Introducing radiomics model to predict active plaque in multiple sclerosis patients using magnetic resonance images.

Multiple Sclerosis (MS) is the most common non-traumatic disabling disease in young people. The prediction active plaque has the potential to offer new biomarkers for assessing the activity of MS disease. Consequently it supports patient management in the clinical setting and trials. This study aims to investigate the predictive capability of radiomics features for identifying active plaques in these patients using T2 FLAIR (Fluid Attenuated Inversion Recovery) images. For this purpose, a dataset images from 82 patients with 122 lesions was analyzed. Feature selection was performed using the Least Absolute Shrinkage and Selection Operator (LASSO) method. Six different classifier algorithms, namely K-Nearest Neighbors (KNN), Logistic Regression (LR), Decision Tree (DT), Support Vector Machine (SVM), Naive Bayes (NB), and Random Forest (RF), were employed for modeling. The models were evaluated using 5-fold cross-validation, and performance metrics including sensitivity, specificity, accuracy, area under the curve (AUC), and mean squared error were computed. A total of 107 radiomics features were extracted for each lesion, and 11 robust features were identified through the feature selection process. These features consisted of four shape features (elongation, flatness, major axis length, mesh volume), one first-order feature (energy), one Gray Level Co-occurrence Matrix feature (correlation), two Gray Level Run Length Matrix features (gray level non-uniformity, gray level non-uniformity normalized), and three Gray Level Size Zone Matrix features (low gray level zone emphasis, size zone non-uniformity, small area low gray level emphasis). The NB classifier demonstrated the best performance with an AUC, sensitivity, and specificity of 0.85, 0.82, and 0.66, respectively. The findings indicate the potential of radiomics features in predicting active MS plaques in T2 FLAIR images.

Investigating dose homogeneity in radiotherapy of oral cancers in the presence of a dental implant system: an in vitro phantom study.

BACKGROUND: Materials with high atomic numbers are part of the composition of dental implant systems. In radiotherapy of oral cavity cancers, an implant can cause dose perturbations that affect target definition, dose calculation, and dose distribution. In consequence, this may result in poor tumor control and higher complications. In this study, we evaluated dose homogeneity when a dental implant replaced a normal tooth. We also aimed to evaluate the concordance of dose calculations with dose measurements. MATERIALS AND METHODS: In this study, 2 sets of planning CT scans of a phantom with a normal tooth and the same phantom with the tooth replaced by a Z1 TBR dental implant system were used. The implant system was composed of a porcelain-fused-to-metal crown and titanium with a zirconium collar. Three radiotherapy plans were designed when the density of the implant material was corrected to match their elements, or when all were set to the density of water, or when using the default density conversion. Gafchromic EBT-3 films at the level of isocenter and crowns were used for measurements. RESULTS: At the level of crowns, upstream and downstream dose calculations were reduced when metal kernels were applied (M-plan). Moreover, relatively measured dose distribution patterns were most similar to M-plan. At this level, relative to the non-implanted phantom, mean doses values were higher with the implant (215.93 vs. 192.25), also, new high-dose areas appeared around a low-dose streak forward to the implant (119% vs. 95%). CONCLUSIONS: Implants can cause a high dose to the oral cavity in radiotherapy because of extra scattered radiation. Knowledge of the implant dimensions and defining their material enhances the accuracy of calculations.

A comparison of symmetry and flatness measurements in small electron fields by different dosimeters in electron beam radiotherapy.

BACKGROUND: Symmetry and flatness are two quantities which should be evaluated in the commissioning and quality control of an electron beam in electron beam radiotherapy. The aim of this study is to compare symmetry and flatness obtained using three different dosimeters for various small and large fields in electron beam radiotherapy with linac. MATERIALS AND METHODS: Beam profile measurements were performed in a PTW water phantom for 10, 15 and 18 MeV electron beams of an Elekta Precise linac for small and large beams (1.5 × 1.5 cm2 to 20 × 20 cm2 field sizes). A Diode E detector and Semiflex-3D and Advanced Markus ionization chambers were used for dosimetry. RESULTS: Based on the obtained results, there are minor differences between the responses from different dosimeters (Diode E detector and Semiflex-3D and Advanced Markus ionization chambers) in measurement of symmetry and flatness for the electron beams. The symmetry and flatness values increase with increasing field size and electron beam energy for small and large field sizes, while the increases are minor in some cases. CONCLUSIONS: The results indicate that the differences between the symmetry and flatness values obtained from the three dosimeter types are not practically important.

Novel treatment setup for urethral carcinoma radiotherapy: A complete response case report.

A homemade personalized penis holder can provide the reproducibility of the penis during urethra carcinoma (UC) radiotherapy.

Assessment of skin dose in breast cancer radiotherapy: on-phantom measurement and Monte Carlo simulation.

AIM: The main purpose of the present study is assessment of skin dose in breast cancer radiotherapy. BACKGROUND: Accurate assessment of skin dose in radiotherapy can provide useful information for clinical considerations. MATERIALS AND METHODS: A RANDO phantom was irradiated using a 6 MV Siemens Primus linac with medial and tangential radiotherapy fields for simulating breast cancer treatment. Dosimetry was also performed on various positions across the fields using an EBT3 radiochromic film. Similar conditions of measurement on the RANDO phantom including field size, irradiation angle, number of fields, etc. were subsequently simulated via the Monte Carlo N-Particle Transport code (MCNP). Ultimately, dose values for corresponding points from both methods were compared. RESULTS: Considering dosimetry using radiochromic films on the RANDO phantom, there were points having underdose and overdose based on the prescribed dose and skin tolerance levels. In this respect, 81.25% and 18.75% of the points had underdose and overdose, respectively. In some cases, several differences were observed between the measurement and the MCNP simulation results associated with skin dose. CONCLUSION: Based on the results of the points which had underdose, it was suggested that a bolus should be used for the given points. With regard to overdose points, it was advocated to consider skin tolerance dose in treatment planning. Differences between the measurement and the MCNP simulation results might be due to voxel size of tally cells in simulations, effect of beam's angle of incidence, validation time of linac's head, lack of electronic equilibrium in the build-up region, as well as MCNP tally type.

Measurement of fast neutron contamination caused by the presence of wedge and block using CR-39 detector.

OBJECTIVE: Undesired neutron contamination imposed to patients during treatment is among the main factors increasing the risk of secondary cancer in radiotherapy. This additional undesirable dose is due to neutron contamination production in high-energy accelerators. In this study, neutron contamination is investigated in the presence of wedge and block in 15 MV photon fields of Siemens Primus linear accelerator. MATERIALS AND METHODS: Neutron production by 30°, 45°, and 60° wedges and cerrobend block was investigated. Measurements were conducted in a 10 cm × 10 cm field at the source to -surface distance of 100 cm at 0.5, 2, 3, and 4 cm depths of a 30 cm × 30 cm × 30 cm Perspex phantom using the CR-39 passive film detectors. Chemical etching was performed using sodium hydroxide solution with 6.25 M concentration as the etchant at 85°C for 3 h. RESULTS: The neutron dosimetry results reveal that the presence of wedge and block increases the neutron contamination. However, the 45° wedge is most effective in producing neutron contamination. The results also show that the fast neutron contamination is lower in the steeper depths. CONCLUSION: The presence of a wedge in a therapeutic high-energy photon field is a source of neutron contamination and may be of concern regarding clinical aspects. The results of this study show that superficial tissues such as skin will incur higher fast neutron contamination than the deep tissues.

Determination of dosimetric parameters for shielded 153Gd source in prostate cancer brachytherapy.

BACKGROUND: Interstitial rotating shield brachytherapy (I-RSBT) is a recently developed method for treatment of prostate cancer. In the present study TG-43 dosimetric parameters of a 153Gd source were obtained for use in I-RSBT. MATERIALS AND METHODS: A 153Gd source located inside a needle including a Pt shield and an aluminum window was simulated using MCNPX Monte Carlo code. Dosimetric parameters of this source model, including air kerma strength, dose rate constant, radial dose function and 2D anisotropy function, with and without the shields were calculated according to the TG-43 report. RESULTS: The air kerma strength was found to be 6.71 U for the non-shielded source with 1 GBq activity. This value was found to be 0.04 U and 6.19 U for the Pt shield and Al window cases, respectively. Dose rate constant for the non-shielded source was found to be 1.20 cGy/(hU). However, for a shielded source with Pt and aluminum window, dose rate constants were found to be 0.07 cGy/(hU) and 0.96 cGy/(hU), on the shielded and window sides, respectively. The values of radial dose function and anisotropy function were tabulated for these sources. Additionally, isodose curves were drawn for sources with and without shield, in order to evaluate the effect of shield on dose distribution. CONCLUSIONS: Existence of the Pt shield may greatly reduce the dose to organs at risk and normal tissues which are located toward the shielded side. The calculated air kerma strength, dose rate constant, radial dose function and 2D anisotropy function data for the 153Gd source for the non-shielded and the shielded sources can be used in the treatment planning system (TPS).