SCreg: a registration-based platform to compare unicondylar knee arthroplasty SPECT/CT scans.

BACKGROUND: A combination of conventional computed tomography and single photon emitted computed tomography (SPECT/CT) provides simultaneous data on the intensity and location of osteoblastic activity. Currently, since SPECT/CT scans are not spatially aligned, scans following knee arthroplasty are compared by extracting average and maximal values of osteoblastic activity intensity from large subregions of the structure of interest, which leads to a loss of resolution, and hence, information. Therefore, this paper describes the SPECT/CT registration platform (SCreg) based on the principle of image registration to spatially align SPECT/CT scans following unicondylar knee arthroplasty (UKA) and allow full resolution intra-subject and inter-subject comparisons. METHODS: SPECT-CT scans of 20 patients were acquired before and 1 year after UKA. Firstly, scans were pre-processed to account for differences in voxel sizes and divided in volumes of interest. This was followed by optimization of registration parameters according to their volumetric agreement, and alignment using a combination of rigid, affine and non-rigid registration. Finally, radiotracer uptakes were normalized, and differences between pre-operative and post-operative activity were computed for each voxel. Wilcoxon signed rank sum test was performed to compare Dice similarity coefficients pre- and post-registration. RESULTS: Qualitative and quantitative validation of the platform assessing the correct alignment of SPECT/CT scans resulted in Dice similarity coefficient values over 80% and distances between predefined anatomical landmarks below the fixed threshold of (2;2;0) voxels. Locations of increased and decreased osteoblastic activity obtained during comparisons of osteoblastic activity before and after UKA were mainly consistent with literature. CONCLUSIONS: Thus, a full resolution comparison performed on the platform could assist surgeons and engineers in optimizing surgical parameters in view of bone remodeling, thereby improving UKA survivorship.

High-Detailed evaluation of the right atrial anatomy by three-dimensional rotational angiography during ablation procedures for atrioventricular nodal reentrant tachycardia and atrial flutter.

AIM: 3D Rotational angiography (3DRA) allows for detailed reconstruction of atrial anatomy and is often used to facilitate pulmonary vein isolation. This study aimed to reappraise the anatomy of the right atrium (RA) using 3DRA, specifically looking at Koch's triangle and the cavotricuspid isthmus (CTI) in atrio-ventricular reentrant tachycardia (AVNRT) and atrial flutter (AFl) ablation. METHODS AND RESULTS: 3DRA was performed in 97 patients: AVNRT = 51 and AFl = 46. Dimensions of Koch's triangle and CTI were highly variable between individuals but were not different in both ablation groups. RA volume was significantly larger in AFl patients (p = .004) while indexed RA volume to the body surface area (RAVI) was lightly different (p = .024). In univariate Cox analysis, age (p = .003), RAVI (p < .001) and previous ablation of AFl (p = .003) were predictors of AF occurrence . In multivariate Cox analysis, RAVI was the only independent predictor of AF occurrence. RAVI >80 ml/m2 was a strong predictor for AF during follow-up. CONCLUSION: 3DRA allows for detailed per-procedural evaluation of RA anatomy and revealed a great variability in Koch's triangle and CTI dimensions and morphology. RA enlargement as measured by RAVI was an independent predictor for AF occurrence during follow-up.

Left ventricular four-dimensional rotational angiography with low radiation dose through interphase registration.

AIMS: Ventricular tachycardia ablations could benefit from four-dimensional (4D) (dynamic 3D) visualization of the left ventricle (LV) as roadmap for anatomy-guided procedures. Our aim was to develop an algorithm that combines information of several cardiac phases to improve signal-to-noise ratio in low-dose, noisy rotational angiography [three-dimensional rotational angiography (3DRA)] image datasets, enabling semi-automatic segmentation and generation of 4D rotational angiography (4DRA) LV surface models. METHODS AND RESULTS: We developed a novel slow pacing protocol for low-dose 4DRA imaging and applied interphase registration (IPR) to improve contrast-to-noise ratio (CNR) such that 4D LV segmentation could be achieved using a single iso-intensity value (ISO). The method was applied to construct four-phase dynamic LV models from five porcine experiments. Optimal choice of IPR and ISO parameters and resulting LV model accuracy were assessed by comparison with 'groundtruth' manual LV delineations using surface distance measures [root mean square distance (RMSD), Hausdorff distance (HD), fraction of surface distances ≤3 mm (d3 mm)]. Using IPR with optimized parameters, CNR improved by 88% (P < 0.0001) and increased segmentation accuracy was proven irrespective of ISO. Significant improvement was achieved in RMSD [mean at optimal ISO: -28.3% (95% confidence interval (CI) -21.7 to -35.0, P < 0.0001)], HD [-21.4% (95% CI -18.6 to -24.1, P < 0.0001)], and d3 mm [+7.8% (95% CI +4.6 to +10.9, P < 0.0001)]. An average d3 mm of 95.6 ± 2.8% was reached at optimal ISO. Time to generate a 4D model was ±11.5 min with IPR vs. ±22 min without. CONCLUSION: Interphase registration significantly improves 4DRA image quality and facilitates semi-automatic segmentation, resulting in clinically useful accuracy despite low-dose image acquisition protocols, while shortening 4D model generation time. This opens the prospect of 4D imaging in clinical settings.

Phantom study of augmented reality framework to assist epicardial punctures.

Purpose: The objective of this study is to evaluate the accuracy of an augmented reality (AR) system in improving guidance, accuracy, and visualization during the subxiphoidal approach for epicardial ablation. Approach: An AR application was developed to project real-time needle trajectories and patient-specific 3D organs using the Hololens 2. Additionally, needle tracking was implemented to offer real-time feedback to the operator, facilitating needle navigation. The AR application was evaluated through three different experiments: examining overlay accuracy, assessing puncture accuracy, and performing pre-clinical evaluations on a phantom. Results: The results of the overlay accuracy assessment for the AR system yielded 2.36±2.04 mm. Additionally, the puncture accuracy utilizing the AR system yielded 1.02±2.41 mm. During the pre-clinical evaluation on the phantom, needle puncture with AR guidance showed 7.43±2.73 mm, whereas needle puncture without AR guidance showed 22.62±9.37 mm. Conclusions: Overall, the AR platform has the potential to enhance the accuracy of percutaneous epicardial access for mapping and ablation of cardiac arrhythmias, thereby reducing complications and improving patient outcomes. The significance of this study lies in the potential of AR guidance to enhance the accuracy and safety of percutaneous epicardial access.

Cardiac three-dimensional rotational angiography can be performed with low radiation dose while preserving image quality.

AIMS: The effective radiation dose (ED) of three-dimensional rotational angiography (3DRA) is 5-8 mSv, leading to reticence on its use. We evaluated the potential of 3DRA with a reduced number of frames (RNF) and a reduced dose per frame. METHODS AND RESULTS: Three-dimensional rotational angiography was performed in 60 patients (52.5 ± 9.6 years, 16 females) referred for ablation in the right (RA; n = 10) and left atrium (LA; n = 50). In a simulation group (n = 20), the effect of dropping frames from a conventional 248 frames 3DRA LA acquisition was simulated. In a prospective group (n = 40), RNF 3DRA were acquired of LA (n = 30) and RA (n = 10) with 67 frames (0.24 Gy/frame) and 45 frames (0.12 µGy/frame), respectively. Accuracy was evaluated qualitatively and quantitatively. Effective radiation dose was determined by Monte Carlo simulation on every frame. In the simulation group, surface errors increased minimally and non-significantly when reducing frames from 248 to 124, 83, 62, 50, 42, and 31: 0.49 ± 0.51, 0.52 ± 0.46, 0.61 ± 0.49, 0.62 ± 0.47, 0.71 ± 0.48, and 0.81 ± 0.47 mm, respectively (Pearson coefficient 0.20). All 3D LA images were clinically useful, even with only 31 frames. In the prospective group, good or optimal 3D image quality was achieved in 80% of LA and all of RA reconstructions. These accurate models were obtained with ED of 2.6 ± 0.4 mSv for LA and 1.2 ± 0.5 mSv for RA. CONCLUSION: Three-dimensional rotational angiography is possible with a significant reduction in ED (to the level of prospectively gated cardiac computed X-ray tomography) without compromising image quality. Low-dose 3DRA could become the preferred online 3D imaging modality for pulmonary vein isolation and other anatomy-dependent ablations.

Alginate sulfate-nanoparticles loaded with hepatocyte growth factor and insulin-like growth factor-1 improve left ventricular repair in a porcine model of myocardial ischemia reperfusion injury.

Nanomedicine offers great potential for the treatment of cardiovascular disease and particulate systems have the capacity to markedly improve bioavailability of therapeutics. The delivery of pro-angiogenic hepatocyte growth factor (HGF) and pro-survival and pro-myogenic insulin-like growth factor (IGF-1) encapsulated in Alginate-Sulfate nanoparticles (AlgS-NP) might improve left ventricular (LV) functional recovery after myocardial infarction (MI). In a porcine ischemia-reperfusion model, MI is induced by 75 min balloon occlusion of the mid-left anterior descending coronary artery followed by reperfusion. After 1 week, pigs (n = 12) with marked LV-dysfunction (LV ejection fraction, LVEF < 45%) are randomized to fusion imaging-guided intramyocardial injections of 8 mg AlgS-NP prepared with 200 µg HGF and IGF-1 (HGF/IGF1-NP) or PBS (Control). Intramyocardial injection is safe and pharmacokinetic studies of Cy5-labeled NP confirm superior cardiac retention compared to intracoronary infusion. Seven weeks after intramyocardial-injection of HGF/IGF1-NP, infarct size, measured using magnetic resonance imaging, is significantly smaller than in controls and is associated with increased coronary flow reserve. Importantly, HGF/IGF1-NP-treated pigs show significantly increased LVEF accompanied by improved myocardial remodeling. These findings demonstrate the feasibility and efficacy of using AlgS-NP as a delivery system for growth factors and offer the prospect of innovative treatment for refractory ischemic cardiomyopathy.

Asymmetric collimation can significantly reduce patient radiation dose during pulmonary vein isolation.

AIMS: Current fluoroscopic and 3D image-guided treatment of atrial fibrillation (AF) by radiofrequency ablation is characterized by a substantial amount of X-ray radiation. We investigated the potential of an asymmetric collimation technique to reduce dose. METHODS AND RESULTS: For 30 patients, referred for AF ablation, we determined the received fluoroscopy dose for various collimation scenarios: a single collimation window encompassing all veins as used in most labs (Sc 1), an optimal adjusted symmetric collimation window encompassing each two ipsilateral veins (Sc 2) or each individual vein (Sc 3) and an optimal asymmetric collimation window encompassing each two ipsilateral veins (Sc 4) or each individual vein (Sc 5). Twenty patients were studied retrospectively and 10 were studied prospectively. Total fluoroscopy effective dose for all collimation strategies amounted to 45 ± 31 mSv for a single collimation field (Sc 1), 36 ± 25 mSv (Sc 2), and 24 ± 14 mSv (Sc 3) for a symmetrically adjusted collimation window and 15 ± 10 (Sc 4) and 5 ± 3 mSv (Sc 5) for an asymmetrically adjusted collimation approach. Validation of symmetric (Sc 2) and asymmetric (Sc 4) collimation in 10 patients confirmed the retrospective analysis. CONCLUSIONS: Implementation and effective application of an optimal asymmetric collimation approach would yield an average three- to nine-fold reduction of fluoroscopy dose during AF ablation procedures. This reduction exceeds what has been previously reported by implementing an electromagnetic catheter tracking approach. Furthermore, it can be easily integrated in the clinical workflow with limited additional one-time cost. Manufacturers of imaging systems should consider its implementation a priority, and physicians should adopt it in their workflow.

MeVisLab-OpenVR prototyping platform for virtual reality medical applications.

PURPOSE: Virtual reality (VR) can provide an added value for diagnosis and/or intervention planning. Several VR software implementations have been proposed but they are often application dependent. Previous attempts for a more generic solution incorporating VR in medical prototyping software (MeVisLab) were still lacking functionality precluding easy and flexible development. METHODS: We propose an alternative solution that uses rendering to a graphical processing unit (GPU) texture to enable rendering arbitrary Open Inventor scenes in a VR context. It facilitates flexible development of user interaction and rendering of more complex scenes involving multiple objects. We tested the platform in planning a transcatheter cardiac stent placement procedure. RESULTS: This approach proved to enable development of a particular implementation that facilitates planning of percutaneous treatment of a sinus venosus atrial septal defect. The implementation showed it is intuitive to plan and verify the procedure using VR. CONCLUSION: An alternative implementation for linking OpenVR with MeVisLab is provided that offers more flexible development of VR prototypes which can facilitate further clinical validation of this technology in various medical disciplines.

3D imaging added value in the treatment and diagnosis of displaced intra-articular calcaneal fractures (DIACF): measuring the orientation of the posterior talo-calcaneal facet in the space.

PURPOSE: Measure the reduction quality of calcaneal fractures on 3 D segmented images. METHODS: The Ethics Review Board approved this study and written informed consent was collected from all patients. Bilateral CT scans of fifty-four patients with unilateral displaced calcaneal fracture were obtained before and after osteosynthesis. Orientation angle of the posterior subtalar joint facet (PTC) of displaced intra-articular calcaneal fractures of 54 patients was measured on segmented 3 D images before and after surgery and compared to the uninjured side. This orientation angle (OAC) is the average of every normal vector of each point of the PTC, as compared to the main calcaneal axis (calculated by first principal component analysis). The PTC is a well-known anatomical structure, relatively easy to identify on 3 D imaging. RESULTS: This OAC angle was low before surgery (mean= 95°, std dev= 6°), statistically significantly different from the uninjured side value, p < 0.001. The OAC angle of the operated bone was nearly equal to the uninjured side (mean= 103°, std dev= 5°), without any statistically significant difference between postoperative values and uninjured side values. We found linear correlation between the quality of the reduction when assessed with this OAC and the functional score (AOFAS) (Adjusted R2=0.62, p = 0.04). CONCLUSIONS: This angle seems to be useful to quantify the quality of the operative reduction of displaced intra-articular calcaneal fractures.

Preprocedural imaging for transcatheter mitral valve-in-valve replacement: Planning makes perfect.

Transcatheter mitral valve-in-valve replacement (TMViVR) in degenerated bioprostheses or valvular rings shows promise as an alternative to surgical MVR in selected high-risk patients. However, these procedures are particularly challenging given the complex anatomy of the mitral valve apparatus and the surrounding structures, potentially causing LV outflow tract obstruction (LVOTO). Preprocedural planning with virtual implantation and planimetric estimation of the neo-LVOT at end-systole is crucial for improving procedural results. In this case, we also include a dynamic evaluation of the neo-LVOT and implement virtual reality imaging for immersive assessment of the implanted valve.

Efficacy of radiofrequency catheter ablation in athletes with atrial fibrillation.

AIMS: Endurance sports activities have been associated with the development of atrial fibrillation (AF). Pulmonary vein isolation (PVI) by means of radiofrequency catheter ablation has been established as an effective treatment for AF. The aim of the present study was to analyse the efficacy of AF ablation in athletes. METHODS AND RESULTS: We compared procedural outcome and median term follow-up in 94 consecutive athletes (>3 h of sports/week for ≥ 10 years or ≥ 1500 h lifetime) who underwent PVI (94% men, 51 ± 8 years, 87% paroxysmal AF, left atrial (LA) diameter 40 ± 8 mm, mean follow-up 41 months), and 41 contemporary controls. Sixty-three per cent of athletes performed endurance sports (running, cycling, swimming, and rowing). Documented focal induction of AF and failed treatment with ≥ 1 anti-arrhythmic drug were pre-requisites for selection of ablation treatment. Patients with long-standing persistent or permanent AF or an LA diameter ≥ 55 mm were not considered for ablation. Median lifetime cumulative hours of sports was 8638 (4175-13 688) in athletes vs. 450 (280-600) in controls (P < 0.001). Other baseline characteristics except for gender (94 vs. 66% men, respectively, P < 0.001) were comparable between both groups, as was the total number of ablation procedures per patient (1.2 ± 0.5, P = 0.62). Survival analysis showed similar AF recurrence rate after a first ablation for controls and endurance athletes, though non-endurance athletes had a significantly higher AF recurrence rate (48 vs. 46 vs. 34% freedom from AF at 3 year follow-up after a single ablation, P= 0.04). Final outcome after all ablations was similar (87 vs. 84 vs. 85% freedom from AF at 3-year follow-up, P = 0.88). No other independent predictor for AF recurrence was identified. CONCLUSION: In patients with documented focal induction of non-permanent AF and absence of structural heart disease, PVI is as effective in endurance athletes as in other patients.

Discrete sites of frequent premature ventricular complexes cluster within the infarct border zone and coincide with high frequency of delayed afterdepolarizations under adrenergic stimulation.

BACKGROUND: Sympathetic activation in ischemic heart disease can cause lethal arrhythmias. These often are preceded by premature ventricular complexes (PVCs), which at the cellular level could result from delayed afterdepolarizations. OBJECTIVE: The purpose of this study was to identify and map vulnerable areas for arrhythmia initiation after myocardial infarction (MI) and to explore the link between PVCs and cellular events. METHODS: Anterior-septal wall MI was induced by 120 minutes of coronary occlusion followed by reperfusion (27 MI and 16 sham pigs). After 4 weeks, EnSite™ electroanatomic mapping combined with imaging was performed to precisely locate PVC sites of origin and subsequently record monophasic action potentials. Cardiomyocytes were isolated from different regions to study regional cellular remodeling. Isoproterenol was used as a surrogate for adrenergic stimulation both in vivo and in cardiomyocytes. RESULTS: PVCs originated from the MI border zone (BZ) and occurred at discrete areas with clusters of PVCs within the BZ. At these sites, frequent delayed afterdepolarizations and occasional associated spontaneous action potentials translating to a PVC were present. Cardiomyocytes isolated from the MI BZ exhibited more spontaneous action potentials than cardiomyocytes from remote regions. Sensitivity to adrenergic stimulation was increased in MI, in vivo and in cardiomyocytes. In awake, freely moving MI animals, frequent PVCs, ventricular arrhythmia, and sudden cardiac death occurred spontaneously at moderately elevated heart rates. CONCLUSION: Post-MI, arrhythmias initiate from discrete vulnerable areas within the BZ, where delayed afterdepolarizations, related to increased adrenergic response of BZ cardiomyocytes, can generate PVCs.

Three-dimensional cardiac rotational angiography: effective radiation dose and image quality implications.

AIMS: Three-dimensional rotational angiography (3DRA) is a promising new online tool for 3D imaging during cardiac ablation procedures. No precise data exist concerning its associated radiation dose. The current study evaluated the effective dose (ED) of cardiac rotational angiography and its relation to patient properties, imaging system input settings, and quality of reconstructed 3D images. METHODS AND RESULTS: We performed Monte Carlo simulation-based radiation dose calculations in 42 patients referred for ablation of cardiac arrhythmias. Detailed tube setting information from the 3DRA system (Siemens Axiom Artis dBC with Syngo DynaCT Cardiac software) was used to provide an accurate input for dose calculations in all 248 frames used during image acquisition. Our calculations yielded an overall mean ED of 6.6 +/- 1.8 mSv (based on ICRP 103 weighing factors). Manual collimation of the radiation beam can reduce ED by more than 20%. Image quality did not significantly relate to patient body mass index (BMI), dose per frame setting, or dose-area product (DAP), but was rather explained by contrast filling, cardiac motion reduction, and absence of image reconstruction artefacts. In the system evaluated, DAP values are nearly independent from BMI (R(2) = 0.30), due to its technical specifications. Therefore, patient BMI showed an unexpected strong inverse relation to ED. CONCLUSION: Three-dimensional rotational angiography can be performed with acceptable patient radiation dose, comparable to cardiac CT. With the 3DRA system studied (Siemens Axiom), slender patients may currently receive unnecessarily high radiation doses when compared with obese patients, so that further dose reduction seems feasible for many patients. Adequate collimation is imperative to limit patient exposure.

Adenosine-induced ventricular asystole or rapid ventricular pacing to enhance three-dimensional rotational imaging during cardiac ablation procedures.

AIMS: Rotational angiography with digital three-dimensional reconstruction (3DRA) allows per-procedural 3D imaging to facilitate cardiac ablation procedures. We developed a new approach that allows per-procedural 3D imaging of the atria and ventricles with a single C-arm rotation, combining higher 3D image quality with a lower contrast and radiation dose. METHODS AND RESULTS: Forty patients underwent 3DRA of the left atrium (LA, n = 26), right atrium (RA, n = 11), left ventricle (LV, n = 2), or right ventricle (RV, n = 1) during ablation procedures performed under general anaesthesia. Contrast agent (60 +/- 12 mL) was diluted and injected directly in the chamber of interest, during adenosine-induced ventricular asystole (n = 31) or rapid RV pacing (n = 9, atrial imaging only) to reduce cardiac motion artefacts and enhance contrast opacification during rotational imaging. Reconstructed 3D data sets were graded according to predefined quality criteria (n = 40) and quantitatively compared with cardiac computed tomography (CT) (LA, n = 14). Adenosine-induced ventricular asystole and rapid pacing both allowed a sustained and homogeneous contrast opacification of target cardiac chambers, resulting in useful 3D data sets in 39 of 40 (98%) patients. Moreover, it was possible to achieve 'good' or 'optimal' 3D image quality in the majority of patients (adenosine: 61%, pacing 78%, P = 0.69). When compared with rapid pacing, the total elimination of cardiac motion artefacts with adenosine more frequently resulted in 'optimal' 3D image quality (42% vs. 11%, P = 0.01) and added the possibility for single-rotation 3D imaging of the ventricles. Quantitative analysis showed an excellent agreement between pulmonary vein diameters measured on cardiac CT and 3DRA images. Integration of 3DRA-based LA surfaces with real-time fluoroscopy was easy and highly accurate. CONCLUSION: Adenosine-induced ventricular asystole or rapid ventricular pacing allow acquisition of 3DRA with an excellent direct contrast opacification of any cardiac chamber and a reduction of cardiac motion artefacts, resulting in high-quality per-procedural 3D imaging with a single C-arm rotation.

Changes in left atrial anatomy due to respiration: impact on three-dimensional image integration during atrial fibrillation ablation.

INTRODUCTION: Patient respiration influences the accuracy of image integration approaches used during atrial fibrillation (AF) ablation procedures. We assessed both absolute and relative changes in left atrial (LA) and pulmonary venous (PV) anatomy due to respiration and their implications for 3D image integration. METHODS AND RESULTS: Intensity-based segmentation of the LA and PVs was performed on cardiac computed tomography (CT) images obtained during both inspiration and expiration in 16 patients referred for AF ablation. A 3D LA-PV surface model was reconstructed for each respiratory phase. Absolute and relative respiratory motion components were evaluated from corresponding landmarks in both models. The mean 3D respiratory motion distance for all four PVs was 19 +/- 9 mm. The most important motion component was in the inferior direction, with a mean inferior motion distance of 15 +/- 8 mm. The mean 3D respiratory motion of the PV centers due to relative geometrical changes was small at the ostial level (2.6 +/- 1.4 mm, 95% CI 2.3-3.0 mm) but significantly larger at the level of the first PV bifurcation (4.0 +/- 2.3 mm, 95% CI 3.4-4.6 mm, P < 0.001). Relative geometrical changes of the LA body were most pronounced in regions near the mitral valve, resulting in a changed configuration of the mitral annulus during inspiration. CONCLUSIONS: Respiration causes important movements of the PVs and LA. Relative changes in LA-PV geometry are most pronounced in the distal PVs and in the LA body near the mitral valve. Therefore, these regions should be avoided during registration of pre- and per-procedural images unless they are acquired in the same phase of respiration.

Cardiac three-dimensional magnetic resonance imaging and fluoroscopy merging: a new approach for electroanatomic mapping to assist catheter ablation.

BACKGROUND: Modern nonfluoroscopic mapping systems construct 3D electroanatomic maps by tracking intracardiac catheters. They require specialized catheters and/or dedicated hardware. We developed a new method for electroanatomic mapping by merging detailed 3D models of the endocardial cavities with fluoroscopic images without the need for specialized hardware. This developmental work focused on the right atrium because of the difficulties in visualizing its anatomic landmarks in 3D with current approaches. METHODS AND RESULTS: Cardiac MRI images were acquired in 39 patients referred for radiofrequency catheter ablation using balanced steady state free-precession sequences. We optimized acquisition and developed software for construction of detailed 3D models, after contouring of endocardial cavities with cross-checking of different imaging planes. 3D models were then merged with biplane fluoroscopic images by methods for image calibration and registration implemented in a custom software application. The feasibility and accuracy of this merging process were determined in heart-cast experiments and electroanatomic mapping in patients. Right atrial dimensions and relevant anatomic landmarks could be identified and measured in all 3D models. Cephalocaudal, posteroanterior, and lateroseptal diameters were, respectively, 65+/-11, 54+/-11, and 57+/-9 mm; posterior isthmus length was 26+/-6 mm; Eustachian valve height was 5+/-5 mm; and coronary sinus ostium height and width were 16+/-3 and 12+/-3 mm, respectively (n=39). The average alignment error was 0.2+/-0.3 mm in heart casts (n=40) and 1.9 to 2.5 mm in patient experiments (n=9), ie, acceptable for clinical use. In 11 patients, reliable catheter positioning and projection of activation times resulted in 3D electroanatomic maps with an unprecedented level of anatomic detail, which assisted ablation. CONCLUSIONS: This new approach allows activation visualization in a highly detailed 3D anatomic environment without the need for a specialized nonfluoroscopic mapping system.

Multi-phase rotational angiography of the left ventricle to assist ablations: feasibility and accuracy of novel imaging.

AIMS: Interventional left ventricular (LV) procedures integrating static 3D anatomy visualization are subject to mismatch with dynamic catheter movements due to prominent LV motion. We aimed to evaluate the accuracy of a recently developed acquisition and post-processing protocol for low radiation dose LV multi-phase rotational angiography (4DRA) in patients. METHODS AND RESULTS: 4DRA image acquisition of the LV was performed as investigational acquisition in patients undergoing left-sided ablation (11 men; BMI = 24.7 ± 2.5 kg/m²). Iodine contrast was injected in the LA, while pacing from the RA at a cycle length of 700 ms. 4DRA acquisition and reconstruction were possible in all 11 studies. Reconstructed images were post-processed using streak artefact reduction algorithms and an interphase registration-based filtering method, increasing contrast-to-noise ratio by a factor 8.2 ± 2.1. This enabled semi-automatic segmentation, yielding LV models of five equidistant phases per cardiac cycle. For evaluation, off-line 4DRA fluoroscopy registration was performed, and the 4DRA LV contours of the different phases were compared with the contours of five corresponding phases of biplane LV angiography, acquired in identical circumstances. Of the distances between these contours, 95% were <4 mm in both incidences. Effective radiation dose for 4DRA, calculated by patient-specific Monte-Carlo simulation, was 5.1 ± 1.1 mSv. CONCLUSION: Creation of 4DRA LV models in man is feasible at near-physiological heart rate and with clinically acceptable radiation dose. They showed high accuracy with respect to LV angiography in RAO and LAO. The presented technology not only opens perspectives for full cardiac cycle dynamic anatomical guidance during interventional procedures, but also for 3DRA without need for very rapid pacing.

An augmented reality system for patient-specific guidance of cardiac catheter ablation procedures.

We present a system to assist in the treatment of cardiac arrhythmias by catheter ablation. A patient-specific three-dimensional (3-D) anatomical model, constructed from magnetic resonance images, is merged with fluoroscopic images in an augmented reality environment that enables the transfer of electrocardiography (ECG) measurements and cardiac activation times onto the model. Accurate mapping is realized through the combination of: a new calibration technique, adapted to catheter guided treatments; a visual matching registration technique, allowing the electrophysiologist to align the model with contrast-enhanced images; and the use of virtual catheters, which enable the annotation of multiple ECG measurements on the model. These annotations can be visualized by color coding on the patient model. We provide an accuracy analysis of each of these components independently. Based on simulation and experiments, we determined a segmentation error of 0.6 mm, a calibration error in the order of 1 mm and a target registration error of 1.04 +/- 0.45 mm. The system provides a 3-D visualization of the cardiac activation pattern which may facilitate and improve diagnosis and treatment of the arrhytmia. Because of its low cost and similar advantages we believe our approach can compete with existing commercial solutions, which rely on dedicated hardware and costly catheters. We provide qualitative results of the first clinical use of the system in 11 ablation procedures.

Three-dimensional rotational angiography fused with multimodal imaging modalities for targeted endomyocardial injections in the ischaemic heart.

AIM: Biological therapies for ischaemic heart disease require efficient, safe, and affordable intramyocardial delivery. Integration of multiple imaging modalities within the fluoroscopy framework can provide valuable information to guide these procedures. We compared an anatomo-electric method (LARCA) with a non-fluoroscopic electromechanical mapping system (NOGA(®)). LARCA integrates selective three-dimensional-rotational angiograms with biplane fluoroscopy. To identify the infarct region, we studied LARCA-fusion with pre-procedural magnetic resonance imaging (MRI), dedicated CT, or (18)F-FDG-PET/CT. METHODS AND RESULTS: We induced myocardial infarction in 20 pigs by 90-min LAD occlusion. Six weeks later, we compared peri-infarct delivery accuracy of coloured fluospheres using sequential NOGA(®)- and LARCA-MRI-guided vs. LARCA-CT- and LARCA-(18)F-FDG-PET/CT-guided intramyocardial injections. MRI after 6 weeks revealed significant left ventricular (LV) functional impairment and remodelling (LVEF 31 ± 3%, LVEDV 178 ± 15 mL, infarct size 17 ± 2% LV mass). During NOGA(®)-procedures, three of five animals required DC-shock for major ventricular arrhythmias vs. one of ten during LARCA-procedures. Online procedure time was shorter for LARCA than NOGA(®) (77 ± 6 vs. 130 ± 3 min, P < 0.0001). Absolute distance of injection spots to the infarct border was similar for LARCA-MRI (4.8 ± 0.5 mm) and NOGA(®) (5.4 ± 0.5 mm). LARCA-CT-integration allowed closer approximation of the targeted border zone than LARCA-PET (4.0 ± 0.5 mm vs. 6.2 ± 0.6 mm, P < 0.05). CONCLUSION: Three-dimensional -rotational angiography fused with multimodal imaging offers a new, cost-effective, and safe strategy to guide intramyocardial injections. Endoventricular procedure times and arrhythmias compare favourably to NOGA(®), without compromising injection accuracy. LARCA-based fusion imaging is a promising enabling technology for cardiac biological therapies.