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Stereotactic imaging in functional neurosurgery
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: The birth of stereotactic functional neurosurgery in 1947 was to a great extent dependent on the development of ventriculography. The last decades have witnessed a renaissance of functional stereotactic neurosurgery in the treatment of patients with movement disorders. Initially, these procedures were largely based on the same imaging technique that had been used since the birth of this technique, and that is still used in some centers. The introduction of new imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) provided new potentials, but also new challenges for accurate identification and visualisation of the targets in the basal ganglia and the thalamus with an urge to thoroughly evaluate and optimize the stereotactic targeting technique, as well as evaluate accurately in stereotactic space the location and extent of stereotactic Radiofrequency (RF) lesions and the position of deep brain stimulation (DBS) electrodes.

Aims: To study the differences between CT and MRI regarding indirect atlas coordinates in thalamic and pallidal procedures and to evaluate and validate visualisation of the pallidum and the subthalamic nucleus in view of direct targeting irrespective of atlas-derived coordinates. Furthermore, to evaluate the contribution of RF parameters on the size of stereotactic lesions, as well as the impact of size and location on clinical outcome.

Method: The coordinates in relation to the landmarks of the 3rd ventricle of the targets in the pallidum and ventrolateral thalamus were compared between CT and MRI in 34 patients. In another 48 patients direct visualization  of the pallidum was evaluated and compared to indirect atlas based targeting. The possibility and versatility of visualizing the Subthalamic Nucleus (STN) on short acquisition MRI were evaluated in a multicentre study, and the use of alternative landmarks in identification of the STN was demonstrated in another study. In 46 patients CT and MRI were compared regarding the volume of the visible RF lesions. The volume was analysed with regard to coagulation parameters, and the location and size of the lesions were further evaluated concerning the clinical outcome.

Results:Minor deviations were seen between MRI and  CT coordinates of brain targets. The rostro-caudal direction of these deviations were such that they would be easily accounted for during surgery, why MRI can obviate the need for CT in these procedures. MRI using a proton density sequence provided detailed images of the pallidal structures, which demonstrated considerable inter-individual variations in relation to the landmarks of the 3rd ventricle. By using a direct visualization of the target, each patient will act as his or her own atlas, avoiding the uncertainties of atlas-based targeting. The STN could be visualized on various brands of MRI machines in 8 centers in 6 countries with good discrimination and with a short acquisition time, allowing direct visual targeting. The same scanning technique could be used for postoperative localization of the implanted electrodes. In cases where the lateral and inferior borders of the STN cannot be easily distinguished on MRI the Sukeroku sign and the dent internal-capsule-sign signs might be useful. The volume of a stereotactic RF lesion could be as accurately assessed by CT as by MRI. The lesion´s size was most strongly influenced by the temperature used for coagulation. The lesions´ volumes were however rather scattered and difficult to predict in the individual patient based solely on the coagulation parameters. For thalamotomy, the results on tremor was not related to the lesion´s volume. For pallidotomy, larger and more posterior-ventral lesions had better effect on akinesia while effects on tremor and dyskinesias were not related to size or location of the lesions.

Conclusions: The minor deviations of MRI from CT coordinates can be accounted for during surgery, why MRI can obviate the need of CT in these procedures. Direct visualized targeting on MRI of the pallidum is superior to atlas based targeting. The targets in the pallidum and the STN, as well as the location of the electrodes, can be well visualized with short acquisition MRI. When borders of the STN are poorly defined on MRI the Sukeroku sign and the dent internal-capsule-sign signs proved to be useful. The volumes of RF lesions can be accurately assessed by both stereotactic thin slice CT and MRI. The size of these lesions is most strongly influenced by the temperature of coagulation, but difficult to predict in the individual patient based on the coagulation parameters.

Within certain limits, there were no clear relationships between lesions´ volume and location and clinical effects of thalamotomies and pallidotomies.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2012. , 48 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1462
Keyword [en]
Deep brain stimulation, pallidotomy, thalamotomy, Parkinson's disease, essential tremor, CT, MRI
National Category
Neurology
Research subject
Neurosurgery
Identifiers
URN: urn:nbn:se:umu:diva-55141ISBN: 978-91-7459-325-9 (print)OAI: oai:DiVA.org:umu-55141DiVA: diva2:525698
Public defence
2012-06-08, Room E04, Building 6E, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2012-05-16 Created: 2012-05-09 Last updated: 2012-05-16Bibliographically approved
List of papers
1. Comparison between stereotactic CT and MRI coordinates of pallidal and thalamic targets using the Laitinen noninvasive stereoadapter
Open this publication in new window or tab >>Comparison between stereotactic CT and MRI coordinates of pallidal and thalamic targets using the Laitinen noninvasive stereoadapter
1998 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 71, no 3, 117-130 p.Article in journal (Refereed) Published
Abstract [en]

The coordinates of one and the same target were compared between stereotactic CT and MRI studies, using the original Laitinen noninvasive Stereoadapter, and a slightly modified stereoadapter in 34 patients scheduled for pallidotomy or thalamotomy. The differences between CT and MRI coordinates were significant for the anteroposterior y (p < 0.001) and the vertical z (p < 0.01) coordinates. When the targets were analyzed separately for the coordinates in the right and left hemispheres, only those of the left-sided targets were significantly different between CT and MRI measurements. In patients where a vertex support was added to the Stereoadapter, there were no differences between CT and MRI target coordinates, regardless of the side of the target. However, in all patient groups, the three-dimensional vectorial difference between CT and MRI coordinates showed that the MRI-defined targets lay anterior and dorsal, that is, rostral, to the CT-defined targets, with a 95% confidence interval of the differences ranging from 1.8 to 2.4 mm. This rostral shift in target coordinates on MRI versus CT happens to coincide with the usual approach of the probe towards the target during surgery. It is concluded that the differences in target coordinates in our study are due partly to MRI distortion and partly to repositioning error of the Stereoadapter on the head. The relatively low magnitude of these differences does not preclude the use of the Stereoadapter for MRI-guided functional stereotactic surgery, provided careful impedance monitoring and macrostimulation of the target area prior to lesioning.

Keyword
Pallidotomy, Thalamotomy, Parkinson’s disease, Essential tremor, CT, MRI, Stereoadapter
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55145 (URN)10.1159/000029655 (DOI)10420145 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved
2. Stereotactic imaging of the pallidal target
Open this publication in new window or tab >>Stereotactic imaging of the pallidal target
2002 (English)In: Movement Disorders, ISSN 0885-3185, E-ISSN 1531-8257, Vol. 17, no suppl 3, S130-S134 p.Article in journal (Refereed) Published
Abstract [en]

In 48 consecutive patients, we applied a new stereotactic imaging technique to individually visualize the pallidal target before surgery. A turbo spin-echo proton density sequence (acquisition time, 6 minutes 5 seconds) was used for 2-mm-thick contiguous axial scanning. Pallidocapsular border, medial putaminal border, and optic tract were visualized bilaterally in all patients. Boundaries of globus pallidus internus, globus pallidus externus, and lamina medullaris interna were clearly visualised in 71% of the patients. The anatomic target point was chosen in the middle of the visualized posteroventral pallidum, irrespective of the position of this point in relation to commissures. The lateralities of pallidocapsular border, lamina medullaris interna, and medial boundary of putamen were measured bilaterally in each patient, and the width of the posteroventral pallidum was assessed. The laterality of structures (measured from a point 2 mm anterior to midcommissural point and at a level 2-4 mm below anterior commissure-posterior commissure line) showed a wide range. The position of the pallidocapsular border varied by up to almost 1 cm between the most medial and the most lateral one. There were also variations in the position of the pallidal structures between left and right hemispheres in the same patients. The posteroventral pallidum was slightly more wide on the left than the right side. Given the significant inter- and intra-individual variabilities of the position of pallidal structures, it may be hazardous to rely solely on the atlas and the commissures for targeting. A magnetic resonance imaging sequence that enables visualization in each individual patient of the target area and its surroundings may contribute to less electrode passes during intraoperative physiological exploration and to more exact location of the lesion or chronic electrode in the posteroventral pallidum.

Keyword
deep brain stimulation;Parkinson's disease;MRI;stereotactic surgery;pallidum
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55146 (URN)10.1002/mds.10154 (DOI)11948767 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved
3. A quick and universal method for stereotactic visualization of the subthalamic nucleus before and after implantation of deep brain stimulation electrodes
Open this publication in new window or tab >>A quick and universal method for stereotactic visualization of the subthalamic nucleus before and after implantation of deep brain stimulation electrodes
Show others...
2003 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 80, no 1-4, 96-101 p.Article in journal (Refereed) Published
Abstract [en]

For deep brain stimulation (DBS) of the subthalamic nucleus (STN), it would be an advantage if the STN could be visualized with fast acquisition of MR images, allowing direct and individual targeting. We present a protocol for T2-weighted, nonvolumetric fast-acquisition MRI, implemented at 8 centers in 6 countries. Acquisition time varied between 3 min 5 s and 7 min 48 s according to the center, and imaging often provided visualization of the STN on axial and coronal scans. Postoperatively, the same imaging protocol permitted visualization of the target area and DBS electrodes with minimum artifacts. This imaging technique may contribute to a decrease in the number of electrode passes at surgery.

Keyword
Deep brain stimulation, Subthalamic nucleus, Magnetic resonance imaging, Parkinson’s disease
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55147 (URN)10.1159/000075167 (DOI)14745216 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved
4. "Sukeroku sign" and "dent internal-capsule sign": identification guide for targeting the subthalamic nucleus for placement of deep brain stimulation electrodes
Open this publication in new window or tab >>"Sukeroku sign" and "dent internal-capsule sign": identification guide for targeting the subthalamic nucleus for placement of deep brain stimulation electrodes
Show others...
2009 (English)In: Neuroradiology, ISSN 0028-3940, E-ISSN 1432-1920, Vol. 51, no 1, 11-6 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: The purpose of this study was to assess the usefulness of signs ("Sukeroku sign" and "dent internal-capsule sign") for the recognition of subthalamic nucleus (STN).

MATERIALS AND METHODS: Five Parkinson's disease cases in which there was a successful placement of deep brain stimulation (DBS) electrodes at the STN were retrospectively reviewed. Five radiologists who were not engaged in localization of STNs in clinical practice were asked to locate the STNs before and after instructions on the signs. We evaluated the deviation between the reader-located points and the location of the DBS electrode for which there had been a successful installation.

RESULTS: After instruction, there was a significant reduction in the deviation between the reader-located points and the DBS electrode. The time required for localization was also reduced after the instructions.

CONCLUSION: Sukeroku sign and dent internal-capsule sign are feasible indicators of STN and seem to be useful in helping to identify the STN.

National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55148 (URN)10.1007/s00234-008-0451-1 (DOI)18769907 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved
5. Is there a relationship between size and site of the stereotactic lesion and symptomatic results of pallidotomy and thalamotomy?
Open this publication in new window or tab >>Is there a relationship between size and site of the stereotactic lesion and symptomatic results of pallidotomy and thalamotomy?
1997 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 69, no 1-4, 28-45 p.Article in journal (Refereed) Published
Abstract [en]

Forty-six patients who had 50 stereotactic procedures (36 pallidotomies and 14 thalamotomies) were assessed clinically with regard to akinesia, tremor, dyskinesias and dystonias, and underwent a stereotactic imaging study 6 months after surgery. The surgical results were rated as excellent, good/fair or no change, respectively, for each symptom, and were correlated to the volume and location of the stereotactic lesion. The effect of pallidotomy on akinesia was moderate and correlated with a larger lesion volume. The positive effect of pallidotomy on dyskinesias, dystonia and tremor was more pronounced and unrelated to the size of the lesion. The effect of thalamotomy on tremor was also unrelated to the lesion volume. The location of the pallidal lesions correlated only with the effect on akinesia: the more posterior the lesion in the pallidum, the better the effect on this symptom. For thalamotomy, there was no relationship between lesion location and effect on tremor. It is concluded that improvement in akinesia following pallidotomy is more difficult to obtain than improvement of the other parkinsonian symptoms, and this improvement requires a larger lesion which is located very posterior in the ventral pallidum.

Keyword
Parkinson's disease, Pallidotomy, Thalamotomy, Stereotactic surgery
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55149 (URN)10.1159/000099848 (DOI)9711732 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved
6. Impact of parameters of radiofrequency coagulation on volume of stereotactic lesion in pallidotomy and thalamotomy
Open this publication in new window or tab >>Impact of parameters of radiofrequency coagulation on volume of stereotactic lesion in pallidotomy and thalamotomy
2012 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 90, no 5, 307-315 p.Article in journal (Refereed) Published
Abstract [en]

Background: One of the many reasons why lesional surgery for movement disorders has been more or less abandoned may have been the difficulty in predicting the shape and size of the stereotactic radiofrequency (RF) lesion. Objectives: To analyse the contribution of various RF coagulation parameters towards the volume of pallidotomies and thalamotomies. Methods: The relationship between temperature of coagulation, length of coagulated area and duration of coagulation on the one hand, and lesion volume on the other was retrospectively evaluated. Lesion diameters were measured on stereotactic thin-slice CT and MRI scans, and volumes of lesions were calculated concerning 36 pallidotomies and 14 thalamotomies in 46 patients who were operated using the same RF generator and same RF electrode. Results: The coagulation temperature, length of coagulated area and duration of coagulation were all correlated to the lesion volume. However, for a given length of coagulated area, the lesion's size was most strongly influenced by the temperature. Despite this clear correlation, and the relatively homogenous coagulation parameters, the lesions' volumes were markedly scattered. Conclusions: The volume of the stereotactic RF lesions could be correlated with the coagulation parameters, especially the temperature, at a group level, but could not be predicted in individual patients based solely on the RF coagulation parameters.

Keyword
Pallidotomy, Thalamotomy, Radiofrequency, Parkinson's disease
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-55153 (URN)10.1159/000338249 (DOI)000310356900004 ()22797780 (PubMedID)
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2017-12-07Bibliographically approved

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