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INTRODUCTION Multiple cardiac magnetic resonance (CMR)-derived indices of atrial fibrillation (AF) substrate have been shown in isolation to predict long-term outcome following catheter ablation. Left atrial (LA) fibrosis, LA volume, LA ejection fraction (EF), left ventricular ejection fraction (LVEF), LA shape (sphericity) and pulmonary vein anatomy have all been shown to correlate with late AF recurrence. This study aimed to validate and assess the relative contribution of multiple indices in a long-term single-center study. METHODS AND RESULTS Eighty-nine patients (53% paroxysmal AF, 73% male) underwent comprehensive CMR study before first-time AF ablation (median follow-up 726 days [IQR: 418-1010 days]). The 3D late gadolinium-enhanced acquisition (1.5T, 1.3 × 1.3 × 2 mm) was quantified for fibrosis; LA volume and sphericity were assessed on manual segmentation at atrial diastole; LAEF and LVEF were quantified on multislice cine imaging. AF recurred in 43 patients (48%) overall (31 at 1 year). In the recurrence group, LA fibrosis was higher (42% vs 29%; hazard ratio [HR]: 1.032; P = .002), left atrial ejection fraction (LAEF) lower (25% vs 34%; HR: 0.063; P = .016) and LVEF lower (57% vs 63%; HR: 0.011; P = .008). LA volume (135 vs 124 mL) and sphericity (0.819 vs 0.822) were similar. Multivariate Cox regression analysis was adjusted for age and sex (Model 1), additionally AF type (Model 2) and combined (Model 3). In Models 1 and 2, LA fibrosis, LAEF, and LVEF were independently associated with outcome, but only LA fibrosis was independent in Model 3 (HR: 1.021; P = .022). CONCLUSIONS LAEF, LVEF, and LA fibrosis differed significantly in the AF recurrence cohort. However, on combined multivariate analysis only LA fibrosis remained independently associated with outcome.

[Background] Improvements in outcomes for patients with congenital heart disease (CHD) have increased the need for diagnostic and interventional procedures. Cumulative radiation risk is a growing concern. MRI-guided interventions are a promising ionizing radiation-free, alternative approach., [Purpose] To assess the feasibility of MRI-guided catheterization in young patients with CHD using advanced visualization passive tracking techniques., [Study Type] Prospective., [Population] A total of 30 patients with CHD referred for MRI-guided catheterization and pulmonary vascular resistance analysis (median age/weight: 4 years / 15 kg)., [Field Strength/Sequence] 1.5T; partially saturated (pSAT) real-time single-shot balanced steady-state free-precession (bSSFP) sequence., [Assessment] Images were visualized by a single viewer on the scanner console (interactive mode) or using a commercially available advanced visualization platform (iSuite, Philips). Image quality for anatomy and catheter visualization was evaluated by three cardiologists with >5 years' experience in MRI-catheterization using a 1–5 scale (1, poor, 5, excellent). Catheter balloon signal-to-noise ratio (SNR), blood and myocardium SNR, catheter balloon/blood contrast-to-noise ratio (CNR), balloon/myocardium CNR, and blood/myocardium CNR were measured. Procedure findings, feasibility, and adverse events were recorded. A fraction of time in which the catheter was visible was compared between iSuite and the interactive mode., [Statistical Tests] T-test for numerical variables. Wilcoxon signed rank test for categorical variables., [Results] Nine patients had right heart catheterization, 11 had both left and right heart catheterization, and 10 had single ventricle circulation. Nine patients underwent solely MRI-guided catheterization. The mean score for anatomical visualization and contrast between balloon tip and soft tissue was 3.9 ± 0.9 and 4.5 ± 0.7, respectively. iSuite provided a significant improvement in the time during which the balloon was visible in relation to interactive imaging mode (66 ± 17% vs. 46 ± 14%, P, [Data Conclusion] MRI-guided catheterizations were carried out safely and is feasible in children and adults with CHD. The pSAT sequence offered robust and simultaneous high contrast visualization of the catheter and cardiac anatomy.

Clinical evidence suggests a link between fibrosis in the left atrium (LA) and atrial fibrillation (AF), the most common sustained arrhythmia. Image-derived fibrosis is increasingly used for patient stratification and therapy guidance. However, locations of re-entrant drivers (RDs) sustaining AF are unknown and therapy success rates remain suboptimal. This study used image-derived LA models to explore the dynamics of RD stabilization in fibrotic regions and generate maps of RD locations. LA models with patient-specific geometry and fibrosis distribution were derived from late gadolinium enhanced magnetic resonance imaging of 6 AF patients. In each model, RDs were initiated at multiple locations, and their trajectories were tracked and overlaid on the LA fibrosis distributions to identify the most likely regions where the RDs stabilized. The simulations showed that the RD dynamics were strongly influenced by the amount and spatial distribution of fibrosis. In patients with fibrosis burden greater than 25%, RDs anchored to specific locations near large fibrotic patches. In patients with fibrosis burden below 25%, RDs either moved near small fibrotic patches or anchored to anatomical features. The patient-specific maps of RD locations showed that areas that harboured the RDs were much smaller than the entire fibrotic areas, indicating potential targets for ablation therapy. Ablating the predicted locations and connecting them to the existing pulmonary vein ablation lesions was the most effective in-silico ablation strategy., Author summary Atrial fibrillation (AF) is the most common cardiac arrhythmia and a huge healthcare problem, but its mechanisms are incompletely understood, and clinical therapies such as catheter ablation (CA) have poor long-term outcomes. This is due to the empirical nature of the procedure and lack of mechanistic knowledge of optimal ablation sites and strategies in patients whose atria is altered by AF-induced structural remodelling. In this study, we developed 3D atrial models with patient-specific geometry and distribution of fibrosis obtained from AF patient imaging and applied the models to explore the mechanisms of re-entrant drivers (RD) sustaining AF. Moreover, we used the novel mechanistic knowledge to simulate CA based on the model predictions and compared its success with existing clinical CA strategies. We discovered that the RD dynamics were strongly influenced by the spatial distribution of fibrosis, and RDs typically anchored to specific locations near large fibrotic patches. Virtual ablations of such anchoring locations by connecting them with linear lesions to the nearest pulmonary veins (PV) had superior efficacy compared to clinically used strategies such as the PV isolation. After incorporating further patient-specific information and careful validation, the proposed in-silico approach can help evaluate and potentially guide CA therapy in the clinic.

Ventricular volumetric ejection fraction (VV EF) is often normal in patients with single ventricle circulations despite them experiencing symptoms related to circulatory failure. We sought to determine if kinetic energy (KE) could be a better marker of ventricular performance. KE was prospectively quantified using four-dimensional flow MRI in 41 patients with a single ventricle circulation (aged 0.5–28 yr) and compared with 43 healthy volunteers (aged 1.5–62 yr) and 14 patients with left ventricular (LV) dysfunction (aged 28–79 yr). Intraventricular end-diastolic blood was tracked through systole and divided into ejected and residual blood components. Two ejection fraction (EF) metrics were devised based on the KE of the ejected component over the total of both the ejected and residual components using 1) instantaneous peak KE to assess KE EF or 2) summating individual peak particle energy (PE) to assess PE EF. KE EF and PE EF had a smaller range than VV EF in healthy subjects (97.9 ± 0.8 vs. 97.3 ± 0.8 vs. 60.1 ± 5.2%). LV dysfunction caused a fall in KE EF ( P = 0.01) and PE EF ( P = 0.0001). VV EF in healthy LVs and single ventricle hearts was equivalent; however, KE EF and PE EF were lower ( P < 0.001) with a wider range indicating a spectrum of severity. Those reporting the greatest symptomatic impairment (New York Heart Association II) had lower PE EF than asymptomatic subjects ( P = 0.0067). KE metrics are markers of healthy cardiac function. PE EF may be useful in grading dysfunction. NEW & NOTEWORTHY Kinetic energy (KE) represents the useful work of the heart in ejecting blood. This article details the utilization of KE indexes to assess cardiac function in health and a variety of pathophysiological conditions. KE ejection fraction and particle energy ejection fraction (PE EF) showed a narrow range in health and a lower wider range in disease representing a spectrum of severity. PE EF was altered by functional status potentially offering the opportunity to grade dysfunction.

Journal of Cardiovascular Magnetic Resonance, 20, ISSN:1097-6647, ISSN:1532-429X

Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside. CT perfusion imaging is not frequently used but CT offers coronary angiography data, and invasive catheter-based methods can measure coronary flow and pressure. Technical improvements to the quantification of pathophysiological parameters of myocardial ischaemia can be achieved. Clinical consensus recommendations on the appropriateness of each technique were derived following a European quantitative cardiac imaging meeting and using a real-time Delphi process. SPECT using new detectors allows the quantification of myocardial blood flow and is now also suited to patients with a high BMI. PET is well suited to patients with multivessel disease to confirm or exclude balanced ischaemia. MRI allows the evaluation of patients with complex disease who would benefit from imaging of function and fibrosis in addition to perfusion. Echocardiography remains the preferred technique for assessing ischaemia in bedside situations, whereas CT has the greatest value for combined quantification of stenosis and characterization of atherosclerosis in relation to myocardial ischaemia. In patients with a high probability of needing invasive treatment, invasive coronary flow and pressure measurement is well suited to guide treatment decisions. In this Consensus Statement, we summarize the strengths and weaknesses as well as the future technological potential of each imaging modality., Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. In this Consensus Statement, the authors summarize the use of SPECT, PET, MRI, echocardiography, CT and invasive coronary flow and pressure measurement, and describe the relative strengths and weaknesses of each modality.

Catheter Ablation (CA) is an effective strategy for rhythm control in atrial fibrillation (AF) patients. However, success rate remains suboptimal in chronic AF patients, where targets for optimal ablation are unknown. Recent clinical evidence suggests an association of atrial fibrosis with locations of re-entrant drivers (RDs) sustaining AF. However, the knowledge of optimal ablation locations based on patient-specific fibrosis distribution is lacking. The aim of this study is to provide a proof-of-concept method to (1) predict patient-specific ablation targets from 3D models of fibrotic atria and (2) perform virtual ablation.

Background Cardiovascular magnetic resonance (CMR) imaging may be used to visualize post-ablation atrial scar (PAAS), and three-dimensional late gadolinium enhancement (3D LGE) is the most widely employed technique for imaging of chronic scar. Detection of PAAS provides a unique non-invasive insight into the effects of the ablation and may help guide further ablation procedures. However, there is evidence that PAAS is often not detected by CMR, implying a significant sensitivity problem, and imaging parameters vary between leading centres. Therefore, there is a need to establish the optimal imaging parameters to detect PAAS. Methods Forty subjects undergoing their first pulmonary vein isolation procedure for AF had detailed CMR assessment of atrial scar: one scan pre-ablation, and two scans post-ablation at 3 months (separated by 48 h). Each scan session included ECG- and respiratory-navigated 3D LGE acquisition at 10, 20 and 30 min post injection of a gadolinium-based contrast agent (GBCA). The first post-procedural scan was performed on a 1.5 T scanner with standard acquisition parameters, including double dose (0.2 mmol/kg) Gadovist and 4 mm slice thickness. Ten patients subsequently underwent identical scan as controls, and the other 30 underwent imaging with a reduced, single, dose GBCA (n = 10), half slice thickness (n = 10) or on a 3 T scanner (n = 10). Apparent signal-to-noise (aSNR), contrast-to-noise (aCNR) and imaging quality (Likert Scale, 3 independent observers) were assessed. PAAS location and area (%PAAS scar) were assessed following manual segmentation. Atrial shells with standardised %PAAS at each timepoint were then compared to ablation lesion locations to assess quality of scar delineation. Results A total of 271 3D acquisitions (out of maximum 280, 96.7%) were acquired. Likert scale of imaging quality had high interobserver and intraobserver intraclass correlation coefficients (0.89 and 0.96 respectively), and showed lower overall imaging quality on 3 T and at half-slice thickness. aCNR, and quality of scar delineation increased significantly with time. aCNR was higher with reduced, single, dose of GBCA (p = 0.005). Conclusion 3D LGE CMR atrial scar imaging, as assessed qualitatively and quantitatively, improves with time from GBCA administration, with some indices continuing to improve from 20 to 30 min. Imaging should be performed at least 20 min post-GBCA injection, and a single dose of contrast should be considered. Trial registration Trial registry- United Kingdom National Research Ethics Service 08/H0802/68 – 30th September 2008. Electronic supplementary material The online version of this article (10.1186/s12968-018-0449-8) contains supplementary material, which is available to authorized users.

Background: Cardiovascular magnetic resonance (CMR) imaging has been used to visualise post-ablation atrial scar (PAAS), generally employing a three-dimensional (3D) late gadolinium enhancement (LGE) technique. However the reproducibility of PAAS imaging has not been determined. This cross-over study is the first to investigate the reproducibility of the technique, crucial for both future research design and clinical implementation. Methods: Forty subjects undergoing first time ablation for atrial fibrillation (AF) had detailed CMR assessment of PAAS. Following baseline pre-ablation scan, two scans (separated by 48 h) were performed at three months post-ablation. Each scan session included 3D LGE acquisition at 10, 20 and 30 min post administration of gadolinium-based contrast agent (GBCA). Subjects were allocated at second scan post-ablation to identical imaging parameters (‘Repro’, n = 10), 3 T scanner (‘3 T’, n = 10), half-slice thickness (‘Half-slice’, n = 10) or half GBCA dose (‘Half-gad’, n = 10). PAAS was compared to baseline scar and then reproducibility was assessed for two measures of thresholded scar (% left atrial (LA) occupied by PAAS (%LA PAAS) and Pulmonary Vein Encirclement (PVE)), and then four measures of non-thresholded scar (point-by-point assessment of PAAS, four normalisation methods). Thresholded measures of PAAS were evaluated against procedural outcome (AF recurrence). Results: A total of 271 3D acquisitions (out of maximum 280, 96.7%) were acquired. At 20 and 30 min, inter-scan reproducibility was good to excellent (coefficient of variation at 20 min and 30 min: %LA PAAS 0.41 and 0.20; PVE 0.13 and 0.04 respectively for ‘Repro’ group). Changes in imaging parameters, especially reduced GBCA dose, reduced inter-scan reproducibility, but for most measures remained good to excellent (ICC for %LA PAAS 0.454–0.825, PVE 0.618–0.809 at 30 min). For non-thresholded scar, highest reproducibility was observed using blood pool z-score normalisation technique: inter-scan ICC 0.759 (absolute agreement, ‘Repro’ group). There was no significant relationship between indices of PAAS and AF recurrence. Conclusion: PAAS imaging is a reproducible finding. Imaging should be performed at least 20 min post-GBCA injection, and a blood pool z-score should be considered for normalisation of signal intensities. The clinical implications of these findings remain to be established in the absence of a simple correlation with arrhythmia outcome. The research was performed at King’s College London Medical Engineering Centre, funded by the Wellcome Trust and the Engineering and Physical Sciences Research Council (EPSRC). The research was also supported by the National Institute for Health Research (NIHR) Biomedical Research Centre awards to Guy’s and St Thomas’ NHS Foundation Trust in partnership with King’s College London, by the NIHR Healthcare Technology Co-operative for Cardiovascular Disease at Guy’s and St Thomas’ NHS Foundation Trust, and by the Cardiovascular HTC. Work upon the PVE methodology was partially funded by the Spanish Ministry of Economy and Competitiveness (DPI2015-71640-R) and by the “Fundació La Marató de TV3” (no. 20154031).

Introduction Many heart failure patients with dyssynchrony do not reverse remodel (RR) in response to cardiac resynchronization therapy (CRT). The presence of focal and diffuse interstitial myocardial fibrosis may explain this high nonresponse rate. T1 mapping is a new cardiac magnetic resonance imaging (CMR) technique that overcomes the limitations of conventional contrast CMR and provides reliable quantitative assessment of diffuse myocardial fibrosis. The study tested the hypothesis that focal and diffuse fibrosis quantification would correlate with a lack of left ventricular (LV) RR to CRT. Methods and results In a prospective study of 48 consecutive patients (27 ischemic cardiomyopathy, 21 dilated cardiomyopathy) LV scar burdens were quantified (scar core and gray zone using late gadolinium enhancement LGE CMR; interstitial fibrosis using T1 mapping) before CRT implant. LV RR was defined by a ≥ 15% reduction in LV end-systolic volume 6 months postimplant. Twenty-seven (56%) patients were responders with RR. Association between scar quantification and LV RR was assessed using the Poisson regression model. Univariate analysis showed that QRS duration/morphology, scar core, and gray zone volumes expressed as % of LV mass and extracellular volume index (ECV) (a measure of interstitial fibrosis from T1 mapping) to be significant predictors of LV RR. Multivariable-adjusted analyses demonstrated scar core quantification (≥ 13.7% LV mass) to be the only independent predictor of LV RR (prevalence ratio 0.40, P = 0.038). Conclusions Focal scar burden detected by LGE CMR is associated with a poor response to CRT. Diffuse interstitial fibrosis assessment by T1 mapping, however, is not independently predictive of CRT response.

Objectives This study sought to determine the effect of contact force (CF) on atrial lesion size, quality, and transmurality by using a chronic porcine model of radiofrequency ablation. Background CF is a major determinant of ventricular lesion formation, but uncertainty exists regarding the most appropriate CF parameters to safely achieve permanent, transmural lesions in the atria. Methods Intercaval linear ablation (30 W, 42°C, 17 ml/min irrigation) was performed in 8 Gottingen minipigs by using a force-sensing catheter with CF >20 g (high force) or Results Mean CF was 22.6 ± 11.4 g and 7.8 ± 4.0 g in the high and low CF regions. Acute tissue edema was greater with high CF, both caudally (7.0 mm vs. 4.6 mm; p = 0.016) and cranially (6.9 mm vs. 4.6 mm; p = 0.038). There was no difference in chronic lesion size (voltage mapping) or volume (late gadolinium enhancement CMR) between high and low CF regions. There was no difference in scar density (assessed by low-voltage criteria and late gadolinium enhancement signal intensity) or histological transmurality between high and low CF regions. Conclusions Although high CF (>20 g) resulted in more acute tissue edema than low CF (

We have carried out a PET performance evaluation a silicon photo-multiplier (SiPM) based PET scanner designed for fully simultaneous pre-clinical PET/MR studies. The PET scanner has an inner diameter of 20 cm with an LYSO crystal size of 1.3 by 1.3 by 10 mm. The axial PET field of view (FOV) is 30.2 mm. The PET detector modules, which incorporate SiPMs, have been designed to be MR-compatible allowing them to be located directly within a Philips Achieva 3T MR scanner. The spatial resolution of the system measured using a point source in a non-active background, is just under 2.3 mm full width at half maximum (FWHM) in the transaxial direction when single slice rebinning (SSRB) and 2D filtered back-projection (FBP) is used for reconstruction, and 1.3 mm FWHM when resolution modeling is employed. The system sensitivity is 0.6% for a point source at the center of the FOV. The true coincidence count rate shows no sign of saturating at 30 MBq, at which point the randoms fraction is 8.2%, and the scatter fraction for a rat sized object is approximately 23%. Artifact-free images of phantoms have been obtained using FBP and iterative reconstructions. The performance is currently limited because only one of three axial ring positions is populated with detectors, and due to limitations of the first-generation detector readout ASIC used in the system. The performance of the system as described is sufficient for simultaneous PET-MR imaging of rat-sized animals and large organs within the mouse. This is demonstrated with dynamic PET and MR data acquired simultaneously from a mouse injected with a dual-labeled PET/MR probe.

Background— Studies have reported an inverse relationship between late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) signal intensity and left atrial (LA) endocardial voltage after LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage. Methods and Results— Twenty patients who had previous ablation for atrial fibrillation and represented with paroxysmal atrial fibrillation or atrial tachycardia underwent preablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. Three-dimensional CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right pulmonary vein antra and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ≤0.05 mV. There was only a weak inverse correlation between either unipolar ( r =−0.18) or bipolar ( r =−0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions. Conclusions— This study demonstrates that there is only a weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.

Background Cardiac catheterization is a common procedure in patients with congenital heart disease (CHD). Although cardiovascular magnetic resonance imaging (CMR) represents a promising alternative approach to fluoroscopy guidance, simultaneous high contrast visualization of catheter, soft tissue and the blood pool remains challenging. In this study, a novel passive tracking technique is proposed for enhanced positive contrast visualization of gadolinium-filled balloon catheters using partial saturation (pSAT) magnetization preparation. Methods The proposed pSAT sequence uses a single shot acquisition with balanced steady-state free precession (bSSFP) readout preceded by a partial saturation pre-pulse. This technique was initially evaluated in five healthy subjects. The pSAT sequence was compared to conventional bSSFP images acquired with (SAT) and without (Non-SAT) saturation pre-pulse. Signal-to-noise ratio (SNR) of the catheter balloon, blood and myocardium and the corresponding contrast-to-noise ratio (CNR) are reported. Subjective assessment of image suitability for CMR-guidance and ideal pSAT angle was performed by three cardiologists. The feasibility of the pSAT sequence is demonstrated in two adult patients undergoing CMR-guided cardiac catheterization. Results The proposed pSAT approach provided better catheter balloon/blood contrast and catheter balloon/myocardium contrast than conventional Non-SAT sequences. It also resulted in better blood and myocardium SNR than SAT sequences. When averaged over all volunteers, images acquired with a pSAT angle of 20° to 40° enabled simultaneous visualization of the catheter balloon and the cardiovascular anatomy (blood and myocardium) and were found suitable for CMR-guidance in >93% of cases. The pSAT sequence was successfully used in two patients undergoing CMR-guided diagnostic cardiac catheterization. Conclusions The proposed pSAT sequence offers real-time, simultaneous, enhanced contrast visualization of the catheter balloon, soft tissues and blood. This technique provides improved passive tracking capabilities during CMR-guided catheterization in patients. Electronic supplementary material The online version of this article (doi:10.1186/s12968-017-0368-0) contains supplementary material, which is available to authorized users.

Cardiac PET is a versatile imaging technique providing important diagnostic information about ischemic heart diseases. Respiratory and cardiac motion of the heart can strongly impair image quality and therefore diagnostic accuracy of cardiac PET scans. The aim of this study was to investigate a new cardiac PET/MR approach providing respiratory and cardiac motion-compensated MR and PET images in less than 5 min. Methods: Free-breathing 3-dimensional MR data were acquired and retrospectively binned into multiple respiratory and cardiac motion states. Three-dimensional cardiac and respiratory motion fields were obtained with a nonrigid registration algorithm and used in motion-compensated MR and PET reconstructions to improve image quality. The improvement in image quality and diagnostic accuracy of the technique was assessed in simultaneous 18F-FDG PET/MR scans of a canine model of myocardial infarct and was demonstrated in a human subject. Results: MR motion fields were successfully used to compensate for in vivo cardiac motion, leading to improvements in full width at half maximum of the canine myocardium of 13% ± 5%, similar to cardiac gating but with a 90% ± 57% higher contrast-to-noise ratio between myocardium and blood. Motion correction led to an improvement in MR image quality in all subjects, with an increase in sharpness of the canine coronary arteries of 85% ± 72%. A functional assessment showed good agreement with standard MR cine scans with a difference in ejection fraction of 22% ± 3%. MR-based respiratory and cardiac motion information was used to improve the PET image quality of a human in vivo scan. Conclusion: The MR technique presented here provides both diagnostic and motion information that can be used to improve MR and PET image quality. Reliable respiratory and cardiac motion correction could make cardiac PET results more reproducible.

OBJECTIVES: To compare a standard sequential 2D Planning Method (2D-PM) with a 3D offline Planning Method (3D-PM) based on 3D contrast-enhanced magnetic resonance angiography (CE-MRA) in children with congenital heart disease (CHD).DESIGN: In 14 children with complex CHD (mean: 2.6 years, range: 3 months to 7.6 years), axial and coronal cuts were obtained with single slice spin echo sequences to get the final double oblique longitudinal cut of the targeted anatomical structure (2D-PM, n = 31). On a separate workstation, similar maximal intensity projection (MIP) images were generated offline from a 3D CE-MRA. MIP images were localizers for repeated targeted imaging using the previous spin echo sequence (3D-PM). Finally, image coverage, spatial orientation and acquisition time were compared for 2D-PM and 3D-PM.MAIN OUTCOME MEASURES: 2D-PM and 3D-PM images were similar: both perfectly covered the selected anatomic regions and no spatial differences were found (p>0.05). The mean time for creation of the final imaging plane was 241 ± 31 s (2D-PM) compared to 71 ± 18 s (3D-PM) (pCONCLUSIONS: 3D-PM shows similar results compared to 2D-PM, but allows faster and offline planning thereby reducing the scan time significantly. As newly developed high-resolution 3D datasets can also be used further improvement of this technology is expected.

Background— The incidence of abdominal aortic aneurysms (AAAs) has increased during the last decades. However, there is still controversy about the management of medium-sized AAAs. Therefore, novel biomarkers, besides aneurysmal diameter, are needed to assess aortic wall integrity and risk of rupture. Elastin is the key protein for maintaining aortic wall tensile strength and stability. The progressive breakdown of structural proteins, in particular, medial elastin, is responsible for the inability of the aortic wall to withstand intraluminal hemodynamic forces. Here, we evaluate the usefulness of elastin-specific molecular MRI for the in vivo characterization of AAAs. Methods and Results— To induce AAAs, ApoE –/– mice were infused with angiotensin-II. An elastin-specific magnetic resonance molecular imaging agent (ESMA) was administered after 1, 2, 3, and 4 weeks of angiotensin-II infusion to assess elastin composition of the aorta (n=8 per group). The high signal provided by ESMA allowed for imaging with high spatial resolution, resulting in an accurate assessment of ruptured elastic laminae and the compensatory expression of elastic fibers. In vivo contrast-to-noise ratios and R1-relaxation rates after ESMA administration were in good agreement with ex vivo histomorphometry (Elastica van Gieson stain) and gadolinium concentrations determined by inductively coupled plasma mass spectroscopy. Electron microscopy confirmed colocalization of ESMA with elastic fibers. Conclusions— Changes in elastin content could be readily delineated and quantified at different stages of AAAs by elastin-specific molecular magnetic resonance imaging. ESMA-MRI offers potential for the noninvasive detection of the aortic rupture site prior to dilation of the aorta and the subsequent in vivo monitoring of compensatory repair processes during the progression of AAAs.

Left Atrial Scar Formation After Contact Force-Guided AF AblationBackground Catheter contact force (CF) is an important determinant of radiofrequency (RF) lesion quality during pulmonary vein isolation (PVI). Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) allows good visualization of ablation lesions. Objective This study describes a new technique to examine the relationship between CF during RF delivery and LGE signal intensity (SI) following PVI. Methods Six patients underwent PVI for paroxysmal AF using a CF-sensing catheter and following preprocedural MRI. During ablation, CF-time integral (FTI) and position was documented for each RF application. All patients underwent repeat LGE MRI 3 months later. The LGE SIs were projected onto a MRI-derived 3-dimensional left atrial (LA) shell and a CF map was generated on the same shell. The entire LA surface was divided into 5 mm2 segments. Force and LGE maps were fused and compared for each 5 mm2 zone. An effective lesion was defined when MRI-defined scar occupied >90% of a 5 mm2 analysis zone. Results Acute PVI was achieved in 100%. Two hundred sixty-eight RF lesions were tagged on the LA shells and given a lesion-specific FTI. Increasing FTI correlated with increased LGE SI, which was greater when the FTI was > 1,200 gs. Below an FTI of 1,200 gs, an increment in the FTI resulted in only a small increment in scar, whereas above 1,200 gs an increment in the FTI resulted in a large change of scar. Conclusion There is a correlation between FTI and LGE SI in MRI following AF ablation. Real-time FTI maps are feasible and may prevent inadequate lesion formation.

Background— The magnetic resonance longitudinal relaxation time (T 1 ) changes with thrombus age in humans. In this study, we investigate the possible mechanisms that give rise to the T 1 signal in venous thrombi and whether changes in T 1 relaxation time are informative of the susceptibility to lysis. Methods and Results— Venous thrombosis was induced in the vena cava of BALB/C mice, and temporal changes in T 1 relaxation time correlated with thrombus composition. The mean T 1 relaxation time of thrombus was shortest at 7days following thrombus induction and returned to that of blood as the thrombus resolved. T 1 relaxation time was related to thrombus methemoglobin formation and further processing. Studies in inducible nitric oxide synthase ( iNOS −/− )–deficient mice revealed that inducible nitric oxide synthase mediates oxidation of erythrocyte lysis–derived iron to paramagnetic Fe 3+ , which causes thrombus T 1 relaxation time shortening. Studies using chemokine receptor-2–deficient mice ( Ccr2 −/− ) revealed that the return of the T 1 signal to that of blood is regulated by removal of Fe 3+ by macrophages that accumulate in the thrombus during its resolution. Quantification of T 1 relaxation time was a good predictor of successful thrombolysis with a cutoff point of Conclusions— The source of the T 1 signal in the thrombus results from the oxidation of iron (released from the lysis of trapped erythrocytes in the thrombus) to its paramagnetic Fe 3+ form. Quantification of T 1 relaxation time appears to be a good predictor of the success of thrombolysis.

Purpose Thoracic pulse wave velocity (PWV) variation due to modulated trans-mural pressure (TMP) may indicate mechanical properties of the aorta. Our aim was to measure beat-to-beat thoracic PWV and TMP to observe its normal variation during respiratory maneuvers. Methods We validated PWV measurements from a real-time velocity projection MRI scan in a pulsatile phantom. A volunteer study showed inter-scan repeatability of steady-state PWV, and observed PWV variation when performing Mueller and Valsalva maneuvers. Synchronized to the real-time projection velocity data, TMP was measured using a mouth piece and pressure sensor arrangement monitoring the intra-thoracic pressure and a single arterial pressure measurement. Results In the phantom, beat-to-beat PWV derived from real-time projection (5.33 ± 0.32 m s−1) agreed well with experimentally derived PWV using ultrasound probes (5.72 ± 0.50 m s−1). The within-subject PWV variation between scans was 0.28 m s−1. Volunteers' PWVs increased during Mueller maneuver (TMP increase of 14.67 ± 10.69 mmHg) by 32% (P

Background To compare the ventricular response to dobutamine stress between adult patients with chronic pulmonary regurgitation (PR) after repair of tetralogy of Fallot (r-TOF) and healthy volunteers using a staged dobutamine stress MR (DS-MR) protocol. Methods Eighteen r-TOF patients (median age 31.9years, range 16.2–60.1) with severe PR and 10 healthy controls (median age 40.6years, range 23.9–51.8) completed staged DS-MR (baseline, 10 and 20μg/kg/min) with ventricular volumetry and pulmonary flow quantification. Comparative analysis involved 3-way ANOVA, t -test, regression analysis, and coefficient of variance. Results All controls had significant increase of ejection fraction (EF) at each stress level for both ventricles (normal contractile reserve, all p 2 , RV-EF 55±7%, LV-EF 58±6%, PR-fraction 43±15%), low-dose DS-MR at 10μg/kg/min demonstrated normal biventricular contractile reserve as seen in volunteers. On increase from 10 to 20μg/kg/min a subgroup showed worsening ejection fraction (n=8, p Conclusions In r-TOF patients with chronic PR, DS-MR at 10μg/kg/min showed normal biventricular systolic response compared with controls. Increase to 20μg/kg/min provoked abnormal RV-ESV response in some r-TOF patients, suggesting presence of ventricular systolic dysfunction not evident at rest.

ObjectivesThe aim of this study was to examine the value of native and post-contrast T1 relaxation in the differentiation between healthy and diffusely diseased myocardium in 2 model conditions, hypertrophic cardiomyopathy and nonischemic dilated cardiomyopathy.BackgroundT1 mapping has been proposed as potentially valuable in the quantitative assessment of diffuse myocardial fibrosis, but no studies to date have systematically evaluated its role in the differentiation of healthy myocardium from diffuse disease in a clinical setting.MethodsConsecutive subjects undergoing routine clinical cardiac magnetic resonance at King's College London were invited to participate in this study. Groups were based on cardiac magnetic resonance findings and consisted of subjects with known hypertrophic cardiomyopathy (n = 25) and nonischemic dilated cardiomyopathy (n = 27). Thirty normotensive subjects with low pre-test likelihood of cardiomyopathy, not taking any regular medications and with normal cardiac magnetic resonance findings including normal left ventricular mass indexes, served as controls. Single equatorial short-axis slice T1 mapping was performed using a 3-T scanner before and at 10, 20, and 30 minutes after the administration of 0.2 mmol/kg of gadobutrol. T1 values were quantified within the septal myocardium (T1native), and extracellular volume fractions (ECV) were calculated.ResultsT1native was significantly longer in patients with cardiomyopathy compared with control subjects (p < 0.01). Conversely, post-contrast T1 values were significantly shorter in patients with cardiomyopathy at all time points (p < 0.01). ECV was significantly higher in patients with cardiomyopathy compared with controls at all time points (p < 0.01). Multivariate binary logistic regression revealed that T1native could differentiate between healthy and diseased myocardium with sensitivity of 100%, specificity of 96%, and diagnostic accuracy of 98% (area under the curve 0.99; 95% confidence interval: 0.96 to 1.00; p < 0.001), whereas post-contrast T1 values and ECV showed lower discriminatory performance.ConclusionsThis study demonstrates that native and post-contrast T1 values provide indexes with high diagnostic accuracy for the discrimination of normal and diffusely diseased myocardium.

Contains fulltext : 178051.pdf (Publisher’s version ) (Open Access) Background Systemic cancer spread is preceded by the establishment of a permissive microenvironment in the target tissue of metastasis - the premetastatic niche. As crucial players in establishment of the pre-metastatic niche, myeloid derived suppressor cells (MDSC) release S100A8/A9, an exosomal protein that contributes to metastasis, angiogenesis, and immune suppression. We report the application of antibody-based single-photon emission computed tomography (SPECT) for detection of S100A8/A9 in vivo as an imaging marker for pre-metastatic tissue priming. Methods A syngeneic model system for invasive breast cancer with (4T1.2) or without (67NR) the tendency to form lung metastasis was established in BALB/c mice. A SPECT-probe has been generated and tested for visualization of S100A9 release. Tumor-associated changes in numbers and fuction of immune cells in pre-metastatic tissue were evaluated by flow cytometry and confocal microscopy. Results S100A8/A9 imaging reflected MDSC abundance and the establishment of an immunosuppressive environment in pre-metastatic lung tissue (activity 4T1.2 vs. healthy control: 0.95 vs. 0.45 %ID; p

Objectives This study sought to develop an actively tracked cardiac magnetic resonance-guided electrophysiology (CMR-EP) system and perform first-in-human clinical ablation procedures. Background CMR-EP offers high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Implementation of active tracking, where catheter position is continuously transmitted in a manner analogous to electroanatomic mapping (EAM), is crucial for CMR-EP to take the step from theoretical technology to practical clinical tool. Methods The setup integrated a clinical 1.5-T scanner, an EP recording and ablation system, and a real-time image guidance platform with components undergoing ex vivo validation. The full system was assessed using a preclinical study (5 pigs), including mapping and ablation with histological validation. For the clinical study, 10 human subjects with typical atrial flutter (age 62 ± 15 years) underwent MR-guided cavotricuspid isthmus (CTI) ablation. Results The components of the CMR-EP system were safe (magnetically induced torque, radiofrequency heating) and effective in the CMR environment (location precision). Targeted radiofrequency ablation was performed in all animals and 9 (90%) humans. Seven patients had CTI ablation completed using CMR guidance alone; 2 patients required completion under fluoroscopy, with 2 late flutter recurrences. Acute and chronic CMR imaging demonstrated efficacious lesion formation, verified with histology in animals. Anatomic shape of the CTI was an independent predictor of procedural success. Conclusions CMR-EP using active catheter tracking is safe and feasible. The CMR-EP setup provides an effective workflow and has the potential to change the way in which ablation procedures may be performed.

Cardiac and respiratory motion cause image quality degradation in PET imaging, affecting diagnostic accuracy of the images. Whole-body simultaneous PET-MR scanners allow for using motion information estimated from MR images to correct PET data and produce motion-compensated PET images. This article reviews methods that have been proposed to estimate motion from MR images and different techniques to include this information in PET reconstruction, in order to overcome the problem of cardiac and respiratory motion in PET-MR imaging. MR-based motion correction techniques significantly increase lesion detectability and contrast, and also improve accuracy of uptake values in PET images.

Purpose An isolated perfused pig heart model has recently been proposed for the development of novel methods in standard clinical magnetic resonance (MR) scanners. The original set-up required the electrical system to be within the safe part of the MR-room, which introduced significant background noise. The purpose of the current work was to refine the system to overcome this limitation so that all electrical parts are completely outside the scanner room. Methods Four pig hearts were explanted under terminal anaesthesia from large white cross landrace pigs. All hearts underwent cardiovascular magnetic resonance (CMR) scanning in the MR part of a novel combined 3T MR and x-ray fluoroscopy (XMR) suite. CMR scanning included real-time k-t SENSE functional imaging, k-t SENSE accelerated perfusion imaging and late gadolinium enhancement imaging. Interference with image quality was assessed by spurious echo imaging and compared to noise levels acquired while operating the electrical parts within the scanner room. Results Imaging was performed successfully in all hearts. The system proved suitable for isolated heart perfusion in a novel 3T XMR suite. No significant additional noise was introduced into the scanner room by our set-up. Conclusions We have substantially improved a previous version of an isolated perfused pig heart model and made it applicable for MR imaging in a state of the art clinical 3T XMR imaging suite. The use of this system should aid novel CMR sequence development and translation into clinical practice.

In hybrid PET/MR systems, attenuation maps can be derived from MR to correct for attenuation in PET. However, MR-based attenuation correction (AC) in abdominal applications remains challenging (i) because of poor signal from important tissue types in common MR sequences (e.g., cortical bone) and (ii) because of respiratory motion which results in misalignments between the derived attenuation maps and the PET emissions. Furthermore, respiratory motion also leads to motion-blurring artefacts in the final PET reconstructions. In this paper, we compute an MR-based 4D attenuation map including cortical bone by combining an Ultrashort Echo Time (UTE) acquisition with a subject-specific motion model derived from a second near real-time 3D MR image acquisition. This model allows us to create attenuation maps at any respiratory position which are used for AC in the reconstruction of different respiratory resolved PET images. The inverse of the model is used for motion compensation (MC) of these images. We demonstrate our approach on MR data from 5 healthy volunteers including 3 manually inserted artificial lesions. The impact of bone tissue and respiratory motion on AC is investigated in PET simulations (i) by misclassifying bone to soft tissue in the attenuation maps leading to errors of up to 26.0% in mean uptake for lesions close to bone, and (ii) by using a non-moving attenuation map leading to errors of up to 24.2%. The impact of respiratory motion on MC showed errors of up to 50.7% in areas of strong motion if MC was not performed. The results show that the effect of motion has to be considered both for attenuation correction and for motion-compensating PET emissions. This additive effect of motion is larger than the effect of a wrong AC.

Background— Pulmonary vein reconnection after pulmonary vein isolation is common and is usually associated with recurrences of atrial fibrillation. We used cardiac magnetic resonance imaging after radiofrequency ablation to investigate the hypothesis that acute pulmonary vein isolation results from a combination of irreversible and reversible atrial injury. Methods and Results— Delayed enhancement (DE; representing areas of acute tissue injury/necrosis) and T2-weighted (representing tissue water content, including edema) cardiac magnetic resonance scans were performed before, immediately after (acute), and later than 3 months (late) after pulmonary vein isolation in 25 patients with paroxysmal atrial fibrillation undergoing wide-area circumferential ablation. Images were analyzed as pairs of pulmonary veins to quantify the percentage of circumferential antral encirclement composed of DE, T2, and combined DE+T2 signal. Fourteen of 25 patients were atrial fibrillation free at 11-month follow-up (interquartile range, 8–16 months). These patients had higher DE (71±6.0%) and lower T2 signal (72±7.8%) encirclement on the acute scans compared with recurrences (DE, 55±9.1%; T2, 85±6.3%; P Conclusions— The higher T2 signal on acute scans and greater decline in DE on chronic imaging in patients with recurrences suggest that they have more reversible tissue injury, providing a potential mechanism for pulmonary vein reconnection, resulting in arrhythmia recurrence.

To identify which rest phase (systolic or diastolic) is optimum for assessing or measuring cardiac structures in the setting of three-dimensional (3D) whole-heart imaging in congenital heart disease (CHD).The study was approved by the institutional review board; informed consent was obtained. Fifty children (26 male and 24 female patients) underwent 3D dual-phase whole-heart imaging. Cardiac structures were analyzed for contrast-to-noise ratio (CNR) and image quality. Cross-sectional measurements were taken of the aortic arch, right ventricular (RV) outflow tract (RVOT) and pulmonary arteries. Normally distributed variables were compared by using paired t tests, and categorical data were compared by using Wilcoxon signed-rank test.Mean CNR and image quality were significantly (all P.05) greater in systole for the right atrium (CNR, 8.9 vs 7.5; image quality, 438 vs 91), left atrium (CNR, 8.0 vs 5.3; image quality, 1006 vs 29), RV (CNR, 10.6 vs 8.2; image quality, 131 vs 23), LV (CNR, 9.4 vs 7.7; image quality, 125 vs 28), and pulmonary veins (CNR, 6.2 vs 4.9; image quality, 914 vs 32). Conversely, diastolic CNR was significantly higher in the aorta (9.2 vs 8.2; P = .013) and diastolic image quality was higher for the left pulmonary artery (238 vs 62; P = .007), right pulmonary artery (219 vs 35; P.001), and for imaging of an area after an arterial stenosis (164 vs 7; P.001). All aortic arch and RVOT cross-sectional measurements were significantly (P.05) greater in systole (narrowest point of arch, 70 vs 53 mm(2); descending aorta, 71 vs 58 mm(2); transverse arch, 293 vs 275 mm(2); valvar RVOT, 291 vs 268 mm(2); supravalvar RVOT, 337 vs 280 mm(2); prebifurcation RVOT, 329 vs 259 mm(2)).Certain structures in CHD are better imaged in systole and others in diastole, and therefore, the dual-phase approach allows a higher overall success rate. This approach also allows depiction of diameter changes between systole and diastole and is therefore preferable to standard single-phase sequences for the planning of interventional procedures.

Myocardial fibrosis is a common denominator in a wide spectrum of cardiomyopathies; it plays a major role in the pathophysiology of structural remodelling and as a predictor of adverse outcome. Quantification of myocardial fibrosis by invasive biopsy is limited in clinical practice due to the commonly scattered tissue distribution and procedural risks. Late gadolinium enhancement by cardiac magnetic resonance has revolutionized the assessment of ischemic cardiomyopathy by visualization of regional scarring after myocardial infarction. The binary (white-black) principle of contrast development and a requirement for well separated layers of healthy and diseased myocardium is straightforward for clinical decision making in ischemic heart disease, but renders this technique less powerful in conditions where the myocardium is affected diffusely. Recently emerged T1 mapping techniques allow for an individualized quantification of global and regional myocardial signal and are promising tools to separate between healthy and diseased. In this article we review the emerging evidence for T1 mapping techniques and outline the necessary future directions for a successful translational pathway.

Cardiovascular diseases, including arrhythmias and heart failure, are commonly treated with percutaneous procedures guided by X-ray fluoroscopy. The visualization of the targeted structures can be enhanced using preacquired respiratory-resolved anatomic data (dynamic roadmap), which is displayed as an overlay onto X-ray fluoroscopy images. This article demonstrates how dynamic roadmaps using an affine motion model can be obtained from one respiratory-resolved three-dimensional whole-heart acquisition using the previously introduced Radial Phase Encoding-Phase Ordering with Automatic Window Selection method. Respiratory motion in different regions of the heart was analyzed in 10 volunteers, and it was shown that the use of dynamic roadmaps can reduce misalignment errors from more than 10 down to less than 1.5 mm. Furthermore, the results suggest that reliable motion information can be obtained from highly undersampled images due to the advantageous undersampling properties of the radial phase encoding trajectory. Finally, results of a three-dimensional dynamic roadmap obtained from a patient before catheter ablation for atrial fibrillation treatment are presented.

Background False lumen thrombosis after aortic dissection is a major predictor of prognosis. First pass computed tomography (CT) and magnetic resonance (MR) imaging are used routinely, where the image acquisition is timed to the arrival of contrast in the proximal unaffected aorta. Delayed phase imaging is difficult to refine because flow rates in the false lumen are often very slow and highly variable between patients. Blood pool contrast agents bind to albumin and become homogenously distributed in the intravascular circulation, allowing accurate imaging of areas where flow is low. We compared first pass MR and CT with a delayed phase MR acquisition using a blood pool agent to assess whether this more accurately quantified false lumen thrombosis. Methods Patients with medically treated chronic type B aortic dissection and evidence of false lumen thrombosis on previous CT imaging underwent first pass CT, first pass MR, and delayed phase MR with blood pool agent. Absence of false lumen contrast enhancement was quantified to assess the apparent differences in thrombosis. Phase-contrast MR data were also obtained to assess the affect of flow velocity on false lumen contrast enhancement, and direct thrombus MR images were used to confirm the presence of thrombus. Results Twelve patients were recruited. No difference was seen in apparent thrombus volume between first pass CT and first pass MR imaging (146.9 cm 3 [SD, 88.6] vs 187.6 cm 3 [SD, 136.1], P = .1119; R 2 = .67 [95% confidence interval (CI), r = .46-.95], P = .0012). In all patients, the volume of thrombus derived from first pass acquisitions was greater than the volume derived from delayed phase MR imaging with blood pool agent: first pass CT (paired t test, P = .0007; mean difference=83.4 cm 3 [95% CI, 44.1-122.6]) and first pass MR (paired t test, P = .0009; mean difference=124.0 cm 3 [95% CI, 63.2-184.9]). The difference in thrombus volume between first pass and delayed phase MR imaging with blood pool agent correlated significantly with the mean velocity of flow in the false lumen, with lower flow related to a greater difference ( R 2 = .61, P = .0028 [95% CI, r = −.94-−.37]). Direct thrombus MR images were able to correctly discriminate between thrombus and blood and matched the area of contrast absence on delayed phase MR with blood pool agent images. Conclusion First pass techniques to assess false lumen thrombosis in aortic dissection consistently overestimate the apparent thrombus volume by five to six times. This has implications for interpretation of cohort studies and clinical trials that use false lumen thrombosis as an outcome measure. We recommend delayed phase MR imaging with a blood pool agent when accurate assessment of false lumen thrombosis is required.

Item does not contain fulltext PURPOSE: To evaluate the feasibility and accuracy of magnetic resonance (MR) coronary angiography for the detection of coronary artery anomalies in infants and children by using surgical findings as a reference. MATERIALS AND METHODS: The data analysis was approved by the institutional review board. One hundred children with congenital heart disease underwent MR coronary angiography while under general anesthesia (mean age +/- standard deviation, 3.9 years +/- 3; age range, 0.2-11 years). A navigator-gated, T2-prepared, three-dimensional steady-state free precession whole-heart protocol (isotropic voxel size, 1.0-1.3 mm(3); mean imaging time, 4.6 minutes +/- 1.2; mean navigator efficiency, 70%; 3-mm gating window) was used after injection of gadopentetate dimeglumine. The cardiac rest period (end systole or middiastole) and acquisition window were prospectively assessed for each patient. Coronary artery image quality (score of 0 [nondiagnostic] to 4 [excellent]), vessel sharpness, and coronary artery anomalies were assessed by two observers. Surgery was performed in 58 patients, and those findings were used to define accuracy. Variables were assessed between age groups by using either analysis of variance or Kruskal-Wallis tests. RESULTS: Diagnostic image quality (score, >/=1 for all coronary artery segments) was obtained in 46 of the 58 patients (79%) who underwent surgery. The origin and course of the coronary artery anatomy depicted with MR imaging was confirmed at surgery in all 46 patients-including the four (9%) with substantial coronary artery anomalies. Diagnostic-quality images were obtained in 84 of the 100 patients. The rate of success improved significantly when patients were older than 4 months (88% for patients >4 months vs 17% for patients

Purpose To evaluate a cardiac MR (CMR) examination with slow infusion of a high-relaxivity contrast agent to visualize coronary venous anatomy (CVA) and myocardial scar in heart failure patients awaiting cardiac resynchronization therapy (CRT). Materials and Methods Fourteen patients awaiting CRT (seven ischemic cardiomyopathy (ICM) and seven non-ICM) and two with normal LV function underwent CMR on a 1.5 Tesla (T) MR scanner. Dimeglumine-gadobenate was slowly infused. Bolus arrival in the LV was measured by a dynamic electrocardiogram (ECG) -triggered inversion recovery (IR) scan subsequent to starting an ECG-triggered respiratory-navigated three-dimensional (3D) SSFP MR scan with IR preparation to acquire systolic whole-heart anatomy for vein visualization. Delayed contrast-enhanced MR scan was performed to assess myocardial scar. CVA obtained by CMR was compared with X-ray venography in 11 patients. CVA and scar were segmented and registered for visual inspection. Results For all subjects, there was excellent visualization of the CVA. All ICM and one non-ICM patient showed scar. There was excellent correlation between veins seen by CMR and venography. Conclusion We have demonstrated that slow infusion protocol of dimeglumine-gadobenate can be used to assess both CVA and myocardial scar in a single MR examination. Furthermore, an image overlay technique has been used to show the relationship of scar to the CVA. J. Magn. Reson. Imaging 2011;33:87–95. © 2010 Wiley-Liss, Inc.

An MR-electrophysiology (EP) catheter is presented that provides full diagnostic EP functionality and a high level of radiofrequency safety achieved by custom-designed transmission lines. Highly resistive wires transmit intracardiac electrograms and currents for intracardiac pacing. A transformer cable transmits the localization signal of a tip coil. Specific absorption rate simulations and temperature measurements at 1.5 T demonstrate that a wire resistance > 3 kΩ/m limits dielectric heating to a physiologically irrelevant level. Additional wires do not increase tip specific absorption rate significantly, which is important because some clinical catheters require up to 20 electrodes. It is further demonstrated that radiofrequency-induced and pacing-induced resistive heating of the wires is negligible under clinical conditions. The MR-EP catheters provided uncompromised recording of electrograms and cardiac pacing in combination with a standard EP recorder in MR-guided in vivo EP studies, and the tip coil enabled fast and robust catheter localization. In vivo temperature measurements during such a study did not detect any device-related heating, which confirms the high level of safety of the catheter, whereas unacceptable heating was found with a standard EP catheter. The presented concept for the first time enables catheters with full diagnostic EP functionality and active tracking and at the same time a sufficient level of radiofrequency safety for MRI without specific absorption rate-related limitations.

Background: Failure rate for left ventricular (LV) lead implantation in cardiac resynchronization therapy (CRT) is up to 12%. The use of segmentation tools, advanced image registration software, and high-fidelity images from computerized tomography (CT) and cardiac magnetic resonance (CMR) of the coronary sinus (CS) can guide LV lead implantation. We evaluated the feasibility of advanced image registration onto live fluoroscopic images to allow successful LV lead placement. Methods: Twelve patients (11 male, 59 ± 16.8 years) undergoing CRT had three-dimensional (3D) whole-heart imaging (six CT, six CMR). Eight patients had at least one previously failed LV lead implant. Using segmentation software, anatomical models of the cardiac chambers, CS, and its branches were overlaid onto the live fluoroscopy using a prototype version of the Philips EP Navigator software to guide lead implantation. Results: We achieved high-fidelity segmentations of cardiac chambers, coronary vein anatomy, and accurate registration between the 3D anatomical models and the live fluoroscopy in all 12 patients confirmed by balloon occlusion angiography. The CS was cannulated successfully in every patient and in 11, an LV lead was implanted successfully. (One patient had no acceptable lead values due to extensive myocardial scar.) Conclusion: Using overlaid 3D segmentations of the CS and cardiac chambers, it is feasible to guide CRT implantation in real time by fusing advanced imaging and fluoroscopy. This enabled successful CRT in a group of patients with previously failed implants. This technology has the potential to facilitate CRT and improve implant success. (PACE 2011; 34:226–234)

We have designed and constructed an MR-compatible PET system for fully simultaneous PET/MR studies of small animals. The scanner uses long optical fibers to distance the magnetic field sensitive PET PMTs from the high magnetic field at the center of an MR scanner. It is a single slice system with an inner diameter of 7 cm. A full evaluation of the performance of the PET system and the results of an MR compatibility assessment in a Philips Achieva whole body 3 T MRI scanner are presented. The reconstructed resolution of the PET scanner is 1.5 mm at the center falling to 2.5 mm at the edge of the field of view; the system sensitivity is 0.95%; the count rate is linear up to an activity of 6 MBq (~4 kcps) and the scatter fraction is 42% which can be reduced to 26% using MR-compatible gamma shields. Simultaneous PET/MR images of phantoms and a mouse have been acquired. The system is highly MR compatible, as demonstrated here, showing no degradation in performance of either the MR or PET system in the presence of the other modality. The system will be used to demonstrate novel pre-clinical applications of simultaneous PET/MR.

The aim of this work was to investigate fast T (1)-mapping for the characterization of deep vein thrombosis (DVT).The accuracy and reproducibility of the T (1)-mapping sequence was tested in phantoms and in 8 healthy volunteers on a 1.5 T clinical scanner using a 32-channel array coil. Furthermore, the feasibility of the technique was tested in 5 patients diagnosed with DVT by measuring the volume and T (1) values of the thrombus at 5 time points over a period of 6 months.The results of the phantom and volunteer study showed a high accuracy and reproducibility for the quantification of T (1). The resolution of the T (1)-maps was high enough to identify small anatomical structures. T (1) values derived for normal blood and various other tissues were comparable to those reported in the literature. In all patients, the T (1) times of thrombi showed decreased values (T (1) = 843 +/- 91 ms) in the acute phase and recovered back to normal values of blood (T (1) = 1,317 +/- 36 ms) after 6 months.Measurement of all relevant T (1) values of acute thrombi and normal blood achieved accurate and reproducible results in vivo. Fast T (1) quantification of the thrombus can provide information about tissue characteristics such as thrombus resolution. Such a quantitative MRI technique may be valuable in studying the factors that influence natural resolution and in evaluating treatment effects that enhance this process.

Four-dimensional (4D) flow imaging has been used to study flow patterns and pathophysiology, usually focused on specific thoracic vessels and cardiac chambers. Whole-heart 4D flow at high measurement accuracy covering the entire thoracic cardiovascular system would be desirable to simplify and improve hemodynamic assessment. This has been a challenge because compensation of respiratory motion is difficult to achieve, but it is paramount to limit artifacts and improve accuracy. In this work we propose a self-gating technique for respiratory motion-compensation integrated into a whole-heart 4D flow acquisition that overcomes these challenges. Flow components are measured in all three directions for each pixel over the complete cardiac cycle, and 1D volume projections are obtained at certain time intervals for respiratory gating in real time during the acquisition. The technique was tested in 15 volunteers, in which stroke volumes (SVs) in the great arteries showed excellent agreement with standard 2D phase-contrast (PC) scans. In contrast, nongated 4D flow with two averages had substantial disagreement with 2D flow. Applied to patients with congenital cardiac left-to-right shunting, the precision of flux data was highly beneficial. The methodology presented here has the potential to allow a complete study of flow pathophysiology of the thoracic cardiovascular system from a single free-breathing scan.

Delayed contrast-enhanced magnetic resonance imaging (DCE-MRI) provides prognostic information by delineating regions of myocardial scar. The mechanism of this delayed enhancement in myocardial infarctions (MIs) is hypothesized to result from altered kinetics and changes in the volumes of distribution in the myocardium. Pharmacokinetic models with two and three compartments were fitted to the concentration-time curves of dynamic contrast-enhanced MRI data obtained from five patients with known MI. Furthermore, the parameter stability was investigated in simulations for the two different models. The transfer constants and volumes of distribution showed a good correlation with imaging findings on early and delayed contrast-enhanced MRI. The two compartment model showed higher parameter stability. The three compartment model allows a more in-depth quantification of myocardial scarring. These models have the potential to improve the diagnosis of myocardial pathologies involving scar, with differing kinetics and volumes of distribution such as infarction or cardiomyopathy.

Patient-specific preoperative planning in complex congenital heart disease may be greatly facilitated by virtual cardiotomy. Surgeons can perform an unlimited number of surgical incisions on a virtual 3-D reconstruction to evaluate the feasibility of different surgical strategies.To quantitatively evaluate the quality of the underlying imaging data and the accuracy of the corresponding segmentation, and to qualitatively evaluate the feasibility of virtual cardiotomy.A whole-heart MRI sequence was applied in 42 children with congenital heart disease (age 3 +/- 3 years, weight 13 +/- 9 kg, heart rate 96 +/- 21 bpm). Image quality was graded 1-4 (diagnostic image qualityor =2) by two independent blinded observers. In patients with diagnostic image quality the segmentation quality was also graded 1-4 (4 no discrepancies, 1 misleading error).The average image quality score was 2.7 - sufficient for virtual reconstruction in 35 of 38 patients (92%) older than 1 month. Segmentation time was 59 +/- 10 min (average quality score 3.5). Virtual cardiotomy was performed in 19 patients.Accurate virtual reconstructions of patient-specific cardiac anatomy can be produced in less than 1 h from 3-D MRI. The presented work thus introduces a new, clinically feasible noninvasive technique for improved preoperative planning in complex cases of congenital heart disease.

Objectives The aim of this study was to investigate the impact of BMI on late gadolinium enhancement (LGE) of the coronary artery wall in identical monozygous twins discordant for BMI. Coronary LGE represents a useful parameter for the detection and quantification of atherosclerotic coronary vessel wall disease. Methods Thirteen monozygote female twin pairs (n = 26) with significantly different BMIs (>1.6 kg/m2) were recruited out of >10,000 twin pairs (TwinsUK Registry). A coronary 3D-T2prep-TFE MR angiogram and 3D-IR-TFE vessel wall scan were performed prior to and following the administration of 0.2 mmol/kg of Gd-DTPA on a 1.5 T MR scanner. The number of enhancing coronary segments and contrast to noise ratios (CNRs) of the coronary wall were quantified. Results An increase in BMI was associated with an increased number of enhancing coronary segments (5.3 ± 1.5 vs. 3.5 ± 1.6, p

We thank Bisbal et al for their interest in our study and for raising several important questions. First, and importantly, we would like to clarify that pulmonary vein reconnection and conduction across the mitral and roof lines were assessed using electrophysiological techniques and not voltage mapping. We agree that using point-by-point voltage mapping to identify gaps in ablation lesions is unreliable. The number of voltage points is therefore not relevant to our finding that late gadolinium enhancement (LGE) cardiac magnetic resonance was unable to reliably predict sites of electric conduction. However, our study did use voltage mapping to determine the relationship between LGE cardiac magnetic resonance signal intensity and endocardial voltage. The number of points in our study was greater than in 3 previous studies comparing these 2 parameters,1–3 and the weak correlation seen in all 20 patients (including 12 with over 300 points) makes insufficient point density an improbable cause for the negative result. Regarding the image …

Background Atrial fibrillation (AF) is the most common cardiac arrhythmia. It is often treated using catheter ablation, which aims to isolate arrhythmogenic regions by delivering localized energy. Whereas an insufficient energy delivery can lead to AF recurrence, excessive power can cause potentially lethal complications. Knowledge of atrial wall thickness can help select an optimal amount of energy, but clinical imaging does not currently provide atrial wall thickness data for patients. Even ex-vivo studies have only measured the thickness of the atrial wall in discrete locations using CT or post-mortem samples. In this study, we apply black-blood MR imaging to reconstruct both epiand endocardial surfaces of the entire atria and compute wall thickness maps in healthy volunteers. To our knowledge, this is the first study to provide a complete 3D map of the wall thickness of both right and left atria.

Purpose To evaluate the advantages of using an active marker (active micro coil) for MR-guided breast biopsy procedures. Materials and Methods An add-on breast biopsy guidance device used with a standard breast coil was equipped with an active marker. The marker's position was determined with a dedicated MRI sequence. In combination with custom software, the biopsy planning process was reduced basically to defining the target in the diagnostic MR images. Automatic control scans verified the settings of the biopsy guidance device. To measure the targeting accuracy, x-ray control of the needle placement was performed in phantoms containing 36 small titanium cylinders. The reliability of the procedure was evaluated in 24 core needle biopsies on phantoms. Workflow enhancements were analyzed. Results The root mean square deviation of the needle position from the target perpendicular to the needle axis was 1.25 mm, in three-dimensions it was 1.35 mm. All targets were sampled successfully. The duration of a phantom biopsy was nine minutes. Conclusion The use of an active marker can offer advantages for MR-guided breast biopsies in terms of handling and procedure time as well as accuracy. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

The purpose of this study was to test the in vivo feasibility of safe automatic catheter tracking based on an optically detunable resonant marker installed on the catheter tip, and also to test the compatibility of this approach with guidewire materials. The design of the resonant marker and the integration into the real-time MR environment is described. The catheter was used for real-time MR-guided catheterization of the aorta, left ventricle, and carotid in two swine. For in-plane visualization, the marker was repeatedly detuned. For automatic slice tracking, a projection difference measurement including detuning was interleaved with the imaging sequence. In vitro experiments were conducted to investigate the RF-safety of the marker and the effect of the guidewires on the signal intensity. For all orientations the marker provided excellent in vivo contrast using a radial steady-state free-precession sequence. Flashing of the marker by repetitive tuning/detuning further improved the in-plane visualization. Automatic slice tracking during real-time imaging was successfully performed. The plastic guidewires did not interfere with the marker, and detuning by guidewires containing nitinol could be compensated. In conclusion, automatic slice tracking as well as excellent in-plane visualization can be achieved with this approach and it is safe with respect to RF transmission.

Rationale and Objectives. Cardiac and respiratory controlled MR-imaging is the gold standard for imaging of cardiac masses. However, this technique may be limited in patients with dyspnoe or arrhythmia. The aim of this study was the evaluation of an interactive MR-approach for the detection and localization of cardiac masses. Methods. Interactive real-time spiral gradient-echo (spiralGE) and radial steady-state-free-precession (radialSSFP) MR-imaging was performed during free-breathing and without cardiac triggering in 15 patients with 14 intracardiac or paracardiac masses. Standard cardiac triggered segmented k-space breath-hold steady-state-free-precession cine MR-imaging was used as the reference MR-imaging technique. Two groups of investigators blinded to clinical data were ask to rank image quality and to identify cardiac masses on real-time MR-images. Results. Image quality was superior using radialSSFP when compared with spiralGE. Using radialSSFP all masses were correctly detected while 6 of 14 masses were missed on spiralGE. Mean real-time MR-imaging time was less than 3 minutes for both techniques. Conclusion. Interactive real-time radialSSFP MR-imaging allows for accurate and fast detection of cardiac masses without the need of cardiac or respiratory triggering.

Background — Magnetic resonance (MR)–guided coronary artery stent placement is a challenging vascular intervention because of the small size of the coronary arteries combined with incessant motion during the respiratory and cardiac cycles. These obstacles necessitate higher temporal and higher spatial resolution real-time MR imaging techniques when compared with interventional peripheral MR angiography. Methods and Results — A new, ultrafast, real-time MR imaging technique that combines steady-state free precession (SSFP) for high signal-to-noise ratio and radial k-space sampling (rSSFP) for motion artifact suppression was implemented on a 1.5-T clinical whole-body interventional MR scanner. The sliding window reconstruction technique yielded a frame rate of 15/s allowing for data acquisition during free breathing and without cardiac triggering. Eleven balloon-expandable stainless steel coronary stents were placed in both coronary arteries of 7 pigs (40 to 70 kg body weight) using a nitinol guidewire and passive device visualization. Position of the coronary stents was controlled by a navigator-gated free-breathing ECG–triggered three-dimensional SSFP coronary MRA sequence and confirmed visually on the ex vivo heart. The presented real-time MR imaging sequence reliably allowed for high-quality coronary MR fluoroscopy without motion artifacts in all pigs. Ten of 11 coronary stents were correctly placed under MR guidance. One stent dislodged proximally from the left main coronary artery because of too-small balloon size. Stent dislocation was correctly predicted during real-time MR imaging. Conclusion — The presented approach allows for real-time MR-guided coronary artery stent placement in a swine model.

Aortic pulse wave velocity (aPWV), a major prognostic indicator of cardiovascular events, may be augmented in hypertension as a result of the aorta being stretched by a higher distending blood pressure or by a structural change. We used a novel technique to modulate intrathoracic pressure and thus aortic transmural pressure (TMP) to examine the variation of intrathoracic aPWV with TMP in hypertensive (n=20; mean±SD age, 52.1±15.3 years; blood pressure, 159.6±21.2/92.0±15.9 mm Hg) and normotensive (n=20; age, 55.5±11.1 years; blood pressure, 124.5±11.9/72.6±9.1 mm Hg) subjects. aPWV was measured using dual Doppler probes to insonate the right brachiocephalic artery and aorta at the level of the diaphragm. Resting aPWV was greater in hypertensive compared with normotensive subjects (897±50 cm/s versus 784±43 cm/s; P P