3D sodium ( Na) magnetic resonance fingerprinting for time-efficient relaxometric mapping.

Purpose: To develop a framework for 3D sodium ( Na) MR fingerprinting (MRF), based on irreducible spherical tensor operators with tailored flip angle (FA) pattern and time-efficient data acquisition for simultaneous quantification of T , , , and in addition to ΔB .

Methods: Na-MRF was implemented in a 3D sequence and irreducible spherical tensor operators were exploited in the simulations. Furthermore, the Cramér Rao lower bound was used to optimize the flip angle pattern.

Stability of conventional and machine learning-based tumor auto-segmentation techniques using undersampled dynamic radial bSSFP acquisitions on a 0.35 T hybrid MR-linac system.

Purpose: Hybrid MRI-linear accelerator systems (MR-linacs) allow for the incorporation of MR images with high soft-tissue contrast into the radiation therapy procedure prior to, during, or post irradiation. This allows not only for the optimization of the treatment planning, but also for real-time monitoring of the tumor position using cine MRI, from which intrafractional motion can be compensated. Fast imaging and accurate tumor tracking are crucial for effective compensation.

Sodium relaxometry using Na MR fingerprinting: A proof of concept.

Purpose: To evaluate the feasibility of Na MR fingerprinting (MRF) for simultaneous quantification of T , , , in addition to ΔB .

Methods: A framework for sodium relaxometry using MRF at 7T was developed, allowing simultaneous measurement of relaxation times and inhomogeneities in the static field. The technique distinguishes between bi- and monoexponential transverse relaxation and was validated in simulations with respect to the ground truth.

Beyond T2 and 3T: New MRI techniques for clinicians.

Technological advances in Magnetic Resonance Imaging (MRI) in terms of field strength and hybrid MR systems have led to improvements in tumor imaging in terms of anatomy and functionality. This review paper discusses the applications of such advances in the field of radiation oncology with regards to treatment planning, therapy guidance and monitoring tumor response and predicting outcome.

Mapping the human brainstem: Brain nuclei and fiber tracts at 3 T and 7 T.

Structural high-resolution imaging of the brainstem can be of high importance in clinical practice. However, ultra-high field magnetic resonance imaging (MRI) is still restricted in use due to limited availability. Therefore, quantitative MRI techniques (quantitative susceptibility mapping [QSM], relaxation measurements [ , R ], diffusion tensor imaging [DTI]) and T - and proton density (PD)-weighted imaging in the human brainstem at 3 T and 7 T are compared.

Quantification of patellofemoral cartilage deformation and contact area changes in response to static loading via high-resolution MRI with prospective motion correction.

Background: Higher-resolution MRI of the patellofemoral cartilage under loading is hampered by subject motion since knee flexion is required during the scan.

Purpose: To demonstrate robust quantification of cartilage compression and contact area changes in response to in situ loading by means of MRI with prospective motion correction and regularized image postprocessing.

Study Type: Cohort study.

High-resolution FLAIR MRI at 7 Tesla for treatment planning in glioblastoma patients.

Ultra-high field MRI is an emerging technique promising high-resolution images for radiotherapy planning. We compared a 7 Tesla FLAIR sequence with clinical FLAIR imaging at 3 Tesla in glioblastoma patients before radiotherapy. High-resolution 7 Tesla FLAIR imaging may enhance the depiction of organs at risk and possibly modify target volumes.

Comparative T and T mapping of patellofemoral cartilage under in situ mechanical loading with prospective motion correction.

Purpose: To demonstrate improved T and T mapping of patellofemoral cartilage with in situ loading by means of prospective motion correction and to assess load-induced changes in healthy subjects.

Materials And Methods: Established T and T mapping sequences were augmented with prospective motion correction based on optical tracking. Protocols were optimized for robust imaging of the patellofemoral cartilage at a field strength of 3T.

Prospective motion correction in functional MRI.

Due to the intrinsic low sensitivity of BOLD-fMRI long scanning is required. Subject motion during fMRI scans reduces statistical significance of the activation maps and increases the prevalence of false activations. Motion correction is therefore an essential tool for a successful fMRI data analysis.

Cardiovascular magnetic resonance imaging of scar development following pulmonary vein isolation: a prospective study.

Aims: Cardiovascular magnetic resonance (MR) provides non-invasive assessment of early (24-hour) edema and injury following pulmonary vein isolation (by ablation) and subsequent scar formation. We hypothesize that 24-hours after ablation, cardiovascular MR would demonstrate a pattern of edema and injury due to ablation and the severity would correlate with subsequent scar.

Methods: Fifteen atrial fibrillation patients underwent cardiovascular MR prior to pulmonary vein isolation, 24-hours post (N = 11) and 30-days post (N = 7) ablation, with T2-weighted (T2W) and late gadolinium enhancement (LGE) imaging.

Left atrial late gadolinium enhancement with water-fat separation: the importance of phase-encoding order.

Purpose: To compare two late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) methods: a Dixon LGE sequence with sequential phase-encoding order, reconstructed using water-fat separation, and standard fat-saturated LGE.

Materials And Methods: We implemented a dual-echo Dixon LGE method for reconstructing water-only images and compared it to fat-saturated LGE in 12 patients prior to their first pulmonary vein isolation (PVI) procedure. Images were analyzed for quality and fat-suppression.

Three-dimensional late gadolinium-enhanced MR imaging of the left atrium: a comparison of spiral versus Cartesian k-space trajectories.

Purpose: To investigate the feasibility of high-resolution late gadolinium enhancement (LGE) imaging using a three-dimensional (3D) stack of spirals k-space trajectory for the detection of left atrial (LA) ablation lesions. LGE imaging inherently suffers from low SNR, so that improvements in spatial resolution and imaging time are challenging. The spiral trajectory offers greater acquisition efficiency, and this is used for increased spatial resolution.

Respiratory bellows-gated late gadolinium enhancement of the left atrium.

Purpose: To compare bellows-gated late gadolinium enhancement (LGE) with standard navigator-gated (NAV-gated) LGE for left atrial (LA) imaging, to eliminate the inflow artifacts associated with NAV-gating.

Materials And Methods: Eleven subjects, including six patients with atrial fibrillation (AF), were imaged with a 3D free-breathing NAV-gated and bellows-gated LGE. Motion compensation was compared by blinded grading of image sharpness and motion ghosting (0 = worst, 2 = best).

Cardiac MRI to investigate myocardial scar and coronary venous anatomy using a slow infusion of dimeglumine gadobenate in patients undergoing assessment for cardiac resynchronization therapy.

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.

Advanced image fusion to overlay coronary sinus anatomy with real-time fluoroscopy to facilitate left ventricular lead implantation in CRT.

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.

3-D visualization of acute RF ablation lesions using MRI for the simultaneous determination of the patterns of necrosis and edema.

Catheter ablation using RF energy is a common treatment for atrial arrhythmias. Although this treatment provides a potential cure, currently, there remains a high proportion of patients returning for repeat ablations. Electrophysiologists have little information to verify that a lesion has been created in the myocardium.

Pharmacokinetic modeling of delayed gadolinium enhancement in the myocardium.

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.