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A heart-transplanted patient is at risk of developing several complications such as rejection, which is one of the leading causes of deaths in the first year after the transplant. The regional myocardial motion is known to be depressed early on during rejection before the reduction in global systolic function. Therefore, early detection of regional anomalies is crucial. We use a magnetic resonance (MR) imaging method called tissue phase mapping (TPM) to capture regional myocardial motion of heart-transplanted patients in a longitudinal study. We compare the individual scans of the longitudinal study to a cohort of healthy volunteers to detect anomalies. We use a spatio-temporal visualization based on a radial layout where myocardial regions are laid out in an angular pattern similar to the American Heart Association (AHA) model and where the temporal dimension increases with increasing radius. We compute nested envelopes of central regions for the time series of each region and each of the three velocity directions using the concept of functional boxplots. We propose visual encodings to analyze regional anomalies of a scan of an individual patient dataset and perform a qualitative user study with medical experts. We extend this layout to the visual analysis of longitudinal data to monitor changes in regional anomalies of a patient for multiple scans taken at different times. We apply our approach to data from a longitudinal study of patients under observation after a heart-transplant procedure and evaluate this mechanism with medical and non-medical experts.

Identification of possible amorphous phases of micron or submicron size in metallic alloys usually relies on transmission electron microscopy, which often faces great challenge in sample preparation. In this study, nanoindentation was introduced as an efficient approach to map possible amorphous phases in a Cu–Zr system processed by accumulative roll bonding. This was achieved by taking the advantage that the amorphous phases of CuZr are associated with characteristic “pop-in” events in the nanoindentation load-displacement curves, which are absent for crystalline CuZr phases of similar composition. By combining nanoindenation with scanning electron microscopy, it was found that significant mechanical alloying has occurred in Cu–Zr during accumulative roll bonding, which resulted in regions of ultra-fined composite of both crystalline and amorphous CuZr phases. Such structure was consistent with that found by high-resolution transmission electron microscopy. It thus suggests that nanoindentation offers an alternative method for preliminary but effective mapping of possible amorphous phases in metallic alloy system over a relatively large scale than transmission electron microscopy.

Background Current phase mapping systems for atrial fibrillation create 2-dimensional (2D) maps. This process may affect the accurate detection of rotors. We developed a 3-dimensional (3D) phase mapping technique that uses the 3D locations of basket electrodes to project phase onto patient-specific left atrial 3D surface anatomy. Objective We sought to determine whether rotors detected in 2D phase maps were present at the corresponding time segments and anatomical locations in 3D phase maps. Methods One-minute left atrial atrial fibrillation recordings were obtained in 14 patients using the basket catheter and analyzed off-line. Using the same phase values, 2D and 3D phase maps were created. Analysis involved determining the dominant propagation patterns in 2D phase maps and evaluating the presence of rotors detected in 2D phase maps in the corresponding 3D phase maps. Results Using 2D phase mapping, the dominant propagation pattern was single wavefront (36.6%) followed by focal activation (34.0%), disorganized activity (23.7%), rotors (3.3%), and multiple wavefronts (2.4%). Ten transient rotors were observed in 9 of 14 patients (64%). The mean rotor duration was 1.1 ± 0.7 seconds. None of the 10 rotors observed in 2D phase maps were seen at the corresponding time segments and anatomical locations in 3D phase maps; 4 of 10 corresponded with single wavefronts in 3D phase maps, 2 of 10 with 2 simultaneous wavefronts, 1 of 10 with disorganized activity, and in 3 of 10 there was no coverage by the basket catheter at the corresponding 3D anatomical location. Conclusion Rotors detected in 2D phase maps were not observed in the corresponding 3D phase maps. These findings may have implications for current systems that use 2D phase mapping.

Objectives The purpose of this study was to determine the mechanistic overlap between paroxysmal and persistent forms of atrial fibrillation (AF), focusing on AF sources as a classification approach. Background The role of AF substrates is unclear in patients with paroxysmal AF (PAF) that recurs after pulmonary vein isolation (PVI). We hypothesized that patients with recurrent post-ablation (redo) PAF despite PVI have electrical substrates marked by rotors and focal sources and structural substrates that resemble persistent AF more than patients with (de novo) PAF at first ablation. Methods In 175 patients at 11 centers, we compared AF substrates in both atria using 64-pole basket catheters and phase mapping, and indices of anatomical remodeling between patients with de novo or redo PAF and first ablation for persistent AF. Results Sources were seen in all patients. More patients with de novo PAF (78.0%) had sources near pulmonary veins (PVs) than patients with redo PAF (47.4%; p = 0.005) or persistent AF (46.9%; p = 0.001). The total number of sources per patient (p = 0.444), and number of non-PV sources (p = 0.701) were similar between groups, indicating that redo PAF patients had residual non-PV sources after elimination of PV sources by prior PVI. Structurally, left atrial size did not separate de novo from redo PAF (49.5 ± 9.5 mm vs. 49.0 ± 7.1 mm; p = 0.956) but was larger in patients with persistent AF (55.2 ± 8.4 mm; p = 0.001). Conclusions Patients with PAF despite prior PVI show electrical substrates that resemble persistent AF more closely than patients with PAF at first ablation. Notably, these subgroups of PAF are indistinguishable by structural indices. These data motivate studies of trigger versus substrate mechanisms for patients with recurrent PAF after PVI.

Background The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the re-entry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites. Methods For patients who underwent catheter ablation of scar-related VT, CT scan was obtained prior to the ablation procedure and 120-lead body-surface electrocardiograms (ECGs) were acquired during induced VTs. These data were used for noninvasive ECG imaging to computationally reconstruct electrical potentials on the epicardium and on the endocardium of both ventricles. Activation time and phase maps of the VT circuit were extracted from the reconstructed electrograms. They were analyzed with respect to scar substrate obtained from catheter mapping, as well as VT exits confirmed through ablation sites that successfully terminated the VT. Results The reconstructed re-entry circuits correctly revealed both epicardial and endocardial origins of activation, consistent with locations of exit sites confirmed from the ablation procedure. The temporal dynamics of the re-entry circuits, particularly the slowing of conduction as indicated by the crowding and zig-zag conducting of the activation isochrones, collocated well with scar substrate obtained by catheter voltage maps. Furthermore, the results indicated that some re-entry circuits involve both the epicardial and endocardial layers, and can only be properly interpreted by mapping both layers simultaneously. Conclusions This study investigated the potential of ECG-imaging for beat-to-beat mapping of unstable reentrant circuits. It shows that simultaneous epicardial and endocardial mapping may improve the delineation of the 3D spatial construct of a re-entry circuit and its exit. It also shows that the use of phase mapping can reveal regions of slow conduction that collocate well with suspected heterogeneous regions within and around the scar.

Experimental and clinical data demonstrate that atrial fibrillation (AF) maintenance in animals and groups of patients depends on localized reentrant sources localized primarily to the pulmonary veins (PVs) and the left atrium(LA) posterior wall in paroxysmal AF but elsewhere, including the right atrium (RA), in persistent AF. Moreover, AF can be eliminated by directly ablating AF-driving sources or “rotors,” that exhibit high-frequency, periodic activity. The RADAR-AF randomized trial demonstrated that an ablation procedure based on a more target-specific strategy aimed at eliminating high frequency sites responsible for AF maintenance is as efficacious as and safer than empirically isolating all the PVs. In contrast to the standard ECG, global atrial noninvasive frequency analysis allows non-invasive identification of high-frequency sources before the arrival at the electrophysiology laboratory for ablation. Body surface potential map (BSPM) replicates the endocardial distribution of DFs with localization of the highest DF (HDF) and can identify small areas containing the high-frequency sources. Overall, BSPM had a sensitivity of 75% and specificity of 100% for capturing intracardiac EGMs as having LARA DF gradient. However, raw BSPM data analysis of AF patterns of activity showed incomplete and instable reentrant patterns of activation. Thus, we developed an analysis approach whereby a narrow band-pass filtering allowed selecting the electrical activity projected on the torso at the HDF, which stabilized the projection of rotors that potentially drive AF on the surface. Consequently, driving reentrant patterns (“rotors”) with spatiotemporal stability during >70% of the AF time could be observed noninvasibly after HDF-filtering. Moreover, computer simulations found that the combination of BSPM phase mapping with DF analysis enabled the discrimination of true rotational patterns even during the most complex AF. Altogether, these studies show that the combination of DF analysis with phase maps of HDF-filtered surface ECG recordings allows noninvasive localization of atrial reentries during AF and further a physiologically-based rationale for personalized diagnosis and treatment of patients with AF.

To simultaneously acquire the B 1 + magnitude and B 1 + phase, a modified multi-echo actual flip-angle imaging (AFI) sequence is proposed. A multi-echo gradient echo sequence was integrated into every even TR of AFI to measure both magnitude and phase of B 1 + . In addition, to increase the signal-to-noise ratio of the B 1 + phase, a double-angle multi-echo AFI sequence, in which the flip-angle of the RF pulses is α at the odd TR and 2α at the even TR is proposed. Images were simulated to evaluate the performance of this method under various imaging and physical parameters. The performance was compared to the spin echo based B 1 + mapping method in phantom and in vivo studies. In the simulation, the estimation error decreased as TR 1 /T 1 decreased and TR 2 /TR 1 increased. For double-angle AFI, flip-angle ranges that could estimate B 1 + magnitude and phase better than the original AFI were identified. Using the proposed method, B 1 + phase estimation was similar to spin echo phase. In the phantom study, correlation coefficient between the estimated B 1 + phases using the spin echo and the proposed method was 0.9998. The results show that the B 1 + magnitude and B 1 + phase can be simultaneously acquired and accurately estimated using the proposed double-angle AFI method.

Aim: We evaluated a Siemens software of flow quantification (FQ) by MR phase mapping, in the framework of a common practical use. Methods: Experiments with a laminar flow phantom and in vivo pulsatile flow were performed. In particular, FQ in ascending aorta was investigated in healthy volunteers. Results and conclusion: Flow phantom experiments reveal that the FQ slightly underestimates (8% on the average) actual velocities (mean velocities over a vessel area), and also that velocity uncertainties are related to the encoding velocity value, whatever the measured velocity. Furthermore, using well characterized working criteria, we found low intraobserver variability and negligible interobserver variability in ascending aorta FQs. The role played by the choice of reference area in FQ accuracy is emphasized. When recording several cardiac cycles during the same acquisition, it is shown that the FQ software may provide erroneous results. Several comments for FQ software use in the ascending aorta are added.

Thermodynamic evaluations of the systems SiZn and AlSiZn are presented. In the evaluation of the system AlSiZn, use is made of available thermodynamic evaluations of the binary subsystems. The results of the calculations are compared with published experimental data and cover a temperature range of 400–1700 K. In these calculations, the vapour phase has been included. It is shown that the thermodynamic behaviour of the three elements can be explained by a summation of binary interactions between the elements. The calculations in the ternary system are performed using “Txy-Calc”. A short outline of the “two dimensional phase mapping” method used in this program is given.

A non-invasive measurement of a temperature distribution within a target body using a nuclear magnetic resonance imaging, capable of realizing a high speed and a high precision measurement, and accounting for a displacement of the target body during the measurement. The chemical shift data from the target body at each voxel in an imaging target region on the target body are collected with and without a temperature change of the target body, a difference between the chemical shift data collected with the temperature change and the chemical shift data collected without the temperature change at each voxel, and a temperature distribution image is constructed and displayed according to the difference calculated. The chemical shift data are preferably collected by using a phase mapping imaging sequence.