| 1. |
- Lindgren, Arne, et al.
(författare)
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Clinical lacunar syndromes as predictors of lacunar infarcts. A comparison of acute clinical lacunar syndromes and findings on diffusion-weighted MRI
- 2000
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Ingår i: Acta Neurologica Scandinavica. - : Hindawi Limited. - 1600-0404 .- 0001-6314. ; 101:2, s. 128-134
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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.
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| 2. |
- Staaf, Gert, et al.
(författare)
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Diffusion-weighted MRI findings in patients with capsular warning syndrome
- 2004
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Ingår i: Cerebrovascular Diseases. - : S. Karger AG. - 1421-9786 .- 1015-9770. ; 17:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Background and Purpose: The 'capsular warning syndrome' (CWS) of recurrent stereotyped episodes of motor or sensory dysfunction is clinically well recognized, and is associated with a high risk of imminent lacunar infarction with permanent deficits resembling those of CWS. However, the pathophysiology of CWS has not been well characterized. We report a clinicoanatomic correlation with MR imaging studies in the acute and chronic phases in patients with CWS. Material and Methods: Between April 1997 and March 2001, we prospectively studied 8 patients, mean age 73.3 years, presenting with 4 - 17 motor or sensorimotor transient ischemic attacks ( TIAs; duration 2 - 90 min) up to 3 days after onset of the first episode. Four patients were free of symptoms between the attacks and had no residua, whereas 4 patients developed a pure motor or sensorimotor stroke within 1 - 3 days after symptom onset. Diffusion-weighted echoplanar MRI (DWI) and T-2-weighted MRI studies were performed within 1 week after symptom onset and were repeated 1 - 2 months later. Results: Seven of the 8 patients had an appropriate lesion on DWI in the acute phase. DWI abnormalities in the 3 patients with TIAs were 4 - 10 mm in diameter and confined to the lateral thalamus or medial globus pallidus without involving the internal capsule, whereas 4 patients who developed a stroke had abnormalities localized to the putamen extending to corona radiata ( 3 patients), or the pontomesencephalic junction ( 1 patient). All 6 patients who underwent follow-up MRI had an infarct on T-2-weighted images corresponding to, but usually smaller than, the acute phase DWI abnormality. Conclusions: Small infarcts in the basal ganglia or the pons, close to central motor pathways, appear to be the primary lesion in CWS. The pathophysiology of CWS is complex, and may involve hemodynamic mechanisms in penetrating arterial territories, as well as molecular mechanisms, such as peri-infarct depolarizations affecting adjacent motor pathways. Copyright (C) 2004 S. Karger AG, Basel.
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| 3. |
- Björkman-Burtscher, Isabella, et al.
(författare)
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Proton MR spectroscopy and preoperative diagnostic accuracy: an evaluation of intracranial mass lesions characterized by stereotactic biopsy findings
- 2000
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Ingår i: AJNR. - 1936-959X. ; 21:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: MR imaging has made it easier to distinguish among the different types of intracranial mass lesions. Nevertheless, it is sometimes impossible to base a diagnosis solely on clinical and neuroradiologic findings, and, in these cases, biopsy must be performed. The purpose of this study was to evaluate the hypothesis that proton MR spectroscopy is able to improve preoperative diagnostic accuracy in cases of intracranial tumors and may therefore obviate stereotactic biopsy. METHODS: Twenty-six patients with intracranial tumors underwent MR imaging, proton MR spectroscopy, and stereotactic biopsy. MR spectroscopic findings were evaluated for the distribution pattern of pathologic spectra (NAA/Cho ratio < 1) across the lesion and neighboring tissue, for signal ratios in different tumor types, and for their potential to improve preoperative diagnostic accuracy. RESULTS: Gliomas and lymphomas showed pathologic spectra outside the area of contrast enhancement while four nonastrocytic circumscribed tumors (meningioma, pineocytoma, metastasis, and germinoma) showed no pathologic spectra outside the region of enhancement. No significant correlation was found between different tumor types and signal ratios. MR spectroscopy improved diagnostic accuracy by differentiating infiltrative from circumscribed tumors; however, diagnostic accuracy was not improved in terms of differentiating the types of infiltrative or circumscribed lesions. CONCLUSION: MR spectroscopy can improve diagnostic accuracy by differentiating circumscribed brain lesions from histologically infiltrating processes, which may be difficult or impossible solely on the basis of clinical or neuroradiologic findings.
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| 4. |
- Cronqvist, Mats, et al.
(författare)
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Diffusion- and perfusion-weighted MRI in therapeutic neurointerventional procedures
- 2001
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 43:8, s. 662-671
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Tidskriftsartikel (refereegranskat)abstract
- We describe three patients in whom we used MRI, including diffusion- and perfusion-weighted imaging (DWI, PWI) in conjunction with endovascular therapy. Two had intracranial aneurysms and one an arteriovenous malformation (AVM). The aneurysms were treated by coil embolisation or detachable balloons for proximal artery occlusion; the AVM was obliterated by intranidal glue injection. All patients had transient or permanent neurological deficits after treatment. The MRI techniques and interventional procedures are described and the DWI and PWI patterns found are correlated with the clinical features. We discuss how the information gained from MRI may increase our understanding of procedure-related complications and its potential impact on our therapeutic interventions, in order to prevent or limit the clinical consequences of such events.
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| 5. |
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| 6. |
- Geijer, Bo
(författare)
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Diffusion MRI of Small Ischemic Brain Lesions: Technical aspects, clinical experiences and diagnostic criteria.
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: To compare the visualization of small ischemic brain lesions using diffusion using diffusion-weighted (DW) MRI and conventional imaging, with special regard to diagnostic efficiency. Imaging features of lesions of different ages, diagnostic limitations and technical principles were also investigated. Methods: All studies were performed with the same 1.5 T MR scanner. In the first study the diagnostic efficiencies of a conventional spin-echo (SE) PD and T2-weighted sequence, an echo-planar (EP) DW sequence and a DW conventional SE sequence in detecting acute stroke lesions in 27 patients were compared. In the second study imaging features of small ischemic lesions from 21 of the 27 patients in the first study were observed until the lesions became chronic. In the third study 18 preexisting chronic lacunar infarcts were selected from the EP DW images in the first study. The lowest value of b which led to them all being invisible in the DW images was determined. In the fourth study three EP DW acquisitions with and without ECG triggering were obtained in 6 healthy volunteers. Maps of the apparent diffusion coefficient (ADC) were calculated from all the acquisitions. The value of the ADC was measured in the same four positions on each map. The dependence of the measured values of ADC on ECG triggering was evaluated. In the fifth study 12 patients with brain metastases were examined with an EP DW sequence and a T2-weighted sequence. The features of the metastases were compared with the diagnostic criteria commonly used for acute and subacute small infarcts. Results and conclusions: An EP DW sequence is very efficient in detecting new ischemic lesions. A DW SE sequence performs well but it requires a perfectly cooperative patient. A conventional PD and T2-weighted sequence has low sensitivity and specificity. Ten of 21 small ischemic lesions exhibited persisting high signals in the DW images and 2 of them exhibited a decrease in ADC two months after the stroke. All these lesions became invisible and showed a high ADC at an examination after 1 year or more. A value of b = 1000•10E06 s/m2 was sufficient to make chronic lacunar infarcts invisible in DW images when the echo time was no longer than 120 ms. Some metastases have imaging features in common with small acute and subacute ischemic lesions when a standard MR protocol for acute stroke is used.
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| 7. |
- Geijer, Bo, et al.
(författare)
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Diffusion-weighted imaging of brain metastases: their potential to be misinterpreted as focal ischaemic lesions.
- 2002
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 44:7, s. 568-573
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Tidskriftsartikel (refereegranskat)abstract
- Small focal ischaemic brain lesions are said to be easy to identify in the acute stage and to differentiate from older lesions using diffusion-weighted imaging (DWI). Brain metastases are common and the aim of this study was to evaluate the risk of misinterpretation as ischaemic lesions in a standard MRI protocol for clinical stroke. Of 26 patients investigated with MRI for possible metastases, 12 did have metastatic brain lesions, including most of the common tumours. On a 1.5 tesla imager, we obtained DWI, plus T2- and T1-weighted images, the latter before and after triple-dose contrast medium. Well-circumscribed brain lesions with a decreased apparent diffusion coefficient and a slightly or moderately increased signal on T2-weighted images were found in patients with metastases from a small-cell bronchial carcinoma and a pulmonary adenocarcinoma. The same features were also found in metastases from a breast carcinoma but the lesions were surrounded by oedema. With a standard DWI protocol, the features of common brain metastases may overlap with those of small acute and subacute ischaemic lesions.
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| 8. |
- Geijer, Bo, et al.
(författare)
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Persistent high signal on diffusion-weighted MRI in the late stages of small cortical and lacunar ischaemic lesions
- 2001
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 43:2, s. 115-122
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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.
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| 9. |
- Geijer, Bo, et al.
(författare)
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The value of b required to avoid T2 shine-through from old lucunar infarcts in diffusion-weighted imaging
- 2001
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 43:7, s. 511-517
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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.
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| 10. |
- Holtås, Stig, et al.
(författare)
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A ring-enhancing metastasis with central high signal on diffusion-weighted imaging and low apparent diffusion coefficients
- 2000
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 42:11, s. 824-827
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion-weighted imaging (DWI) has been reported to be useful in the differential diagnosis between abscesses and cystic or necrotic tumours. However, experience is still limited and the true sensitivity and specificity remain to be determined. Our purpose is to describe a ring-enhancing metastasis of adenocarcinoma with a DWI pattern similar to that reported for abscesses. The tumour had a diameter of 1.5 cm and give signal from its centre similar to that of normal brain on T1-weighted images, whereas it was increased on T2-weighted images, and surrounded by a low signal ring, suggesting a capsule. The signal was high on DWI and the apparent diffusion coefficient (ADC) was low (0.55 x 10(-3) mm2/s). The findings were misinterpreted as representing an abscess in the early capsule-formation stage, but the signal pattern probably represented early tumour necrosis with intracellular oedema, but without liquefaction. Findings on DWI during the early capsule formation stage in abscesses and early tumour necrosis are probably similar and must be interpreted with caution.
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