Long, Zaiyang

ABSTRACT BACKGROUND AND PURPOSE SISCOM and STATISCOM were clinically proved to be effective for ictal/inter‐ictal single‐photon emission computed tomography (SPECT) analysis coregistered with magnetic resonance imaging (MRI) for seizure localization. Recently, a software package also became available for this analysis. This study aimed to investigate and compare the performance of these analysis methods for seizure localization. METHODS A total of 378 patients who underwent 99m Tc‐ethyl cysteinate dimer (ECD) SPECT scans were retrospectively reviewed and 28 remained after applying exclusion criteria. Their SPECT and MRI images were analyzed with SISCOM (with z ‐score of 1.5 and 2), STATISCOM, and MIMneuro, resulting in a total of 112 image data sets. Two experienced radiologists participated in the blind review process using a custom tool and they can mark up to two hyper‐ and/or hypoperfusion regions. Their review results were analyzed using the Jackknife Free Response Receiver‐Operating Characteristics (JAFROC) test and the JAFROC figure‐of‐merit (FoM) was reported for each method. The interobserver agreement was also assessed using Cohen's kappa test. RESULTS Based on the readers’ two choices, averaged FoM was 85.7%, 83.9%, 66.1%, and 51.8% for STATISCOM, MIMneuro, SISCOM ( z ‐score = 2), and SISCOM ( z ‐score = 1.5), respectively. The average confidence rating was 2.5, 2.3, 1.6, and 1.1 for STATISCOM, MIMneuro, SISCOM ( z ‐score = 2), and SISCOM ( z ‐score = 1.5), respectively. For interobserver agreement, kappa was .742 for STATISCOM, .816 for MIMneuro, .517 for SISCOM ( z ‐score = 2), and .441 for SISCOM ( z ‐score = 1.5; all P < .001). CONCLUSION Our study demonstrated that STATISCOM showed the best performance for seizure localization, which was closely followed by MIMneuro. In addition, MIMneuro was not inferior to SISCOM with either z ‐score.

MRS provides a valuable tool for the non‐invasive detection of brain γ‐aminobutyric acid (GABA) in vivo. GABAergic dysfunction has been observed in the aging cerebellum. The study of cerebellar GABA changes is of considerable interest in understanding certain age‐related motor disorders. However, little is known about the reproducibility of GABA MRS in an aged population. Therefore, this study aimed to explore the feasibility and reproducibility of GABA MRS in the aged cerebellum at 3.0 T and to examine the effect of differing tissue composition on GABA measurements. MRI and 1H MRS examinations were performed on 10 healthy elderly volunteers (mean age, 75.2 ± 6.5 years) using a 3.0‐T Siemens Tim Trio scanner. Among them, five subjects were scanned twice to assess the short‐term reproducibility. The MEGA‐PRESS (Mescher–Garwood point‐resolved spectroscopy) J‐editing sequence was used for GABA detection in two volumes of interest (VOIs) in the left and right cerebellar dentate. MRS data processing and quantification were performed with LCModel 6.3‐0L using two separate basis sets, generated from density matrix simulations using published values for chemical shifts and J couplings. Raw metabolite levels from LCModel outputs were corrected for cerebrospinal fluid contamination and relaxation. GABA‐edited spectra yielded robust and stable GABA measurements with averaged intra‐individual coefficients of variation for corrected GABA+ between 4.0 ± 2.8% and 13.4 ± 6.3%, and inter‐individual coefficients of variation between 12.6% and 24.2%. In addition, there was a significant correlation between GABA+ obtained with the two LCModel basis sets. Overall, our results demonstrated the feasibility and reproducibility of cerebellar GABA‐edited MRS at 3.0 T in an elderly population. This information might be helpful for studies using this technique to study GABA changes in normal or diseased aging brain, e.g. for power calculations and the interpretation of longitudinal observations. Copyright © 2015 John Wiley & Sons, Ltd.