SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Brockstedt Sara) "

Sökning: WFRF:(Brockstedt Sara)

  • Resultat 11-20 av 38
  • Föregående 1[2]34Nästa
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
11.
  •  
12.
  • Geijer, Bo, et al. (författare)
  • Persistent high signal on diffusion-weighted MRI in the late stages of small cortical and lacunar ischaemic lesions
  • 2001
  • Ingår i: Neuroradiology. - : Springer. - 1432-1920. ; 43:2, s. 115-122
  • Tidskriftsartikel (refereegranskat)abstract
    • Diffusion-weighted imaging (DWI) is very sensitive to early brain infarcts. However, the late stages have been insufficiently studied. Infarcts in small vessel disease are often multiple and of different ages, and differentiation between new and old lesions might be difficult. We have therefore studied the change with time in DWI of small (< 3 ml) ischaemic lesions. We imaged 21 patients with an acute lacunar syndrome and a lesion visible on early DWI. They all had three MRI examinations 12-58 h (early), 7-16 and 54-144 days after the onset of stroke; 10 patients with high DWI signal on the third examination had a fourth examination 12-28 months after the stroke. MRI was performed at 1.5 T, using echo-planar DWI with 7 b-values from 0 to 1200 x 10(6) s/m2 and conventional T2-weighted imaging. After 7-16 days 18 of 21 lesions gave high signal on DWI, and 12/16 measurable lesions had a decreased apparent diffusion coefficient (ADC). After 54-144 days ten lesions still gave high DWI signal and two still had an ADC below normal. On the fourth examination there was no remaining high DWI signal and all ADC were higher than normal.
  •  
13.
  • Geijer, Bo, et al. (författare)
  • Radiological diagnosis of acute stroke. Comparison of conventional MR imaging, echo-planar diffusion-weighted imaging, and spin-echo diffusion-weighted imaging
  • 1999
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455. ; 40:3, s. 255-262
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To compare conventional MR imaging, echo-planar diffusion-weighted imaging (EP-DWI) and spin-echo diffusion-weighted imaging (SE)-DWI at radiological diagnosis of acute stroke. MATERIAL AND METHODS: Twenty-seven patients (30-85 years old) were examined. Clinical examination was performed before MR imaging. All MR examinations were assessed by an experienced neuroradiologist blinded to clinical findings. RESULTS: In EP-DWI, every patient had a lesion corresponding to the clinical findings. EP-DWI was used as the gold standard. In conventional PD+T2 imaging, 23/59 focal lesions were interpreted as acute, which was false in 11 lesions, and 36/59 lesions were considered to be old, 6 were in fact acute. Nine acute lesions were only detected retrospectively and 12 acute lesions were not detected at all on PD+T2. SE-DWI including the apparent diffusion coefficient correlated fairly well with EP-DWI but the procedure was impractical. CONCLUSION: EP-DWI is reliable for diagnosis of early ischemic stroke, while SE-DWI performs reasonably well. Conventional PD+T2 imaging is not reliable for diagnosis of early ischemia.
  •  
14.
  • Geijer, Bo, et al. (författare)
  • The value of b required to avoid T2 shine-through from old lucunar infarcts in diffusion-weighted imaging
  • 2001
  • Ingår i: Neuroradiology. - : Springer. - 1432-1920. ; 43:7, s. 511-517
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiple small infarcts of different ages are common in small-vessel disease. Diffusion-weighted imaging (DWI) is a powerful method for discriminating new from chronic lesions. This can be done on the diffusion-weighted images provided that b is sufficiently high. Our purpose was to determine that critical value of b. We reviewed DWI from a previous study of acute, mainly lacunar strokes, and selected 18 old lacunar infarcts, well defined on uncoded images with b 0 s/m2 (i. e., T2-weighted images) but invisible on DWI with b 1,200 x 10(6) s/m2. We used a 1.5 tesla imager and single-shot echo-planar technique. We had seven separate acquisitions with echo time 123 ms and b in steps between 0 and 1,200 x 10(6) s/m2. Two neuroradiologists blinded to the selection of lesions carried out two different lesion-detection procedures, thereby testing each lesion four times, giving a total of 72 tests of b values. The results were consistent, indicating a level for detection of 800 x 10(6) s/m2 in two tests, 400-600 x 10(6) s/m2 in 65 tests and at lower values in the remainder. For imagers up to 1.5 tesla, at long repetition times and an echo time up to 120 ms T2-shine through of old lacunar infarcts can be avoided using b of 1,000 x 10(6) s/m2.
  •  
15.
  •  
16.
  • Holmqvist, Catarina, et al. (författare)
  • Pre-operative evaluation with MR in tetralogy of fallot and pulmonary atresia with ventricular septal defect
  • 2001
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455. ; 42:1, s. 63-69
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To assess whether MR imaging could replace angiography in preoperative evaluation of patients with tetralogy of Fallot and pulmonary atresia with ventricular septal defect (VSD), especially since the surgical correction was done earlier than was previously the rule. MATERIAL AND METHODS: Fourteen patients with tetralogy of Fallot (n = 10) or pulmonary atresia with VSD (n = 4), mean age 7.5 +/- 4.4 months, were evaluated with angiocardiography and MR before definitive surgical correction. RESULTS: There was good diagnostic agreement between the two modalities when evaluating right ventricular outflow obstruction; 86% for valvular and 93% for supravalvular stenosis, but the agreement was somewhat lower for the subvalvular obstruction (57%). Surgery findings, however, were in favour of MR in 5 patients concerning the subvalvular right ventricular outflow tract obstruction. MR images identified all stenoses in the right and left pulmonary arteries, but overlooked one stenosis in the main pulmonary artery. MR could evaluate patency in all palliative shunts. CONCLUSION: Even in this young age group, MR imaging offers a good alternative to angiocardiography for the pre-operative evaluation of the right ventricular outflow tract, the main pulmonary artery and the proximal right and left pulmonary arteries, before definitive surgical correction of tetralogy of Fallot and pulmonary atresia with VSD.
  •  
17.
  •  
18.
  • Lindgren, Arne, et al. (författare)
  • Clinical lacunar syndromes as predictors of lacunar infarcts. A comparison of acute clinical lacunar syndromes and findings on diffusion-weighted MRI
  • 2000
  • Ingår i: Acta Neurologica Scandinavica. - : Wiley-Blackwell. - 1600-0404. ; 101:2, s. 128-134
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: To evaluate if patients with acute lacunar syndromes have acute lacunar infarcts or other types of cerebral lesions on diffusion-weighted MRI. METHODS: Patients with acute lacunar syndromes underwent echo-planar diffusion MRI of the brain within 3 days after stroke onset. Localization and size of lesions with hyperintense signal were determined, compared with clinical characteristics and with findings on follow-up T2-weighted MRI. RESULTS: Twenty-three patients participated in the study. Thirteen patients had pure motor stroke, 1 pure sensory stroke, 8 sensorimotor stroke, and 1 ataxic hemiparesis. Twenty-two patients had at least one lesion with increased signal on diffusion-weighted MR images. These acute lesions were in the internal capsule/ basal ganglia/thalamus in 13 patients, subcortical white matter in 5 patients, brainstem in 2 patients, cortex (multiple small lesions) in 1 patient, and cortex + basal ganglia in 1 patient. The median volume of the lesions was 0.6 ml on the initial examination and on follow-up, of 17 patients after 1 to 5 months, 0.5 ml. CONCLUSIONS: Almost all patients with acute ischemic lacunar syndromes have acute lesions on echo-planar diffusion-weighted MRI within 3 days after stroke onset. These lesions are mostly small and subcortical, compatible with lacunar infarcts caused by single penetrating artery occlusion, but in a minor proportion of patients (2 of 23 in our study) a cortical involvement is found.
  •  
19.
  • Lätt, Jimmy, et al. (författare)
  • Accuracy of q-space related parameters in MRI: Simulations and phantom measurements
  • 2007
  • Ingår i: IEEE Transactions on Medical Imaging. - : IEEE - Institute of Electrical and Electronics Engineers Inc.. - 1558-254X. ; 26:11, s. 1437-1447
  • Tidskriftsartikel (refereegranskat)abstract
    • The accuracy of q-space measurements was evaluated at a 3.0-T clinical magnetic resonance imaging (MRI) scanner, as compared with a 4.7-T nuclear magnetic resonance (NMR) spectrometer. Measurements were performed using a stimulated-echo pulse-sequence on n-decane as well as on polyethylene glycol (PEG) mixed with different concentrations of water, in order to obtain bi-exponential signal decay curves. The diffusion coefficients as well as the modelled diffusional kurtosis K-fit, were obtained from the signal decay curve, while the full-width at half-maximum (FWHM) and the diffusional kurtosis K were obtained from the displacement distribution. Simulations of restricted diffusion, under conditions similar to those obtainable with a clinical MRI scanner, were carried out assuming various degrees of violation of the short gradient pulse (SGP) condition and of the long diffusion time limit., The results indicated that an MRI system can not be used for quantification of structural sizes less than about 10 mu m by means of FWHM since the parameter underestimates the confinements due to violation of the SGP condition. However, FWHM can still be used as an important contrast parameter. The obtained kurtosis values were lower than expected from theory and the results showed that care must be taken when interpreting a kurtosis estimate deviating from zero.
  •  
20.
  • Lätt, Jimmy, et al. (författare)
  • Diffusion-weighted MRI measurements on stroke patients reveal water-exchange mechanisms in sub-acute ischaemic lesions.
  • 2009
  • Ingår i: NMR in Biomedicine. - : John Wiley and Sons Inc.. - 0952-3480. ; 22:6, s. 619-628
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to investigate the diffusion time dependence of signal-versus-b curves obtained from diffusion-weighted magnetic resonance imaging (DW-MRI) of sub-acute ischaemic lesions in stroke patients. In this case series study, 16 patients with sub-acute ischaemic stroke were examined with DW-MRI using two different diffusion times (60 and 260 ms). Nine of these patients showed sufficiently large lesions without artefacts to merit further analysis. The signal-versus-b curves from the lesions were plotted and analysed using a two-compartment model including compartmental exchange. To validate the model and to aid the interpretation of the estimated model parameters, Monte Carlo simulations were performed. In eight cases, the plotted signal-versus-b curves, obtained from the lesions, showed a signal-curve split-up when data for the two diffusion times were compared, revealing effects of compartmental water exchange. For one of the patients, parametric maps were generated based on the extracted model parameters. These novel observations suggest that water exchange between different water pools is measurable and thus potentially useful for clinical assessment. The information can improve the understanding of the relationship between the DW-MRI signal intensity and the microstructural properties of the lesions. Copyright (c) 2009 John Wiley & Sons, Ltd.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 11-20 av 38
  • Föregående 1[2]34Nästa
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy