of speech audiometry in Chinese audiology clinics.

[Evaluation of right ventricular function of patients with intraoperative device closure of atrial septal defect by ultrasonic Doppler tissue imaging].

OBJECTIVE: To study the application of Doppler tissue imaging (TDI) in the assessment of right ventricular function of patients with intraoperative device closure of atrial septal defect (ASD). METHODS: A total of 48 ASD patients, 18 males and 30 females, were selected for intraoperative device closure. The mean age was 31 +/- 16 years old. Color Doppler echocardiographic instrument (Sonos 4500) was employed to perform the Doppler tissue imaging before and at 3-5 days after operation. The parameters included: (1) Time and peak speed of systolic motion of anterior tricuspid valve annulus (TDI-TS, TDI-PVS), early diastole motion time (TDI-TE) and late diastolic motion time (TDI-TA) and peak speed of early and late diastolic motion (TDI-PVE, TDI-PVA), interval between the early diastolic motion and late diastolic motion (TDI-TE-A); (2) Peak speed of systolic, early diastolic and late diastolic motions of the middle lateral and basic lateral walls of right ventricle. RESULTS: The TDI-PVS (0.16 +/- 0.05) m/s in post-operation was decreased than TDI-PVS (0.20 +/- 0.04) m/s in pre-operation and TDI-PVA (0.12 +/- 0.03) m/s in post-operation was decreased than TDI-PVA (0.16 +/- 0.02) m/s in pre-operation apparently (P < 0.01). The TDI-TS (231 +/- 36) msec in post-operation were shorter than TDI-TS (265 +/- 24) msec in pre-operation (P < 0.01). Peak spead of Systolic, early diastolic and late diastolic motions of middle lateral and basic lateral walls of right ventricle declined post-operatively (P < 0.01). CONCLUSION: TDI is an effective method to evaluate the function of right ventricle quantitatively in patients with intraoperative device closure of ASD.

[Application of transesophageal echocardiography in intraoperative device closure of secundum atrial septal defects].

OBJECTIVE: To evaluate the clinical value of transesophageal echocardiography (TEE) in guiding intraoperative device closure of secundum atrial septal defect (ASD). METHODS: Fifty ASD patients, aged 40 +/- 18 (15-72), 34 with an ASD ranging from 30 to 40 mm and 16 with atrial septal aneurysm accompanied by double or more ASDs, underwent intraoperative device closure through a right minithoracotomy without cardiopulmonary bypass and fluoroscopy. Under general anesthesia, a probe was inserted into the esophagus, and TEE was conducted at different planes to observe the characteristics of the ASD. The size of implanted device was determined by TEE. Small parasternal incision was made in the right third or fourth intercostal space. A specially designed plastic sheath loaded with Amplatzer occlusion device was inserted through the purse-string sutures placed on the right atrium. Guided by transesophageal echocardiography, the Amplatzer occlusion device was advanced through the ASD into the left atrium and was deployed in place. The right ventricular end diastolic volume (RVEDV), right ventricular end systolic volume (RVESV), right ventricular stroke volume (RVSV), right ventricular ejection fraction (RVSV), left ventricular end diastolic volume (LVEDV), left ventricular end systolic volume (LVESV), left ventricular stroke volume (LVSV), and left ventricular ejection fraction (LVEF) before and after the operation were calculated. RESULTS: The procedure was successful conducted in 48 patients. And the other two patients failing to receive this procedure, one having a large ASD that could not be occluded and the other with ASD accompanied by partial anomalous pulmonary venous connection, were shifted to operation with cardiopulmonary bypass. After the operation, the RVEDV was (94 +/- 32) ml, and the RVSV was (52 +/- 20) ml respectively, both significantly lower than those before the operation [(78 +/- 23) ml and (41 +/- 13) ml respectively, both P < 0.05]. The LVEDV and LVSV after operation were (73 +/- 19) ml and (50 +/- 11) ml respectively, both significantly higher than those before operation [(56 +/- 14) ml and (34 +/- 12) ml respectively, both P < 0.05]. CONCLUSION: TEE provides valuable information in further confirmation of diagnosis of ASD, selection of appropriate size of Amplatzer occluder, guidance of the deployment of occluder, observation of the effects of operation, and prompt detection of complication.

[Experimental study on effects of self-made miniature axial flow blood pump as left ventricle assistance for postischemic heart].

OBJECTIVE: To evaluate the effects of self-made miniature axial flow blood pump as left ventricle assistance for postischemic heart. METHODS: Sixteen adult healthy sheep were divided into two groups of 8 sheep. After acute left heart failure was induced by selective ligation of the left anterior descending branch of coronary artery for 1.5 hours and ligation of the left circumflex branch for half an hour, one hour of reperfusion with assistance by self-made blood pump was offered in experimental group and no mechanical assistance was given to the control group. The sheep were killed after the experiment and their hearts were taken to be observed. During the experiment, the changes in hemodynamic and hemologic indices were compared between the two groups to assess the effects of left heart assistance on hemodynamics and blood by self-made blood pump. RESULTS: After 1 hour of assistance by self-made blood pump, experimental group, in comparison with the control group, showed a significant (P < 0.05) increase in total cardial output (3.11 +/- 0.3 vs 2.37 +/- 0.3 L/min), mean aortic pressure (73 +/- 5.4 vs 66 +/- 3.1 mm Hg), and left ventricular Dp/Dt(max) (1 415 +/- 2 549 vs 986 +/- 8 mm Hg/sec); and a significant decrease in left ventricular end diastolic pressure (11.8 +/- 2.1 vs 13.5 +/- 1.4 mm Hg) and left atrial pressure (14.1 +/- 1.6 vs 16.0 +/- 1.6 mm Hg) (all P < 0.05). There was no significant difference in plasma free hemoglobin (12.4 +/- 3.1 vs 13.8 +/- 4.7 mg/dl) and fibrinogen (0.32 +/- 0.12 vs 0.42 +/- 0.12 g/dl) between these two groups. CONCLUSION: 1, Animal model for acute left heart failure can be achieved by selective ligation of coronary arteries and satisfactorily used in left ventricular assist device assessment. 2. Self-made blood pump can be used in assistance for failure heart without serious event.

[Studies on the blood compatibility of the polyurethane/nano-sized carbon composite].

OBJECTIVE: To investigate the effects of nano-sized carbon as a dispersed phase on blood compatibility of polyurethanes. METHODS: A novel nanoscale polymeric composite film was prepared by dispersing nano-sized carbon fiber (vapor growth carbon fiber) into the polyurethane solutions. The surface blood compatibilities of the composites were analyzed and evaluated through platelet adhesion measurement using epifluorescent video microscopy and the variation of fibrinogen and free hemoglobin concentration in the blood contacting the composite respectively. RESULTS: It was showed that the platelet adhesions were highly suppressed on the composite surfaces pre-adsorbed or non-pre-adsorbed with fibrinogen. The changes of the concentration for both free hemoglobin and fibrinogen in the blood contacting the composite surface in the circulations were less than the ones contacting the reference surface. CONCLUSIONS: Introducing nano-sized carbon into the polyurethane matrix showed an improvement of antithrombogenicity for the polyurethane materials. It might be a new promising way to develop biomaterials with good blood compatibility.

[Hemolysis test of the five kinds of impeller blood pumps in vitro].

Hemolysis caused by blood pumps is a very important characteristic. In vitro hemolysis test circuits were constructed to operate the model I centrifugal pump, the model II axial flow pump, the magnetic coupling pump and the model I & II spiral mixed pump. The output of all pumps was set at flow 5 L/min, an average pressure of 100 mmHg. Experiments were conducted for 4 hours at room temperature(25 degrees C) with 500 ml fresh anticoagulant sheep blood. Blood samples were taken for plasma free-hemoglobin measurement, and the change in temperature at the pump outlet port was measured during the experiment. Calculate the normalized index of hemolysis (NIH). The results showed that there was no relationship either between the pump rotational speed and the NIH in five types of blood pumps, or between change in temperature at the pump outlet port and NIH. The dynamic fluid field caused by pump design and structure could be the main cause of blood damage.