Flowchart
According to the flowchart of this work (Fig. 1), the Gd-EOB-DTPA-enhanced hepatic MRI (MRI) data from 112 patients and contrast-enhanced CT (CT) data from 190 patients were retrospectively collected. The hepatobiliary phase at 15 minutes of MRI and the portal venous phase of CT were selected, the ROI liver region was segmented, and the features were extracted from the image. Next, the features were further screened through P-value and correlation coefficient. The dataset was randomly divided into a training dataset and a test dataset, the training dataset aimed to train the model, while the features associated with the label of ICG-R15 were screened by using the least absolute shrinkage and selection operator (LASSO) algorithm. Multiple machine learning algorithms were also used for training on the training dataset and predicting functional liver reserve classification results on the test dataset. At last, the best model was selected to evaluate functional liver reserve classification.
Patients
By reviewing the patients who were diagnosed with HCC in our hospital from May 2017 to April 2022, he inclusion criteria were the following: (1) all patients were confirmed to have HCC; (2) Gd-EOB-DTPA-enhanced hepatic MRI or contrast-enhanced CT in all phases was completed one week before treatment or surgery; (3) ICG clearance test within one week before treatment or surgery; (4) patients without jaundice during ICG clearance test [17]; (5) all patients had no history of previous liver surgery. A total of 190 patients were included in this study. Details are listed in Table 1. The Ethics Committee of the Affiliated Hospital of Qingdao University approved this study with the ethical approval number QYFY-WZLL-27465.
Table 1
Demographics and preoperative data of patients
Characteristic | Categories | Value | Number |
MRI | CT | MRI | CT |
dataset | Training dataset (80%) | | | 89 | 152 |
| Test dataset (20%) | | | 23 | 38 |
Age (mean ± SD) | | 58.62 ± 8.62 y | 59.42 ± 8.93 y | | |
Gender | Female | | | 25 | 44 |
| Male | | | 87 | 146 |
HBV infection | Yes | | | 104 | 168 |
| No | | | 8 | 22 |
Liver cirrhosis | Yes | | | 75 | 122 |
| No | | | 37 | 68 |
BMI (mean ± SE) | | 25.02 ± 0.39 kg/m2 | 24.75 ± 0.27 kg/m2 | | |
TBIL (mean ± SE) | | 21.32 ± 1.60 µmol/L | 22.37 ± 1.10 µmol/L | | |
ALB (mean ± SE) | | 36.26 ± 0.66 g/L | 36.99 ± 0.43 g/L | | |
ALT (mean ± SE) | | 48.38 ± 10.21 IU/L | 49.06 ± 5.96 IU/L | | |
PT (mean ± SE) | | 11.34 ± 0.14s | 11.45 ± 0.11s | | |
AST (mean ± SE) | | 52.31 ± 6.81 IU/L | 56.08 ± 5.24 IU/L | | |
GGT (mean ± SE) | | 99.44 ± 16.15 IU/L | 108.12 ± 12.23 IU/L | | |
ICG-R15 | ICG-R15 ≤ 10% vs ICG-R15༞10% | | | 62vs128 | 45vs67 |
| ICG-R15 ≤ 20% vs ICG-R15༞20% | | | 126vs64 | 78vs34 |
| ICG-R15 ≤ 30% vs ICG-R15༞30% | | | 160vs30 | 93vs19 |
ALT: alanine transaminase, BMI: Body Mass Index, HBV: Hepatitis B Virus; TBIL: total Bilirubin, ALB: albumin, PT: prothrombin time, AST: aspartate aminotransferase, GGT: gamma-glutamyltransferase, ICG-R15: indocyanine green retention rate at 15 min, y: years. |
ICG Clearance Test
After 6 hours of fasting, the patient was in a supine position and injected 0.5 mg/kg ICG (Dandong Yichuang Pharmaceutical Co., Ltd., Liaoning, China) intravenously into a peripheral vein within 10 seconds. The ICG retention rate was measured with ICG pulse spectrophotometry (DDG 3300K, Japan) after 15 minutes of injection. The ICG-R15 value was expressed as the percentage of ICG retention in serum 15 minutes after injection.
MRI and CT acquisition
The MRI examination was conducted by using a Siemens Verio-Dot 3.0 T MRI scanner. The CT examination was conducted by using a Siemens SOMATOM Definition Flash scanner. From the top of the liver to the pelvis, scans were performed. The MRI scanning parameters were selected as below: the scanning layer thickness was 3 mm, the interval was 1 mm, the matrix was 182 × 320, and the field of view was 40 cm × 40 cm. After the elbow vein injection of 20 mL Gd-EOB-DTPA (with flow rate of 2.0 ml/s and dose of 0.025 mmol/kg), enhanced scans was conducted on the patients. The delay times for the portal and hepatobiliary phases were 7 s and 20 min respectively. The CT scanning parameters were selected as below: voltage of 120 kV, current of 200–350 mA, scanning layer thickness of 1 mm, layer spacing of 5 mm, and matrix of 512 ×512. After the peripheral vein injection of iohexol containing 350 mg/ml of iodine (with flow rate of 3.0 ml/s and dose of 1.5 ml/kg), enhanced scans was conducted on the patients. The delay times for the arterial, portal venous, and equilibrium phases were 30 s, 60 s, and 120 s respectively.
Image segmentation
The computer-assisted surgery system (CAS) (CAS-Lv, Qingdao Hisense Medical Equipment Co., Ltd.) was used to segment the liver contour automatically from the hepatobiliary phase after 15 minutes of MRI and venous phase of the CT, to obtain the regions of interest (ROI) of the liver. For liver segmentation of MRI and CT, the Dice coefficient was more than 0.95 (this Dice coefficient is the manufacturer reference data of CAS-Lv). Each automatically segmented liver contour was visually inspected and any inaccurate liver contour were manually corrected by a doctor with over a decade of experience. All patients’ images and liver contour were saved as .NII files.
Radiomic feature extraction
The preprocessing steps include Pixelspacing resampling and normalization of the image. We extracted 107 radiomics features from CT and MRI of patient. The features were split into seven different groups: (1) first-order statistics of voxel intensity features (n = 18), (2) shape features (n = 14), (3) gray level co-occurrence matrix (GLCM) features (n = 24), (4) gray level dependence matrix (GLDM) features (n = 14), (5) gray level run-length matrix(GLRLM) features (n = 16), (6) gray level size zone matrix (GLSZM) features (n = 16), and (7) neighboring gray tone difference matrix (NGTDM) features (n = 16). PyRadiomics package implemented in Python (version 3.7) was utilized to automatically conduct the feature extraction process. In addition, each part of the feature name was concatenated with underlines, it includes image type, feature group, and the feature name. For example, original_firstorder_Skewness represents a feature extracted from the original image, firstorder group, and feature name was Skewness.
Radiomic feature selection
At first, statistical tests were performed to calculate the p value between the features. When the two-tailed p value of features was p < 0.1, the features was retained. Second, spearman correlation analysis was performed to calculate the correlation coefficient between features. When the correlation coefficient of many features was r༞0.9, one feature randomly retained. This step was applied to reduce the collinearity of features. At last, the least absolute shrinkage and selection operator (LASSO) algorithm was used to reduce the unimportant features. The statistical tests, correlation analysis, and LASSO algorithm were also implemented by importing the “scipy”, “numpy”, and “sklearn” packages in Python (version 3.7).
Model construction and performance evaluation
Supervised learning was used for training and prediction. More specifically, six machine learning algorithms were applied to investigate the performance of the model, whereas these classifiers were K-Nearest Neighbors (KNN), Support Vector Machines (SVM), Extra Trees(ET), Random Forest (RF), Light Gradient Boosting Machine (LightGBM) and eXtreme Gradient Boosting (XGBoost). All selected features were used as input to classify the evaluation of functional liver reserve (ICG-R15 ≤ 10% vs ICG-R15༞10%, ICG-R15 ≤ 20% vs ICG-R15༞20%, and ICG-R15 ≤ 30% vs ICG-R15༞30% as 2-class classifier). All patients were randomly split into two cohorts. One was called the training dataset (80%) and the other was called the test dataset (20%). Each of the models was trained on the training dataset, and five cross-validated was performed on the dataset by using StratifiedKFold, which was provided by the “sklearn” package in Python (version 3.7). StratifiedKFold can ensure that each set contains approximately the percentage of samples in each class, which can reduce the sampling deviation of the set. We used the ACC and AUC of ROC with 95% CI to evaluate the performance of classification models. The models and values calculation was implemented by importing the “pandas” and “sklearn” packages in Python (version 3.7).