The gamma evaluation method as a routine QA procedure of IMRT

BackgroundThe conventional QA procedures dedicated to 3D CRT are unsatisfactory if the dMLC is in operation. In the case of IMRT not only should the dose on the beam axis, but also its distribution in the total plane perpendicular to the beam be taken under control. The comparison between the predicted and the observed fluence can be achieved using the gamma method. It takes into consideration the dose difference and the spatial displacement between analyzed points to provide a γ-index as a result of comparison.AimThe aim of the investigation was to develop the procedure of IMRT verification based on the gamma algorithm.Materials and Methods700 patients have been irradiated using IMRT since 2002. Over 1500 images recorded on the film and/or EPID have been analyzed with the help of self-made software. Histograms of γ-value and the γ-images have been created for each field. The fields have been classified depending on tumour location and the method of dose delivery, to obtain an average result for each class. We have performed a comparison of γ-histograms acquired with the help of different methods of recording.ResultsWe have observed a correlation between results of verification obtained with the help of the gamma algorithm and the method of intensity modulation.ConclusionGamma evaluation allows one to find local hot-spots caused by irregularities in leaf motion or the tongue-and-groove effect

Significance of neutrophil to lymphocyte ratio as a predictor of outcome in head and neck cancer treated with definitive chemoradiation

Background: The role of host immune system in carcinogenesis and response to treatment is increasingly studied, including predictive potential of circulating neutrophils and lymphocytes. The objective of the study was to evaluate the prognostic value of pre- and post-treatment neutrophil-to-lymphocyte (NLR) for treatment outcome in patients diagnosed with squamous cell carcinoma of head and neck (HNSCC) treated with definitive chemoradiation. Materials and methods: Electronic medical records of patients were evaluated and NLR was calculated. Cox regression was used to assess the impact of selected variables on overall survival (OS), disease specific survival (DSS), progression free survival (PFS) and distant failure free survival (DFFS). Logistic regression was used to estimate odds ratios of complete response with NLR. Results: 317 patients' records were included in the study. Increases in both pre-and post-NLR were associated with decreased OS in univariable analysis [hazard ratio (HR): 2.26 (1.25–4.07), p = 0.0068 and HR: 1.57 (1.03–2.37), p = 0.035 respectively). Post-NLR remained significant for OS in multivariable analysis [HR: 1.93 (1.22–3.1), p = 0.005] as well as for unfavorable DSS [HR: 2.31 (1.22–4.4), p = 0.01]. Pre-treatment NLR and nodal status correlated with shorter DFFS in multivariable analysis [HR 4.1 (1.14–14), p = 0.03 and HR 5.3: (1.62–18), p = 0.0062, respectively]. Strong correlation of increased both pre- and post-NLR with probability of clinical tumor response (CR) was found [odds ratio (OR): 0.23 (0.08–0.6), p = 0.003, and OR: 0.39 (0.2–0.8), p = 0.01 respectively]. Conclusion: NLR evaluated before and post treatment was a strong predictor of unfavorable treatment outcome and can be used for risk evaluation and clinical decision about treatment and post-treatment surveillance

The gamma evaluation method as a routine QA procedure of IMRT

AbstractBackgroundThe conventional QA procedures dedicated to 3D CRT are unsatisfactory if the dMLC is in operation. In the case of IMRT not only should the dose on the beam axis, but also its distribution in the total plane perpendicular to the beam be taken under control. The comparison between the predicted and the observed fluence can be achieved using the gamma method. It takes into consideration the dose difference and the spatial displacement between analyzed points to provide a γ-index as a result of comparison.AimThe aim of the investigation was to develop the procedure of IMRT verification based on the gamma algorithm.Materials and Methods700 patients have been irradiated using IMRT since 2002. Over 1500 images recorded on the film and/or EPID have been analyzed with the help of self-made software. Histograms of γ-value and the γ-images have been created for each field. The fields have been classified depending on tumour location and the method of dose delivery, to obtain an average result for each class. We have performed a comparison of γ-histograms acquired with the help of different methods of recording.ResultsWe have observed a correlation between results of verification obtained with the help of the gamma algorithm and the method of intensity modulation.ConclusionGamma evaluation allows one to find local hot-spots caused by irregularities in leaf motion or the tongue-and-groove effect

Prediction of Incomplete Response of Primary Tumour Based on Clinical and Radiomics Features in Inoperable Head and Neck Cancers after Definitive Treatment

Radical treatment of patients diagnosed with inoperable and locally advanced head and neck cancers (LAHNC) is still a challenge for clinicians. Prediction of incomplete response (IR) of primary tumour would be of value to the treatment optimization for patients with LAHNC. Aim of this study was to develop and evaluate models based on clinical and radiomics features for prediction of IR in patients diagnosed with LAHNC and treated with definitive chemoradiation or radiotherapy. Clinical and imaging data of 290 patients were included into this retrospective study. Clinical model was built based on tumour and patient related features. Radiomics features were extracted based on imaging data, consisting of contrast- and non-contrast-enhanced pre-treatment CT images, obtained in process of diagnosis and radiotherapy planning. Performance of clinical and combined models were evaluated with area under the ROC curve (AUROC). Classification performance was evaluated using 5-fold cross validation. Model based on selected clinical features including ECOG performance, tumour stage T3/4, primary site: oral cavity and tumour volume were significantly predictive for IR, with AUROC of 0.78. Combining clinical and radiomics features did not improve model’s performance, achieving AUROC 0.77 and 0.68 for non-contrast enhanced and contrast-enhanced images respectively. The model based on clinical features showed good performance in IR prediction. Combined model performance suggests that real-world imaging data might not yet be ready for use in predictive models

The kinetics of γ-H2AX during radiotherapy of head and neck cancer potentially allow for prediction of severe mucositis

The aim of the study was to evaluate the changes in γ-H2AX expression in peripheral blood lymphocytes (PBL) according to severity of radiation-induced mucositis

Effect of Low-Temperature Oxygen Plasma Treatment of Titanium Alloy Surface on Tannic Acid Coating Deposition

In this study, the effect of low-temperature oxygen plasma treatment with various powers of a titanium alloy surface on the structural and morphological properties of a substrate and the deposition of a tannic acid coating was investigated. The surface characteristics of the titanium alloy were evaluated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Following this, the tannic acid coatings were deposited on the titanium alloy substrates and the structural and morphological properties of the tannic acid coatings deposited were subject to characterization by XPS, SEM, and spectroscopic ellipsometry (SE) measurements. The results show that the low-temperature oxygen plasma treatment of titanium alloys leads to the formation of titanium dioxides that contain –OH groups on the surface being accompanied by a reduction in carbon, which imparts hydrophilicity to the titanium substrate, and the effect increases with the applied plasma power. The performed titanium alloy substrate modification translates into the quality of the deposited tannic acid coating standing out by higher uniformity of the coating, lower number of defects indicating delamination or incomplete bonding of the coating with the substrate, lower number of cracks, thinner cracks, and higher thickness of the tannic acid coatings compared to the non-treated titanium alloy substrate. A similar effect is observed as the applied plasma power increases