1. A SIMPLE METHOD TO ASSESS ACCURACY OF DEEP BRAIN STIMULATION ELECTRODE PLACEMENT: PREOPERATIVE MRI AND POSTOPERATIVE CT IMAGE FUSION Marco Metello 1 ; Joana Silva 2 ; Paulo Linhares 2 ; Carina Reis 1 ; Miguel Gago 3 ; Maria José Rosas 3 ;Rui Vaz 2 ;Margarida Ayres Basto 1 1 – Neuroradiology Department; 2-Neurosurgery Department; 3-Neurology Department

2. INTRODUCTION One of the possible targets for Parkinson's Disease surgery is the subthalamic nucleus (NST). The small size, deep location and the numerous neural structures and bundles of white matter, that surround it, difficult surgical access and the correct placement of the electrode within this nucleus. One of the possible targets for Parkinson's Disease surgery is the subthalamic nucleus (NST). The small size, deep location and the numerous neural structures and bundles of white matter, that surround it, difficult surgical access and the correct placement of the electrode within this nucleus.

3. OBJECTIVES Describe a method for the measurement of the accuracy of deep brain stimulation (DBS) electrode placement, with the use of the image fusion technologies. Describe a method for the measurement of the accuracy of deep brain stimulation (DBS) electrode placement, with the use of the image fusion technologies. Investigate the relationship between the distance from the active contact and to the NST and degree of clinical improvement. Investigate the relationship between the distance from the active contact and to the NST and degree of clinical improvement.

4. METHODS Twenty six PD patients who underwent bilateral STN-DBS electrode implantation between Febuary and December 2008 were included in this study. Twenty six PD patients who underwent bilateral STN-DBS electrode implantation between Febuary and December 2008 were included in this study. MRI scan preoperative imaging MRI scan preoperative imaging CT scan postoperative imaging CT scan postoperative imaging Axial plane parallel to the stereotactic ring without gantry tilting contiguous slices of mm thickness Axial plane parallel to the stereotactic ring without gantry tilting contiguous slices of mm thickness 512/512 matrix 512/512 matrix Square pixel Square pixel 280 mm FOV 280 mm FOV  High resolution T1 weighted 3D MPRAGE  Whole brain axial plane  Double dose of contrast  1 mm thichness; no gap; isotropic pixel  256/256 matrix  280 mm FOV  T2 weighted sequence  Coronal plane  1 mm thichness; no gap; isotropic pixel  256/256 matrix  280 mm FOV

5. METHODS The accuracy of DBS electrode placement technique depends on: The accuracy of DBS electrode placement technique depends on: Direct visualization of the STN in preoperative MRI; standard anatomical coordinates (x,y,z) Direct visualization of the STN in preoperative MRI; standard anatomical coordinates (x,y,z)

6. METHODS The accuracy of DBS electrode placement technique depends on: The accuracy of DBS electrode placement technique depends on: Intraoperative electrophysiological results (microregistration and clinical assesment with microstimulation) Intraoperative electrophysiological results (microregistration and clinical assesment with microstimulation)

7. METHODS – Studies with different methods for the measurement of the accuracy of DBS electrode placement, resorting to image fusion technologies.  Bibliography – Studies with different methods for the measurement of the accuracy of DBS electrode placement, resorting to image fusion technologies.   MRI postoperative imaging VS CT postoperative imaging Artefacts from the electrode interfere with the visualization of the correct boundaries of the NST and the electrode Artefacts from the electrode interfere with the visualization of the correct boundaries of the NST and the electrode Security Security

8. METHODS MRI preoperative imaging-CT scan postoperative imaging MRI preoperative imaging-CT scan postoperative imaging /TC Pós-operatório /TC Pós-operatório - Direct assessment of the STN; MRI scan preoperative imaging- Direct assessment of the STN; theoretical anatomical coordinates. Registration of the coordinates (x;y;z) Assessment of the four contacts in the eletrode; CT scan postoperative imaging - Assessment of the four contacts in the eletrode; registration of the coordinates (x;y;z)

9. METHODS Seven days after surgery, CT scan was performed to locate the position of the implanted electrodes Seven days after surgery, CT scan was performed to locate the position of the implanted electrodes These images were transferred to the Surgiplan workstation to be fused with preoperative MRI. These images were transferred to the Surgiplan workstation to be fused with preoperative MRI. Evaluation of the correctly superimposed fused CT-MR images by comparing anatomic landmarks Evaluation of the correctly superimposed fused CT-MR images by comparing anatomic landmarks The DBS lead and its four contacts (numbered zero to three from caudal to rostral) were visualized on postoperative slices. The DBS lead and its four contacts (numbered zero to three from caudal to rostral) were visualized on postoperative slices. Registration of the coordinates of the four contacts (x;y;z)

10. METHODS NS T esq teoric o conta cto 0 conta cto 1 conta cto 2 conta cto 3 NST dto teoric o conta cto 0 conta cto 1 conta cto 2 conta cto 3 NST esq teoric o conta cto 0 conta cto 1 conta cto 2 conta cto 3 NST dto teoric o conta cto 0 conta cto 1 conta cto 2 conta cto 3 X112,8104,2104,9105,5106,2X110,2110109,5109,3 X112,1113,2114,3115,5116,6X88,186,184,783,381,9 Y91,394,194,895,596,2Y90,890,790,5 90,2Y90,988,988,287,586,9Y90,786,685,98584,3 Z116,5115113,2111,5109,7Z112,5112,4 112,2112Z111,8108,5106,4104,3102,2Z111,5107,9105,4102,6100,5 X107,5108,8109,1110,5111,1X87,584,584,183,682,9X99,3108108,3109109,7X88,387,587,386,185,4 Y99,599,399,299,198,9Y99,8103,5104,2105,1105,4Y104,689,689,188,587,9Y93,588,788,187,787 Z100,796,29491,884,2Z101,395,994,192,590,8Z117,4109,4107,7105,5103,1Z111,4110,5108,5107104,5 X109,9108,9109,6109,811,7Dez9291,390,691,690X110,4110,6110,7111,3111,6X90,49089,188,487,9 Y97,398,698,899,198,7Y99,19897,497,797Y97,6 Y9898,1 98,2 Z112,2109,7107,8106,3104,6Z115,3111,3109,2109,5107,4Z128,4124,2122119,8118,2Z128,8125,3123,8122120,1 X113114,2114,9116,6117,2X9391,691,590,790,2X113,6115,8116,7117,4118X92,593,693,392,591,8 Y94,197,6 97,797,8Y93,995,3 95,4 Y91,790,390,19089,9Y92,292,492,392,292,1 Z9792,791,790,188,5Z95,893,891,89087,8Z101,298,596,895,193,5Z94,698,596,594,692,6 X112,5114,1114,4115,6116X89,188,787,586,284,9X108,6110,7111,7113113,9X85,68483,182,581,7 Y93,292,8 92,993Y95,291,191,391,591,7Y95,999,799,499,298,9Y96,694,69695,895,6 Z102,2103101,199,297Z101,397,595,593,691,6Z117,1113,4117,1110108,5Z116,3113,9110,8108,6106,8 X111,2110,1110,7111,6111,9X89,491,190,288,887,5X109,5111,4112,1113,1114,1X89,487,886,68684,8 Y97,496,897,797,498,3Y98,296,396,998,599,1Y94,694,4 94,394,2Y94,393,3 93,2 Z108,2103,5102,6100,699,7Z110,8104,8103,1101,199,1Z100,496,49593,391,6Z98,496,194,592,391 X110,3112,3113,4113,9114,5X87,388,68886,986,1X113,2114,3114,7115,5116,3X91,490,189,688,888,6 Y91,994,694,7 94,8Y91,792,1 92,292,3Y98,296,195,795,294,7Y96,195,194,69493,5 Z98,496,995,291,488,2Z98,498,296,394,792Z120,2118,1116,6115113,1Z119,8116114,2112,1110,1 X106,2105,3106,2106,8107,3X82,981,680,780,178,1X109,2112,9113,3113,9114,6X87,286,78685,685,1 Y90,68787,38786,7Y89,791,390,0990,590,2Y89,988,4 88,5 Y9088,5 Z105,8108,3103,4101,299,4Z108,3107,1105,1102,6101,4Z109,2106,8104,9103,1101,4Z109,4109,3107,5105,8103,8 X107,6101,3104,5104,9105,6X85,385,28482,180,2X108,4109109,8110,4109,6X83,781,981,480,679,9 Y96,298,195,294,994,6Y94,994,493,993,392,7Y93,593,192,892,594,3Y9796,596,295,995,6 Z109,5116111,3109,9108,5Z112,8109107,6105,4103,5Z102,6100,999,397,698,1Z103,499,697,695,593,4 X107,8104,3104,9105,1105,6X85,983,782,681,880,7X109,7111,6112,3113,2113,9X86,887,687,186,485,7 Y88,98382,782,482,1Y87,683,182,782,482Y92,891,39190,890,5Y93,191,991,791,491,2 Z106,9110,3108,6106,2104,1Z107,3107,9105,7103,6101,4Z105,3101,699,898,196,3Z104,2 102,3100,298,2 X110,7111,5112,3112,7113,5X88,287,486,486,285,2X109,8110,7111,8112,2113,4X87,885,785,685,184,7 Y98,297,997,897,697,5Y98,298,197,997,797,6Y90,389,589,38988,7Y90,286,886,586,185,8 Z119,2118,4116,6114,4113Z118,2114,1111,9109,7107,2Z101,5101,9100,498,496,4Z102,198,196,293,891,9 X111,7114,6115,4116,5117,3X89,789,489,188,487,3X112,7114,8115,7116,7117,6X91,789,988,988,587,7 Y97,59796,896,696,3Y97,396,996,796,596,3Y100,510099,899,599,2Y100,79998,898,598,2 Z104,3104,498,396,193,9Z103,8100,29895,492,9Z95,992,590,888,987,2Z95,191,389,387,685,5

11. METHODS Assessment of the distance between NST and the active electrode d:(X 2 +Y 2 +Z 2 ) 1/2

12. METHODS Registration of the clinical improvement by the UPDRS scale (pre-op, med-off/post-op, med off/stim-on) Distance and clinical improvement were compared using a paired t-test (p<0,05 was considered significant) Distance and clinical improvement were compared using a paired t-test (p<0,05 was considered significant) Distance (mm) Clinical improvement (%) 0,92439324376 0,68949256773 0,46583258866 0,66294796247 0,43243496678 0,56302754358 0,83546394384 0,58719467379 0,30232432937 0,70526590781 0,30789608680 0,95441081385 0,64257295383 2,03798920563 0,64070273990 0,56151580681 0,46754678967 0,79661785171 0,38807215887 0,61278054881 0,36523964775 0,44215381986 Distance (mm) Clinical improvement (%) 0,51325046666 0,67029384847 0,39782894878 0,54376325558 0,81623253384 0,68957643379 0,38046749337 0,74202332681 0,36923375480 1,0163563285 0,61523532783 0,49679768863 0,60499750990 0,51702986481 0,49370513867 0,84678765571 0,42894645487 0,65890956781 0,39565311275 0,37920987786 0,76739562286 0,89306452375

13. RESULTS The average distance between the NST and the active contact was 0.6 mm. The average distance between the NST and the active contact was 0.6 mm. Evaluating the three orthogonal planes, the average deviation was greater in the vertical plane (average error - 3.4 mm). Evaluating the three orthogonal planes, the average deviation was greater in the vertical plane (average error - 3.4 mm). Anatomical variability of the surgical target coordinates (mean error) Anatomical variability of the surgical target coordinates (mean error) 2,5 mm - axial plane 3,15 mm - coronal plane 7 mm - sagital plane The CT-MRI fusion was found to be accurate. The position of anatomic landmarks corresponded well between postoperative CT and preoperative MRI. The mean error was 0,5 mm (ranging from 0,3 to 0,7 mm). The CT-MRI fusion was found to be accurate. The position of anatomic landmarks corresponded well between postoperative CT and preoperative MRI. The mean error was 0,5 mm (ranging from 0,3 to 0,7 mm). In 62% of the patients the active contact was second contact In 62% of the patients the active contact was second contact Reduction in daily dose of Dopa (64%) Reduction in daily dose of Dopa (64%) Improvement of the motor symptoms (75%) (preop med off/postop med off stim on) Improvement of the motor symptoms (75%) (preop med off/postop med off stim on)

14. CONCLUSIONS The data found in our study are similar to literature. The data found in our study are similar to literature. In our study, we didn’t confirm the relationship between clinical improvement and the distance between the active contact and the NST. Maybe because the success of this procedure is multifactorial, and we must consider all the facts together. In our study, we didn’t confirm the relationship between clinical improvement and the distance between the active contact and the NST. Maybe because the success of this procedure is multifactorial, and we must consider all the facts together. We should consider facts that could bias our data, such as: We should consider facts that could bias our data, such as: implied brain shift implied brain shift possible errors in register of the data possible errors in register of the data differences in the references of the NST in the day of the surgery and collected in our study. differences in the references of the NST in the day of the surgery and collected in our study.