High Resolution Ictal SPECT: Enhanced Epileptic Source Targeting?

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1 High Resolution Ictal SPECT: Enhanced Epileptic Source Targeting? Marvin A Rossi MD, PhD RUSH Epilepsy Center Research Lab Chicago, IL USA Medically-Refractory Epilepsy 500, ,000 individuals with epilepsy in the U.S., 00,000 epilepsy surgery candidates 4,500-5,000/yr epilepsy surgeries are perfomed 50,000+ VNS generators implanted to date Hauser & Hesdorffer. (990). Kwan & Brodie (000). NEJM, 4:4-9. Wiebe et al (00). NEJM, 45:-8 SPECT Static tracers 99m Tc-HMPAO (Ceretec) 99m Tc- ECD (Neurolite) I-IMP (Spectamine) I-HIPDM Diffusible Tracers Xe, 7 Xe What is Gamma Camera SPECT? If images are taken at angular increments around a center of rotation, a -D cross-sectional image can be reconstructed. Projection of Original Data Multiple heads are used to increase the number of images per unit time 5

2 . Filtering the Data Spiral Scanning Focused Collimators InSPira HD SPECT (NeuroLogica, Corp) Clamshell detectors 8 Scan Sequence Focal spots describe an interleaved spiral. Each slice scans from in-toout or out-to-in. Radial scan direction alternates with slice. Collimator Field of view Spacing 7 mm 6 mm 5 mm Inspira Image Inspira Profile Prism 000 Image Prism 000 Profile Capillary ID = mm Detector sees activity in entire bore at each position of focal spot. 4 mm.5 mm Focal Spot Trajectory Focal Spot Collimator 9 Voxel Size (mm).x. x..x. x.5 Scan Time 4 min. 0 min. Single Photon Emission Tomography (SPECT) Peri-ictal Related Transient Blood Flow Changes Early tracers became available following development of first dedicated single head SPECT camera (Ronald Jaszczak) ~984 Soon after, interictal SPECT scanning was incorporated into clinical practice. ~986 Ictal SPECT was first attempted and compared with baseline interictal SPECT. Interictal Ictal 0- min Post-ictal Mild hypo-perfusion Marked hypo-perfusion hyper-perfusion -0 min Post-ictal

3 Criteria Essential to performing Ictal SPECT:. Ictal SPECT must be performed in the video-eeg monitoring unit Subtraction Ictal SPECT Co-registered to MRI (SISCOM) 998. The availability of the setup and team is critical from at least early morning to at least early evening. 4 hr vigilance is not possible.. Brain-perfusion tracer with consistent quality control as well as reliable delivery is critical. 4. A reliable fast injector system should be available 5. Injecting Personnel must communicate closely with the EEG tech and patient/ family 6. Excellent cooperation between the neurology and nuclear medicine department is crucial O Brien TJ, So EL, Mullan BP et al (998). Subtraction Ictal SPECT Co-registered to MRI Improves Clinical Usefulness of SPECT in Localizing the Surgical Seizure Focus. Neurology 50: Favorable Outcome Data Following Resection of Medically Intractable Focal-Onset Epilepsy Lesional: Mesial Temporal Lobe Sclerosis 70-80% Temporal Neocortical 60-70% Extratemporal 40-60% Non-lesional: Temporal Neocortical 0-50% Extratemporal 0-0% 0-50% epilepsy cases have non-localizable epileptic sources or foci Two focal-onset epilepsy categories are typically grouped: Temporal Lobe Epilepsy (TLE) Extratemporal Lobe Epilepsy (ETE) challenging due to rapid ictal propagation Therefore, the potential role of SISCOM is to identify Non-localizing lesions not detected with standard presurgical techniques (that is by MRI and scalp EEG) -. Brinkman B, O Brien T, Mullan B, et al (000). Subtraction Ictal Spect Coregistered to MRI for seizure focus localization in partial epilepsy, Mayo Clin Prod, 75(6): Ahnlide J-A et al (007). Does SISCOM contribute to favorable seizure outcome after epilepsy surgery? Epilepsia 48: Early Ictal Circuit Temporal lobe amygdala hippocampus Sylvian fissure Frontal lobe orbitofrontal mesial frontal

4 SISCOM (SPECT) Recording Electrode Implants For Guiding Resection Hippocampal Formation MEG /6/ cm Lateral Frontal Post-Resection Basal Frontal Basal Temporal Lateral Frontal Pre-Resection Rush Medical Center Experience A total of 80 patients had or more SPECT scans performed at our institution from Nov 00 until April 009 Craniotomy +/- resection/transection n=0 (7%) (with follow up of months or longer) 4

5 Discussion SISCOM can provide, non-invasive information for preoperative planning High concordance with intracranial recording in ETE patients with a localizing SISCOM without structural lesions on MRI O Brien et al, Ahnlide et al concordance predictive of improved surgical outcome (Engel s Class I,II) In ETE, reported /9 (57.9%) Rush series ( months) TLE + ETE: 7/ (58%) ETE alone: 5/0 (50%) Discussion How useful is SISCOM for epilepsy arising from outside of the temporal lobe with non-lesional MRI data? Data suggest that SISCOM may improve detection of the epileptogenic zone, Concordance between SISCOM and site of resection may reflect overall outcome. Kaminska et al (00). Ictal SPECT in children with epilepsy: Comparison with intracranial EEG and relation to postsurgical outcome. Brain: a j neurol 6: Ahnlide et al (007). Does SISCOM contribute to favorable seizure outcome after epilepsy surgery? Epilepsia 48: Favorable Outcome Data Following Resection of Medically Intractable Focal-Onset Epilepsy Lesional: Mesial Temporal Lobe Sclerosis 70-80% Temporal Neocortical 60-70% Extratemporal 40-60% Nonlesional: Temporal Neocortical 0-50% Extratemporal 50-58% Limitations Published data sets have used small patient populations A limited follow-up period AS IMPORTANTLY, What do we do about the subgroup of patients without MRI lesion and nonlocalizing SISCOM (What to do?) Patient JC (RUSH): MRI-Negative SISCOM-Positive Anterior Insular Epileptic Source Associated with Bradycardia. Wetjen et al (006). Subtraction ictal single-photon emission computed tomography coregistered to magnetic resonance imaging in evaluating the need for repeated epilepsy surgery. J Neurosurg 05:7-6. 5

6 Patient RA Utilizing -Detector Gamma Camera Next Steps Higher resolution SPECT (ring scanners) Dynamic SPECT Activated SPECT mapping atlases Multimodal (addition of) DTI/MEG/PET RA RA RA Preoperative Stereotypic Seizure Onset PD PD 6

7 A Subtracted Activated SPECT (SAS) Mapping Deliver current & inject Tc-HMPAO B Tc-HMPAO equilibrates in brain msec RHD RHD- 4 LST RHD-4 LST- 0 msec LST-4 4 msec Rossi et al, (005). AES Abstract.69 SAS (-Detector Gamma Camera) & DTI Rossi et al, (005). AES Abstract.69 Dynamic SPECT Imaging Protocol (InSPira HD SPECT) Sagittal Coronal Diffusion Rossi et al, (00). Predicting white matter targets for direct neurostimulation therapy. Epilepsy Research Acknowledgements: Alan TenHarmsel, Spencer Brinker, Alan Goldberg, David Sarcu.. Students! Glen Stebbins Functional Neuroimaging Laboratory Amjad Ali Director Rush Nuclear Medicine/Diagnostic Radiology Kristoph Krug BluePointDx Inc. Tom Hoeppner..Co-programmer for the NeuroPace Study Steve Bild..Chief EEG Technologist Volodymyr Pylypyuk.Nuclear Medicine/SISCOM Technologist Richard W Byrne..Chair Dept Neurosurgery Support: Institutional/Rush Philanthropy NeuroLogica Corp (utilizing Rush as a Luminary Site) NeuroPace, Inc. 7