Cardiovascular magnetic resonance (CMR) can evaluate cardiac diseases from various viewpoints. Recently, compressed sensing (CS), which allows for rapid magnetic resonance imaging (MRI) using signal sparsity and random sampling, has been applied to clinical CMR, which could overcome the existing limitations. This review presents and discusses the clinical applications of CS in cardiovascular MRI.
Fetal magnetic resonance imaging (MRI) is an important diagnostic modality in adjunct with ultrasound (US). The purpose of fetal MRI is to complement an US, either by confirming the US findings or by acquiring additional findings. The use of fetal MRI has been increasing in the prenatal diagnosis of fetal neck, chest, and abdominal malformations, and it is well established in other fields, especially in that of fetal CNS anomalies. This study aimed to review the application and safety of fetal MRI.
Objective : The objective of this study was to evaluate the clinical value of right ventricular (RV) strain in RV heart disease by cardiac magnetic resonance-based feature tracking (CMR-FT).
Methods : Steady-state free precession images were acquired in 15 subjects : 5 had pulmonary arterial hypertension (PAH) (age : 27.6±14.2 years ; group A), 5 had repaired tetralogy of Fallot without PAH (age : 29.4±10.3 years ; group B), and 5 were normal subjects (age : 32.7±8.6 years ; group C). RV end-diastolic and end-systolic volumes, stroke volume, and ejection fraction (RVEF) were calculated as conventional functional parameters. A developing CMR software was used to obtain the global longitudinal strain (GLS) and strain rate from the 4-chamber view of the heart and global circumferential strain (GCS) and strain rate (GCSR) at the RV mid-cavity from the standard short-axis view of the heart.
Results : Group A had larger and more hypertrophied right ventricles compared to groups B (p<0.05) and C (p<0.05). The RVEF was significantly impaired in group A compared to groups B (p<0.05) and C (p<0.05). The strain values were lower in group A than in groups B (0.01<p<0.05) and C (0.01<p<0.05). The GLS was lower in group B than in group C (p<0.05), while GCS and GCSR had no significant differences between the groups. The strain values correlated with the increasing RV volume and decreasing RVEF in all cases (r=0.41 to 0.52 and r=-0.32 to -0.55, respectively).
Conclusions : The quantification of RV strain values was feasible in most patients by CMR-FT, suggesting that this approach could have clinical relevance in understanding the myocardial mechanics in RV heart disease. The preservation of circumferential strain was important in maintaining the RV function in group B.
Purpose : Radiofrequency (RF)-induced heating in magnetic resonance imaging (MRI) may pose risks to patients with metallic implants. An electromagnetic wave suppression sheet (EWS-sheet) may be useful in suppressing RF-induced heating. However, no data have proven that EWS-sheets prevent temperature increases in metallic implants. This study assessed the effect of EWS-sheets on attenuation of RF-induced heating of conductive implants in MRI, and investigated appropriate methods of covering the implants with EWS-sheets to reduce temperature increases.
Materials and Methods : The method employed to measure implant heating conformed to the American Society for Testing and Materials F2182-02a criteria. An orthopedic Kirschner wire was selected for testing. All experiments were performed using a clinical 1.5T MR system. MRI was performed at a whole-body average specific absorption rate of 1.5 W/kg for 15 min. Efficacy for reduction of RF-induced heating of implants was investigated by covering test phantoms with EWS-sheets (full, half, and upper covering) ; the distance between the sheet and parallel overlapping of the implant and the vertical distance between the implant and sheet were evaluated.
Results and Discussion : The efficacy of the EWS-sheet for reduction of RF-induced heating depended on the covering method and placement. By ensuring adequate overlap in the parallel direction, full and half covering allowed the implant to resist heating within safety limits. It was noted that deficient overlapping in the parallel direction and a large vertical space between the sheet and implant caused higher temperature increases in the implant than in cases without use of the EWS-sheet, as a result of enhancement of RF power and incident RF pulses.
Conclusion : EWS-sheets may be useful for protecting patients with conductive implants from the risks of RF-induced heating. Further investigation is needed to define the safety guidelines more precisely.
Pseudocontinous arterial spin labeling (pCASL) renal perfusion imaging is typically restricted to a single post-label delay (PLD) time. While multiple PLD (mPLD) times can be achieved using sequential scans with different PLD times, this procedure is time consuming. A rapid acquisition method was developed using Hadamard encoding for mPLD pCASL imaging, combined with a motion robust timing and readout strategy to permit free-breathing renal ASL. The feasibility study explores the application of Hadamard encoding to renal perfusion imaging where spin labeling is affected by pulsatile flow, and demonstrated that a cardiac-triggered scan provided stable perfusion images achieving arterial transit time-corrected renal blood flow with seven PLD acquisitions.
We investigated the orbitofrontal cortex (OFC), using functional magnetic resonance imaging (fMRI) to determine which OFC subregions are related to autobiographical odor memory (AM odor). fMRI analysis indicated robust activation in the left posterior OFC (POFC). Connectivity between the POFC and bilateral precuneus, bilateral rostral dorsal anterior cingulate cortex (rdACC), and left parahippocampus was increased. Odor associated with emotionally significant autobiographical memories was accompanied by slow and deep breathing, possibly involving rdACC processing.
The purpose of this study was to compare the capability for pulmonary functional loss and clinical stage evaluations between inspiratory/ expiratory UTE-MRI and thin-section CT in smokers. Finally, this study showed UTE-MRI was at least as valuable as thin-section CT in this setting.
Indirect proton MRI can be used for the measurement of 17O. We evaluated the safety and feasibility of 17O-labeled water. No adverse effects were seen, and the measured concentrations were proportional to the injection dose. 17O-labeled water may be used for safe tracer of blood flow.
We have proposed a new method for fabricating gradient coils (GCs) using printed circuit boards. This technique has the advantages of the reducing cost, high patterning accuracy. We evaluate the performance of the GCs and apply the method to vertical-bore superconducting magnet MRI systems.
We developed new TSE-DWI combining SPLICE and MultiVane, named MV-SPLICE to reduce image distortion. The SE and STE were separately acquired in separate k-space. In this study, ADCs and SNRs in TZ and PZ, and distortion in the AP direction of prostate diameter for MV-SPLICE were investigated.