Abstracts

Rationale: Patients with drug-resistant epilepsy (DRE) should undergo a timely pre-surgical evaluation to look for a potentially resectable epileptogenic focus as surgery is the best treatment option for selected patients with DRE. Ictal SPECT is one of the established tools towards this goal and is used in many modern epilepsy centers. Timely isotope injection is critical for its optimal yield. Injection of SPECT radioisotope in the Epilepsy Monitoring Unit (EMU) has been traditionally done manually. This method has several limitations; it is operator-dependent, requires the availability of trained staff, may expose the staff to radiation and may increase the injection latency (IL) which may lead to less localizing iSPECTs.  The use of the ASIs can potentially solve all these challenges. Methods: We retrospectively reviewed all cases admitted to the University of Pittsburgh Medical Center Presbyterian University Hospital EMU from Jan 1, 2010 through Dec 31, 2016, who underwent an iSPECT.  Two ASIs (Spectris Solaris EP MR Injection System; Medrad, Inc., Indianola, PA) were initiated on Jul 1, 2013.  We compared the iSPECTs done with manual injections (Jan 1, 2010 - June 30, 2013) with those done with ASIs (July 1, 2013 - Dec 31, 2016) in terms of ability to successfully localize the seizure onset zone(s), and, subsequently, we classified the zones into unilateral focal (sublobar, lobar, regional), unilateral hemispheric, bilateral, and multifocal.  Results: A total of 123 iSPECTs were reviewed (65 males, 53.3%), age range from 18 – 75 years. Thirty five (35) iSPECTs were performed with manual tracer injection and 22 of these iSPECTs (62.8%) were able to localize the seizure onset zone(s); 18 (81.8%) were unilateral focal, 3 (13.6%) were unilateral hemispheric, 1 (0.5%) was bilateral. Eighty eight (88) iSPECTs were performed with ASIs, and 73 (82.9%) of these iSPECTs were able to localize the seizure onset zone(s); 55 (75.3%) were unilateral focal, 10 (13.6%) were unilateral hemispheric, 3 (4.1%) were bilateral, and 5 (6.8%) were multifocal. This improvement (82.9% vs. 62.8%) in the number of successfully localized iSPECTs with the use of ASIs was statistically significant (P = 0.016).Since the baseline characteristics of both groups were comparable, including no significant difference in focal features on EEG or MRI, the improvement in localizing yield of iSPECT is likely attributable solely to the use of ASIs. This difference is probably a result of the improvement in the average IL attained by ASIs as compared with that of manual injections (29 s vs. 66 s; P <0.001, CI: 22-53).  Conclusions: Utilization of ASIs leads to a significant improvement in the number of successfully localizing iSPECTs, which is likely due to the significant shortening of the iSPECT IL. Potentially significant cost consequences are being assessed.  Funding: No funding