Keran Ma^{1}, Jingliang Cheng^{1}, Xiaonan Zhang^{1}, Ankang Gao^{1}, Chengru Song^{1}, Shaoyu Wang^{2}, Xu Yan^{2}, and Huiting Zhang^{2}

This study aimed to explore the value of mean apparent propogation (MAP)-MRI parameters in the diagnosis of hippocampal sclerosis. By comparing the MAP-MRI parameters of hippocampus from both the hippocampal sclerosis patients and the healthy controls, the study found that the MAP-MRI parameters showed high consistency with pathological results, particularly for MSD and QIV. It suggests that MAP-MRI may be used as a diagnostic method with high sensitivity and specificity besides magnetic resonance spectroscopy(MRS) in the future.

**Introduction**

**Method**

Thirteen patients (average age: 30.7 ± 14.1 years; median age: 28 years) with unilateral HS (left: 5 cases; right: 8 cases) confirmed by pathology were enrolled in the study. Five healthy age-matched controls (average age: 26.0 ± 4.06 years; median age: 25 years) with no history of brain injury or cognitive problems were also recruited. All the patients and the healthy controls underwent MRI acquisition on a 3T scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany), including the T2 FLAIR sequence and the DSI sequence. The parameters of the DSI sequence were as follows: b = 0 and 3000 s/mm^{2}, TR/TE = 3800/72 ms, FOV = 220 × 220 mm^{2}, GRAPPA = 2, slice acceleration factor = 2, slice thickness = 2.2 mm, voxel size = 2.0 × 2.0 × 2.2 mm^{3}, slice number = 60, scan time = 4.45 min. The MAP-MRI parameters were calculated using software developed in-house with Python, called DWINeuro, which is based on an open-resource tool DIPY (Diffusion Imaging In Python, http://nipy.org/dipy). The parameters of MAP-MRI included the mean square displacement (MSD), the q-space inverse variance (QIV), the return to the origin probability (RTOP), the return to the axis probability (RTAP), and the return to the plane probability (RTPP).

The region of interest (ROI) was drawed in the hippocampal sclerosis side of the patients and both sides of the healthy people, then the results obtained from the two groups were compared . Statistical analysis was performed using SPSS 21.0 (Chicago, IL) and MedCalc (MedCalc, Mariakerke, Belgium). For the statistically significant parameter, the optimal threshold value and diagnostic threshold were determined by plotting the receiver's operating characteristic (ROC) curve and the Yoden index, respectively. P < 0.05 was considered statistically significant.

**Result **

**Discussion**

1.Ozarslan E, Koay C G, Shepherd T M, et al. Mean apparent propagator (MAP) MRI: a novel diffusion imaging method for mapping tissue microstructure. Neuroimage.2013;78:16-32.

2.Santyr BG, Goubran M, Lau JC, et al. Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T. J Magn Reson Imaging. 2017 ; 45: 1359-1370.

Figure 1. Neuroanatomical variation of MAP-MRI parameters of a representative subject who was confirmed by pathology to have right hippocampal sclerosis. It shows that the red area in T2Flair represents the selected ROI, and the ROI of other DSI parameter maps are copied from it.

Figure 2. Reproducibility of all parameters of DSI on the HS group and healthy control(HC) group .

Figure 3.ROC plots with statistically significant parameters.

Table 1. Analysis of the efficacy of MAP-MRI parameters for the diagnosis of hippocampal sclerosis