TABLE 3.
Summary of features used as inputs to ML/DL models for IMRT/VMAT QA outcome predictions.
Input features | QA technique | Feature selection technique | Important features | Reference |
---|---|---|---|---|
Plan complexity features | 2D array detector | LASSO | 4 features: MU factor, aperture score, irregularity factor, and fraction of the plan delivered at the corners of a 40 × 40 cm2 field | Valdes et al.33 |
2D array detector and EPID | LASSO | 7 features: irradiated area outline, Jaw position, fraction of the area receiving dose from penumbra, Duty cycle, irregularity factor, and others | Valdes et al.34 | |
Film dosimetry | Dropout technique | 4 features: MU values, the PTV volume, the rectum volume, and the overlapping region volume | Tomori et al.35 | |
3D array detector | Pearson's correlation coefficient | 28 features: plan complexity parameters (n = 18), machine type (n = 4), and photon beam energy (n = 6). | Ono et al.46 | |
3D array detector | SVM recursive feature elimination | 30 features: Linac output, MU factor, total number of control points, and others | Granville et al.47 | |
2D array detector | Manually | 54 features: MU value, union aperture area, plan area/irregularity/modulation, average leaf gap/dose rate/travel distance, modulation index of leaf speed/acceleration, and others | Li et al.45 | |
EPID | Manually | 10 features: modulation complexity score, beam irregularity, MUs/control point in a beam, maximum of x–y jaw positions, edge metric, and others | Lam et al.38 | |
3D array detector | Manually | 54 features: plan modulation‐complexity and delivery‐characteristics | Wang et al.51 | |
2D array detector | Extra‐trees, mutual information, and linear regression | 100 features: aperture score, MU factor, edge metric, leaf gap/travel/motion, plan irregularity, plan modulation, and others | Wall and Fontenot48 | |
2D array detector | Manually | 6 features: leaf position, instantaneous velocity, movement away/toward the center, leaf movement status, the control point number, and the leaf bank | Carlson et al.44 | |
EPID | Manually | 14 features: leaf previous/current/next positions, dose fraction, gantry angle, leaf speed/acceleration, leaf gap, leaf movement status, and others | Osman et al.41 | |
EPID | Manually | 7 features: leaf velocity, acceleration, control point, dose rate, gravity vector, gantry velocity (VMAT), and gantry acceleration (VMAT) | Chuang et al.43 | |
Radiomics features | EPID | Wilcoxon rank‐sum Test | 13 features: radiomics features (size zone metric) and intensity histogram metrics derived from gamma map images | Wootton et al.37 |
2D array detector | Dropout technique | CNN features derived from fluence map images | Interian et al.36 | |
2D array detector | Dropout technique | CNN features derived from dose distribution images | Tomori et al.50 | |
EPID | SVM recursive feature elimination | 11 features: radiomics features e.g. contrast, uniformity, zone entropy, and others | Ma et al.40 | |
3D array detector | Dropout technique | CNN features derived from dose difference or gamma map images | Kimura et al.52 | |
EPID | Random forest regression | 11 features: radiomics intensity histogram features and the texture features derived from fluence difference map images | Sakai et al 42 | |
Combined features | EPID | Principal component analysis, and triplet networks | 81 features: 17 texture features (hand‐crafted) from intensity histograms and size zone matrices) and 64 CNN features derived from gamma map images | Nyflot et al.39 |
3D array detector | Random forest | 502 features: plan complexity features (e.g. aperture area/perimeter/irregularity, and others), radiomics features (shape, statistical information, and texture features), and clinical parameters (treatment site/machine, beam energy, and dose calculation algorithm) | Hirashima et al.49 |
Abbreviations: CNN, convolutional neural network; EPID, electronic portal imaging device; LASSO, Least Absolute Shrinkage and Selection Operator; MU, monitor unit; PTV, planning target volume; SVM, support vector machine; VMAT, volumetric‐arc radiation therapy.