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MR perfusion imaging can be used to estimate parameters indicating the metabolic process, including cerebral blood flow (CBF). Specifically singular value decomposition (SVD) method is applied in this paper to obtain CBF with a predefined conventional arterial input function (AIF), and the effects of threshold and tracer delay are investigated. While the simulation results show that SVD method can estimate CBF with good accuracy by using different thresholds for different flow values, the method is found to be sensitive to tracer delay. A delay correction scheme is advocated, where CBF is determined by SVD after time-shifting of the tracer concentration curve. With the correction the simulation results are considerably improved in the flow estimation.

The authors presented a first application of 2-D contrast-enhanced ICE in localizing RF ablation lesions and, more importantly, accurately and reproducibly quantifying their extent and depth within the myocardium in the intact beating heart. Furthermore, the study extended this application and presented, for the first time, a novel method based on contrast-enhanced 3-D ICE to describe details of contiguous linear lesions.

Background— The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation because of its autonomic innervation, its location anterior to the left pulmonary veins, and its drainage in the coronary sinus. Methods and Results— We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium toward the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation. The ERP decreased from 113.6�35.0 to 82.2�25.4 ms ( P P =NS). The abolition of vagal effects was limited to sites near the VOM (ERP, 104�14 versus 98.6�12.2 ms postvagal stimulation; P =NS), as opposed to sites remote to VOM (ERP, 107.2�14.9 versus 78.6�14.7 ms postvagal stimulation; P Conclusions— Ethanol infusion in the VOM achieves significant left atrial tissue ablation, abolishes local vagal responses, and is feasible in humans.

Multiple imaging modalities are employed independent of one another while managing complex cardiac arrhythmias. To combine electrical, anatomical, and functional imaging in a single catheter system, we developed a balloon catheter that carried 64 electrodes on its surface and an intracardiac echocardiography (ICE) catheter through a central lumen. The catheter system was inserted, and the balloon was inflated inside the left ventricle (LV) of eight dogs with 6-wk-old infarction, created by occlusion in the left anterior descending coronary artery. Anatomy was constructed by ICE imaging (9 MHz) through the balloon. Single-beat noncontact mapping (NCM) was performed via the multielectrode array to reconstruct unipolar endocardial electrograms during sinus rhythm. Standard contact mapping (CM) of the endocardium was also carried out for reference. Myocardial infarction in anterior LV extending from the middle to apical regions was localized both by ICE and NCM and validated by CM and pathology. The overall difference in the activation times between NCM and CM was 3 ± 1 ms. Unipolar voltage in infarcted middle anterior LV was smaller than the voltage in normal middle inferior LV both by NCM (11 ± 4 vs. 16 ± 3 mV; P = 0.002) and CM (11 ± 3 vs. 20 ± 4 mV; P < 0.001). Unipolar voltage was also inversely related to infarct transmurality, both by NCM ( r = −0.87; P = 0.005) and CM ( r = −0.94; P < 0.001). The infarct area by ICE (7.7 ± 2.9 cm2) was in agreement with CM (bipolar voltage, 2; r = 0.80; P = 0.016). Meanwhile, the voltage threshold that depicted the infarct area by NCM was directly related to the smallest unipolar voltage reconstructed within the infarct ( r = 0.96; P < 0.001). In conclusion, combining NCM and ICE imaging in a single catheter system is feasible. The preclinical development of such an integrated system and its evaluation in experimental myocardial infarction demonstrate capabilities for single-beat mapping at multiple sites as well as the online assessment of anatomy and myocardial function.

Objectives The aim of this study was to validate a novel, angle-independent, feature-tracking method for the echocardiographic quantitation of regional function. Background A new echocardiographic method, Velocity Vector Imaging (VVI) (syngo Velocity Vector Imaging technology, Siemens Medical Solutions, Ultrasound Division, Mountain View, California), has been introduced, based on feature tracking—incorporating speckle and endocardial border tracking, that allows the quantitation of endocardial strain, strain rate (SR), and velocity. Methods Seven dogs were studied during baseline, and various interventions causing alterations in regional function: dobutamine, 5-min coronary occlusion with reperfusion up to 1 h, followed by dobutamine and esmolol infusions. Echocardiographic images were acquired from short- and long-axis views of the left ventricle. Segment-length sonomicrometry crystals were used as the reference method. Results Changes in systolic strain in ischemic segments were tracked well with VVI during the different states of regional function. There was a good correlation between circumferential and longitudinal systolic strain by VVI and sonomicrometry (r = 0.88 and r = 0.83, respectively, p Conclusions Velocity Vector Imaging, a new feature-tracking method, can accurately assess regional myocardial function at the endocardial level and is a promising clinical tool for the simultaneous quantification of regional and global myocardial function.

In this paper, the Fourier transform based minimum mean square error (FT-based MMSE) method is used to calculate the regional cerebral blood volume (rCBV) in magnetic resonance (MR) perfusion imaging, and the method is improved to handle the existing noise in the imaging process. In the experiments with signal-to-noise ratio (SNR) of 50 dB, the rCBV values were compared with the results using MMSE method. The effects of different SNRs on the estimation of rCBV were analyzed. The experimental results showed that MMSE was a simple way to filter the measurement noise, and could calculate rCBV accurately. Compared with other existing methods, the present method is not sensitive to environment, and furthermore, it is suitable to deal with the perfusion images acquired from the environment with larger SNR.

We sought to examine the hemodynamic determinants and clinical application of the peak acceleration rate of early (Ea) diastolic velocity of the mitral annulus by tissue Doppler. Simultaneous left atrial and left ventricular (LV) catheterization and Doppler echocardiography were performed in 10 dogs. Preload was altered using volume infusion and caval occlusion, whereas myocardial lusitropic state was altered with dobutamine and esmolol. The clinical application was examined in 190 consecutive patients (55 control, 41 impaired relaxation, 46 pseudonormal, and 48 restrictive LV filling). In addition, in 60 consecutive patients, we examined the relation between it and mean wedge pressure with simultaneous Doppler echocardiography and right heart catheterization. In canine studies, a significant positive relation was present between peak acceleration rate of Ea and transmitral pressure gradient only in the stages with normal or enhanced LV relaxation, but with no relation in the stages where the time constant of LV relaxation (τ) was ≥50 ms. Its hemodynamic determinants were τ, LV minimal pressure, and transmitral pressure gradient. In clinical studies, peak acceleration rate of Ea was significantly lower in patients with impaired LV relaxation irrespective of filling pressures ( P < 0.001) and with similar accuracy to peak Ea velocity (area under the curve for septal and lateral peak acceleration rates: both 0.78) in identifying these patients. No significant relation was observed between peak acceleration rate and mean wedge pressure. Peak acceleration rate of Ea appears to be a useful index of LV relaxation but not of filling pressures and can be applied to identify patients with impaired LV relaxation irrespective of their filling pressures.

A novel method combined differential evolution algorithm and modified Newton-Raphson method is proposed in this paper to solve the electrical impedance tomography (EIT) inverse problem. This method is applied to the two-dimensional impedance reconstruction of brain section based on a four-layer concentric circle model and real head geometric model. Our simulations demonstrate that the novel combination method is robust and time saving in obtaining high-quality reconstruction in EIT problems for brain imaging studied in this paper.

Cardiac function and hemodynamics are routinely evaluated during catheterization in patients with heart disease. Although intracardiac echocardiography (ICE) has been employed in guiding electrophysiology procedures, it has not been effectively used in assessing hemodynamics. We tested the utility of ICE in measuring left ventricular (LV) volume throughout the cardiac cycle. In four normal dogs (weight = 26 to 37 kg), a 10-F sheath was inserted through the femoral artery and placed inside the LV along its major axis. An ICE catheter (9 F, 9 MHz) was then inserted through the sheath into the LV. The ICE catheter was pulled back inside the sheath in 1-mm intervals starting from the apex, and 2-D tomographic images were continuously acquired while gating to respiration. Subsequently, the ICE catheter was replaced by a conductance catheter to measure single-beat volume signals. Stroke volume was determined by thermodilution for validation. All measurements were made in each dog while pacing the atrium at two different cycle lengths (range = 300 to 500 ms). The endocardial boundary was digitized from the ICE images throughout the cardiac cycle and LV volume was computed by integrating multiple segments along the major axis (range = 55 to 70 mm). We found that ICE accurately reconstructed LV 3-D anatomy. Stroke volume by ICE was in excellent agreement with thermodilution (error = 3.8 +/- 3.0%, r = 0.99, n = 8) and was highly reproducible. Morphology of LV volume signals correlated well with corresponding instantaneous volume signals derived by conductance (r = 0.93, n = 8). In conclusion, ICE accurately reconstructs LV anatomy and volume throughout the cardiac cycle in the normal heart. This approach could facilitate interventional diagnostic and therapeutic procedures.

We recently combined noncontact mapping and intracardiac echocardiography (ICE) in a single catheter-system that permitted 3D electrical-anatomical imaging of the heart. The objective of the present study was to develop a nonfluoroscopic method to localize standard, navigational electrode-catheters, which also operated in conjunction with noncontact electrical-anatomical imaging. Accordingly, electrode-catheters were fixed at the endocardium in the LV of three dogs and in the RA of two other dogs. A catheter-system was placed inside the heart cavity, and consisted of a 9-F sheath carrying a coaxial noncontact 64-electrode lumen-probe on the outside (diameter = 7 mm), and a central ICE catheter on the inside (9 MHz). To reconstruct the endocardial anatomy, the ICE catheter was pulled back inside the sheath and multiple 2D tomographic images were acquired. The noncontact probe was then advanced over the sheath and into the heart cavity. Current pulses were injected into the endocardial contact electrodes and all probe electrodes sensed corresponding potentials. Measured probe potentials localized the endocardial electrodes based on the least squares numeric method, and was verified by ICE. We found that the 3D endocardial geometry reconstructed by ICE depicted important anatomical details. All endocardial electrodes were identified by ICE and were correctly matched with corresponding endocardial anatomy. The difference in computed electrode locations compared to ICE was 5.4 +/- 2.4 mm (n = 10). In conclusion, nonfluoroscopic localization of standard navigational electrode-catheters within true and detailed 3D images of cardiac anatomy is feasible. Integrating this approach with noncontact electrical-anatomical imaging could facilitate diagnosing arrhythmias and advancing their therapy.

The study objective was to integrate noncontact mapping and intracardiac echocardiography (ICE) in a single catheter system that enables both electrical and anatomical imaging of the endocardium. We developed a catheter system on the basis of a 9-F sheath that carried a coaxial 64-electrode lumen-probe on the outside and a central ICE catheter (9 F, 9 MHz) on the inside. The sheath was placed in the right atrium (RA) of 3 dogs, and in the left ventricle (LV) of 3 other dogs. To construct cardiac anatomy, the ICE catheter was pulled back over several beats inside the sheath starting from the tip and two-dimensional tomographic images were continuously acquired. To recover endocardial electrograms, the probe was advanced over the sheath and single-beat noncontact electrograms were simultaneously recorded. Endocardial contact electrodes were placed at select sites for validation as well as for pacing. Three-dimensional electrical-anatomical images reconstructed during sinus and paced rhythms correctly associated RA and LV activation sequences with underlying endocardial anatomy (overall activation error = 3.4 +/- 3.2 ms; overall spatial error = 8.0 +/- 3.5 mm). Therefore, accurate fusion of electrical imaging with anatomical imaging during catheterization is feasible. Integrating single-beat noncontact mapping with ICE provides detailed, three-dimensional electrical-anatomical images of the endocardium, which may facilitate management of arrhythmias.

In the right atrium (RA) we globally investigated: (1) the properties of noncontact electrograms measured by multielectrode cavitary probes, (2) the features of endocardial electrograms computed from the noncontact probe electrograms, and (3) the impact of the probe size on both the noncontact and the computed electrograms. We deployed a custom catheter in the dog RA, which consisted of a cylindrical probe with 64 electrodes on its surface, for measuring noncontact cavitary electrograms, and a concentric endocardial basket carrying an additional array of 64 electrodes, for measuring contact endocardial electrograms (the “gold standard”). Both a 5-mm- and a 10-mm-diam probe (P5 and P10, respectively) were sequentially tested in the same RA of one dog. Unipolar electrograms from both the probe and the basket were simultaneously acquired during normal as well as during paced rhythms (n ⩾24 protocols per probe). Boundary element method and numeric regularization were applied to compute endocardial electrograms at the basket electrode locations. We found that noncontact electrograms were attenuated and smoothed, and this effect was exaggerated with the small probe. Computed endocardial electrograms more accurately reconstructed important amplitude distribution and morphological features; peak-to-peak amplitude error, 35% for P5 and 34% for P10. Activation and spatial errors of computed endocardial electrograms were 8.8 ± 6.8 ms and 5.1 ± 6.1 mm for P5, respectively, and 6.0 ± 5.5 ms and 3.2 ± 4.4 mm for P10, respectively. In conclusion, global RA activation may be delineated directly from noncontact cavitary electrograms alone, but may be affected by volume attenuation, smoothing, and probe size. Accurate endocardial electrograms, however, can be successfully computed from noncontact electrograms acquired with small probes and be used to reconstruct both electrogram amplitude and detailed morphology. © 2001 Biomedical Engineering Society.

Methods for constructing a real head model from MRI (magnetic resonance imaging) data and its boundary element mesh are proposed. Based on this real head model, forward computations of electroencephalography and magnetoencephalography are investigated and numerical simulation results are presented. Deflation is adopted in order to solve the singularity of discrete system equations in the boundary element method. An isolated problem approach is applied to overcome the smear effect of skull conductivity. An improved auto solid angle algorithm is developed to speed up the computation of kernel matrix.

This paper proposes a new method for biomedical electromagnetic inverse problems based on the technique of maximum mutual information. The new method is different from the conventional methods for it will not depend on the widely used regularization technique. The new method provides a general paradigm for developing algorithms dealing with various biomedical inverse problems that can be described using lead field, including localization and imaging of neural source activities in brain and heart from EEG/MEG and ECG/MCG; it is also possible to apply it to other, electromagnetic inverse problems like electrical impedance tomography. This paper mainly provides the theoretical development, with MEG inverse problems as case studies.

An efficient improvement, based on the idea of homotopy, is proposed to improve and ensure the convergence of the modified Newton-Raphson (MNR) algorithm through the continuous mapping of solution space, and the behavior of solution is restrained towards the global convergence after several initial solution mappings. Comparisons of the new algorithm with MNR are presented, and the advantage of new algorithm is demonstrated for the problem of electrical impedance tomography.

This paper presents an optimal design method by means of mean field annealing (MFA). The mean field theory (MFT) is introduced, and a certain MFA application extension based on Peierls inequality is explained in detail, the critical temperature that is important for classes of problem while applying MFA is discussed. With MFA, the optimal size design of electromagnetic device is carried out. The results are compared with two existing algorithms, the modified simulated annealing (MSA) and one-variable stochastic simulated annealing based MFA (S-MFA), in both operating cost and final quantities. To modify the final results to reach the global optimum, Hooke-Jeeves pattern search method is adopted. Favorable results show the effectiveness of the proposed scheme.

In this paper, electrical impedance endotomography (EIE) is studied using the sensitivity matrix method. Due to the ill-posedness of the inverse problem, the truncated singular value decomposition (TSVD) method and Tikhonov regularization are applied to solve the inverse matrix respectively. Studies are on 2D model and the simulation results show that sensitivity matrix algorithm is efficient and effective in finding the lesion area in EIE.

The Infrared images have been applied in clinical diagnoses, but the images are noisy and blurred. Therefore the smooth processing that can keep edges is needed. Traditional smoothing methods have the common defect that they smooth not only the noise region but also the edges. AMSS (affine morphological scale space) algorithm can be used to better save the edge information, it has the Partial Differential Equation that is of morphological affine invariability and contrast invariability. The smooth processing method based on AMSS is introduced to handle the infrared image in this paper, and the better performance is obtained.

Electrical impedance tomography (EIT) detects tissue composition inside a medium by determining its resistive properties, and uses various electrode configurations to pass a small electric current and measure corresponding potential. We investigated the feasibility of reconstructing scarred tissue inside the heart wall by employing EIT on the basis of a catheter carrying a plurality of electrodes and placed inside the blood-filled heart cavity. We built a computer model of the biological medium, and reconstructed the resistivity distribution using the finite element method and Tikhonov regularization. The results established the successful implementation of the numeric methods and the possibility of localizing and quantifying scarred myocardium. Novel application of EIT from inside the heart cavity could be useful during catheterization and may complement other diagnostic modalities. Further research is necessary to assess the impact of several factors on the accuracy of the reconstruction and include number of electrodes, catheter location, and scar size.

The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation and its location anterior to the left pulmonary veins and drainage in the coronary sinus. We studied 14 dogs. A coronary sinus venogram showed a VOM in 10, which was successfully cannulated with an angioplasty wire and a 2 mm balloon. In 5 dogs, electroanatomical (Carto) maps of the left atrium were performed at baseline and after ethanol (100%, 4 – 8 cc) was infused in the VOM, which demonstrated the creation of a new crescent-shaped scar in the left atrium, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 dogs, both cervical vagal trunks were isolated in the carotid sheath and cuff stimulation electrodes were attached to them. Effective refractory periods (ERP) were measured in 3 sites of the left atrium, before and after high-frequency bilateral vagal stimulation. The baseline ERP was 113.6±35.0 ms, and decreased to 82.2±25.4 ms (p

The aim of this study was to validate a novel, angle-independent, feature-tracking method for the echocardiographic quantitation of regional function.A new echocardiographic method, Velocity Vector Imaging (VVI) (syngo Velocity Vector Imaging technology, Siemens Medical Solutions, Ultrasound Division, Mountain View, California), has been introduced, based on feature tracking-incorporating speckle and endocardial border tracking, that allows the quantitation of endocardial strain, strain rate (SR), and velocity.Seven dogs were studied during baseline, and various interventions causing alterations in regional function: dobutamine, 5-min coronary occlusion with reperfusion up to 1 h, followed by dobutamine and esmolol infusions. Echocardiographic images were acquired from short- and long-axis views of the left ventricle. Segment-length sonomicrometry crystals were used as the reference method.Changes in systolic strain in ischemic segments were tracked well with VVI during the different states of regional function. There was a good correlation between circumferential and longitudinal systolic strain by VVI and sonomicrometry (r = 0.88 and r = 0.83, respectively, p0.001). Strain measurements in the nonischemic basal segments also demonstrated a significant correlation between the 2 methods (r = 0.65, p0.001). Similarly, a significant relation was observed for circumferential and longitudinal SR between the 2 methods (r = 0.94, p0.001 and r = 0.90, p0.001, respectively). The endocardial velocity relation to changes in strain by sonomicrometry was weaker owing to significant cardiac translation.Velocity Vector Imaging, a new feature-tracking method, can accurately assess regional myocardial function at the endocardial level and is a promising clinical tool for the simultaneous quantification of regional and global myocardial function.

Differential evolution (DE) method is used in This work to solve the EEG source localization problem based on equal current dipole model. The single dipole sources with four-shell concentric sphere model are reconstructed. Our simulations demonstrate that DE algorithm is robust in obtaining high quality reconstruction for EEG problems with single current dipole sources.

INTRODUCTION The study tested the feasibility of differentiating radiofrequency ablation lesions from normal myocardium and quantifying their dimensions by myocardial contrast echocardiography (MCE). METHODS AND RESULTS In 11 normal dogs, we created 14 focal and 4 linear lesions at different left ventricular sites.MCE was performed both before and after ablation by using an intracardiac echocardiography catheter (9 MHz)and infusing contrast microbubbles through the left coronary artery. An independent observer examined the lesion pathology. We found that intracardiac echocardiography alone could not delineate lesion dimensions. However, after ablation, MCE localized the lesions as well-defined, low-contrast areas within the normally opacified myocardium. Lesion dimensions byMCE immediately after ablation and 30 minutes later were similar. In 12 focal lesions, the average maximum depth (5.55 +/- 1.38 mm) and average maximum diameter(10.38 +/- 2.09 mm) by MCE were in excellent agreement with the pathologic depth (5.20 +/- 1.45 mm) and diameter(10.61 +/- 1.67 mm). Two focal lesions could not be detected by MCE and later were found to be superficial. Three-dimensional MCE correctly reconstructed the extent and shape of linear lesions compared to pathology (length: 18.7+/- 5.7 vs 18.5 +/- 5.6 mm; maximum longitudinal cross-sectional area: 81.2 +/- 9.6 vs 76.0 +/-10.3 mm(2)). CONCLUSION MCE accurately localized and quantified radiofrequency ablation lesions in the normal leftv entricle. This new application of MCE may advance'ablation for managing ventricular arrhythmias that involve intramural or epicardial regions by providing instantaneous anatomic feedback on the effects of ablation during catheterization.

The improved Differential Evolution (DE) algorithm is proposed in this paper to s olve the resistivity parameters estimation problem based on 2D real head model. Our simulations demonstrate that the improved DE algorithm is robust in obtaining high quality reconstruction, and the convergence is much faster than the usual DE algorithm. Furthermore, the selection of the amplification parameters is much easier. I. INTRODUCTION HE impedance information of a subject is important in many researches of biomedical engineering. Electrical impedance tomography (EIT) (1), (2) is a useful technique for reconstructing the impedance distribution in the subject from the voltages measured on the surface given the injected current. As a typical inverse problem, EIT imaging is intrinsic non-linear and ill-posed. Usually the solutions can be described in terms of some unknown parameters, and the task is to find the optimal parameters estimation that will cause a minimum error of the cost function, which is always as some sorts of residuals between the measured data and theoretic data. Differential Evolution (DE) algorithm (3)-(5) is a relative newer evolutionary approach for minimizing possibly nonlinear and non-differentiable functions in continuous space. Since it is first introduced by Price and Storn in 1995, amount of studies demonstrated that it converges faster and with more certainty than many other global optimization methods. Furthermore, it is robust, simple in use, and requires only a few control parameters. In this paper, we applied DE algorithm and its improvement to resistivity parameters estimation of 2D head section based on real head model. The simulations demonstrated that DE algorithm has the ability for obtaining high quality reconstructions, and the improved DE algorithm has the better performances than the usual DE algorithm.

We globally investigated (1) the properties of noncontact cardiac electrograms measured by multielectrode cavitary probes, (2) the features of endocardial electrograms computed from the noncontact probe electrograms, and (3) the impact of the probe size on both the noncontact and the computed electrograms. We deployed a custom catheter in the dog RA, which consisted of a cylindrical probe with 64 electrodes on its surface, for measuring noncontact cavitary electrograms, and a concentric endocardial basket carrying an additional array of 64 electrodes, for measuring contact endocardial electrograms. Both a 5-mm and a 10-mm diameter probe were sequentially tested during normal as well as during paced rhythms. A boundary element method and numeric regularization were applied to compute endocardial electrograms at the basket electrode locations. We found that noncontact electrograms were attenuated and smoothed, and this effect was exaggerated with the small probe. Computed endocardial electrograms more accurately reconstructed important amplitude distribution and morphological features. In conclusion, global RA activation may be delineated directly from noncontact cavitary electrograms alone, but may be affected by volume attenuation, smoothing, and probe size. Accurate endocardial electrograms, however, can be successfully computed from noncontact electrograms acquired with small probes.

We tested the utility of intracardiac echocardiography (ICE) in measuring left ventricular (LV) volume. In 4 normal dogs, a 10-F percutaneous sheath was placed inside the LV along its major axis. An ICE catheter (9 F, 9 MHz) was then inserted through the sheath into the LV. The ICE catheter was pulled back in 1-mm intervals starting from the apex, and 2-D tomographic images were continuously acquired. Subsequently, the ICE catheter was replaced in the LV by a conductance catheter to measure single-beat volume signals. Stroke volume was determined by thermodilution for validation. All measurements were made in each dog while pacing the atrium at two different cycle lengths (range=300-500 ms). The endocardium was segmented in the ICE images throughout the cardiac cycle, and LV volume was computed by integrating multiple segments (range=55-70 mm). We found that ICE accurately reconstructed LV 3-D anatomy. Stroke volume by ICE was in excellent agreement with thermodilution (error = 3.8+/-3.0%, r = 0.99, n = 8). Morphology of LV volume signals correlated well with instantaneous volume signals derived by conductance (r=0.93, n=8). In conclusion, ICE accurately reconstructs LV anatomy and volume throughout the cardiac cycle in the normal heart. This approach could facilitate interventional diagnostic and therapeutic procedures.

Imaging RF Ablation Lesions. Introduction: The inability to determine the extent and intramural depth of ablation lesions can hamper the success of catheter ablation. The study tested the feasibility of differentiating radiofrequency ablation lesions from normal myocardium and quantifying their dimensions by myocardial contrast echocardiography (MCE). Methods and Results: In 11 normal dogs, we created 14 focal and 4 linear lesions at different left ventricular sites. MCE was performed both before and after ablation by using an intracardiac echocardiography catheter (9 MHz) and infusing contrast microbubbles through the left coronary artery. We initially used two-dimensional MCE to image focal lesions and subsequently three-dimensional MCE to image linear lesions. An independent observer examined the lesion pathology. We found that intracardiac echocardiography alone could not delineate lesion dimensions. However, after ablation, MCE localized the lesions as well-defined, low-contrast areas within the normally opacified myocardium. Lesion dimensions by MCE immediately after ablation and 30 minutes later were similar. In 12 focal lesions, the average maximum depth (5.55 ′ 1.38 mm) and average maximum diameter (10.38 ′ 2.09 mm) by MCE were in excellent agreement with the pathologic depth (5.20 ′ 1.45 mm) and diameter (10.61 ′ 1.67 mm). Two focal lesions could not be detected by MCE and later were found to be superficial. Three-dimensional MCE correctly reconstructed the extent and shape of linear lesions compared to pathology (length: 18.7 ′ 5.7 vs 18.5 ′ 5.6 mm; maximum longitudinal cross-sectional area: 81.2 ′ 9.6 vs 76.0 ′ 10.3 mm 2 ). Conclusion: MCE accurately localized and quantified radiofrequency ablation lesions in the normal left ventricle. This new application of MCE may advance ablation for managing ventricular arrhythmias that involve intramural or epicardial regions by providing instantaneous anatomic feedback on the effects of ablation during catheterization.

Differential evolution (DE) algorithm is used in this paper to solve the inverse problem of EIT, where the cost function is determined by solving the forward problem using finite element method (FEM). This method is applied to the 2D impedance reconstruction of brain section based on real head model. Our simulations demonstrate that DE algorithm is robust in obtaining high quality reconstruction for EIT problems studied in this paper.

The goal of this study was to examine the diagnostic utility of the time to onset of early (Ea) diastolic velocity of the mitral annulus by tissue Doppler (TD) in comparison with the time to onset of mitral inflow (T(Ea-E)) for the assessment of left ventricular (LV) relaxation.Tissue Doppler imaging of the mitral annulus provides useful information about myocardial function. So far, studies have focused on the measurement of peak Ea, but have not evaluated the diagnostic utility of the time to onset of Ea.Simultaneous left heart catheterization and Doppler echocardiography (DE) were performed in 10 dogs. Left atrial pressures and LV volumes and pressures were measured before and after constriction of the circumflex (cx) coronary artery. The delay in Ea was next examined in 60 consecutive patients, undergoing simultaneous right heart catheterization and DE. Furthermore, (T(Ea-E)) was used to predict filling pressures in a prospective group of 33 patients.In canine studies, significant prolongation in the time interval (T(Ea-E)) was noted after cx constriction, which had a significant relation with tau (tau) (r = 0.93, p0.01). In human studies, Ea was significantly delayed in patients with impaired relaxation and pseudonormal LV filling in comparison with age-matched controls. In the prospective group, pulmonary capillary wedge pressure (PCWP) derived as: PCWP(Doppler) = LV(end-systolic pressure) x e(-IVRT/(T(Ea-E))), where IVRT is isovolumetric relaxation time; PCWP(Doppler) related well to PCWP(catheter) (r = 0.84, p0.001).T(Ea-E) is a useful novel index of LV relaxation. It can be used to identify patients with diastolic dysfunction and predict PCWP.

In the present study, we performed simultaneous epicardial echocardiography and left heart catheterization on ten adult dogs to investigate the effects of ischaemia and tachycardia on the mitral annulus early (Ea) and late (Aa) diastolic velocities and the haemodynamic mechanisms involved. Left atrial pressure and left ventricular (LV) volumes and pressures were measured with 5 French Millar catheters. In each dog, inferior vena cava occlusion was used to alter preload and circumflex coronary artery occlusion was applied to induce ischaemia at two different cycle lengths: 450 and 550 ms. At both cycle lengths, ischaemia resulted in a reduction in LV relaxation, LV global and ipsilateral systolic function, transmitral pressure gradient (TMG), Ea and Aa (P

Noncontact, multielectrode catheter mapping derives single-beat endocardial activation, while intracardiac echocardiography constructs detailed three-dimensional endocardial anatomy. The study tested the feasibility of integrating both modalities in a single system that enabled beat-by-beat electrical-anatomical imaging. It was found that integrating intracardiac echocardiography with noncontact mapping was feasible and provided detailed, single-beat, three-dimensional electrical-anatomical images that could facilitate diagnosis of arrhythmias and advance their therapy.

Objectives The goal of this study was to examine the diagnostic utility of the time to onset of early (Ea) diastolic velocity of the mitral annulus by tissue Doppler (TD) in comparison with the time to onset of mitral inflow (TEa-E) for the assessment of left ventricular (LV) relaxation. Background Tissue Doppler imaging of the mitral annulus provides useful information about myocardial function. So far, studies have focused on the measurement of peak Ea, but have not evaluated the diagnostic utility of the time to onset of Ea. Methods Simultaneous left heart catheterization and Doppler echocardiography (DE) were performed in 10 dogs. Left atrial pressures and LV volumes and pressures were measured before and after constriction of the circumflex (cx) coronary artery. The delay in Ea was next examined in 60 consecutive patients, undergoing simultaneous right heart catheterization and DE. Furthermore, (TEa-E) was used to predict filling pressures in a prospective group of 33 patients. Results In canine studies, significant prolongation in the time interval (TEa-E) was noted after cx constriction, which had a significant relation with tau (τ) (r = 0.93, p < 0.01). In human studies, Ea was significantly delayed in patients with impaired relaxation and pseudonormal LV filling in comparison with age-matched controls. In the prospective group, pulmonary capillary wedge pressure (PCWP) derived as: PCWPDoppler= LVend-systolic pressure× e−IVRT/(TEa-E), where IVRT is isovolumetric relaxation time; PCWPDopplerrelated well to PCWPcatheter(r = 0.84, p < 0.001). Conclusions TEa-Eis a useful novel index of LV relaxation. It can be used to identify patients with diastolic dysfunction and predict PCWP.

Three EIT approaches for static imaging of head are investigated in this paper. The modified Newton-Raphson (MNR) method and the differential evolution (DE) algorithm are applied to the impedance reconstruction of 2D section of head based on real head model. Comparisons are carried out on the results obtained using simulated data, and a DE-MNR combination method is proposed, which demonstrated high impedance reconstruction quality with fast convergence in the 2D EIT simulation for static imaging of head.

The modified Newton-Raphson (MNR) method is used to solve the inverse resistivity problem in this paper. Using Tikhonov regularization method, comparisons among the L-curve method, the zero-crossing (ZC) method and the generalized cross validation (GCV) method are carried out for determining the regularization parameters of MNR method. By these criterions the appropriate regularization parameters are self-determined and adjusted with the reconstruction iterations. Our simulation experiments on 2D circle model showed that the GCV method can provide the best reconstruction quality with the fastest speed in inverse resistivity problem using MNR method.