Ergebnisse der Kernspintomographie des Temporomandibulargelenkes mittels optimierter Oberflächenspulen
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One hundred temporo-mandibular joints were examined with a super-conducting nuclear resonance tomograph (1.0 Tesla) using various high resolution surface coils. The optimal method proved to be a spin echo sequence with a repetition time of 1,000 msec and an echo period of 28 msec with a 4 mm slice width. There were significant advantages from the non-invasive MRT diagnosis of the temporo-mandibular joints when compared with CT and with arthrography in recognising abnormal discs, changes in the tissues and for post-operative control.Keywords:
Fast spin echo
Echo time
Background Magnetic resonance imaging (MRI) visualization of meniscal signal is particularly challenging as the highly organized ultrastructure of meniscal fibrocartilage yields very short T2 values (∼6 ms) and a paucity of signal intensity during conventional image acquisition. Question/Purpose The purpose of this study was to evaluate the feasibility of imaging postoperative menisci using an experimental, quantitative ultrashort echo time (UTE) MRI pulse sequence. This sequence acquires short echo images (echo time (TE) ∼0.3 ms) to produce multi-echo images for quantitative T2* calculations that provide an objective measure of collagen organization. Patients and Methods MRI scans of the knee were acquired at 6- and 12-month intervals on a clinical 3.0 T scanner following meniscal surgery in eight patients (ages 13–41), four of whom underwent repair and the other four partial meniscectomy. Conventional MRI sequences were qualitatively evaluated for meniscal morphology and signal and correlated with quantitative UTE results. Results A wide range of mean T2* values for both postsurgical groups was measured, and these values changed for each patient between the 6- and 12-month intervals. In many instances, the UTE sequence demonstrated quantitative differences between the two time intervals that were not detected with conventional sequences. Conclusions This pilot study presents preliminary, observational data to be used as a baseline for future studies. Although the T2* values did not reveal a trend in either group or correlate with expected signal changes on conventional MRI, we speculate that the UTE sequence may detect ultrastructural alterations in meniscal composition that are otherwise not perceived with routine fast spin echo (FSE) sequences.
Fast spin echo
Pulse sequence
Echo (communications protocol)
Echo time
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Abstract Multislice MR images obtained using a fast spin‐echo (FSE) readout are strongly affected by magnetization transfer (MT) effects, which will cause a decrease in the observed longitudinal relaxation times for tissues with a large bound water component. This is pertinent for FSE‐based inversion‐recovery (IR) sequences, as it would be expected to cause a change in the required inversion times. Furthermore, the effect will be greater as the number of slices that are acquired within the repetition time (TR) is increased. A pseudo‐3D IR‐FSE sequence was used to obtain images of a phantom consisting of thermally crosslinked bovine serum albumin. It was found that increasing the number of slabs acquired per TR period led to a decrease in the inversion time that maximally suppressed the signal from the MT phantom; this was not the case for water. This has important consequences for any IR imaging sequence that uses an FSE readout. Magn Reson Med 58:825–829, 2007. © 2007 Wiley‐Liss, Inc.
Magnetization transfer
Fast spin echo
Echo time
Multislice
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Axial MR images of 65 lumbar disks with herniated nucleus pulposus imaged by gradient-refocused-echo (GRE) and spin-echo (SE) MR pulse sequences of 200-400/15 with a flip angle of 15-30 degrees was selected as optimal because of its high signal-to-noise ratio and good contrast between CSF, nucleus pulposus, and bone. The GRE technique was confirmed to be more sensitive in detecting prolapsed disks than the SE technique, but was less sensitive in demonstrating extruded disks. The combination of axial GRE and SE resulted in high detectability of herniated nucleus pulposus on axial MR images. Our results suggest that the GRE technique is an important adjunct to SE imaging in studying herniated nucleus pulposus.
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Flip angle
Intervertebral disk
Gradient echo
Fast spin echo
Echo (communications protocol)
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Surrogate endpoint
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We describe three-dimensional magnetic resonance imaging (MRI) of a liquid foam. Difficulties in imaging arise from the rate of evolution of the foam and the magnetic susceptibility mismatch at the boundaries between liquid and air. We used a protein gelatin foam, for which we improved relaxation rates and matched the susceptibility. A three-dimensional spin-echo sequence yielded strongly T2 weighted signals. The reconstructed data represents the first such full three-dimensional image of a liquid foam.
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PURPOSE To investigate the lesser lesion conspicuity after gadolinium contrast infusion with radio-frequency spoiled gradient-echo (SPGR) sequences relative to conventional T1-weighted spin-echo techniques. METHODS The influences of repetition time, echo time, and flip angle on spin-echo and SPGR signal were studied with mathematical modeling of the image signal amplitude for concentrations of gadopentetate dimeglumine solute from 0 to 10 mM. Predictions of signal strength were verified in vitro by imaging of a doped water phantom. The effects of standard (0.1 mmol/kg) and high-dose (0.3 mmol/kg) gadoteridol on spin-echo and SPGR images were also investigated in three patients. RESULTS The measured amplitude of undoped water and the rate of increase of doped water signal with increasing gadopentetate concentration (slope) for spin-echo 600/11/1/90 degrees (repetition time/echo time/excitations/flip angle) and SPGR (600/11/190 degrees) were similar and exceeded those of SPGR (35/5/145 degrees). Greater increases in SPGR doped water signal and its slope were produced by increasing TR than by varying echo-time or flip angle. The subjective lesion conspicuity and measured lesion contrast at 0.3 mmol/kg were greater with spin-echo (600/11/1/90 degrees) than with SPGR (35/5/145 degrees) in all three patients; the measured lesion enhancement was similar for both techniques in two patients and decreased for SPGR in the third patient. CONCLUSIONS The phantom studies suggest that the short repetition time of 35 msec, typically used in clinical SPGR imaging, is largely responsible for a reduced signal amplitude and a diminished rate of increase of signal with increasing gadopentetate concentration, relative to spin-echo. Phantom and clinical studies suggest that the dose of paramagnetic agent required to achieve SPGR lesion conspicuity with short repetition time comparable with spin-echo would have to be higher than the dose in current clinical use.
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Echo (communications protocol)
Fast spin echo
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Gradient echo
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We investigated the effects of fast recovery (FR) to increase the sensitivity of fluorine-19 (19F) fast spin echo (FSE) in mapping 5-fluorouracil (5-FU) and its metabolites. We added an additional 90° pulse (which flips back longitudinal magnetization at the end of the sequence) to the chemical shift selective 19F FSE pulse sequence. In 5-FU solution, FR remarkably improved the signal-to-noise (S/N) ratio of 19F 5-FU images, having higher effects with shorter repetition time and smaller echo train numbers. In animal studies, FR produced a conspicuous increase in 19F signals in the urinary bladder. FR effects for 19F signals in the liver were smaller than those in other organs but still substantial. Utilization of FR in 19F FSE images promises more sensitive observation of 19F metabolite maps of 5-FU and other 19F-containing compounds that have relatively long relaxation times.
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Fluorine
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Study Design. The magnetic resonance artifact susceptibility of traces of surgical aluminum, titanium, and stainless steel in a human spine model was investigated. Metallic filings were deposited in noncontiguous disc spaces in five human thoracic spines before magnetic resonance imaging with spin echo and gradient echo sequences. Objectives. Spin echo and gradient echo sequences were used to quantitate and compare void artifact produced by commonly used surgical metals. This was compared to a liquid paraffin control. Summary of Background Data. No significant susceptibility artifact was seen with any metal in all spin echo sequences, including T1 (TR 600, TE 12), T2 (TR 2000, TE 30), proton density (TR 2000, TE 80), and fast T2 scanning (TR 3800, TE 96, Ef). Methods. Sagittal magnetic resonance imaging permitted void artifact quantification and comparison between different metallic alloys. Two neuroradiologists, working on a blinded basis, evaluated all data and rated the void susceptibility artifact on a scale of 1 (least) to 4 (greatest). Results. In general, the magnitude of an imaging artifact during magnetic resonance imaging correlated with the magnetism of the metal. Nickel, found in a larger concentration in 316L than in 304 stainless steel, decreases the magnetic resonance artifact of specific metals because of its ability to stabilize iron in a nonmagnetic state. Therefore, the 316L stainless steel yielded less artifact production than 304 stainless steel on gradient echo imaging. Conclusion. If upon gradient echo imaging in the postoperative period significant artifact production is noted, stainless steel deposition should be suspected as the causative agent. In this situation, spin echo techniques should be the first approach for attempting optimal visualization of the spinal cord and soft tissue structures. [Key words: artifact production, ferromagnetic, gradient echo, magnetic resonance imaging, metal alloys] Spine 1994;19:1237–1242
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Бұл зерттеужұмысындaКaно моделітурaлы жәнеоғaн қaтыстытолықмәліметберілгенжәнеуниверситетстуденттерінебaғыттaлғaн қолдaнбaлы (кейстік)зерттеужүргізілген.АхметЯссaуи университетініңстуденттеріүшін Кaно моделіқолдaнылғaн, олaрдың жоғaры білімберусaпaсынa қоятынмaңыздытaлaптaры, яғнисaпaлық қaжеттіліктері,олaрдың мaңыздылығытурaлы жәнесaпaлық қaжеттіліктерінеқaтыстыөз университетінқaлaй бaғaлaйтындығытурaлы сұрaқтaр қойылғaн. Осы зерттеудіңмaқсaты АхметЯсaуи университетіндетуризмменеджментіжәнеқaржы бaкaлaвриaт бaғдaрлaмaлaрыныңсaпaсынa қaтыстыстуденттердіңқaжеттіліктерінaнықтaу, студенттердіңқaнaғaттaну, қaнaғaттaнбaу дәрежелерінбелгілеу,білімберусaпaсын aнықтaу мен жетілдіружолдaрын тaлдaу болыптaбылaды. Осы мaқсaтқaжетуүшін, ең aлдыменКaно сaуaлнaмaсы түзіліп,116 студенткеқолдaнылдыжәнебілімберугежәнеоның сaпaсынa қaтыстыстуденттердіңтaлaптaры мен қaжеттіліктерітоптықжұмыстaрaрқылыaнықтaлды. Екіншіден,бұл aнықтaлғaн тaлaптaр мен қaжеттіліктерКaно бaғaлaу кестесіменжіктелді.Осылaйшa, сaпa тaлaптaры төрт сaнaтқa бөлінді:болуытиіс, бір өлшемді,тaртымдыжәнебейтaрaп.Соңындa,қaнaғaттaну мен қaнaғaттaнбaудың мәндеріесептелдіжәнестуденттердіңқaнaғaттaну мен қaнaғaттaнбaу деңгейлерінжоғaрылaту мен төмендетудеосытaлaптaр мен қaжеттіліктердіңрөліaйқын aнықтaлды.Түйінсөздер:сaпa, сaпaлық қaжеттіліктер,білімберусaпaсы, Кaно моделі.
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Twenty cases of different brain pathology have been studied via MRI using an open resistive magnet with magnetic field strength of 0.2 Tesla. The relative signal intensity with respect to the repetition time (TR) at fixed echo time (TE) 0.117 sec. has been studied. It was found that the signal intensity saturates for most lesions beyond a certain TR~6 sec in the T2 - weighted image. The signal intensity differs with respect to the inversion time (TI) for fat and cerebrospinal fluid (CSF). It was found that the intensity is nulled for CSF at TI ~1.5 sec. and for Fat at TI~0.10 sec in the FLAIR imaging sequence. Thus the intensity of the lesions is qualitatively different for the two sequences. From the radiological diagnostic point of view, it was concluded that the FLAIR sequence is more useful for the detection of lesions compared to T2 sequences.
Fast spin echo
Characterization
Sequence (biology)
T2 weighted
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