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  • 1
    In: Brain and Behavior, Wiley, Vol. 6, No. 2 ( 2016-02)
    Abstract: We elaborate on existing analysis methods for breath‐hold ( BH )‐derived cerebrovascular reactivity ( CVR ) measurements and describe novel insights and models toward more exact CVR interpretation. Methods Five blood‐oxygen‐level‐dependent ( BOLD ) fMRI datasets of neurovascular patients with unilateral hemispheric hemodynamic impairment were used to test various BH CVR analysis methods. Temporal lag (phase), percent BOLD signal change ( CVR ), and explained variance (coherence) maps were calculated using three different sine models and two novel “Optimal Signal” model‐free methods based on the unaffected hemisphere and the sagittal sinus fMRI signal time series, respectively. Results All models showed significant differences in CVR and coherence between the affected—hemodynamic impaired—and unaffected hemisphere. Voxel‐wise phase determination significantly increases CVR (0.60 ± 0.18 vs. 0.82 ± 0.27; P   〈  0.05). Incorporating different durations of breath hold and resting period in one sine model (two‐task) did increase coherence in the unaffected hemisphere, as well as eliminating negative phase commonly obtained by one‐task frequency models. The novel model‐free “optimal signal” methods both explained the BOLD MR data similar to the two task sine model. Conclusions Our CVR analysis demonstrates an improved CVR and coherence after implementation of voxel‐wise phase and frequency adjustment. The novel “optimal signal” methods provide a robust and feasible alternative to the sine models, as both are model‐free and independent of compliance. Here, the sagittal sinus model may be advantageous, as it is independent of hemispheric CVR impairment.
    Type of Medium: Online Resource
    ISSN: 2162-3279 , 2162-3279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 2623587-0
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  • 2
    In: Lasers in Surgery and Medicine, Wiley, Vol. 42, No. 5 ( 2010-07), p. 418-424
    Abstract: A key element in the Excimer Laser Assisted Non‐occlusive Anastomosis (ELANA) technique is the retrieval of a disc (“flap”) of artery wall from the anastomosis by the laser catheter tip. We assessed if the flap retrieval rate could be optimized. Methods We used a specially designed in vitro model using rabbit aortas. We tested three essential elements of the technique: (1) laser energy (10, 13, 15, or 18 mJ), (2) pressure on the catheter (0, 0.1, 0.2, or 0.4 N), and (3) number of lasing episodes (1 or 2). We made 2,280 anastomoses using different combinations of settings. With a logistic regression model we assessed the influence of each parameter. Current clinical settings (10 mJ, 0.2 N, 1 episode) were reference categories. Results Flap retrieval rate using conventional settings was 86.7%, equivalent to earlier reported clinical data. A significantly higher flap retrieval appeared when laser energy was increased to 13 mJ (OR 3.0, 95% CI 1.8–4.8), 15 mJ (OR 3.2, 95% CI 1.9–5.3), and 18 mJ (OR 3.7, 95% CI 2.2–6.2). A second lasing episode also significantly increased flap retrieval (OR 2.1, 95% CI 1.4–3.0). However, if we increased energy to 15 or 18 mJ, the effect of a second laser episode was insignificant. When the catheter was pushed down with 0.4 N, flap retrieval decreased significantly in all subgroups (OR 0.07, 95% CI 0.04–0.14). Conclusion The flap retrieval of the ELANA anastomosis technique can be optimized to 100% by setting the laser energy at 15 mJ. However, safety studies are necessary before clinical application. A second lasing episode of 10 mJ is a good alternative to increase the flap retrieval. Moreover, the surgeon should be trained to apply not more than 0.2 N on the catheter. Lasers Surg. Med. 42:418‐424, 2010. © 2010 Wiley‐Liss, Inc.
    Type of Medium: Online Resource
    ISSN: 0196-8092 , 1096-9101
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2010
    detail.hit.zdb_id: 1475539-7
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  • 3
    In: Lasers in Surgery and Medicine, Wiley, Vol. 43, No. 6 ( 2011-08), p. 522-527
    Type of Medium: Online Resource
    ISSN: 0196-8092
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 1475539-7
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  • 4
    In: Epilepsia, Wiley, Vol. 63, No. 10 ( 2022-10)
    Abstract: Seizures in patients with brain metastases have an impact on morbidity and quality of life. The influence of tumor growth on the risk of seizures in these patients is not well defined. In this cohort study, we evaluated adult patients from the University Hospital of Zurich following resection of brain metastases from solid tumors, with or without preoperative seizures, at 3, 6, 9, and 12 months postoperatively. Brain magnetic resonance imaging was assessed for tumor progression using the Response Assessment in Neuro‐Oncology criteria. The quarterly risk of unprovoked seizures was modeled with mixed effects logistic regression. We analyzed 444 time frames in 220 patients. Progression of brain metastases was independently associated with seizures during the respective quarterly follow‐up period (odds ratio = 3.9, 95% confidence interval = 1.3–11.3, p  = .014). Complete resection of brain metastases was associated with a lower risk of seizures (odds ratio = .2, 95% confidence interval = .04–.7, p  = .015). Postoperative progression of brain metastases quadrupled the risk of seizures; therefore, vigorous follow‐up may be useful to identify tumor progression and gauge the risk of seizures. The identification of patients at high seizure risk may have implications for treatment decisions and influence aspects of daily life. Breakthrough seizures may indicate brain metastases progression.
    Type of Medium: Online Resource
    ISSN: 0013-9580 , 1528-1167
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2002194-X
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  • 5
    In: Cancer Medicine, Wiley, Vol. 12, No. 11 ( 2023-06), p. 12316-12324
    Abstract: Established models for prognostic assessment in patients with brain metastasis do not stratify for prior surgery. Here we tested the prognostic accuracy of the Graded Prognostic Assessment (GPA) score model in patients operated for BM and explored further prognostic factors. Methods We included 285 patients operated for brain metastasis at the University Hospital Zurich in the analysis. Information on patient characteristics, imaging, staging, peri‐ and postoperative complications and survival were extracted from the files and integrated into a multivariate Cox hazard model. Results The GPA score showed an association with outcome. We further identified residual tumor after surgery ( p  = 0.007, hazard ratio (HR) 1.6, 95% confidence interval (CI) 1.1–2.3) steroid use ( p  = 0.021, HR 1.7, 95% CI 1.1–2.6) and number of extracranial metastasis sites ( p  = 0.009, HR 1.4, 95% CI 1.1–1.6) at the time of surgery as independent prognostic factors. A trend was observed for postoperative infection of the subarachnoid space ( p  = 0.102, HR 3.5, 95% CI 0.8–15.7). Conclusions We confirm the prognostic capacity of the GPA score in a cohort of operated patients with brain metastasis. However, extent of resection and steroid use provide additional aid for the prognostic assessment in these patients.
    Type of Medium: Online Resource
    ISSN: 2045-7634 , 2045-7634
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2659751-2
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  • 6
    In: Brain and Behavior, Wiley, Vol. 7, No. 9 ( 2017-09)
    Abstract: To improve quantitative cerebrovascular reactivity ( CVR ) measurements and CO 2 arrival times, we present an iterative analysis capable of decomposing different temporal components of the dynamic carbon dioxide‐ Blood Oxygen‐Level Dependent ( CO 2 ‐ BOLD ) relationship. Experimental Design Decomposition of the dynamic parameters included a redefinition of the voxel‐wise CO 2 arrival time, and a separation from the vascular response to a stepwise increase in CO 2 (Delay to signal Plateau – DTP ) and a decrease in CO 2 (Delay to signal Baseline – DTB ). Twenty‐five (normal) datasets, obtained from BOLD MRI combined with a standardized pseudo‐square wave CO 2 change, were co‐registered to generate reference atlases for the aforementioned dynamic processes to score the voxel‐by‐voxel deviation probability from normal range. This analysis is further illustrated in two subjects with unilateral carotid artery occlusion using these reference atlases. Principal Observations We have found that our redefined CO 2 arrival time resulted in the best data fit. Additionally, excluding both dynamic BOLD phases ( DTP and DTB ) resulted in a static CVR , that is maximal response, defined as CVR calculated only over a normocapnic and hypercapnic calibrated plateau. Conclusion Decomposition and novel iterative modeling of different temporal components of the dynamic CO 2 ‐ BOLD relationship improves quantitative CVR measurements.
    Type of Medium: Online Resource
    ISSN: 2162-3279 , 2162-3279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2623587-0
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  • 7
    Online Resource
    Online Resource
    Wiley ; 2006
    In:  Journal of Neuroscience Research Vol. 83, No. 7 ( 2006-05-15), p. 1231-1240
    In: Journal of Neuroscience Research, Wiley, Vol. 83, No. 7 ( 2006-05-15), p. 1231-1240
    Abstract: Cerebral edema contributes to morbidity and mortality in stroke. Aquaporins (AQPs)‐1, ‐4, and ‐9 have been identified as the three main water channels in the brain. To clarify their role in water movement, we have compared their expression patterns with brain swelling after transient focal brain ischemia. There were two peaks of maximal hemispheric swelling at 1 hr and at 48 hr after ischemia, coinciding with two peaks of AQP4 expression. At 1 hr after occlusion, AQP4 expression was significantly increased on astrocyte endfeet in the core and in the border of the lesion. At 48 hr, AQP4 expression was increased in astrocytes in the border of the lesion over the whole cell. AQP9 showed a significant induction at 24 hr that increased gradually with time, without correlation with the swelling. The expression of AQP1 remained unchanged. These results suggest that AQP4, but not AQP1 or AQP9, may play an important role in water movement associated with the pathophysiology of edema after transient cerebral ischemia in the mouse. © 2006 Wiley‐Liss, Inc.
    Type of Medium: Online Resource
    ISSN: 0360-4012 , 1097-4547
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 1474904-X
    SSG: 12
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  • 8
    In: Magnetic Resonance in Medicine, Wiley, Vol. 77, No. 2 ( 2017-02), p. 806-813
    Abstract: To assess the feasibility of functional blood oxygen‐level dependent (BOLD) MRI to evaluate intraoperative cerebrovascular reactivity (CVR) at 3 Tesla field strength. Methods Ten consecutive neurosurgical subjects scheduled for a clinical intraoperative MRI examination were enrolled in this study. In addition to the clinical protocol a BOLD sequence was implemented with three cycles of 44 s apnea to calculate CVR values on a voxel‐by‐voxel basis throughout the brain. The CVR range was then color‐coded and superimposed on an anatomical volume to create high spatial resolution CVR maps. Results Ten subjects (mean age 34.8 ± 13.4; 2 females) uneventfully underwent the intraoperative BOLD protocol, with no complications occurring. Whole‐brain CVR for all subjects was (mean ± SD) 0.69 ± 0.42, whereas CVR was markedly higher for tumor subjects as compared to vascular subjects, 0.81 ± 0.44 versus 0.33 ± 0.10, respectively. Furthermore, color‐coded functional maps could be robustly interpreted for a whole‐brain assessment of CVR. Conclusion We demonstrate that intraoperative BOLD MRI is feasible in creating functional maps to assess cerebrovascular reactivity throughout the brain in subjects undergoing a neurosurgical procedure. Magn Reson Med 77:806–813, 2017. © 2016 International Society for Magnetic Resonance in Medicine
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1493786-4
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  • 9
    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 53, No. 4 ( 2021-04), p. 1190-1197
    Abstract: In patients with steno‐occlusive disease, recent findings suggest that hemodynamic alterations may also be associated with crossed cerebellar diaschisis (CCD) rather than a functional disruption alone. Purpose To use a quantitative multiparametric hemodynamic MRI to gain a better understanding of hemodynamic changes related to CCD in patients with unilateral anterior circulation stroke. Study Type Prospective cohort study. Population Twenty‐four patients (25 datasets) with symptomatic unilateral anterior circulation stroke. Field Strength/Sequence 3T/two sequences: single‐shot (echo‐planar imaging) EPI sequence and T 2 * gradient echo perfusion‐weighted imaging study. Assessment The presence of CCD was inferred from the cerebellar asymmetry index (CAI) of the blood oxygenation‐level dependent cerebrovascular reactivity (BOLD‐CVR) exam, which was calculated from the mean BOLD‐CVR and standard deviation of the CAI of the healthy control group. For all perfusion‐weighted (PW)‐MRI parameters, the cerebellar and middle cerebral artery (MCA) territory asymmetry indices were calculated. Statistical Tests Independent Student's t ‐test to compare the variables from the CCD positive(+) and CCD negative(–) groups and analysis of covariance (ANCOVA) to statistically control the effect of covariates (infarct volume and time since ischemia onset). Results CCD was present in 33% of patients. In the MCA territory of the affected hemisphere, BOLD‐CVR was significantly more impaired in the CCD(+) group as compared to the CCD(–) group (mean BOLD‐CVR ± SD [%BOLD signal/ΔmmHgCO 2 ]: –0.03 ± 0.12 vs. 0.11 ± 0.13, P   〈  0.05). Moreover, the mean transit time (MTT) (asymmetry index (%) CCD(+) vs. CCD(–): 28 ± 23 vs. 4 ± 11, P   〈  0.05) and time to peak (TTP) (10 ± 10 vs. 2 ± 5, P   〈  0.05) in the MCA territory of the affected hemisphere were significantly prolonged, while cerebral blood volume was, on average, increased in the CCD(+) group (25 ± 15 vs. 4 ± 19, P   〈  0.05). Data Conclusion Our findings show that, in patients with symptomatic unilateral anterior circulation stroke, CCD is associated with hemodynamic impairment in the ipsilateral MCA territory, which further supports the concept of a vascular component of CCD. Level of Evidence 3 Technical Efficacy Stage 3
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1497154-9
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  • 10
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  Brain Pathology Vol. 27, No. 2 ( 2017-03), p. 235-236
    In: Brain Pathology, Wiley, Vol. 27, No. 2 ( 2017-03), p. 235-236
    Type of Medium: Online Resource
    ISSN: 1015-6305 , 1750-3639
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2029927-8
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