Radiomics and anaesthetic planning: Quantitative imaging as a new frontier in preoperative risk assessment

Table 2 Classification of radiomic features with definitions and perioperative relevance

Feature category	Description	Key features	Perioperative relevance
First-order (histogram)	Statistical measures of voxel intensity distribution without spatial consideration	Mean, median, entropy, skewness, kurtosis, energy, uniformity	Tissue density characterization; hepatic steatosis grading; muscle quality assessment (myosteatosis)
Shape-based	Geometric properties of the segmented region	Volume, surface area, sphericity, compactness, elongation	Organ volumetry; tumour burden estimation; airway dimensional analysis
GLCM	Second-order texture features capturing spatial arrangements of pixel intensity pairs	Contrast, correlation, homogeneity, energy, entropy	Tissue heterogeneity; myocardial fibrosis detection; pulmonary parenchymal characterization
GLRLM	Texture features based on consecutive pixels of identical intensity	Run length non-uniformity, short/long run emphasis, gray-level non-uniformity	Vascular calcification pattern analysis; skeletal muscle architecture
GLSZM	Features characterizing zones of homogeneous intensity	Zone entropy, large/small zone emphasis, zone non-uniformity	Emphysema quantification; adipose tissue distribution
GLDM	Features describing pixel-pair intensity dependencies	Dependence entropy, dependence non-uniformity	Coronary plaque vulnerability assessment
NGTDM	Intensity differences between adjacent pixels	Coarseness, busyness, complexity, contrast	Tissue microstructure characterization; perivascular adipose tissue analysis

GLCM/GLRLM/GLSZM/GLDM/NGTDM: Texture feature matrices.