Objective:Radiomics pipelines have been developed to extract novel information from radiological images, which may help in phenotypic profiling of tumours that would correlate to prognosis. Here, we compared two publicly available pipelines for radiomics analyses on head and neck CT and MRI in nasopharynx cancer (NPC).Methods and materials:100 biopsy-proven NPC cases stratified by T- and N-categories were enrolled in this study. Two radiomics pipeline, Moddicom (v. 0.51) and Pyradiomics (v. 2.1.2) were used to extract radiomics features of CT and MRI. Segmentation of primary gross tumour volume was performed using Velocity v. 4.0 by consensus agreement between three radiation oncologists. Intraclass correlation between common features of the two pipelines was analysed by Spearman’s rank correlation. Unsupervised hierarchical clustering was used to determine association between radiomics features and clinical parameters.Results:We observed a high proportion of correlated features in the CT data set, but not for MRI; 76.1% (51 of 67 common between Moddicom and Pyradiomics) of CT features and 28.6% (20 of 70 common) of MRI features were significantly correlated. Of these, 100% were shape-related for both CT and MRI, 100 and 23.5% were first-order-related, 61.9 and 19.0% were texture-related, respectively. This interpipeline heterogeneity affected the downstream clustering with known prognostic clinical parameters of cTN-status and GTVp. Nonetheless, shape features were the most reproducible predictors of clinical parameters among the different radiomics modules.Conclusion:Here, we highlighted significant heterogeneity between two publicly available radiomics pipelines that could affect the downstream association with prognostic clinical factors in NPCAdvances in knowledge:The present study emphasized the broader importance of selecting stable radiomics features for disease phenotyping, and it is necessary prior to any investigation of multicentre imaging datasets to validate the stability of CT-related radiomics features for clinical prognostication.
Biological uncertainty remains one of the main sources of uncertainties in proton therapy, and is encapsulated in a scalar quantity known as relative biological effective (RBE). It is currently recognised that a constant RBE of 1.1 is not consistent with radiobiological experiment and may lead to sub-optimal exploitation of the benefits of proton therapy. To overcome this problem, several RBE models have been developed, and in most of these models, there is a dependence of RBE on dose-averaged linear energy transfer (LET), . In this work, we show that the estimation in these models during the data-fitting (or parameter estimation) phase could be subjected to a huge uncertainty due to not taking into account cellular materials during simulation, and this uncertainty can propagate down to the resulting RBE models. The dosimetric impact of this uncertainty is then evaluated on a simple clinical spread out Bragg peak (SOBP) and a prostate example. Our simulation shows that uncertainty due to the use of water as cellular material is non-negligible under low and low dose (2 Gy), and can be neglected otherwise. Thus, this study indicates that further dose and range margins may be required for low target under low dose. This is due to greater uncertainties in RBE model associated with incomplete knowledge of cellular composition for computation.
Breast cancer is usually screened using mammography and biopsy is used to confirm diagnosis. Recent radiomics approaches suggest predictive associations between images and medical outcome. This study aims to classify breast cancer subtypes using textural features derived from magnetic resonance imaging (MRI). Thirty-two lesions with histologic results that were definite were studied. A total of 174 textural features were extracted from four MRI sequences (Axial STIR, dynamic contrast enhance (DCE) Phase 2, dynamic contrast enhance (DCE) subtracted Phase 2 and T1-weighted), and analysed using t-test, Kruskal-Wallis and principal component analysis (PCA). Evaluation was done using multinomial logistic regression and leave-one-out-cross-validation (LOOCV) methods. We found 14 texture features that consistently showed significant difference between malignant and normal breast tissues across all MRI sequences. Four textural features were useful in histological status with t-test accuracy of 71.4% and PCA accuracy of 64.3%. In hormonal receptor status, only five textural features were useful. The accuracies were also found to be poorer with 46.4% accuracy based on Kruskal-Wallis method and 46.4% accuracy using PCA method. As this is a preliminary study, the analysis should be extended to a larger sample size to accurately determine the possibility of clinical diagnosis.
Monte Carlo (MC) method is the gold standard dose calculation algorithm. Determination of the electron beam parameters for MC simulation is often estimated using trial and error methods. However, this can be tedious and time-consuming. This paper aims to validate MC simulated data using 1D gamma analysis for 6MV photon beam to obtain the optimal parameters. BEAMnrc codes were used to generate phase space files for conventional field sizes 10 × 10 cm 2 , 6 × 6 cm 2 , 4 × 4 cm 2 and small field sizes 2 × 2 cm 2 , 1 × 1 cm 2 , 0.5 × 0.5 cm 2 . For conventional field sizes, simulations were benchmarked against Golden Beam Data (GBD). Simulations for small fields were benchmarked against measurements obtained using EDGE Detector and PTW Diode SRS detector in a Sun Nuclear 3D scanner. Dose profiles in water were calculated using DOSXYZnrc codes. Initial reference parameters were approximated using average percentage dose differences of different mean electron energy and electron beam radial distribution (Full Width at Half Maximum, FWHM). Subsequently, the optimal parameters were validated by 1D gamma analysis using varying gamma criteria from γ 0.3%/0.3mm to γ 2.0%/2.0mm for depth dose and lateral dose profiles. Comparisons were performed along the central region at depth dose 1.6 cm . Optimal parameters were found to be unique for small field sizes. As field size decreases, smaller FWHM were required to match measured data. By using 95% passing rate, a generic set of optimal electron beam parameters in a MC model for all field sizes could be accurately determined. Our findings provide MC users a set of optimal parameters with sufficient accuracy for MC simulation work.
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