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Purpose: To develop and validate a highly efficient motion compensated free‐breathing isotropic resolution 3D whole‐heart joint T1/T2 mapping sequence with anatomical water/fat imaging at 0.55 T. Methods: The proposed sequence takes advantage of shorter T1 at 0.55 T to acquire three interleaved water/fat volumes with inversion‐recovery preparation, no preparation, and T2 preparation, respectively. Image navigators were used to facilitate nonrigid motion‐compensated image reconstruction. T1 and T2 maps were jointly calculated by a dictionary matching method. Validations were performed with simulation, phantom, and in vivo experiments on 10 healthy volunteers and 1 patient. The performance of the proposed sequence was compared with conventional 2D mapping sequences including modified Look‐Locker inversion recovery and T2‐prepared balanced steady‐SSFP sequence. Results: The proposed sequence has a good T1 and T2 encoding sensitivity in simulation, and excellent agreement with spin‐echo reference T1 and T2 values was observed in a standardized T1/T2 phantom (R2 = 0.99). In vivo experiments provided good‐quality co‐registered 3D whole‐heart T1 and T2 maps with 2‐mm isotropic resolution in a short scan time of about 7 min. For healthy volunteers, left‐ventricle T1 mean and SD measured by the proposed sequence were both comparable with those of modified Look‐Locker inversion recovery (640 ± 35 vs. 630 ± 25 ms [p = 0.44] and 49.9 ± 9.3 vs. 54.4 ± 20.5 ms [p = 0.42]), whereas left‐ventricle T2 mean and SD measured by the proposed sequence were both slightly lower than those of T2‐prepared balanced SSFP (53.8 ± 5.5 vs. 58.6 ± 3.3 ms [p < 0.01] and 5.2 ± 0.9 vs. 6.1 ± 0.8 ms [p = 0.03]). Myocardial T1 and T2 in the patient measured by the proposed sequence were in good agreement with conventional 2D sequences and late gadolinium enhancement. Conclusion: The proposed sequence simultaneously acquires 3D whole‐heart T1 and T2 mapping with anatomical water/fat imaging at 0.55 T in a fast and efficient 7‐min scan. Further investigation in patients with cardiovascular disease is now warranted. [ABSTRACT FROM AUTHOR]

Purpose: The study aims to assess the potential of referenceless methods of EPI ghost correction to accelerate the acquisition of in vivo diffusion tensor cardiovascular magnetic resonance (DT-CMR) data using both computational simulations and data from in vivo experiments. Methods: Three referenceless EPI ghost correction methods were evaluated on mid-ventricular short axis DT-CMR spin echo and STEAM datasets from 20 healthy subjects at 3T. The reduced field of view excitation technique was used to automatically quantify the Nyquist ghosts, and DT-CMR images were fit to a linear ghost model for correction. Results: Numerical simulation showed the singular value decomposition (SVD) method is the least sensitive to noise, followed by Ghost/Object method and entropy-based method. In vivo experiments showed significant ghost reduction for all correctionmethods, with referencelessmethods outperforming navigator methods for both spin echo and STEAM sequences at b = 32, 150, 450, and 600 smm-2. It isworth noting that as the strength of the diffusion encoding increases, the performance gap between the referencelessmethod and the navigator-based method diminishes. Conclusion: Referenceless ghost correction effectively reduces Nyquist ghost in DT-CMR data, showing promise for enhancing the accuracy and efficiency of measurements in clinical practice without the need for any additional reference scans. [ABSTRACT FROM AUTHOR]

Purpose: Simultaneous PET‐MRI improves inflammatory cardiac disease diagnosis. However, challenges persist in respiratory motion and mis‐registration between free‐breathing 3D PET and 2D breath‐held MR images. We propose a free‐breathing non‐rigid motion‐compensated 3D T2‐mapping sequence enabling whole‐heart myocardial tissue characterization in a hybrid 3T PET‐MR system and provides non‐rigid respiratory motion fields to correct also simultaneously acquired PET data. Methods: Free‐breathing 3D whole‐heart T2‐mapping was implemented on a hybrid 3T PET‐MRI system. Three datasets were acquired with different T2‐preparation modules (0, 28, 55 ms) using 3‐fold undersampled variable‐density Cartesian trajectory. Respiratory motion was estimated via virtual 3D image navigators, enabling multi‐contrast non‐rigid motion‐corrected MR reconstruction. T2‐maps were computed using dictionary‐matching. Approach was tested in phantom, 8 healthy subjects, 14 MR only and 2 PET‐MR patients with suspected cardiac disease and compared with spin echo reference (phantom) and clinical 2D T2‐mapping (in‐vivo). Results: Phantom results show a high correlation (R2 = 0.996) between proposed approach and gold standard 2D T2 mapping. In‐vivo 3D T2‐mapping average values in healthy subjects (39.0 ± 1.4 ms) and patients (healthy tissue) (39.1 ± 1.4 ms) agree with conventional 2D T2‐mapping (healthy = 38.6 ± 1.2 ms, patients = 40.3 ± 1.7 ms). Bland–Altman analysis reveals bias of 1.8 ms and 95% limits of agreement (LOA) of −2.4‐6 ms for healthy subjects, and bias of 1.3 ms and 95% LOA of −1.9 to 4.6 ms for patients. Conclusion: Validated efficient 3D whole‐heart T2‐mapping at hybrid 3T PET‐MRI provides myocardial inflammation characterization and non‐rigid respiratory motion fields for simultaneous PET data correction. Comparable T2 values were achieved with both 3D and 2D methods. Improved image quality was observed in the PET images after MR‐based motion correction. [ABSTRACT FROM AUTHOR]

Background: Incomplete atrial lesions resulting in pulmonary vein‐left atrium reconnection after pulmonary vein antrum isolation (PVAI), are related to atrial fibrillation (AF) recurrence. Unfortunately, during the PVAI procedure, fluoroscopy and electroanatomic mapping cannot accurately determine the location and size of the ablation lesions in the atrial wall and this can result in incomplete PVAI lesions (PVAI‐L) after radiofrequency catheter ablation (RFCA). Aim: We seek to evaluate whether cardiac magnetic resonance (CMR), immediately after RFCA of AF, can identify PVAI‐L by characterizing the left atrial tissue. Methods: Ten patients (63.1 ± 5.7 years old, 80% male) receiving a RFCA for paroxysmal AF underwent a CMR before (<1 week) and after (<1 h) the PVAI. Two‐dimensional dark‐blood T2‐weighted short tau inversion recovery (DB‐STIR), Three‐dimensional inversion‐recovery prepared long inversion time (3D‐TWILITE) and three‐dimensional late gadolinium enhancement (3D‐LGE) images were performed to visualize PVAI‐L. Results: The PVAI‐L was visible in 10 patients (100%) using 3D‐TWILITE and 3D‐LGE. Conversely, On DB‐STIR, the ablation core of the PAVI‐L could not be identified because of a diffuse high signal of the atrial wall post‐PVAI. Microvascular obstruction was identified in 7 (70%) patients using 3D‐LGE. Conclusion: CMR can visualize PVAI‐L immediately after the RFCA of AF even without the use of contrast agents. Future studies are needed to understand if the use of CMR for PVAI‐L detection after RFCA can improve the results of ablation procedures. [ABSTRACT FROM AUTHOR]