| 1. |
- Alonso, Fabiola, et al.
(författare)
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Influence of Virchow-Robin spaces on the electric field distribution in subthalamic nucleus deep brain stimulation
- 2021
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Ingår i: Clinical neurology and neurosurgery. - : Elsevier. - 0303-8467 .- 1872-6968. ; 204
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Tidskriftsartikel (refereegranskat)abstract
- Patient MRI from DBS implantations in the subthalamic nucleus (STN) were reviewed and it was found that around 10% had Virchow-Robin spaces (VRS). Patient-specific models were developed to evaluate changes in the electric field (EF) around DBS leads. The patients (n = 7) were implanted bilaterally either with the standard voltage-controlled lead 3389 or with the directional current-controlled lead 6180. The EF distribution was evaluated by comparing simulations using patient-specific models with homogeneous models without VRS. The EF, depicted with an isocontour of 0.2 V/mm, showed a deformation in the presence of the VRS around the DBS lead. For patient-specific models, the radial extension of the EF isocontours was enlarged regardless of the operating mode or the DBS lead used. The location of the VRS in relation to the active contact and the stimulation amplitude, determined the changes in the shape and extension of the EF. It is concluded that it is important to take the patients? brain anatomy into account as the high conductivity in VRS will alter the electric field if close to the DBS lead. This can be a cause of unexpected side effects.
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| 2. |
- Göransson, Nathanael, et al.
(författare)
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Postoperative Lead Movement after Deep Brain Stimulation Surgery and the Change of Stimulation Volume
- 2021
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Ingår i: Stereotactic and Functional Neurosurgery. - : S. Karger. - 1011-6125 .- 1423-0372. ; 99:3, s. 221-229
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Lead movement after deep brain stimulation may occur and influence the affected volume of stimulation. The aim of the study was to investigate differences in lead position between the day after surgery and approximately 1 month postoperatively and also simulate the electric field (EF) around the active contacts in order to investigate the impact of displacement on affected volume. Methods: Twenty-three patients with movement disorders underwent deep brain stimulation surgery (37 leads). Computed tomography at the 2 time points were co-fused respectively with the stereotactic images in Surgiplan. The coordinates (x, y, and z) of the lead tips were compared between the 2 dates. Eleven of these patients were selected for the EF simulation in Comsol Multiphysics. Postoperative changes of EF spread in the tissue due to conductivity changes in perielectrode space and due to displacement were evaluated by calculating the coverage coefficient and the Sorensen-Dice coefficient. Results: There was a significant displacement (mean +/- SD) on the left lead: x (0.44 +/- 0.72, p < 0.01), y (0.64 +/- 0.54, p < 0.001), and z (0.62 +/- 0.71, p < 0.001). On the right lead, corresponding values were: x (-0.11 +/- 0.61, ns), y (0.71 +/- 0.54, p < 0.001), and z (0.49 +/- 0.81, p < 0.05). The anchoring technique was a statistically significant variable associated with displacement. No correlation was found between bilateral (n = 14) versus unilateral deep brain stimulation, gender (n = 17 male), age <60 years (n = 8), and calculated air volume. The simulated stimulation volume was reduced after 1 month because of the perielectrode space. When considering perielectrode space and displacement, the volumes calculated the day after surgery and approximately 1 month later were partly overlapped. Conclusion: The left lead tip displayed a tendency to move lateral, anterior, and inferior and the right a tendency to move anterior and inferior. The anchoring technique was associated to displacement. New brain territory was affected due to the displacement despite considering the reduced stimulated volume after 1 month. Postoperative changes in perielectrode space and small lead movements are reasons for delaying programming to 4 weeks following surgery.
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| 3. |
- Hentschel, Gesine, et al.
(författare)
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Destruction of Unresectable Brain Tumors : Simulation of Thermal Spread and Tissue Damage During MRI-Guided Laser Ablation
- 2021
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Ingår i: Springer Proceedings in Physics. - Cham : Springer. - 9783030811181 - 9783030811198 ; , s. 301-315
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Konferensbidrag (refereegranskat)abstract
- Laser induced thermal therapy (LITT) emerged in recent years as a minimal invasive treatment method for otherwise oftentimes inoperable brain tumors, such as glioblastomas. During the thermal ablation process, the procedure carries the risk of destroying healthy brain tissue adjacent to the tumor. Limitations in the spatial distribution of the real-time monitoring MR thermography system currently allow only a rough representation of the damage zone during surgery. For this reason, improved pre-operative simulations of tissue heating and the resulting tissue damage could be valuable to optimize clinical treatment protocols while minimizing the risks of the procedure. In this study a method is presented, to simulate the ablation process of the LITT with the finite elements method (FEM) using the simulation software COMSOL MULTIPHYSICS. Thereby the temperature distribution is displayed and, based on this, the extent of the tissue damage during the process is simulated. Therefore, relevant parameters for the ablation process, such as optical and thermal properties, blood per-fusion, and the interface between healthy and tumor tissue were investigated and their influence on temperature distribution and extent of tissue damage was described.
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| 4. |
- Johansson, Johannes D, et al.
(författare)
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DBSim and ELMA - Freeware for Simulations of Deep Brain Stimulation.
- 2022
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Ingår i: Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference. - 2694-0604. ; 2022, s. 1719-1724
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Tidskriftsartikel (refereegranskat)abstract
- Finite Element Method (FEM) simulations of the electric field is a useful tool to estimate the activated tissue around Deep Brain Stimulation (DBS) electrodes. Based on our previous research, a two-part software package named DBSim and ELMA is presented. ELMA is used to classify brain tissue into grey matter, white matter, blood, and cerebrospinal fluid and assign electric conductivities accordingly. This data is then used in DBSim to generate patient-specific simulations of the electric field around currently implemented leads Medtronic 3387 and 3389, and Abbott 6180 and 6181. The software is available for free download at https://liu.se/en/article/ne-downloads Clinical Relevance- This is a tool meant for research and educational purposes for e.g. studies on optimal target areas for DBS.
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| 5. |
- Johansson, Johannes D, 1977-, et al.
(författare)
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Open Access Software for Patient-Specific Deep Brain Stimulation Simulations: ELMA and DBSim
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Deep brain stimulation (DBS) is a technique for disruption of pathological activity in the brain by the use of chronically implanted electrodes in the central parts of the brain. DBS is used in e.g. Parkinson’s disease, essential tremor and dystonia and is under investigation for severe cases of Tourette syndrome and obsessive-compulsive disorder. While DBS is nowadays a well-established technique, optimal targeting of brain structures is still not fully known. One way to investigate this is to perform finite element method (FEM) simulations of the activated tissue around the active DBS electrode contacts. The FEM simulations can then be compared with the clinical outcomes of symptom improvement and potential detrimental side effects in the patients. A gratis open access software package for patient-specific FEM simulations based on pre-complied modules is presented. It is based on tissue classification from preoperative magnetic resonance imaging. In the first part, ELMA, the tissue is classified into grey matter, white matter, blood and cerebrospinal fluid. Electric conductivity is assigned based of tissue type and is then used in the second part, DBSim, where patient-specific FEM simulations of the electric field around the DBS electrodes are performed. These simulations can then be used to estimate the volume of tissue activated directly from the electric field magnitude thresholds for different axon diameters or be exported for direct simulation of axon activation in other software. The software package is available for free download at https://liu.se/en/article/ne-downloads
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| 6. |
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| 7. |
- Klint, Elisabeth, et al.
(författare)
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Combined Use of Frameless Neuronavigation and In Situ Optical Guidance in Brain Tumor Needle Biopsies
- 2023
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Ingår i: Brain Sciences. - 2076-3425. ; 13:5
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Tidskriftsartikel (refereegranskat)abstract
- Brain tumor needle biopsies are performed to retrieve tissue samples for neuropathological analysis. Although preoperative images guide the procedure, there are risks of hemorrhage and sampling of non-tumor tissue. This study aimed to develop and evaluate a method for frameless one-insertion needle biopsies with in situ optical guidance and present a processing pipeline for combined postoperative analysis of optical, MRI, and neuropathological data. An optical system for quantified feedback on tissue microcirculation, gray-whiteness, and the presence of a tumor (protoporphyrin IX (PpIX) accumulation) with a one-insertion optical probe was integrated into a needle biopsy kit that was used for frameless neuronavigation. In Python, a pipeline for signal processing, image registration, and coordinate transformation was set up. The Euclidian distances between the pre- and postoperative coordinates were calculated. The proposed workflow was evaluated on static references, a phantom, and three patients with suspected high-grade gliomas. In total, six biopsy samples that overlapped with the region of the highest PpIX peak without increased microcirculation were taken. The samples were confirmed as being tumorous and postoperative imaging was used to define the biopsy locations. A 2.5 ± 1.2 mm difference between the pre- and postoperative coordinates was found. Optical guidance in frameless brain tumor biopsies could offer benefits such as quantified in situ indication of high-grade tumor tissue and indications of increased blood flow along the needle trajectory before the tissue is removed. Additionally, postoperative visualization enables the combined analysis of MRI, optical, and neuropathological data.
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| 8. |
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| 9. |
- Klint, Elisabeth, et al.
(författare)
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FluoRa - a System for Combined Fluorescence and Microcirculation Measurements in Brain Tumor Surgery
- 2021
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Ingår i: 2021 43RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY (EMBC). - : IEEE. - 9781728111797 ; , s. 1512-1515
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Konferensbidrag (refereegranskat)abstract
- In brain tumor surgery it is difficult to distinguish the marginal zone with the naked eye. Fluorescence techniques can help identifying tumor tissue in the zone during resection and biopsy procedures. In this paper a novel system for combined real-time measurements of PpIX-fluorescence, microcirculation and tissue grey-whiteness is presented and experimentally evaluated. The system consists of a fluorescence hardware with a sensitive CCD spectrometer for PpIX peak detection, a laser Doppler system, optical probes, and a LabView software. System evaluation was done on static fluorescing material, human skin, and brain tumor tissue. The static material indicates reproducibility, the skin measurements exemplify simultaneous fluorescence and microcirculation measurement in real-time, and the tumor tissue showed PpIX peaks. These decreased over time, as expected, due to photo bleaching. In addition, the system was prepared for clinical use and thus laser- and electrical safety issues were considered. In summary, a system for multiparameter measurements during neurosurgery was successfully evaluated in an experimental environment. As a next step the system will be applied in clinical brain tumor biopsies and resections.
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| 10. |
- Mauritzon, Stina, et al.
(författare)
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A Laser Doppler System for Long-Term Recording of Cerebral Microcirculation in the Neurointensive Care Unit
- 2021
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Ingår i: TRANSLATIONAL BIOPHOTONICS: DIAGNOSTICS AND THERAPEUTICS. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510647053 - 9781510647046
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Konferensbidrag (refereegranskat)abstract
- Laser Doppler flowmetry (LDF) has been adapted for long-term neurointensive care monitoring of cerebral microcirculation at two sites. The invasive probe was successfully used in a 10-day recording in one patient with subarachnoid hemorrhage (SAH).
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