Inversion Recovery Gradient Echo Sequence Research Articles

Abstract 17723: Non-Contrast Cardiac Magnetic Resonance BOOST Whole Heart Acquisition to Evaluate Coronaries in Children and Young Adults

Introduction: Cardiac magnetic resonance (CMR) coronary evaluation remains challenging in teenagers and young adults using conventional respiratory navigation strategies due to irregular respiratory patterns. Motion correction strategies have shown promise in improving efficiency and quality. We sought to evaluate a non-contrast 3D whole-heart sequence with bright-blood (BB) and dark-blood (DB) phase sensitive inversion recovery (BOOST) using image-based navigation (iNAV) and a variable-density cartesian spiral profile order trajectory (VD-CASPR). Hypothesis: BOOST acquisitions improves delineation of coronary origins and proximal courses. Methods: Pts undergoing clinically indicated CMRs were prospectively enrolled and scanned at 1.5T (AVANTO FIT, Siemens) using 2 different imaging methods: 1) BOOST research sequence employing either T2 or magnetization transfer preparation at 1.0-1.4 mm isotropic resolution. When clinically indicated, 2) a standard navigated inversion recovery gradient echo sequence (IR-FLASH) acquired after gadolinium or ferumoxytol infusion. Both coronary imaging methods were rated on a 1-4 scale: 1=non-diagnostic, 2=coronary origins with significant image degradation, 3=mild image degradation, and 4=sharp delineation of the proximal coronaries. A composite BOOST score (highest score between BB and DB images) was compared to IR-FLASH. Group comparisons used a paired t-test (two-tailed, p<0.05). Results: 18 pts, mean age 18.8 years (range=10-31) underwent BOOST imaging. 15 had an IR-FLASH for comparison. BOOST acquisition times were 7-12 minutes. Three pts had coronary anomalies (2 with right coronary from the left sinus, 1 single coronary). Coronary origins were delineated on all BOOST exams with a mean score=3.6 for BB BOOST and 2.9 for DB compared to 3.1 for the IR-FLASH, neither of which was significantly different. The composite BOOST mean score was 3.8, which was significantly higher than IR-FLASH. Conclusions: In our series in children and young adults, contrast-free BOOST imaging delineated coronary origins in all pts, even in challenging cases of anomalous origins. When utilizing both BB and DB BOOST images, image quality exceeded that of a conventional post-contrast IR-FLASH sequence.

Optimization of MP2RAGE T1 mapping with radial view-ordering for deep brain stimulation targeting at 7 T MRI

PurposeDeep brain stimulation (DBS) is an effective treatment of various neurological disorders. Due to higher intrinsic signal, 7 T MRI can potentially improve delineation of DBS targets. However, the severe RF transmit field (B1+) inhomogeneity at 7 T can compromise the image contrast of traditional single-contrast sequences for DBS targeting, leading to sub-optimal target visualization. The Magnetization Prepared 2 Rapid Acquisition Gradient Echo (MP2RAGE)-based T1 mapping provides an alternative to the traditional single-contrast techniques by allowing retrospective synthesis of images at arbitrary inversion times to aid in visualization of various DBS targets. With this approach, optimization of sequence parameters to create T1 maps with low noise and low quantification bias is critical, as these characteristics directly affect the noise and uniformity of the synthetic images. In this work, we perform sequence optimization for MP2RAGE-based T1 mapping using a radial view-ordering technique to improve image quality, and demonstrate the clinical utility of T1 mapping approach for DBS targeting. MethodsWe first introduce a systematic sequence optimization framework for 7 T MP2RAGE T1 mapping by formulating it into a constrained, multi-dimensional optimization process considering the effect of B1+ inhomogeneity on image noise, T1 quantification bias, and image blurring. With this framework, we investigate the use of radial view-order approach for T1 mapping, in lieu of the conventional linear view-ordering. Bloch's equation-based simulations were performed to compare the T1 maps generated using different approaches. Images of healthy volunteer and patients were acquired on a clinical 7 T MRI scanner for validation and to demonstrate the utility of T1 mapping for DBS targeting. ResultsNumerical experiments demonstrated that the proposed framework allowed optimization of image SNR in T1 maps while controlling the quantification bias and image blurring, therefore facilitating the selection of optimal sequence parameters for visualizing DBS targets. The optimized sequence using radial view-ordering offered 40–60% noise reduction compared to the linear view-ordering. The improvement of SNR was confirmed in the in vivo examples. Clinical images showed that the synthetic images generated from the optimized T1 maps allowed clear visualization of DBS targets. ConclusionWe demonstrated the optimization of MP2RAGE T1 mapping with radial view-ordering technique for DBS targeting at 7 T and showed that the optimized sequence allows retrospective generation of synthetic inversion time images commonly utilized in DBS targeting, such as fast gray matter acquisition T1 inversion recovery (FGATIR) and edge-enhancing gradient echo (EDGE) sequences.

Joint Cardiac T1 Mapping and Cardiac Cine Using Manifold Modeling

The main focus of this work is to introduce a single free-breathing and ungated imaging protocol to jointly estimate cardiac function and myocardial T1 maps. We reconstruct a time series of images corresponding to k-space data from a free-breathing and ungated inversion recovery gradient echo sequence using a manifold algorithm. We model each image in the time series as a non-linear function of three variables: cardiac and respiratory phases and inversion time. The non-linear function is realized using a convolutional neural networks (CNN) generator, while the CNN parameters, as well as the phase information, are estimated from the measured k-t space data. We use a dense conditional auto-encoder to estimate the cardiac and respiratory phases from the central multi-channel k-space samples acquired at each frame. The latent vectors of the auto-encoder are constrained to be bandlimited functions with appropriate frequency bands, which enables the disentanglement of the latent vectors into cardiac and respiratory phases, even when the data are acquired with intermittent inversion pulses. Once the phases are estimated, we pose the image recovery as the learning of the parameters of the CNN generator from the measured k-t space data. The learned CNN generator is used to generate synthetic data on demand by feeding it with appropriate latent vectors. The proposed approach capitalizes on the synergies between cine MRI and T1 mapping to reduce the scan time and improve patient comfort. The framework also enables the generation of synthetic breath-held cine movies with different inversion contrasts, which improves the visualization of the myocardium. In addition, the approach also enables the estimation of the T1 maps with specific phases, which is challenging with breath-held approaches.

Myocardial late gadolinium enhancement using delayed 3D IR-FLASH in the pediatric population: feasibility and diagnostic performance compared to single-shot PSIR-bSSFP

BackgroundThis study compares three-dimensional (3D) high-resolution (HR) late gadolinium enhancement (LGE; 3D HR-LGE) imaging using a respiratory navigated, electrocardiographically-gated inversion recovery gradient echo sequence with conventional LGE imaging using a single-shot phase-sensitive inversion recovery (PSIR) balanced steady-state free precession (bSSFP; PSIR-bSSFP) sequence for routine clinical use in the pediatric population. MethodsPediatric patients (0–18 years) who underwent clinical cardiovascular magnetic resonance (CMR) with both 3D HR-LGE and single-shot PSIR-bSSFP LGE between January 2018 and June 2020 were included. Image quality (0–4) and detection of LGE in the left ventricle (LV) (per 17 segments), in the right ventricle (RV) (per 3 segments), as endocardial fibroelastosis (EFE), at the hinge points, and at the papillary muscles was analyzed by two blinded readers for each sequence. Ratios of the mean signal intensity of LGE to normal myocardium (LGE:Myo) and to LV blood pool (LGE:Blood) were recorded. Data is presented as median (1st–3rd quartiles). Wilcoxon signed rank test and chi-square analyses were used as appropriate. Inter-rater agreement was analyzed using weighted κ-statistics. Results102 patients were included with median age at CMR of 8 (1–13) years-old and 44% of exams performed under general anesthesia. LGE was detected in 55% of cases. 3D HR LGE compared to single-shot PSIR-bSSFP had longer scan time [4:30 (3:35–5:34) vs 1:11 (0:47–1:32) minutes, p < 0.001], higher image quality ratings [3 (3–4) vs 2 (2–3), p < 0.001], higher LGE:Myo [23.7 (16.9–31.2) vs 5.0 (2.9–9.0), p < 0.001], detected more segments of LGE in both the LV [4 (2–8) vs 3 (1–7), p = 0.045] and RV [1 (1–1) vs 1 (0–1), p < 0.001], and also detected more cases of LGE with 13/56 (23%) of patients with LGE only detectable by 3D HR LGE (p < 0.001). 3D HR LGE specifically detected a greater proportion of RV LGE (27/27 vs 17/27, p < 0.001), EFE (11/11 vs 5/11, p = 0.004), and papillary muscle LGE (14/15 vs 4/15, p < 0.001). Inter-rater agreement for the recorded variables ranged from 0.42 to 1.00. Conclusions3D HR LGE achieves greater image quality and detects more LGE than conventional single-shot PSIR-bSSFP LGE imaging, and should be considered an alternative to conventional LGE sequences for routine clinical use in the pediatric population.

Developing a medical device-grade T2 phantom optimized for myocardial T2 mapping by cardiovascular magnetic resonance

IntroductionA long T2 relaxation time can reflect oedema, and myocardial inflammation when combined with increased plasma troponin levels. Cardiovascular magnetic resonance (CMR) T2 mapping therefore has potential to provide a key diagnostic and prognostic biomarkers. However, T2 varies by scanner, software, and sequence, highlighting the need for standardization and for a quality assurance system for T2 mapping in CMR. AimTo fabricate and assess a phantom dedicated to the quality assurance of T2 mapping in CMR. MethodA T2 mapping phantom was manufactured to contain 9 T1 and T2 (T1|T2) tubes to mimic clinically relevant native and post-contrast T2 in myocardium across the health to inflammation spectrum (i.e., 43–74 ms) and across both field strengths (1.5 and 3 T). We evaluated the phantom's structural integrity, B0 and B1 uniformity using field maps, and temperature dependence. Baseline reference T1|T2 were measured using inversion recovery gradient echo and single-echo spin echo (SE) sequences respectively, both with long repetition times (10 s). Long-term reproducibility of T1|T2 was determined by repeated T1|T2 mapping of the phantom at baseline and at 12 months. ResultsThe phantom embodies 9 internal agarose-containing T1|T2 tubes doped with nickel di-chloride (NiCl2) as the paramagnetic relaxation modifier to cover the clinically relevant spectrum of myocardial T2. The tubes are surrounded by an agarose-gel matrix which is doped with NiCl2 and packed with high-density polyethylene (HDPE) beads. All tubes at both field strengths, showed measurement errors up to ≤ 7.2 ms [< 14.7%] for estimated T2 by balanced steady-state free precession T2 mapping compared to reference SE T2 with the exception of the post-contrast tube of ultra-low T1 where the deviance was up to 16 ms [40.0%]. At 12 months, the phantom remained free of air bubbles, susceptibility, and off-resonance artifacts. The inclusion of HDPE beads effectively flattened the B0 and B1 magnetic fields in the imaged slice. Independent temperature dependency experiments over the 13–38 °C range confirmed the greater stability of shorter vs longer T1|T2 tubes. Excellent long-term (12-month) reproducibility of measured T1|T2 was demonstrated across both field strengths (all coefficients of variation < 1.38%). ConclusionThe T2 mapping phantom demonstrates excellent structural integrity, B0 and B1 uniformity, and reproducibility of its internal tube T1|T2 out to 1 year. This device may now be mass-produced to support the quality assurance of T2 mapping in CMR.

Prognostic value of pulmonary transit time by cardiac magnetic resonance in patients with heart failure with preserved ejection fraction

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): National Institute for Health Research Leicester Cardiovascular Biomedical Research Centre Background Quantifying pulmonary transit time (PTT) from cardiac magnetic resonance (CMR) first pass perfusion imaging is a novel technique for the evaluation of haemodynamic congestion in heart failure. Previous studies have demonstrated that PTT is prolonged in patients with heart failure with reduced ejection fraction (HFrEF) and that it provides independent prognostic information in this patient group. However, the potential diagnostic and prognostic roles of PTT assessment in patients with heart failure with preserved ejection fraction (HFpEF) remain to be established. Aim To compare PTT in healthy controls and in patients with HFpEF, and to determine the prognostic value of PTT in HFpEF. Methods In a prospective, observational study, HFpEF and age-matched control subjects underwent multi-parametric CMR at 3-Tesla, comprising quantitative left ventricular volumetric assessment using a standard steady-state free precession (SSFP) pulse sequence, and first-pass perfusion imaging at rest using a T1-weighted segmented inversion recovery gradient echo sequence (following injection of 0.04mmol/kg of contrast). PTT was calculated as the time interval between the peaks of signal intensity curves in the right and left ventricular blood pools (defined on the basal slice of the rest perfusion images). The primary endpoint was the composite of death or hospitalisation with heart failure. Results 88 HFpEF patients (age 73 ± 9 years, 51% male, EF 56.4 ± 5.6%) and 40 controls (age 73 ± 5 years, 43% male, EF 58.5 ± 4.7%) were studied. PTT was comparable in HFpEF patients (7.7 ± 3.8s) and in healthy controls (7.5 ± 1.8, p = 0.69). Normalised to cardiac cycle lengths, PTT remained comparable in HFpEF patients and healthy controls (8.5 ± 4.0 cardiac cycles versus 7.8 ± 1.6 cardiac cycles, respectively, p = 0.19). In the HFpEF group, during median follow-up of 3.4 years, there were 38 events (25 hospitalisations with heart failure, 13 deaths); a significant relationship between survival and PTT was not demonstrated (HR 1.06 [0.99,1.14] for a one-unit increase, p = 0.098). Conclusion In HFpEF, PTT is not prolonged compared with PTT in healthy subjects. Unlike in HFrEF, PTT does not appear to be diagnostically or prognostically significant in HFpEF. Figure 1: Graph showing signal intensity curves in the right (red) and left (green) ventricular blood pools Figure 2: Kaplan-Meier plot showing comparable rates of the composite endpoint in patients with PTT greater/less than median PTT (8 cardiac cycles)

MRI Features of Solitary Vertebral Masses in Dogs: 20 Cases (2010-2019).

The objective of the study was to describe the MRI features of cytologically or histologically diagnosed solitary vertebral masses in dogs and identify potential MRI features enabling differentiation between malignant and benign lesions. Patients were divided into malignant and benign groups according to the final diagnosis. Medical records and MRI studies were retrospectively reviewed, and specific imaging features were compared. The malignant group comprised 15 dogs, with 5 dogs included in the benign group. MRI features of the different histopathologic/cytologic types of masses are described. Involvement of the vertebral body, a hyperintense signal on T2-weighted, short tau inversion recovery, T1-weighted, and T1-weighted gradient echo sequences and evidence of cortical destruction were signifi-cantly associated with malignancy (P < .05). Hypointensity on T1-weighted gradient echo sequence was significantly associated with benign masses (P < .05). The presence of bone sclerosis was significantly associated with osteosarcomas compared with other malignant masses (P < .05). Fractures (5 cases) were only seen in the group of malignant masses. This pilot study identifies some MRI features that may help differentiate between malignant and benign solitary vertebral masses. Greater case numbers are needed in future studies.

Quantitative MRI in patients with gluteal tendinopathy and asymptomatic volunteers: initial results on T1- and T2*-mapping diagnostic accuracy and correlation with clinical assessment.

To determine if T1- and T2*-mapping of the gluteal tendons can discriminate between participants with and without clinical findings of gluteal tendinopathy (GT) and if they correlate with clinical assessment. This prospective study was conducted between January and December 2016. MRI of the hip included spin echo, short-T1 inversion recovery, variable-flip angle, and variable echo-time gradient echo sequences. MRI studies were reviewed independently by two radiologists. Two other readers segmented the gluteal tendons and T1, mono- (T2*m) and bi-exponential T2* (short (T2*s) and long (T2*l) components) were computed. Ten participants with GT (median age; interquartile range: 63 (57-67) years, all women) and 9 participants without GT (57 (55-59) years, 8 women) (P = 0.06) were enrolled. The sensitivity and specificity of reader 1 for disease classification were 40% (95% confidence interval (CI): 17-61%) and 70% (CI: 47-91%), and those of reader 2 were 70% (CI: 43-86%) and 80% (CI: 53-96%), with fair inter-reader agreement (Kappa = .38). T1 values could not discriminate between the two groups. The gluteal tendons T2*m and T2*s showed diagnostic accuracy ranging from .80 to .89. The posterior gluteus medius tendon T2*m and T2*s respectively showed sensitivity and specificity of 90%, and strong correlation (Spearman's rho = -.71; P = 0.02) with the Lower Extremity Functional Scale score. Quantitative MRI could help gain new insight into healthy and diseased gluteal tendons to allow better diagnosis and treatment stratification for patients.

Non-invasive assessment of placental perfusion in vivo using arterial spin labeling (ASL) MRI: A preclinical study in rats

IntroductionNon-invasive assessment of placental perfusion is of great interest to characterize placental function in clinical practice. This article proposes a strictly non-invasive MRI technique using ASL to quantify placental blood flow in vivo. The aim of this study was to develop a fMRI tool to quantify placental blood flow (PBF) in rat, by using arterial spin labeling (ASL) MRI at 4.7 T. Materials and methodsMRI was performed with a dedicated magnet for small animals, in pregnant rats on day 20 of the 22-day gestation period. A Look-Locker flow-sensitive alternating inversion recovery gradient echo sequence was developed as ASL technique (TE: 1.55 ms; TR: 3.5 ms, TI: 56 ms, deltaTI: 56 ms, FA: 20°, Matrix: 128 × 128, 8 segments, 4 Nex). Labeling was performed with global and slice-selective inversions, and T1 map was obtained for each mode of inversion. PBF was then derived from a compartmental model of the variation of T1 between global and slice-selective inversions. ResultsThe full protocol was completed and ASL image post-processing was successful in 18 rats. Forty-seven placentas were analyzed, with a mean PBF of 147 ± 70 ml/min/100 g of placenta, consistent with published values of placental perfusion using invasive techniques. ConclusionASL MRI is feasible for the quantification of PBF in rats at 4.7 T. This technique, which requires no administration of contrast media, could have implications for non-invasive longitudinal and in vivo animal studies and may be useful for the management of human pregnancies.

Cirrhosis-associated liver nodules in Egyptian patients: correlation of histopathologic and MRI with diffusion findings

Aim This study aimed to examine the role of enhanced MRI combined with diffusion in the characterization of cirrhotic nodules, to differentiate benign cirrhotic nodules from premalignant and malignant ones, and to determine treatment planning and management.Patients and methods Precontrast T1, T2, T2-Spectral Attenuated Inversion Recovery, in-phase and out-phase gradient echo sequence, dynamic contrast-enhanced, and diffusion-weighted MRI, b values (0, 500, 1000 s/mm) were obtained in 40 patients with cirrhotic liver (total of 58 focal nodules). The morphological features of each lesion were recorded: size, shape, margin, signal, pattern of contrast enhancement, number, and site of focal lesions in the diffusion images with apparent diffusion coefficient values.Results Lesions were divided according to MR diagnosis and divided histopathologically into four groups: group A: malignant, group B: premalignant (dysplastic), group C: regeneration, and group D: siderotic nodules. Histopathologically, they were divided into 26 hepatocellular carcinoma, nine low-grade dysplastic, nine high-grade dysplastic, 12 regeneration, and two siderotic nodules. The accuracy of MRI was 93%, the sensitivity was 100%, and the specificity was 70% in this study.Conclusion Contrast-enhanced MRI with diffusion-weighted imaging is sensitive for early detection of malignant neoplastic hepatic lesions, and for differentiation between premalignant and malignant lesions.

Optimal Imaging Method for Late Gadolinium-enhanced Cardiovascular Magnetic Resonance in Arrhythmic Cases

We determined the procedure to reduce arrhythmia-related ghosting artifacts in the late gadolinium enhancement (LGE) imaging of cardiovascular magnetic resonance (CMR) in patients with arrhythmia by examining the causing factors using phantoms. Inversion recovery gradient echo and phase-sensitive inversion recovery (PSIR) sequences were compared under normal sinus rhythm and premature ventricular contraction (PVC) conditions. Under the PVC condition, trigger interval irregularly performed induced ghosting artifacts. A phase-corrected real image in PSIR, however; demonstrated an accurately positive contrast of pale LGE area indicative of mild fibrosis with minimal ghosting artifacts. The study results indicate that PSIR has an advantage for LGE CMR in patients with arrhythmia. Even without having PSIR method, the 2R-R method ensures consistency of contrast and enables reduction of ghost artifacts.

Diffuse myocardial fibrosis in adolescents operated with arterial switch for transposition of the great arteries - A CMR study

Diffuse myocardial fibrosis in adolescents operated with arterial switch for transposition of the great arteries - A CMR study

Abstract WP120: Measuring Carotid Stenosis With a Novel Non-contrast Enhanced MR Angiography Technique (SNAP): Comparison With Contrast-enhanced MR Angiography

Introduction: Contrast-enhanced MR angiography (CE-MRA) provides highly accurate measurement of carotid stenosis. But non-contrast techniques are desired as contrast agents may lead to anaphylaxis or nephrogenic system fibrosis. Recently, an inversion-recovery gradient echo sequence with phase-sensitive reconstruction was developed for assessment of lumen and intraplaque hemorrhage in one sequence - Simultaneous Noncontrast Angiography and intraPlaque hemorrhage (SNAP). Hypothesis: We tested the hypothesis that SNAP provides an accurate and reproducible assessment of carotid stenosis compared to CE-MRA. Methods: Fifty-eight subjects with 16-79% stenosis on ultrasound were scanned using a large-coverage (16 cm), isotropic-resolution (0.8 mm) SNAP sequence. Minimum intensity projections were generated at ten degrees increments to get 3D views of carotid arteries. Carotid stenosis was measured bilaterally according to the NASCET criteria by independent readers to estimate inter-reader reproducibility. To assess agreement between SNAP and CE-MRA, 24 subjects also underwent CE-MRA with same resolution (0.8 mm isotropic) after injection of gadolinium contrast (Magnevist). Maximum intensity projections were generated for CE-MRA and analyzed while blinded to SNAP data. Results: Of 116 carotid arteries imaged by SNAP, 10 (8.6%) were excluded by at least one reader due to poor image quality or insufficient coverage. Inter-reader reproducibility was high, yielding an intra-class correlation coefficient (ICC) of 0.95 (95% CI: 0.93, 0.96). When stenosis measurements were categorized as no/mild (0-29%), moderate (30-69%) and severe (70-99%), weighted kappa was 0.77 (95% CI: 0.66, 0.88). In the 48 arteries with CE-MRA images, agreement between SNAP and CE-MRA was excellent (ICC: 0.96, 95% CI: 0.92, 0.98; weighted kappa: 0.90, 95% CI: 0.79, 1.00). Conclusions: SNAP can be used to obtain accurate and reproducible measurement of extracranial carotid artery stenosis without gadolinium contrast. The ability of SNAP to assess both traditional (stenosis) and emerging (intraplaque hemorrhage) risk factors may promote its use in clinical workup of carotid stenosis.

Prognostic value of myocardial T2 mapping post reperfused acute myocardial infarction

Methods Fifty-four patients were enrolled post primary percutaneous coronary intervention (PCI) and underwent CMR on a 1.5T scanner at 48 hours. Myocardial edema was quantified using a T2 mapping technique, while infarct size was assessed via a contrast-enhanced T1-weighted inversion recovery gradient-echo sequence. Information regarding four clinical outcomes: a) mortality, b) repeat myocardial infarction, c) heart failure hospitalization and d) repeat revascularization was collected at 12 months post index primary PCI. Our primary clinical endpoint was a composite of these 4 outcome measures of major adverse cardiovascular events (MACE). The Cox proportional hazards regression model was used to calculate the relative risk of MACE for increased T2 values, adjusted for baseline characteristics related to increased edema (diabetes status, symptom to balloon time, infarct size). Results The mean age was 59.6 ± 8.2 years, 88% were males, 35% were diabetics, 44% were hypertensive. The mean symptom to balloon time was 395 ± 230 minutes and mean door to balloon time was 81.5 ± 39 minutes. The mean T2 value was higher in the infarct segment compared to remote segment (55.1 ± 7.6 ms vs 40.2 ± 2.6 ms, p<0.001). Patients with MACE (n=12) had higher infarct segment T2 values compared to patients that did not (64.4 ± 7.3 ms vs 51.1 ± 5.8 ms, p<0.001). After adjustment for variables associated with increased edema, a T2 value of ≥ 62 ms was associated with a hazard ratio of 1.04 (95% CI:1.01-1.07, p=0.009) for MACE at 12 months (Table 1). Conclusions In reperfused STEMI patients, higher T2 values in the infarct segment are associated with worse prognosis. This suggests the need to develop therapies aimed at reducing myocardial edema post acute myocardial infarction.

Comparison of acquisition time and dose for late gadolinium enhancement imaging at 3.0 T in patients with chronic myocardial infarction using Gd-BOPTA

To compare contrast doses and acquisition times for late gadolinium enhancement (LGE) imaging at 3.0 T using gadobenate dimeglumine (Gd-BOPTA) in patients with chronic myocardial infarction. Thirty-four patients with chronic myocardial infarction were randomised to 0.10, 0.15 and 0.20 mmol/kg of Gd-BOPTA. T1-weighted inversion recovery gradient echo sequences were performed at 5, 10, 15 and 20 min post-administration of contrast in a 3.0-T scanner. Scar-to-myocardium contrast-to-noise ratio (CNR), scar-to-blood CNR, scar size and image quality were assessed. Imaging at 5 min was associated with a lower scar-to-blood CNR in comparison to 10, 15 and 20 min at 0.10 mmol/kg, and in comparison to 15 and 20 min at 0.20 mmol/kg. At 0.10-mmol/kg, imaging at 5 min yielded smaller infarct sizes in comparison to 15 and 20 min. Finally, at 0.20-mmol/kg, imaging at 5 min was associated with poorer image quality in comparison to later times. In LGE imaging at 3.0 T, low doses of Gd-BOPTA perform equally well as higher doses. Early acquisition (5 min) is associated with lower infarct sizes and image quality. Studies with sufficient diagnostic quality can be obtained after 10 min using 0.10 mmol/kg Gd-BOPTA. Good performance of low Gd-BOPTA doses for LGE imaging at 3.0 T. Imaging at 5 min yields lower contrast, infarct sizes and image quality. Diagnostic quality can be obtained after 10 min using 0.10-mmol/kg Gd-BOPTA.

CMR-Guided Approach to Localize and Ablate Gaps in Repeat AF Ablation Procedure

ObjectivesThe aim of this study was to test the feasibility and usefulness of a new delayed-enhancement cardiac magnetic resonance (DE-CMR)–guided approach to ablate gaps in redo procedures. BackgroundRecurrences of atrial fibrillation (AF) after pulmonary vein isolation (PVI) may be related to gaps at the ablation lines. DE-CMR allows identification of radiofrequency lesions and gaps (CMR gaps). MethodsFifteen patients undergoing repeated AF ablations were included (prior procedure was PVI in all patients and roof-line ablation in 8 patients). Pre-procedure 3-dimensional (3D) DE-CMR was performed with a respiratory-navigated (free-breathing) and electrocardiographically gated inversion-recovery gradient-echo sequence (voxel size 1.25 × 1.25 × 2.5 mm). Endocardium and epicardium were manually segmented to create a 3D reconstruction (DE-CMR model). A pixel signal intensity map was projected on the DE-CMR model and color-coded (thresholds 40 ± 5% and 60 ± 5% of maximum intensity). The DE-CMR model was imported into the navigation system to guide the ablation of CMR gaps, with the operator blinded to electrical data. Fifteen conventional procedures were used as controls to compare procedural duration, radiofrequency, and fluoroscopy times. ResultsFifteen patients (56 pulmonary veins [PVs]; 57 ± 8 years of age; 9 with paroxysmal AF) were analyzed. In total, 67 CMR gaps were identified around PVs (mean 4.47 gaps/patient; median length 13.33 mm/gap) and 9 at roof line. All of the electrically reconnected PVs (87.5%) had CMR gaps. The site of electrical PV reconnection (assessed by circular mapping catheter) matched with a CMR gap in 79% of PVs. CMR-guided ablation led to reisolation of 95.6% of reconnected PVs (median radiofrequency time of 13.3 [interquartile range: 7.5 to 21.7] min/patient) and conduction block through the roof line in all patients (1.4 [interquartile range: 0.7 to 3.1] min/patient). Compared with controls, the CMR-guided approach shortened radiofrequency time (1,441 ± 915 s vs. 930 ± 662 s; p = 0.026) but not the procedural duration or fluoroscopy time. ConclusionsDE-CMR can successfully guide repeated PVI procedures by accurately identifying and localizing gaps and may reduce procedural duration and radiofrequency application time.

Detection of left atrial scar and changes of cardiac function in relation to AF ablation, by 3D late gadolinium enhancement

Background Atrial Fibrillation (AF) is the most common arrhythmia in clinical practice; cathete ra blation (AFCA) is aw idespread treatment. Determinants of AFCA success and post-AFCA left atrial remodeling are poorly understood. Delayed Enhancement Cardiac Magnetic Resonance (DE-CMR) has been used to image LA scar post-AFCA and its relation to ablation outcome. Here we explored the role of postablation LA scar in subsequent cardiac remodeling. Methods We correlated post AFCA scar with cardiac volumes and function including LA volume, LV ejection fraction (LVEF), and LV cardiac output (LVCO). In a retrospective analysis, we identified 46 patients who underwent AFCA -pulmonary vein antral isolation in whom DE-CMR was obtained before and after AFCA (174 ± 160 days postablation). In 20 patients, a repeat AFCA procedure was performed due to recurrent AF. DE-CMR procedure was performed utilizing a navigated 3D inversion recovery gradient echo sequence (Siemens 1.5T Avanto or 3.0T Verio) approximately 15 minutes after administration of 0.2 mmol/kg Gadolinium (Magnevist). Scans were ECG-gated and acquired during a 150 ms window in mid-diastole with navigator-gating and fat suppression. We have developed an image analysis method and graphical user interface (GUI) to semi-automatically quantify hyperenhanced regions (scar) in the entire LA wall. Scar was quantified semi-automatically as fraction of LA contour in every slice from base to roof. STATA/IC 13.0 was used for statistical analysis. Two-way Interclass Correlation (ICC) for rater agreement was tested for LA perimeter and LA scar detection between two independent readers for 40 MRI slices. Variable normality was assessed with the Shapiro-Wilk test. The Wilcoxon signed-rank test was used to determine statistical significance between non-parametric variables in pre and post AFCA. Results ICC indicates similarity between observers in both LA Perimeter (ICC: 0.785, CI: 0.59-0.886, p < 0.05) and LA Scar (ICC: 0.609, CI: -0.14-0.844, p < 0.05). The extent of LA Scar was higher in postablation (Median: 8.62, IQR: 5.43-16.4) DE-CMR compared to baseline

Comparison of gadolinium dose and acquisition time for late gadolinium enhancement at 3.0 T

Methods 34 patients with chronic myocardial infarction were randomized to 0.1 (n = 12), 0.15 (n = 11) and 0.2 (n = 11) mmol/ Kg of gadolinium contrast (gadobenate dimeglumine MultiHance). T1-weighted inversion recovery gradient echo sequences were performed at 5, 10, 15 and 20 minutes post-administration of contrast in all groups, with an individually adapted trigger delay at every single time point. Signal-to-noise ratio (SNR) of the scar, contrast-to-noise ratio (CNR) of the scar in comparison to healthy myocardium and the percentage of enhanced area volume relative to the global myocardium were quantified. A 4-point score was used to assess image quality in all studies.

Acute and chronic phase myocardial tissue characteristics in non ST-elevation myocardial infarction in dependence of early versus delayed revascularisation assessed by cardiac magnetic resonance imaging

Background According to current guidelines, an adequate timeframe for revascularisation in the setting of acute non-ST-elevation myocardial infarction (NSTEMI) is considered by current guidelines as being up to 72 hours after symptom onset. Soon after myocardial infarction, changes take place in the affected myocardium that can be visualized and measured by cardiac magnetic resonance imaging (CMR). Aim of the present study was to compare tissue characteristics in patients with NSTEMI that underwent early vs. delayed revascularisation. Therefore, myocardial tissue characteristics were evaluated in the acute and chronic phase of reperfused NSTEMI patients and the findings were correlated to the particular symptom-to-reperfusion time. Methods In 53 patients presenting with NSTEMI, CMR imaging was performed in addition to invasive coronary angiography. The patients were examined on a 1.5 T wholebody scanner using a 32-channel phased-array surface coil. Left-ventricular volumes were assessed by a standard steady-state free-precession sequence. Myocardial edema was evaluated using a 3D T2-weighted blackblood fat-saturated spin-echo sequence. Microvascular obstruction and late gadolinium enhancement were measured by a 3D phase-sensitive inversion-recovery gradient echo sequence about 12 minutes after intravenous administration of gadolinium based contrast agent. CMR imaging was conducted shortly after coronary revascularisation and about 90 days later at follow-up. Results were gained by two experienced readers in consensus.

Comparison of the Frequencies of Myocardial Edema Determined by Cardiac Magnetic Resonance in Diabetic Versus Nondiabetic Patients Having Percutaneous Coronary Intervention for ST Elevation Myocardial Infarction

The specific mechanisms by which diabetes may affect the myocardial tissue response to ischemia are unclear. Our objective was to prospectively quantify the degree of myocardial edema in diabetics versus nondiabetics with ST elevation myocardial infarction using cardiac magnetic resonance. Fifty-two patients (16 diabetics and 36 nondiabetics) were enrolled after primary percutaneous coronary intervention and underwent cardiac magnetic resonance on a 1.5-T scanner at 48 hours and 6 months. Myocardial edema was quantified using a T2 mapping technique, and infarct size and microvascular obstruction size were assessed by way of a contrast-enhanced T1-weighted inversion recovery gradient-echo sequence. The infarct segment T2 was elevated in diabetics compared with nondiabetics (59.0 ± 8.0 vs 50.8 ± 3.1 ms, p <0.001) at 48 hours. Multivariate analysis demonstrated that diabetes (p <0.001) and symptom-to-balloon time (p = 0.04) were independent predictors of the degree of acute myocardial edema. Infarct size was nonsignificantly higher in the diabetic group at 48 hours (26.9 ± 9.4% vs 20.1 ± 10.1% of myocardium, p = 0.07) and 6 months (17.1 ± 6.3% vs 13.4 ± 6.1% of myocardium, p = 0.09). Microvascular obstruction size was equivalent in both groups, and there was a trend toward lower myocardial salvage index in diabetics (34.2 ± 11.8 vs 49.6 ± 13.4, p = 0.08). In conclusion, diabetes is associated with increased myocardial edema in the acute phase after primary percutaneous coronary intervention. Our results offer insight into the complex processes that characterize myocardial tissue response to injury in diabetic patients.