| 1. |
- Fahlström, Markus, et al.
(författare)
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A mathematical model for temporal cerebral blood flow response to acetazolamide evaluated in patients with Moyamoya disease
- 2024
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Ingår i: Magnetic Resonance Imaging. - : Elsevier. - 0730-725X .- 1873-5894. ; 110, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- Background: Paired cerebral blood flow (CBF) measurement is usually acquired before and after vasoactive stimulus to estimate cerebrovascular reserve (CVR). However, CVR may be confounded because of variations in time-to-maximum CBF response (tmax) following acetazolamide injection. With a mathematical model, CVR can be calculated insensitive to variations in tmax, and a model offers the possibility to calculate additional model-derived parameters. A model that describes the temporal CBF response following a vasodilating acetazolamide injection is proposed and evaluated.Methods: A bi-exponential model was adopted and fitted to four CBF measurements acquired using arterial spin labelling before and initialised at 5, 15 and 25 min after acetazolamide injection in a total of fifteen patients with Moyamoya disease. Curve fitting was performed using a non-linear least squares method with a priori constraints based on simulations.Results: Goodness of fit (mean absolute error) varied between 0.30 and 0.62 ml·100 g-1·min-1. Model-derived CVR was significantly higher compared to static CVR measures. Maximum CBF increase occurred earlier in healthy- compared to diseased vascular regions.Conclusions: The proposed mathematical model offers the possibility to calculate CVR insensitive to variations in time to maximum CBF response which gives a more detailed characterisation of CVR compared to static CVR measures. Although the mathematical model adapts generally well to this dataset of patients with MMD it should be considered as experimental; hence, further studies in healthy populations and other patient cohorts are warranted.
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| 2. |
- Abu Hamdeh, Sami, et al.
(författare)
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Extended anatomical grading in diffuse axonal injury using MRI : Hemorrhagic lesions in the substantia nigra and mesencephalic tegmentum indicate poor long-term outcome
- 2017
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 0897-7151 .- 1557-9042. ; 5:34, s. 341-352
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Tidskriftsartikel (refereegranskat)abstract
- Clinical outcome after traumatic diffuse axonal injury (DAI) is difficult to predict. In this study, three magnetic resonance imaging (MRI) sequences were used to quantify the anatomical distribution of lesions, to grade DAI according to the Adams grading system, and to evaluate the value of lesion localization in combination with clinical prognostic factors to improve outcome prediction. Thirty patients (mean 31.2 years ±14.3 standard deviation) with severe DAI (Glasgow Motor Score [GMS] <6) examined with MRI within 1 week post-injury were included. Diffusion-weighted (DW), T2*-weighted gradient echo and susceptibility-weighted (SWI) sequences were used. Extended Glasgow outcome score was assessed after 6 months. Number of DW lesions in the thalamus, basal ganglia, and internal capsule and number of SWI lesions in the mesencephalon correlated significantly with outcome in univariate analysis. Age, GMS at admission, GMS at discharge, and low proportion of good monitoring time with cerebral perfusion pressure <60 mm Hg correlated significantly with outcome in univariate analysis. Multivariate analysis revealed an independent relation with poor outcome for age (p = 0.005) and lesions in the mesencephalic region corresponding to substantia nigra and tegmentum on SWI (p = 0.008). We conclude that higher age and lesions in substantia nigra and mesencephalic tegmentum indicate poor long-term outcome in DAI. We propose an extended MRI classification system based on four stages (stage I—hemispheric lesions, stage II—corpus callosum lesions, stage III—brainstem lesions, and stage IV—substantia nigra or mesencephalic tegmentum lesions); all are subdivided by age (≥/<30 years).
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| 3. |
- Abu Hamdeh, Sami, et al.
(författare)
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Intracranial pressure elevations in diffuse axonal injury : association with nonhemorrhagic MR lesions in central mesencephalic structures
- 2019
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Ingår i: Journal of Neurosurgery. - 0022-3085 .- 1933-0693. ; 131:2, s. 604-611
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Increased intracranial pressure (ICP) in patients with severe traumatic brain injury (TBI) with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in patients with DAI.Methods: Fifty-two patients with severe TBI (median age 24 years, range 9–61 years), who had undergone ICP monitoring and had DAI on MRI, as determined using T2*-weighted gradient echo, susceptibility-weighted imaging, and diffusion-weighted imaging (DWI) sequences, were enrolled. The proportion of good monitoring time (GMT) with ICP > 20 mm Hg during the first 120 hours postinjury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression.Results: All patients had episodes of ICP > 20 mm Hg. The mean proportion of GMT with ICP > 20 mm Hg was 5%, and 27% of the patients (14/52) spent more than 5% of GMT with ICP > 20 mm Hg. The Glasgow Coma Scale motor score at admission (p = 0.04) and lesions on DWI sequences in the substantia nigra and mesencephalic tegmentum (SN-T, p = 0.001) were associated with the proportion of GMT with ICP > 20 mm Hg. In multivariable linear regression, lesions on DWI sequences in SN-T (8% of GMT with ICP > 20 mm Hg, 95% CI 3%–13%, p = 0.004) and young age (−0.2% of GMT with ICP > 20 mm Hg, 95% CI −0.07% to −0.3%, p = 0.002) were associated with increased ICP.Conclusions: Increased ICP occurs in approximately one-third of patients with severe TBI who have DAI. Age and lesions on DWI sequences in the central mesencephalon (i.e., SN-T) are associated with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in patients with DAI.Abbreviations: ADC = apparent diffusion coefficient; CPP = cerebral perfusion pressure; DAI = diffuse axonal injury; DWI = diffusion-weighted imaging; EVD = external ventricular drain; GCS = Glasgow Coma Scale; GMT = good monitoring time; GOSE = Glasgow Outcome Scale–Extended; ICC = intraclass correlation coefficient; ICP = intracranial pressure; MAP = mean arterial blood pressure; NICU = neurointensive care unit; SN-T = substantia nigra and mesencephalic tegmentum; SWI = susceptibility-weighted imaging; TBI = traumatic brain injury; T2*GRE = T2*-weighted gradient echo.
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| 4. |
- Abu Hamdeh, Sami, et al.
(författare)
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Intracranial pressure elevations in diffuse axonal injury are associated with non-hemorrhagic MR lesions in central mesencephalic structures
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objective: Increased intracranial pressure (ICP) in severe traumatic brain injury (TBI) patients with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in DAI patients.Methods: Fifty-two severe TBI patients (median 24, range 9-61 years), with ICP-monitoring and DAI on MRI, using T2*-weighted gradient echo, susceptibility-weighted and diffusion-weighted (DW) sequences, were enrolled. Proportion of good monitoring time (GMT) with ICP>20 mmHg during the first 120 hours post-injury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression. Results: All patients had episodes of ICP>20 mmHg. The mean proportion of GMT with ICP>20 mmHg was 5% and 27% of the patients (14/52) had more than 5% of GMT with ICP>20 mmHg. Glasgow Coma Scale motor score at admission (P=0.04) and lesions on DW images in the substantia nigra and mesencephalic tegmentum (SN-T, P=0.001) were associated with the proportion of GMT with ICP>20 mmHg. In multivariate linear regression, lesions on DW images in SN-T (8% of GMT with ICP>20 mmHg, 95% CI 3–13%, P=0.004) and young age (-0.2% of GMT with ICP>20 mmHg, 95% CI -0.07–-0.3%, P=0.0008) were associated with increased ICP. Conclusions: Increased ICP occurs in ~1/3 of severe TBI patients with DAI. Age and lesions on DW images in the central mesencephalon (SN-T) associate with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in DAI patients.
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| 5. |
- Abu Hamdeh, Sami, et al.
(författare)
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MRI analysis of diffuse axonal injury - Hemorrhagic lesions in the mesencephalon idicate poor long-term outcome
- 2016
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Ingår i: MRI analysis of diffuse axonal injury - Hemorrhagic lesions in the mesencephalon idicate poor long-term outcome. - : Springer.
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Konferensbidrag (refereegranskat)abstract
- Purpose: Clinical outcome after traumatic diffuse axonal injury (DAI) is difficult to predict. Three MRI techniques were compared in demonstrating acute brain lesions. Relationship of the anatomical distribution of the lesions in combination with clinical prognostic factors to outcome after 6 months was evaluated. Methods and Materials: Thirty patients, aged 16-60 years (mean 31.2 years) with severe DAI (Glasgow Motor Score = GMS < 6) were examined with MRI at 1.5T within one week after the injury. A diffusion-weighted (DW) sequence (SE-EPI, b value 1000 s/mm2), a T2*-weighted gradient echo (T2*GRE) sequence and a susceptibility-weighted (SWI) sequence were evaluated by two independent reviewers with short and long neuroradiological experiences. Clinical outcome was assessed with Extended Glasgow Outcome Score (GOSE) after ≥ 6 months.Results: Interreviewer agreement for DAI classification was very good (ҡ 0.82 – 0.91) with all three sequences. SWI visualized more lesions than the T2*GRE or DW sequence. In univariate analysis, number of DW lesions in the deep gray matter area including the internal capsules, number of SWI lesions in the mesencephalon, age, and GMS at admission and discharge correlated significantly with poor outcome. Multivariate analysis only revealed an independent relation with poor outcome for age (p = 0.011) and lesions in the mesencephalic region including crura cerebri, substantia nigra and tegmentum on SWI (p = 0.032).Conclusion: SWI is the most sensitive technique to visualize lesions in DAI. Age over 30 years and hemorrhagic mesencephalic lesions anterior to the tectum are indicators of poor long-term outcome in DAI.
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| 6. |
- Fahlström, Markus, et al.
(författare)
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Evaluation of single-delay arterial spin labeling-based spatial coefficient of variation and histogram-based parameters in relation to cerebrovascular reserve in patients with Moyamoya disease.
- 2023
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Ingår i: Frontiers in Neurology. - : Frontiers Media S.A.. - 1664-2295. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Single-delay Arterial Spin Labeling (ASL)-based spatial coefficient of variation (CoVCBF) has been suggested as a measure of hemodynamic disturbance in patients with cerebrovascular diseases. However, spatial CoVCBF and other histogram-based parameters such as skewness and kurtosis and the volume of the arterial transit time artefact (ATAvol), has not been evaluated in patients with MMD nor against cerebrovascular reserve (CVR). The aim of this study was to assess whether any associations between spatial CoVCBF, skewness, kurtosis, and ATAvol are present and to analyze any potential associations with CVR, derived from single-delay ASL in patients with MMD.METHODS: Fifteen MMD patients were included before or after revascularization surgery. Cerebral blood flow (CBF) maps were acquired using pseudo-continuous ASL before, and 5, 15, and 25 min after an intravenous acetazolamide injection. CVRmax was defined as the highest percentual increase in CBF at any of the three post-injection time points. A vascular territory template was spatially normalized to each patient, including the bilateral anterior, middle, and posterior cerebral arteries. All affected anterior and middle cerebral artery regions and all unaffected posterior cerebral artery regions were included, based on Suzuki grading by digital subtraction angiography.RESULTS: Significant differences between affected and unaffected regions were found for CBF, CVRmax, and ATAvol. No association was found between CVRmax and any other parameter. High correlations were found between spatial CoVCBF, skewness and ATAvol.CONCLUSION: Spatial CoVCBF derived from single-delay ASL does not correlate with CVR in patients with MMD. Moreover, skewness and kurtosis did not provide additional information of clinical value.
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| 7. |
- Fahlström, Markus, et al.
(författare)
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High Intravascular Signal Arterial Transit Time Artifacts Have Negligible Effects on Cerebral Blood Flow and Cerebrovascular Reserve Capacity Measurement Using Single Postlabel Delay Arterial Spin-Labeling in Patients with Moyamoya Disease
- 2020
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Ingår i: American Journal of Neuroradiology. - 0195-6108 .- 1936-959X. ; 41:3, s. 430-436
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Arterial spin-labeling-derived CBF values may be affected by arterial transit time artefacts. Thus, our aim was to assess to what extent arterial spin-labeling–derived CBF and cerebrovascular reserve capacity values in major vascular regions are overestimated due to the arterial transit time artifacts in patients with Moyamoya disease.MATERIALS AND METHODS: Eight patients with Moyamoya disease were included before or after revascularization surgery. CBF maps were acquired using a 3D pseudocontinuous arterial spin-labeling sequence, before and 5, 15, and 25 minutes after an IV acetazolamide injection and were registered to each patient’s 3D-T1-weighted images. Vascular regions were defined by spatial normalization to a Montreal Neurological Institute–based vascular regional template. The arterial transit time artifacts were defined as voxels with high signal intensity corresponding to the right tail of the histogram for a given vascular region, with the cutoff selected by visual inspection. Arterial transit time artifact maps were created and applied as masks to exclude arterial transit time artifacts on CBF maps, to create corrected CBF maps. The cerebrovascular reserve capacity was calculated as CBF after acetazolamide injection relative to CBF at baseline for corrected and uncorrected CBF values, respectively.RESULTS: A total of 16 examinations were analyzed. Arterial transit time artifacts were present mostly in the MCA, whereas the posterior cerebral artery was generally unaffected. The largest differences between corrected and uncorrected CBF and cerebrovascular reserve capacity values, reported as patient group average ratio and percentage point difference, respectively, were 0.978 (95% CI, 0.968–0.988) and 1.8 percentage points (95% CI, 0.3–3.2 percentage points). Both were found in the left MCA, 15 and 5 minutes post-acetazolamide injection, respectively.CONCLUSIONS: Arterial transit time artifacts have negligible overestimation effects on calculated vascular region-based CBF and cerebrovascular reserve capacity values derived from single-delay 3D pseudocontinuous arterial spin-labeling.
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| 8. |
- Fahlström, Markus, et al.
(författare)
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Variable Temporal Cerebral Blood Flow Response to Acetazolamide in Moyamoya Patients Measured Using Arterial Spin Labeling
- 2021
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Ingår i: Frontiers in Neurology. - : Frontiers Media S.A.. - 1664-2295. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrovascular reserve capacity (CVR), an important predictor of ischaemic events and a prognostic factor for patients with moyamoya disease (MMD), can be assessed by measuring cerebral blood flow (CBF) before and after administration of acetazolamide (ACZ). Often, a single CBF measurement is performed between 5 and 20 min after ACZ injection. Assessment of the temporal response of the vasodilation secondary to ACZ administration using several repeated CBF measurements has not been studied extensively. Furthermore, the high standard deviations of the group-averaged CVRs reported in the current literature indicate a patient-specific dispersion of CVR values over a wide range. This study aimed to assess the temporal response of the CBF and derived CVR during ACZ challenge using arterial spin labeling in patients with MMD. Eleven patients with MMD were included before or after revascularisation surgery. CBF maps were acquired using pseudo-continuous arterial spin labeling before and 5, 15, and 25 min after an intravenous ACZ injection. A vascular territory template was spatially normalized to patient-specific space, including the bilateral anterior, middle, and posterior cerebral arteries. CBF increased significantly post-ACZ injection in all vascular territories and at all time points. Group-averaged CBF and CVR values remained constant throughout the ACZ challenge in most patients. The maximum increase in CBF occurred most frequently at 5 min post-ACZ injection. However, peaks at 15 or 25 min were also present in some patients. In 68% of the affected vascular territories, the maximum increase in CBF did not occur at 15 min. In individual cases, the difference in CVR between different time points was between 1 and 30% points (mean difference 8% points). In conclusion, there is a substantial variation in CVR between different time points after the ACZ challenge in patients with MMD. Thus, there is a risk that the use of a single post-ACZ measurement time point overestimates disease progression, which could have wide implications for decision-making regarding revascularisation surgery and the interpretation of the outcome thereof. Further studies with larger sample sizes using multiple CBF measurements post-ACZ injection in patients with MMD are encouraged.
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| 9. |
- Lewén, Anders, 1965-, et al.
(författare)
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ASL-MRI-guided evaluation of multiple burr hole revascularization surgery in Moyamoya disease
- 2023
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Ingår i: Acta Neurochirurgica. - : Springer Nature. - 0001-6268 .- 0942-0940. ; 165:8, s. 2057-2069
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Moyamoya (MM) disease is characterized by progressive intracranial arterial stenosis. Patients commonly need revascularization surgery to optimize cerebral blood flow (CBF). Estimation of CBF and cerebrovascular reserve (CVR) is therefore necessary before and after surgery. However, assessment of CBF before and after indirect revascularization surgery with the multiple burr hole (MBH) technique in MM has not been studied extensively. In this study, we describe our initial experience using arterial spin labeling magnetic resonance perfusion imaging (ASL-MRI) for CBF and CVR assessment before and after indirect MBH revascularization surgery in MM patients.METHODS: Eleven MM patients (initial age 6-50 years, 1 male/10 female) with 19 affected hemispheres were included. A total of 35 ASL-MRI examinations were performed using a 3D-pCASL acquisition before and after i.v. acetazolamide challenge (1000 mg in adults and 10 mg/kg in children). Twelve MBH procedures were performed in seven patients. The first follow-up ASL-MRI was performed 7-21 (mean 12) months after surgery.RESULTS: Before surgery, CBF was 46 ± 16 (mean ± SD) ml/100 g/min and CVR after acetazolamide challenge was 38.5 ± 9.9 (mean ± SD)% in the most affected territory (middle cerebral artery). In cases in which surgery was not performed, CVR was 56 ± 12 (mean ± SD)% in affected hemispheres. After MBH surgery, there was a relative change in CVR compared to baseline (preop) of + 23.5 ± 23.3% (mean ± SD). There were no new ischemic events.CONCLUSION: Using ASL-MRI we followed changes in CBF and CVR in patients with MM. The technique was encouraging for assessments before and after revascularization surgery.
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| 10. |
- Svedung-Wettervik, Teodor, et al.
(författare)
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Cerebrovascular reserve in moyamoya disease: relation to cerebral blood flow, capillary dysfunction, oxygenation, and energy metabolism
- 2023
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Ingår i: Frontiers in Neurology. - 1664-2295. ; :14
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cerebral hemodynamics in moyamoya disease (MMD) is complex and needs further elucidation. The primary aim of the study was to determine the association of the cerebrovascular reserve (CVR) with cerebral blood flow (CBF) disturbances, oxygen extraction fraction (OEFmax), and energy metabolism (CMROmax2) in MMD, using arterial spin label magnetic resonance imaging (ASL-MRI) before and after acetazolamide administration.Methods: Thirty-nine ASL-MRI scans with a concurrent acetazolamide challenge from 16 MMD patients at the Uppsala University Hospital, Sweden, 2016–2021, were retrospectively analyzed. CBF was assessed before and 5, 15, and 25 min after acetazolamide administration, and the maximal response CVRmax was used for further analyses. Dynamic susceptibility contrast (DSC) MRI was performed 30 min after acetazolamide injection, and the data were analyzed using the Cercare Medical Neurosuite to assess capillary transit time heterogeneity (CTTH; indicating microvascular function), OEFmax, and CMROmax2.Results: In the ACA territory, a lower CVRmax was associated with lower baseline CBF, higher CTTH, and higher OEFmax but not with CMROmax2 in generalized estimating equation models. In the MCA territory, lower CVRmax was associated with lower baseline CBF and higher CMROmax2but not with CTTH and OEFmax..Conclusion: Altogether, a compromised CVR in MMD patients reflected disturbances in macro-/microvascular blood flow, oxygenation, and CMRO2. ASL-MRI with acetazolamide challenge is a feasible and radiation-free alternative to positron emission tomography (PET) imaging in MMD.
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