Study design and participants
The study included 165 patients with T2DM admitted to A Medical Center from January 2020 to May 2021 and 29 patients admitted to B Medical Center from January 2021 to October 2021. Patients from Medical Center A were randomly stratified into the training set (n = 116) and internal validation set (n = 49) in a 7:3 ratio. Patients from Medical Center B were included in the external validation set.
Inclusion criteria were: ① Right-handed patients aged 45 to 75; ② Patients with T2DM meeting 1999 WHO diagnostic criteria, with a diabetes duration over 0.5 years; ③ Patients capable of completing neuropsychological assessments, including the Montreal Cognitive Assessment (MoCA), Hamilton Depression Scale (HAMD), Hamilton Anxiety (HAMA), Hachinski Ischemic Score (HIS), Clinical Dementia Rating (CDR), and Activity of Daily Living (ADL);[16; 17; 18; 19] ④ Patients were conscious and cooperative during head MRI examinations, with an absence of stroke (excluding lacunar infarction) or noticeable motion artifacts in the images. Exclusion criteria were: ① Patients with acute diabetes mellitus complications such as severe ketoacidosis, hyperglycemic hyperosmolar state, and hypoglycemic coma; ② Patients with other endocrine system disorders (hyperthyroidism, hypothyroidism, pituitary dysfunction); ③ Patients with a history of alcoholism, drug addiction or substance abuse.; ④Patients with anxiety (HAMA > 14), depression (HAMD > 20), clinical dementia (CDR > 1), vascular dementia (HIS > 7), impaired daily living activities (ADL > 26), and patients with MoCA < 18 score. Patients with MoCA scores ≥ 26 constituted the normal control (NC) group, while those with scores between 18 and 25 comprised the Mild Cognitive Impairment (MCI) group. The process of including and excluding patients is illustrated in Fig. 1.
Education levels were defined based on the education system used in our country. 0 = illiterate, 1 = primary school, 2 = junior high school, 3 = high school or technical secondary school, 4 = undergraduate, 5 = graduate. Drinking history referred to consuming over 100g of alcohol per week in the past year, not meeting the criteria for alcoholism (60 g/day).[20; 21] Smoking history involved smoking one or more cigarettes per day for over 6 months.
Acquisition and analysis of MR images
MRI data was obtained using 3.0 T MRI scanner. Routine sequences included T1WI, T2WI, T2 FLAIR, and DWI. The parameters of T1WI imaging: TR = 1750ms, TE = 24m, FOV = 220× 220 cm, matrix = 256 × 256, flip angle = 111°, echo chain = 10, bandwidth = 31.25, layer thickness = 5mm, gap = 1.5mm. The parameters of T2 FLAIR: TR = 9000ms, TE = 120ms, FOV = 220 × 220 cm, matrix = 256 × 256, flip angle = 160°, echo chain = 18, bandwidth = 50, layer thickness = 5 mm, and gap = 1.5 mm. T1WI images were automatically segmented into GM, WM and CSF using the spm12 package (https://www.fil.ion.ucl.ac.uk/spm/software/spm12/) in Matlab software. Then, Experienced neuroradiologists, blinded to clinical data, manually adjusted GM, WM, and CSF boundaries using ITK-SNAP software (http://www.itksnap.org). Modification involved: (1) removal of nonbrain tissue, brainstem, and cerebellum, and (2) adjustment of GM, WM, and CSF segmentation. T2 FLAIR imaging was used for observing and automatically segmenting WMH using the spm12 package.
Acquisition and selection of radiomics features
Whole-brain GM, WM and CSF were selected as regions of interest (ROIs). To minimize the central effect of MR images from different hospitals and scanners [37], all T1WI images underwent preprocessing. [22] Initially, all images were resampled to 1× 1× 1mm3 resolution through linear interpolation to eliminate anisotropy effects on features. Subsequently, a Gaussian filter reduced noise, and correction of magnetic field inhomogeneity helped minimize external interference effects. Finally, intensity was standardized by limiting grayscale values to a range of 0–32 to ensure unbiased comparisons. Preprocessing of images and extraction of features were performed using AK software (Artificial Intelligence Kit V3.0.0.R, GE Healthcare). Features with intraclass correlation coefficient (ICC) values exceeding 0.75 were included in the follow-up analysis to assess their reproducibility. The Mann-Whitney U test and Elastic Net Regression were then applied to filter out redundant and irrelevant features.
Radiomics model construction and validation
The model was constructed by six machine learning algorithms: LR (Logistic Regression), SVM (Support Vector Machine), Random Forest (RF), Bayes, KNN (k-nearest neighbor), and XGBoost (eXtreme Gradient Boosting Machine). The XGBoost algorithm, a decision-tree-based approach, demonstrates notable efficiency in handling missing data and aggregating weak prediction models to create highly accurate ones.[23] The SHapley Additive exPlanations (SHAP) summary plot, derived from game theory, explains the output of various machine learning models.[24] SHAP summary plots provide a visually concise representation of the range and distribution of importance that each feature has on the model's output, relating the feature's value to its impact. Features were initially sorted by their global importance. Each dot, representing the SHAP value of a feature from a patient, was horizontally plotted and vertically stacked to illustrate the density of the same SHAP value. The dots were then color-coded based on the value, ranging from low (blue) to high (red). The Area Under the Curve (AUC) from Receiver Operator Characteristic (ROC) analysis assessed the accuracy and stability of the models. The DeLong test was employed to compare the performance of different ROC curves.
Statistical Analysis
Statistical analyses were conducted using R software (version 3.5.0), SPSS software (version 17.0, Armonk, NY), and Python (version 3.5). Continuous variables were presented as (means ± standard deviations). Normality of distribution was assessed using the Kolmogorov-Smirnov test. Variables were compared using the t-test for normal distributions or the Mann-Whitney test for non-normal distributions. Categorical variables were presented as [median, interquartile interval] and compared using the chi-square test. A p < 0.05 was deemed significant.
Informed consent
to participate in the investigation was obtained in writing from all subjects and/or their legal guardian(s) in accordance with the Declaration of Helsinki.
The study proactively ensured adherence to the highest ethical standards by implementing necessary measures. It sought informed consent to prioritize participants' autonomy by outlining the study's goals and ensuring voluntary participation. Strict protocols protected confidentiality and privacy; personally identifying information was securely managed, available only to the research team, and never revealed in published data or conclusions. These ethical protections highlight the dedication to participant welfare and scientific integrity throughout the study.
Ethics approval
The study has been approved by the Ethic Committee of ZhejiangProvincial People's Hospital(ethical approval number is 2020QT174) and conducted in compliance with Good Clinical Practice guidelines and the Declaration of Helsinki. Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.