Patients
From June 2016 to May 2021, WHO grade I meningioma patients who were pathologically confirmed by our Hospital were retrospectively collected.
Inclusion criteria: 1. Patients with confirmed histopathological meningioma and definite pathological subtype; 2. Patients with meningioma resection one week after MRI examination; 3. Picture archiving and communication systems (PACS) has available pretreatment MRI images, including at least T1C and T2WI, and complete clinical data; 4. The image quality of each patient was good and there were no artifacts.
Exclusion criteria: 1. Patients who had received radiotherapy, chemotherapy, targeted therapy, or other treatments before preoperative MRI scanning; 2. Patients with different parameters of T1C and T2WI sequences in MRI images; 3. Patients with incomplete MRI sequences; 4. Patients with metallic foreign bodies or claustrophobia.
A total of 423 patients with WHO grade I meningiomas were enrolled, including 128 fibroblastic meningiomas (12 male and 116 female) and 295 non-fibroblastic meningiomas (77 male and 218 female).
MRI acquisition
Both plain and enhanced MRI images of the head were obtained using a Siemens Verio 3.0T superconducting MRI scanner (Siemens, Germany). The patient was placed in the supine position. The scanning sequence and parameters were as follows: Gradient echo (GRE): T1WI (TR=550 ms, TE=11 ms), layer thickness 5 mm, layer spacing 1.5 mm, (FOV) 260 mm×260 mm, matrix 256×256; TSE: T2WI (TR=2200 ms, TE=96 ms), echo time 10 ms, echo chain length 8, excitation twice. Enhanced scan: Gd-DTPA was injected into the elbow vein at a dose of 0.1 mmol/kg with a flow rate of 3.0 ml/s.
Image segmentation
The T1C and T2WI images of all 423 patients with meningioma were imported from a post-processing workstation in DICOM. A total of 128 fibroblastic meningiomas and 295 non-fibroblastic meningiomas were manually segmented by two radiologists (Doctors 1 and 2, with 3 and 10 years of experience, respectively) using the open-source ITK-SNAP software (www.itksnap.org ) without knowing the pathology. First, the volume of interest (VOI) of the lesion was manually segmented layer-by-layer on the axial T1C image, including tumor necrosis, cystic changes, and hemorrhage. The lesions were delineated layer-by-layer on axial T2WI, with T1C as a control. All VOI were examined by senior doctors. The process of this section is as follows (Fig. 1).
Radiomics feature extraction and filtering
After all the images were manually segmented, Z-score normalization was used to standardize the image strength normal distribution. A total of 3,376 radiomics features were extracted from T1C and T2WI using Shukun.net, including shape features extracted from the original image, first-order features, and texture features transformed by the original image filtering. Shape features, such as area, volume, diameter, and spherical degree, describe the size of the region of interest (ROI) and its spherical degree of approximation. First-order features, called histogram features, are features related to voxel intensity distribution in the ROI, such as mean, median, minimum, maximum, standard deviation, skewness, and kurtosis. Second-order features, also called texture features, are used to describe the strength of voxel spatial distribution, which mainly includes the gray level co-occurrence matrix (GLCM), gray level run long matrix (GLRLM), gray levelsize zone matrix (GLSZM), neighborhood gray-tone difference matrix (NGTDM), and some first-order features and texture features extracted by filter transformation.
In this study, all the features P<0.05 were screened by Selectpercentile, the dimension of the selected features was reduced by LASSO and 5-fold cross-validation, and the coefficient of the non-strongly correlated features was 0 by L1 regularization. Thirteen radiomics features (seven T2WI and six T1C) were screened to differentiate between non-fibroblastic and fibroblastic meningiomas. SelectKbest was used for univariate analysis of clinical features, and sex was included as the only clinical feature.
Construction and validation of cli-radiomics model
The thirteen radiomics features extracted from T2WI and T1C were fused, and radiomics models were constructed using different classifiers (Support vector machine (SVM), Random forest (RF), Decision tree (DT), Logistic regression (LR), LinearSVC, and Adaboost). Then, the diagnostic efficiencies of the different models were compared using the receiver operating characteristic (ROC) curve. The cli-radiomics model was built using the best radiomics model fused with clinical labels, and a nomogram of cli-radiomics models was constructed for predicting fibroblastic and non-fibroblastic meningiomas. The discriminant ability of the cli-radiomics models was evaluated using calibration curves of the training and validation sets. Decision curve analysis (DCA) was used to quantify the net benefit under different threshold probabilities and to assess the clinical validity of the nomogram.
Statistical methods
In this study, all data were analyzed using R software (version 3.4.1; http://www.Rproject.org), SPSS 25 (SPSS, Inc, Chicago, IL, USA) and Medcalc19.1(MedCalc, Mariakerke, Belgium). The chi-square test was used to compare sex, and an independent sample t-test was used to test the continuous variables, such as age, which accorded with the normal distribution. The Delong test compares the AUC values of different radiomic prediction models. The sensitivity (SEN), specificity (SPE), negative predictive value (NPV), positive predictive value (PPV), and accuracy (ACC) were calculated to distinguish fibroblastic meningiomas from non-fibroblastic meningiomas according to the confusion matrix. Calibration and decision curve analyses were drawn using R software, and the Hosmer-Lemeshow test was used to evaluate the statistical differences between the predicted and actual probabilities. P<0.05 showed significant difference.