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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.

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.

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.

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.

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.

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.