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At least 217 records · Page 12Linked to original sources
PubMed1999

Optimization of gray/white matter contrast with fast inversion recovery for myelin suppression: a comparison of fast spin-echo and echo-planar MR imaging sequences.

We compared two MR imaging sequences, fast inversion recovery for myelin suppression (FIRMS) and echo-planar FIRMS (EP-FIRMS), for depicting gray/white matter contrast. In 18 patients, the frequency bandwidth (BW) was optimized for each sequence; in nine patients, the BW was held constant. In the BW-optimized group, the mean contrast-to-noise ratio (C/N) was three times higher with the FIRMS sequence. In the BW-constant group, the mean C/N was 27% higher with the EP-FIRMS sequence; however, geometric distortion degraded the EP-FIRMS images excessively. For optimal gray/white contrast, FIRMS appears to be the superior pulse sequence.

Brain Diseases↗
PubMed2003

[MR cholangiopancreatography: comparison of 2D single-shot fast spin-echo and 3D fast spin-echo sequences].

PURPOSE: To compare 2D single-shot Fast Spin-Echo (FSE) and two 3D FSE MR cholangiopancreatography (MRCP) sequences with different slice thickness in the evaluation of normal and abnormal biliary and pancreatic duct systems. MATERIALS AND METHODS: Thirty-two consecutive patients, both with normal biliary and pancreatic ducts (n=14) and with different biliary and/or pancreatic duct disease (n=18) underwent MRCP with a 1.5 T superconductive magnet. One 2D single-shot FSE and two 3D FSE MRCP sequences with different slice thickness (1.6 mm and 3 mm) were performed in each patient. Images were analysed with regards to: artefacts (0=none, 1=minimal, 2=present but not affecting the diagnostic evaluation, 3=present and affecting the diagnostic evaluation), image quality (0=non-diagnostic, 1=poor, 2=fair, 3=good, 4=excellent), duct conspicuity (0=not-visible, 1=poor, 2=good, 3=excellent), diagnostic confidence (possible presence of dilatations, stones and stenoses). RESULTS: Artefacts were rarely present, without significant differences among the three sequences. The 2D single-shot FSE sequence provided a significantly better image quality and significantly better conspicuity of the intrahepatic and pancreatic ducts in comparison to both the 1.6-mm and 3-mm thickness 3D FSE sequences. The three sequences yielded identical results in the detection of 17 cases of dilatation and 10 cases of stenosis as well as in the evaluation of their degree. Stones in the biliary tree were detected in 6 cases with the 2D single-shot FSE sequence, in 5 cases in the MIP images of the 3D FSE sequence with slice thickness of 1.6 mm and in 4 cases in the MIP images of the 3D FSE sequence with slice thickness of 3 mm. The diagnostic confidence did not show statistically significant differences among the three sequences. CONCLUSIONS: The 2D single-shot FSE sequence proved to be superior to the 3D FSE sequences in the evaluation of normal and abnormal biliary and pancreatic duct systems.

Adult↗
PubMed1995

MR evaluation of vertebral metastases: T1-weighted, short-inversion-time inversion recovery, fast spin-echo, and inversion-recovery fast spin-echo sequences.

PURPOSE: To compare the detectability of vertebral metastatic disease on T1-weighted, short-inversion-time inversion recovery (STIR), fast spin-echo (FSE), fat-saturated FSE, and inversion recovery FSE (IRFSE) MR sequences using percent contrast and contrast-to-noise ratios. METHODS: Patients with proved metastatic disease underwent imaging on a 1.5-T MR system with sagittal T1-weighted (800/20/2 [repetition time/echo time/excitations]) (91 patients), STIR (1400/43/2; inversion time, 140) (91 patients), FSE (4000/180/2) (46 patients), fat-saturated FSE (4000/180/2) (16 patients), and IRFSE (29 patients) sequences. Percent contrast and contrast-to-noise ratio were calculated for the lesions. The number of metastatic lesions detected with each of the pulse sequences was also calculated. RESULTS: Mean percent contrast was, for T1-weighted sequence, -42.2 +/- 1%; STIR, 262 +/- 34%; FSE, 121 +/- 21%; fat-saturated FSE, 182 +/- 6%; and IRFSE, 272 +/- 47%. The mean contrast-to-noise ratio for T1-weighted was -4.63 +/- 1.7; STIR, 10.8 +/- .98; FSE, 4.16 +/- .76; fat-saturated FSE, 4.87 +/- .19; and IRFSE, 5.2 +/- .87. STIR and IRFSE showed the highest number of lesions, followed by T1-weighted, fat-saturated FSE, and FSE sequences. T1-weighted sequences showed 94%, FSE 55%, and fat-saturated FSE 78% of the lesions detected. Epidural metastatic lesions were better depicted on T1-weighted, FSE, and fat-saturated FSE sequences. CONCLUSION: STIR was superior to both T1-weighted and FSE (with and without fat saturation) for detection of metastatic lesions, in terms of both percent contrast and contrast-to-noise ratio and visibility. IRFSE was equal to STIR for the detection of metastasis by both subjective and objective criteria. T1-weighted, FSE, and fat-saturated FSE sequences were superior to STIR and IRFSE in the detection of epidural metastatic disease. IRFSE provided faster scanning time, which could be translated into greater resolution.

Adolescent↗
PubMed1993

[Dynamic sequential study of hepatic nodular lesions with ultra-fast sequences and fast bolus of gadolinium-DTPA].

Eighty-five patients with single/multiple nodular hepatic lesions (10 focal nodular hyperplasias, 37 liver hemangiomas, 24 metastases and 16 hepatocellular carcinomas; 2 patients had associated lesions) were examined with dynamic single-slice sequences and fast i.v. bolus injection of Gd-DTPA. The dynamic single-slice technique was used to evaluate the peculiar features of the dynamic enhancement. The snapshot sequence proved best to provide the high temporal resolution of the dynamic parenchymal enhancement (scanning time < 1 second, one frame every third second). The following variables were investigated: nodular lesion intensity in the first basal snapshot image, enhancement appearance and its contemporaneity with arterial, venous or portal flows, enhancement gradient relative to surrounding liver parenchyma, morphologic features of the enhancement and its centrifugal/centripetal patterns. The enhancement curve of focal nodular hyperplasia increased very quickly during the first 20-25 seconds. This enhancement was quite similar to the arterial one and always occurred before portal and systemic venous times. Hemangiomas exhibited a typically slow growth-curve in the first 120 seconds, with a positive final gradient value relative to liver parenchyma. The appearance of peripheral contrast enhancement was a typical sign after 30 seconds. Metastases exhibited similar dynamic enhancement to hemangiomas, but peripheral enhancement was never observed and, after 120 seconds, gradient was null or negative relative to the adjacent liver parenchyma. Moreover, enhancement always followed portal times. Hepatocellular carcinomas showed an early growth curve, preceding portal times, but less marked than in hyperplasia. The study of our series provided the preliminary semiology of early dynamic enhancement patterns, which is quite specific to recognize and differentiate nodular hepatic lesions.

Contrast Media↗
PubMed1995

[Fast and ultra-fast magnetic resonance tomography. Basic principles, pulse sequences and special properties].

The aim of this article is the systematic treatment of fast and ultrafast magnetic resonance imaging (MRI) techniques. Based on the basic principles of signal generation and spatial encoding with magnetic field gradients the differences and important similarities of pulse sequences will be explained. We suggest to replace the conventional grouping of pulse sequences in gradient and spin-echo sequences through single and multi-echo sequences, since the latter is more precise and helpful. We illustrate how single-echo sequences such as "spin-echo", FLASH, FISP, PSIF, CISS and DESS can be derived from a single gradient echo and how multi-echo sequences such as turbo spin-echo RARE, HASTE and GRASE are based on echo-planar imaging. The different properties, advantages and disadvantages of the various sequences will be discussed and frequently used acronyms will be explained.

Echo-Planar Imaging↗
PubMed1995

[Rapid spin echo sequences for detection and characterization of focal liver lesions. Use of fast T2-weighted spin echo with fat suppression and fast spin echo with combined gradient echo (GRASE)].

The purpose of this study was to assess the value of fast-spin-echo (FSE) sequences without and with fat suppression as well as gradient-and-spin-echo (GRASE) sequences for the detection and subsequent characterization of focal liver lesions. A total of 51 consecutive patients with clinically suspected focal liver lesions were studied. FSE without fat suppression proved to be valuable for the detection (TE 90 ms) and characterization (TE 158 ms) of focal liver lesions. Fat suppression did not improve the performance of FSE. GRASE sequences with multiple excitations were clinically superior to the faster single-shot approach.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Absorption of theophylline from enteric coated and sustained release formulations in fasted and non-fasted subjects.

The influence of prior food ingestion, and also of varying fluid volumes, on plasma theophylline levels was examined following single oral doses of two sustained-release formulations, Theobid (260 mg) and Theo-Dur (200 mg) and one partially enteric-coated formulation, Choledyl (128 mg), to 9 healthy volunteers. Prior food ingestion tended to delay the absorption of theophylline from all formulations to a small extent. This effect was observed only at early sampling times, and plasma drug profiles were similar for all treatments within a particular formulation. Theobid and Theo-Dur gave rise to plasma profiles that were characteristic of sustained-release formulations, with mean Cmax values of 5.5-5.7 micrograms ml-1 (Theobid) and 2.8-3.2 micrograms ml-1 (Theo-Dur) occurring at 5.8-9.1 h after dosing. Choledyl gave rise to a longer absorption lag time than the other formulations but was subsequently absorbed at a faster rate yielding mean Cmax values of 3.2-3.5 micrograms ml-1 at 2.8-4.1 h. The intersubject variability in theophylline plasma levels, and also in most pharmacokinetic parameter values, was generally less following Theo-Dur compared to the other formulations.

Adult↗
PubMed1977

Bioavailability of metronidazole in fasting and non-fasting healthy subjects and in patients with Crohn's disease.

The possible influence of food intake on the bioavailability of metronidazole was examined in ten health volunteers by administration of a single dose of metronidazole on an empty stomach, and with a standardized breakfast. Food intake did not significantly alter the bioavailability of metronidazole. The interindividual variation in bioavailability appeared to be slight. In nine patients with Crohn's disease, the absorption of metronidazole appeared to be reduced and to be more variable than in healthy subjects. In both groups there was a clear relationship between the amount absorbed and dose/kg body weight. Thus, from the pharmacokinetic point of view, metronidazole can safely be given either with or between meals. The dose should be related to body weight.

Adult↗