Tailoring performance, damping, and surface properties of magnetorheological elastomers via particle-grafting technology

A novel concept based on advanced particle-grafting technology to tailor performance, damping, and surface properties of the magnetorheological elastomers (MREs) is introduced. In this work, the carbonyl iron (CI) particles grafted with poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) of two different molecular weights were prepared via surface-initiated atom transfer radical polymerization and the relations between the PHEMATMS chain lengths and the MREs properties were investigated. The results show that the magnetorheological performance and damping capability were remarkably influenced by different interaction between polydimethylsiloxane chains as a matrix and PHEMATMS grafts due to their different length. The MRE containing CI grafted with PHEMATMS of higher molecular weight exhibited a greater plasticizing effect and hence both a higher relative magnetorheological effect and enhanced damping capability were observed. Besides bulk MRE properties, the PHEMATMS modifications influenced also field-induced surface activity of the MRE sheets, which manifested as notable changes in surface roughness. © 2018 by the authors.Czech Science Foundation [17-24730S]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2017/004]; Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409

Monitoring of CRT-D devices during radiation therapy in vitro

Background: Using of active cardiac medical devices increases steadily. In Europe, there were 183 implants of ICD and 944 implants of PM, 119 of biventricular ICD and 41 of biventricular PM, all per million inhabitants in 2014. Healthcare environments, including radiotherapy treatment rooms, are considered challenging for these implantable devices. Exposure to radiation may cause the device to experience premature elective replacement indicator, decreased pacing amplitude or pacing inhibition, inappropriate shocks or inhibition of tachyarrhythmia therapy and loss of device function. These impacts may be temporary or permanent. The aim of this study was to evaluate the influence of linear accelerator ionizing radiation dose of 10 Gy on the activity of the biventricular cardioverter-defibrillator in different position in radiation beam. Methods: Two identical wireless communication devices with all three leads were used for the measurement. Both systems were soused into solution saline and exposed in different position in the beam of linear accelerator per 10 Gy fractions. In comparison of usually used maximum recommended dose of 2 Gy, the radiation doses used in test were five times higher. Using the simultaneous monitoring wireless communication between device and its programmer allowed watching of the devices activities, noise occurrence or drop of biventricular pacing on the programmer screen, observed by local television loop camera. Results: At any device position in radiation beam, there were no influences of the device activity at dose of 10 Gy neither a significant increase of a solution saline temperature in any of the measured positions of CRT-D systems in linear accelerator. Conclusions: The results of the study indicated, that the recommendation dose for treating the patients with implantable devices are too conservative and the risk of device failure is not so high. The systems can easily withstand the dose fractions of tens Gy, which would allow current single-dose-procedure treatment in radiation therapy. Even though the process of the random alteration of device memory and electrical components by scatter particles not allowed to specify a safe dose during ionizing radiation, this study showed that the safe limit are above the today used dose fractions.Web of Science15art. no. 2

Real-time measurement of ICD lead motion during stereotactic body radiotherapy of ventricular tachycardia

Background: Here we aimed to evaluate the respiratory and cardiac-induced motion of a ICD lead used as surrogate in the heart during stereotactic body radiotherapy (SBRT) of ventricular tachycardia (VT). Data provides insight regarding motion and motion variations during treatment. Materials and methods: We analyzed the log files of surrogate motion during SBRT of ventricular tachycardia performed in 20 patients. Evaluated parameters included the ICD lead motion amplitudes; intrafraction amplitude variability; correlation error between the ICD lead and external markers; and margin expansion in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions to cover 90% or 95% of all amplitudes. Results: In the SI, LL, and AP directions, respectively, the mean motion amplitudes were 5.0 +/- 2.6, 3.4. +/- 1.9, and 3.1 +/- 1.6 mm. The mean intrafraction amplitude variability was 2.6 +/- 0.9, 1.9 +/- 1.3, and 1.6 +/- 0.8 mm in the SI, LL, and AP directions, respectively. The margins required to cover 95% of ICD lead motion amplitudes were 9.5, 6.7, and 5.5 mm in the SI, LL, and AP directions, respectively. The mean correlation error was 2.2 +/- 0.9 mm. Conclusions: Data from online tracking indicated motion irregularities and correlation errors, necessitating an increased CTV-PTV margin of 3 mm. In 35% of cases, the motion variability exceeded 3 mm in one or more directions. We recommend verifying the correlation between CTV and surrogate individually for every patient, especially for targets with posterobasal localization where we observed the highest difference between the lead and CTV motion.Web of Science26113712

The use of a battery of examination methods for detection of cervical metastases in squamous cell carcinoma of the oral cavity

Introduction. In patients with squamous cell carcinoma of the orofacial area, the presence of cervical metastases represents a single most significant prognostic factor. This fact underlines the importance of thorough examination of the cervical lymph nodes for potential tumor involvement. To verify this, the most common investigative methods are physical examination (PE), sonography (US) and computed tomography (CT), which have also been used to assess the stage of the disease in the patients in our research. Objective. To evaluate the performance of individual methods (physical examination, sonography, computed tomography) and combinations. Method. Patients with squamous cell carcinoma of the oral cavity, who had undergone physical, US and CT examinations at our department followed by radical neck dissection were included in this retrospective study. A total of 57 patients were included. Results. The sensitivity of PE, US and CT were 38%, 69% and 61%, respectively, however CT+US combination yielded 83% sensitivity and combination of all these methods 86% sensitivity. The number of false positives was however relatively high with specificity of the 3-way combination at 65%. Conclusion. A combination of our three widely available inexpensive methods detected 86% of metastases in cervical nodes. The large number of false positives however indicates that the method should rather be used for screening in selecting patients who need additional and more expensive imaging than for diagnosing cervical metastases. Also, as 14% of cervical metastases pass undetected using our method, we would recommend an additional examination at least by US+PE several weeks to a few months after the initial examination.Web of Science165222822

STereotactic Arrhythmia Radioablation (STAR): the Standardized Treatment and Outcome Platform for Stereotactic Therapy Of Re-entrant tachycardia by a Multidisciplinary consortium (STOPSTORM.eu) and review of current patterns of STAR practice in Europe

The EU Horizon 2020 Framework-funded Standardized Treatment and Outcome Platform for Stereotactic Therapy Of Re-entrant tachycardia by a Multidisciplinary (STOPSTORM) consortium has been established as a large research network for investigating STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia (VT). The aim is to provide a pooled treatment database to evaluate patterns of practice and outcomes of STAR and finally to harmonize STAR within Europe. The consortium comprises 31 clinical and research institutions. The project is divided into nine work packages (WPs): (i) observational cohort; (ii) standardization and harmonization of target delineation; (iii) harmonized prospective cohort; (iv) quality assurance (QA); (v) analysis and evaluation; (vi, ix) ethics and regulations; and (vii, viii) project coordination and dissemination. To provide a review of current clinical STAR practice in Europe, a comprehensive questionnaire was performed at project start. The STOPSTORM Institutions' experience in VT catheter ablation (83% ≥ 20 ann.) and stereotactic body radiotherapy (59% > 200 ann.) was adequate, and 84 STAR treatments were performed until project launch, while 8/22 centres already recruited VT patients in national clinical trials. The majority currently base their target definition on mapping during VT (96%) and/or pace mapping (75%), reduced voltage areas (63%), or late ventricular potentials (75%) during sinus rhythm. The majority currently apply a single-fraction dose of 25 Gy while planning techniques and dose prescription methods vary greatly. The current clinical STAR practice in the STOPSTORM consortium highlights potential areas of optimization and harmonization for substrate mapping, target delineation, motion management, dosimetry, and QA, which will be addressed in the various WPs

Refining Critical Structure Contouring in STereotactic Arrhythmia Radioablation (STAR): Benchmark Results and Consensus Guidelines from the STOPSTORM.eu Consortium.

BACKGROUND AND PURPOSE In patients with recurrent ventricular tachycardia (VT), STereotactic Arrhythmia Radioablation (STAR) shows promising results. The STOPSTORM consortium was established to investigate and harmonise STAR treatment in Europe. The primary goals of this benchmark study were to standardise contouring of organs at risk (OAR) for STAR, including detailed substructures of the heart, and accredit each participating centre. MATERIALS AND METHODS Centres within the STOPSTORM consortium were asked to delineate 31 OAR in three STAR cases. Delineation was reviewed by the consortium expert panel and after a dedicated workshop feedback and accreditation was provided to all participants. Further quantitative analysis was performed by calculating DICE similarity coefficients (DSC), median distance to agreement (MDA), and 95th percentile distance to agreement (HD95). RESULTS Twenty centres participated in this study. Based on DSC, MDA and HD95, the delineations of well-known OAR in radiotherapy were similar, such as lungs (median DSC=0.96, median MDA=0.1mm and median HD95=1.1mm) and aorta (median DSC=0.90, median MDA=0.1mm and median HD95=1.5mm). Some centres did not include the gastro-oesophageal junction, leading to differences in stomach and oesophagus delineations. For cardiac substructures, such as chambers (median DSC=0.83, median MDA=0.2mm and median HD95=0.5mm), valves (median DSC=0.16, median MDA=4.6mm and median HD95=16.0mm), coronary arteries (median DSC=0.4, median MDA=0.7mm and median HD95=8.3mm) and the sinoatrial and atrioventricular nodes (median DSC=0.29, median MDA=4.4mm and median HD95=11.4mm), deviations between centres occurred more frequently. After the dedicated workshop all centres were accredited and contouring consensus guidelines for STAR were established. CONCLUSION This STOPSTORM multi-centre critical structure contouring benchmark study showed high agreement for standard radiotherapy OAR. However, for cardiac substructures larger disagreement in contouring occurred, which may have significant impact on STAR treatment planning and dosimetry evaluation. To standardize OAR contouring, consensus guidelines for critical structure contouring in STAR were established

Analysis of lung tumor motion in a large sample: patterns and factors influencing precise delineation of internal target volume

Purpose/Objective To evaluate lung tumor motion during respiration and to describe factors affecting the range and variability of motion in patients treated with stereotactic ablative radiation therapy. Methods and Materials Log file analysis from online respiratory tumor tracking was performed in 145 patients. Geometric tumor location in the lungs, tumor volume and origin (primary or metastatic), sex, and tumor motion amplitudes in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions were recorded. Tumor motion variability during treatment was described using intrafraction/interfraction amplitude variability and tumor motion baseline changes. Tumor movement dependent on the tumor volume, position and origin, and sex were evaluated using statistical regression and correlation analysis. Results After analysis of >500 hours of data, the highest rates of motion amplitudes, intrafraction/interfraction variation, and tumor baseline changes were in the SI direction (6.0 ± 2.2 mm, 2.2 ± 1.8 mm, 1.1 ± 0.9 mm, and −0.1 ± 2.6 mm). The mean motion amplitudes in the lower/upper geometric halves of the lungs were significantly different (P15 mm were observed only in the lower geometric quarter of the lungs. Higher tumor motion amplitudes generated higher intrafraction variations (R=.86, P3 mm indicated tumors contacting mediastinal structures or parietal pleura. On univariate analysis, neither sex nor tumor origin (primary vs metastatic) was an independent predictive factor of different movement patterns. Metastatic lesions in women, but not men, showed significantly higher mean amplitudes (P=.03) and variability (primary, 2.7 mm; metastatic, 4.9 mm; P=.002) than primary tumors. Conclusion Online tracking showed significant irregularities in lung tumor movement during respiration. Motion amplitude was significantly lower in upper lobe tumors; higher interfraction amplitude variability indicated tumors in contact with mediastinal structures, although adhesion to parietal pleura did not necessarily reduce tumor motion amplitudes. The most variable lung tumors were metastatic lesions in women.Web of Science96475875