Search results for "Gradient echo"
showing 9 items of 9 documents
Facilitating cartilage volume measurement using MRI.
2010
To compare quantitative cartilage volume measurement (CVM) using different slice thicknesses.Ten knees were scanned with a 1.5T MRI (Sonata, Siemens, Erlangen, Germany) using a 3D gradient echo sequence (FLASH, fast low-angle shot). Cartilage volume of the medial and lateral tibial plateau was measured by two independent readers in 1.5mm, 3.0mm and 5.0mm slices using the Argus software application. Accuracy and time effectiveness served as control parameters.Determining cartilage volume, time for calculation diminished for the lateral tibial plateau from 384.6+/-127.7s and 379.1+/-117.6s to 214.9+/-109.9s and 213.9+/-102.2s to 122.1+/-60.1s and 126.8+/-56.2s and for the medial tibial platea…
Accuracy of SWI sequences compared to T2*-weighted gradient echo sequences in the detection of cerebral cavernous malformations in the familial form
2016
Purpose The purpose of this study was to assess the accuracy of susceptibility-weighted imaging (SWI), compared with T2*-weighted gradient echo (GRE) imaging in assessing cerebral cavernous malformations. Materials and methods We retrospectively evaluated 21 patients with a familial form of cavernous malformation. Magnetic resonance (MR) protocol included non-enhanced and contrast-enhanced fast-spin echo (FSE) T1-weighted sequences, FSE T2-weighted sequences, fluid-attenuated inversion-recovery (FLAIR), GRE T2*-weighted and SWI sequences. Images were reviewed in consensus by two expert neuroradiologists to assess the location, number, size and conspicuity of the lesions on T2*-weighted GRE …
Gradient-echo and CRAZED imaging for minute detection of Alzheimer plaques in an APPV717I x ADAM10-dn mouse model.
2007
Different strategies to visualize amyloid plaques with MRI at 17.6 Tesla were investigated in a novel mouse model of Alzheimer's disease (AD). Large iron-containing plaques were observed in the thalamus, but cortical plaques did not show iron deposits. Plaques in the thalamus were visualized in vivo with the use of low-resolution, 3D gradient-echo (GRE) imaging in 82 s, and with 94-microm resolution in 34 min. The feasibility of obtaining bright contrast from plaques using the COSY revamped with asymmetric z-GRE detection (CRAZED) technique was investigated in experiments on fixed brains. The original CRAZED approach provided reduced signal near the plaques (similarly to GRE imaging) and ad…
Dynamic19F-MRI of pulmonary ventilation using sulfur hexafluoride (SF6) gas
2001
A new method for dynamic imaging of pulmonary wash-in and wash-out kinetics of inhaled sulfur hexafluoride (SF6) gas was developed. Measurements at the fluorine-19 Larmor frequency were performed in pigs using a gradient echo pulse sequence with 0.5 ms echo time and a measurement time of 9.1 s per image. Dynamic MRI was performed during wash-in and wash-out of SF6 gas in mechanically ventilated porcine lungs. A postprocessing strategy was developed for quantitative determination of wash-out time constants in the presence of noise. Mean wash-out constants were 4.78 ± 0.48 breaths vs. 4.33 ± 0.76 breaths for left and right lung when ventilation was performed with low tidal volume, and 1.73 ± …
Preliminary experience with a transcranial magnetic resonance-guided focused ultrasound surgery system integrated with a 1.5-T MRI unit in a series o…
2018
OBJECTIVETranscranial magnetic resonance–guided focused ultrasound surgery (tcMRgFUS) is one of the emerging noninvasive technologies for the treatment of neurological disorders such as essential tremor (ET), idiopathic asymmetrical tremor-dominant Parkinson’s disease (PD), and neuropathic pain. In this clinical series the authors present the preliminary results achieved with the world’s first tcMRgFUS system integrated with a 1.5-T MRI unit.METHODSThe authors describe the results of tcMRgFUS in a sample of patients with ET and with PD who underwent the procedure during the period from January 2015 to September 2017. A monolateral ventralis intermedius nucleus (VIM) thalamic ablation was pe…
Intrapulmonary 3He Gas Distribution Depending on Bolus Size and Temporal Bolus Placement
2008
OBJECTIVE: Dynamic ventilation (3)He-MRI is a new method to assess pulmonary gas inflow. As differing airway diameters throughout the ventilatory cycle can influence gas inflow this study intends to investigate the influence of volume and timing of a He gas bolus with respect to the beginning of the tidal volume on inspiratory gas distribution. MATERIALS AND METHODS: An ultrafast 2-dimensional spoiled gradient echo sequence (temporal resolution 100 milliseconds) was used for dynamic ventilation (3)He-MRI of 11 anesthetized and mechanically ventilated pigs. The applied (3)He gas bolus was varied in volume between 100 and 200 mL. A 150-mL bolus was varied in its application time after the beg…
Abdominal and Thoracic Magnetic Resonance Angiography: Challenges, Technical Approaches, and First Clinical Applications
1993
The main goal of magnetic resonance angiography (MRA) is to enrich the huge potential of magnetic resonance imaging (MRI) by additional morphological and functional information about the vasculature. In spin echo sequences fast flowing blood leads to signal extinction, providing high contrast between tissue and vascular structures without the need for contrast media. However, various artifacts are frequently observed which alter the assessment of the vasculature. They are due to alterations of flow (slow velocity or turbulences) or induced by the acquisition technique (Mills et al. 1983; Bradley and Waluch 1985). By using gradient echo sequences, high-quality angiograms can be obtained from…
Ventrolateral Compression of the Brain Stem in Essential Hypertension: MR Angiography Study
1997
Our purpose was to evaluate neurovascular compression at the level of ventrolateral medulla and NVC with the IXth and the Xth cranial nerves in patients with essential hypertension and in healthy volunteers using high resoluted Spoiled Recalled Gradient Echo (SPGR) sequences, allowing the detection of stationary tissues and moving spins. Thirty patients (19 men and 11 women) with essential hypertension were examined. Patient's ages ranged from 24 to 64 years-old (mean age was 48 y.o.). Patients older than 65 were excluded. The average of systolic blood-pressure of hypertensive patients was 183 ± 10 mmHg, while the diastolic pressure was 98 ± 10.5 mmHg. In conclusion, we consider axial sing…
Magnetic resonance in isolated noncompaction of the ventricular myocardium
2010
Abstract Non-compaction of the ventricular myocardium (LCVM) is a rare disorder of myocardial morphogenesis usually diagnosed in paediatric age. The diagnosis was echocardiographically made on the basis of a reported spongeous/compacted ratio >2 in one or more segments of the left ventricle during the diastolic period. We aimed to test the diagnostic accuracy of cardiovascular magnetic resonance (CMR) imaging in distinguishing pathological left ventricular non-compaction. Methods We collected a consecutive series of 8 patients, 5 males and 3 females, with a mean age of 14.9 years with non-compaction of left ventricular myocardium. All patients were admitted in our divisions of cardiology. I…