RT Journal Article
SR Electronic
T1 The optimal z-score threshold for SISCOM analysis to localize the ictal onset zone
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1673
OP 1673
VO 59
IS supplement 1
A1 De Coster, Liesbeth
A1 Van Laere, Koen
A1 Cleeren, Evy
A1 Baete, Kristof
A1 Dupont, Patrick
A1 Van Paesschen, Wim
A1 Goffin, Karolien
YR 2018
UL http://jnm.snmjournals.org/content/59/supplement_1/1673.abstract
AB 1673Objectives: In epilepsy patients, SISCOM or subtraction ictal single photon emission computed tomography co-registered to magnetic resonance imaging has become a routinely used, non-invasive technique to localize the ictal onset zone (IOZ). Thresholding of clusters with a predefined number of standard deviations from normality (z-score) is generally accepted to localize the IOZ. In this study, we aimed to assess the robustness of this parameter in a group of patients with a well-characterized drug-resistant epilepsy in whom the exact location of the IOZ was known after successful epilepsy surgery. Methods: Eighty patients underwent preoperative SISCOM and were seizure free in a postoperative period of minimum one year. SISCOMs with z-threshold 2 and 1.5 were analyzed by two experienced readers separately, blinded from the clinical ground truth data. Their reported location of the IOZ was compared with the operative resection zone. Furthermore, confidence scores of the SISCOM IOZ were compared for the two thresholds. Results: Visual reporting with a z-score threshold of 1.5 and 2 showed no statistically significant difference in localizing correspondence with the ground truth (70% vs 72% respectively, p=0.17). Interrater agreement was moderate (k=0.65) at the threshold of 1.5, but high (k=0.84) at a threshold of 2, where also reviewers were significantly more confident (p < 0.01). Conclusions: SISCOM is a clinically useful, routinely used modality in the pre-operative work-up in many epilepsy surgery centers. We found no significant differences in localizing value of the IOZ using a threshold of 1.5 or 2, but interrater agreement and reader confidence was higher using a z-score threshold of 2.