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On optical methods for intracerebral measurements during stereotactic and functional neurosurgery: Experimental studies
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radio frequency (RF) lesioning and deep brain stimulation (DBS) are the two prevailing surgical treatments for movement disorders within the field of stereotactic and functional neurosurgery. For RF-lesioning, a small volume of brain tissue is coagulated and knowledge of the lesion size and growth is of great importance for the safety and outcome of the procedure. This thesis deals with adapting the laser Doppler perfusion monitoring (LDPM) technique for measurements in brain tissue during RF-lesioning. The relation between LDPM signal changes and developed lesion size was investigated. LDPM measurements were evaluated both in vitro (albumin protein solution) and in vivo in the porcine brain during RF-lesioning corresponding to a bilateral thalamotomy in man. The investigated signals from the LDPI measurements can be used for following the lesioning time course and to detect if a lesion was created, both in vitro and in the animal model. For the albumin model, both the total backscattered light intensity and the perfusion signal can be used as markers for estimating the final coagulation size, while in the animal model this conclusion was not statistical verified.

Independent on surgical method, RF-lesioning or DBS, intracerebral guidance is an important aspect within stereotactic and functional neurosurgery. To increase the accuracy and precision of reaching the correct target, different methods for intracerebral guidance exist, such as microelectrode recording and impedance methods. In this thesis, the possibility of developing an optical intracerebral guidance method has been investigated. Diffuse reflectance spectroscopy served as technology and all measurements were performed stereotactically in both porcine and human brain. Measurements of white and gray matter showed large differences, with higher reflectivity for white brain matter, both in porcine and in human brain. For the human measurements during DBS-implants, large differences between white matter and functional targets were found. Additionally, differences between native and lesioned porcine brain matter were detected. Both studies support the idea of using diffuse reflectance spectroscopy for developing an intracerebral guidance method.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik , 2007.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1070
Keyword [en]
Laser Doppler perfusion monitoring, Diffuse reflectance spectroscopy, Functional and stereotactic neurosurgery
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-8081ISBN: 978-91-85715-91-6 (print)OAI: oai:DiVA.org:liu-8081DiVA: diva2:22964
Public defence
2007-02-02, Elsa Brändströms sal, Södra Entreén, Universitetssjukhuset, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2016-05-04
List of papers
1. Radio frequency electrode system for optical lesion size estimation in functional neurosurgery
Open this publication in new window or tab >>Radio frequency electrode system for optical lesion size estimation in functional neurosurgery
2005 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 10, no 3, 1-6 p.Article in journal (Refereed) Published
Abstract [en]

Radiofrequency(RF) lesioning in the human brain is one possible surgicaltherapy for severe pain as well as movement disorders. Oneobstacle for a safer lesioning procedure is the lack ofsize monitoring. The aim of this study was to investigateif changes in laser Doppler or intensity signals could beused as markers for size estimation during experimental RF lesioning.A 2 mm in diameter monopolar RF electrode was equippedwith optical fibers and connected to a digital laser Dopplersystem. The optical RF electrode's performance was equal to astandard RF electrode with the same dimensions. An albumin solutionwith scatterers was used to evaluate the intensity and laserDoppler signal changes during lesioning at 70, 80, and 90 °C.Significant signal changes were found for these three different clotsizes, represented by the temperatures (p<0.05,  n=10). The volume, width, andlength of the created coagulations were correlated to the intensitysignal changes (r=0.88, n=30, p<0.0001) and to the perfusion signalchanges (r=0.81, n=30, p<0.0001). Both static and Doppler-shifted light canbe used to follow the lesioning procedure as well asbeing used for lesion size estimation during experimental RF lesioning.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2005
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-14232 (URN)10.1117/1.1924615 (DOI)000235127400040 ()16229664 (PubMedID)2-s2.0-24144476322 (Scopus ID)
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2017-02-21Bibliographically approved
2. Optical measurements during experimental stereotactic radiofrequency lesioning
Open this publication in new window or tab >>Optical measurements during experimental stereotactic radiofrequency lesioning
2006 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 84, no 2-3, 118-124 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to evaluate in vivo a laser Doppler measurement system in porcine brain tissue during thermal lesioning. A 2-mm monopolar radiofrequency lesioning electrode was equipped with optical fibers in order to monitor the lesioning procedure. Laser Doppler and backscattered light intensity signals were measured along the electrode trajectory and during bilateral lesioning in the central gray (70, 80 and 90°C, n = 14). The time course of the coagulation process could be followed by optical recordings. Two separate groups of tissue were identified from the intensity signals. The changes in the perfusion levels in both groups displayed significant changes (p < 0.05, n = 48) at all temperature settings, while backscattered light intensity was significant for only one group at the different temperatures (p < 0.05, n = 39). These results indicate that optical measurements correlate with lesion development in vivo. The study also indicates that it is possible to follow the lesioning process intra-operatively.

Place, publisher, year, edition, pages
S. Karger, 2006
Keyword
Laser Doppler, Radiofrequency lesioning, Functional neurosurgery, Brain electrodes
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:liu:diva-14233 (URN)10.1159/000094463 (DOI)000239562300010 ()16840822 (PubMedID)2-s2.0-33746647435 (Scopus ID)
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2017-02-16Bibliographically approved
3. In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery
Open this publication in new window or tab >>In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery
2003 (English)In: Biophotonics West: Biomedical Optics, 2003, Vol. 4958, 242-250 p.Conference paper, Published paper (Refereed)
Abstract [en]

Radiofrequency (RF) lesioning in the human brain is a commonsurgical therapy for relieving severe pain as well as formovement disorders such as Parkinsonia. During the procedure a smallelectrode is introduced by stereotactic means towards a target arealocalized by CT or MRI. An RF-current is applied throughthe electrode tip when positioned in the target area. Thetissue in the proximity of the tip is heated bythe current and finally coagulated.The overall aim of this studywas to improve the RF-technique and its ability to estimatelesion size by means of optical methods. Therefore, the opticaldifferences between white and gray matter, as well as lesionedand unlesioned tissue were investigated. Reflection spectroscopy measurements in therange of 450-800 nm were conducted on fully anesthetized pigsduring stereotactic RF-lesioning (n=6). Light from a tungsten lamp wasguided to the electrode tip through optical fibers, inserted alonga 2 mm in diameter monopolar RF-electrode. Measurements were performedin steps of 0-10 mm from the target in eachhemisphere towards the entry point of the skull. In thecentral gray of the porcine brain measurements were performed bothbefore and after the creation of a lesion. A totalof 55 spectra were collected during this study. Correlation totissue type was done using post-operative MR-images. The spectral signaturefor white and gray matter differs significantly for the entirespectral range of 450-800 nm. Pre- and post-lesioning reflection spectroscopyshowed the largest differences below 600 and above 620 nm,which implies that lasers within this wavelength range may beuseful for in-vivo measurements of tissue optical changes during RF-lesioning.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14234 (URN)10.1117/12.476131 (DOI)
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2017-02-22Bibliographically approved
4. Diffuse reflectance spectroscopy measurements for tissue type discrimination during deep brain stimulation
Open this publication in new window or tab >>Diffuse reflectance spectroscopy measurements for tissue type discrimination during deep brain stimulation
Show others...
2008 (English)In: Journal of neural engineering, ISSN 1741-2560, Vol. 5, no 2, 185-190 p.Article in journal (Refereed) Published
Abstract [en]

Diffuse reflectance spectroscopy as a method for improving intracerebral guidance during functional neurosurgery has been investigated. An optical probe was developed for measurements during stereotactic and functional neurosurgery in man. The aim of the study was to investigate the spectral differences between white and grey matter and between white matter and functional targets. Diffuse reflectance spectroscopy measurements in ten patients were recorded at incremental steps towards and in three different functional targets (STN, GPi and Zi). The recorded spectra along the trajectory were sorted into white or grey matter, based on preoperative MRI images or the recorded spectral shape and intensity. The difference between tissue types was calculated as a quotient. Significant intensity differences between white and grey matter were found to be at least 14% (p < 0.05) and 20% (p < 0.0001) for MRI and spectral-sorted data respectively. The reflectance difference between white matter and the functional targets of GPi was higher than for STN and Zi. The results indicate that diffuse reflectance spectroscopy has a potential to be developed to a suitable complement to other intracerebral guidance methods.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14235 (URN)10.1088/1741-2560/5/2/009 (DOI)000257253800009 ()18460743 (PubMedID)2-s2.0-48949118315 (Scopus ID)
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2017-02-10Bibliographically approved
5. In vitro measurements of optical properties of porcine brain using a novel compact device
Open this publication in new window or tab >>In vitro measurements of optical properties of porcine brain using a novel compact device
Show others...
2005 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 5, 658-666 p.Article in journal (Refereed) Published
Abstract [en]

Knowledge of the optical properties of tissues can be applied in numerous medical and scientific fields, including cancer diagnostics and therapy. There are many different ways of determining the optical properties of turbid media. The paper describes measurements of the optical properties of porcine brain tissue using novel instrumentation for simultaneous absorption and scattering characterisation of small turbid samples. Integrating sphere measurements are widely used as a reference method for determination of the optical properties of relatively thin turbid samples. However, this technique is associated with bulky equipment, complicated measuring techniques, interference compensation techniques and inconvenient sample handling. It is believed that the sphere for some applications can be replaced by a new, compact device, called the combined angular and spatially resolved head sensor, to measure the optical properties of thin turbid samples. The results compare very well with data obtained with an integrating sphere for well-defined samples. The instrument was shown to be accurate to within 12% for μa and 1% for μ s in measurements of intralipid-ink samples. The corresponding variations of data were 17% and 2%, respectively. The reduced scattering coefficient for porcine white matter was measured to be 100 cm−1 at 633 nm, and the value for coagulated brain tissue was 65 cm−1. The corresponding absorption coefficients were 2 and 3 cm−1, respectively.

Place, publisher, year, edition, pages
Springer, 2005
Keyword
Optical properties, Turbid media, Integrating sphere, CASH sensor, Porcine brain tissue, Scattering
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-14236 (URN)10.1007/BF02351040 (DOI)000234262300016 ()2-s2.0-29244462497 (Scopus ID)
Available from: 2007-01-26 Created: 2007-01-26 Last updated: 2017-02-21Bibliographically approved

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