MIRAB: An Image-Guided Multichannel Robot for Prostate Brachytherapy

Purpose: To date, twelve robotic systems have been developed worldwide for brachytherapy, especially for seed implantation. However, the only system that has provision for simultaneous insertion of multiple needles is the MIRAB system. This article reports the feasibility and efficacy of the MIRAB robot as ultrasound image-guided autonomous delivery of radioactive seeds for treating prostate cancers. American Society for Therapeutic Radiation Oncology (ASTRO) 52nd Annual Meeting October 31 - November 4, San Diego, C

Dosimetric Evaluation of Tumor Tracking in 4D Radiotherapy

Purpose: In some patients the tumors in lung, pancreas, liver, breast, and other organs move significantly during cardiac and breathing cycles. In this study we have investigated the dosimetric benefits of real-time tumor tracking for patients who were diagnosed with lung cancer. American Society for Therapeutic Radiation Oncology (ASTRO) 52nd Annual Meeting October 31 - November 4, San Diego, C

Radioactive seed immobilization techniques for interstitial brachytherapy

Purpose In prostate brachytherapy, seeds can detach from their deposited sites and move locally in the pelvis or migrate to distant sites including the pulmonary and cardiac regions. Undesirable consequences of seed migration include inadequate dose coverage of the prostate and tissue irradiation effects at the site of migration. Thus, it is clinically important to develop seed immobilization techniques. Methods We first analyze the possible causes for seed movement, and propose three potential techniques for seed immobilization: (1) surgical glue, (2) laser coagulation and (3) diathermy coagulation. The feasibility of each method is explored. Experiments were carried out using fresh bovine livers to investigate the efficacy of seed immobilization using surgical glue. Results Results have shown that the surgical glue can effectively immobilize the seeds. Evaluation of the radiation dose distribution revealed that the non-immobilized seed movement would change the planned isodose distribution considerably; while by using surgical glue method to immobilize the seeds, the changes were negligible. Conclusions Prostate brachytherapy seed immobilization is necessary and three alternative mechanisms are promising for addressing this issue. Experiments for exploring the efficacy of the other two proposed methods are ongoing. Devices compatible with the brachytherapy procedure will be designed in futur

Dosimetric Advantages of Active Tracking and Dynamic Dose Delivery

Purpose: To investigate dosimetric effect of tumor tracking. To evaluate changes of treatment volumes when tracking is applied. American Association of Physicists in Medicine (AAPM) 52nd Annual Meeting July 18-22, Philadelphia, PA

Performance Study of Novel Accelerationenhanced Filters in the Prediction of Normal and Irregular Respiration Motion

Purpose: To study the performance of the novel acceleration-enhanced (AE) filters in the prediction of normal and irregular respiration motion and compare them with those of traditional adaptive normalized least mean squares (nLMS) and adaptive neuron network (ANN) filters. This facilitates the real-time tumor tracking and dynamic delivery of radiation dose to the tumor. American Association of Physicists in Medicine (AAPM) 52nd Annual Meeting July 18-22, Philadelphia, P

A Procedure for Standardizing MLC Quality Assurance for Elekta Linac

Purpose: As specified in TG142, MLC position accuracy needs to be tested on weekly/monthly basis, with 1mm tolerance. This study focuses on developing techniques, hardware and software tools for implementation of MLC QA tests for Elekta Linacs. American Association of Physicists in Medicine (AAPM) 52nd Annual Meeting July 18-22, Philadelphia, P

Secretory structures in plants: lessons from the Plumbaginaceae on their origin, evolution and roles in stress tolerance

Special IssueThe Plumbaginaceae (non-core Caryophyllales) is a family well known for species adapted to a wide range of arid and saline habitats. Of its salt-tolerant species, at least 45 are in the genus Limonium; two in each of Aegialitis, Limoniastrum and Myriolimon, and one each in Psylliostachys, Armeria, Ceratostigma, Goniolimon and Plumbago. All the halophytic members of the family have salt glands, which are also common in the closely related Tamaricaceae and Frankeniaceae. The halophytic species of the three families can secrete a range of ions (Na+, K+, Ca2+, Mg2+, Cl−, HCO3 −, SO4 2-) and other elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn). Salt glands are, however, absent in salt-tolerant members of the sister family Polygonaceae. We describe the structure of the salt glands in the three families and consider whether glands might have arisen as a means to avoid the toxicity of Na+ and/or Cl− or to regulate Ca2+ concentrations within the leaves. We conclude that the establishment of lineages with salt glands took place after the split between the Polygonaceae and its sister group the Plumbaginaceaeinfo:eu-repo/semantics/publishedVersio

SU-E-T-131: Influence of Scanning Speed on Measurements of Field Flatness and Symmetry of Photon Beams

The purpose of this study was to investigate influence of different scanning speeds on measurements of photon beam flatness and symmetry. Commissioning and quality assurance of linear accelerators require extensive beam measurements. To increase efficacy, we evaluated flatness, symmetry and penumbra of 6MV photon beam using the Varian-TrueBeamTM system. Scanning speeds were 0.3, 0.5, 0.75, 1, 1.5, and 2.5cm/s. Measurements were performed in water phantom (BluePhantom , IBA-Dosimetry) at depths of maximum dose, 5,10, and 20cm, for 10×10 cm field size. For each scanning speed and depth, measurements were repeated five times to give results sufficient statistical significance, in both crossline and inline directions. Beam flatness was calculated using variation over mean (80%), whereas symmetry was calculated using point difference quotient (IEC) algorithm. After filed scanning chamber (Wellhofer) was fully stopped, system was paused for stabilization time of 15s to avoid buildup of ripples. It was noticed for all measurements that minimum and maximum flatness and symmetry were recorded when scanning speeds were 0.3cm and 2.5cm, respectively. For depth of maximum dose, maximum flatness and symmetry were 0.82% and 100.58% (crossplane), and 0.94% and 100.96% (inplane). The average was 0.76% and 100.38% (SD 0.04 and 0.12) for crossplane; 0.89% and 100.87% (SD 0.04 and 0.06) for inplane measurements. As the scanning depth increased, flatness and symmetry increased, but SD for all measurements was within the same range (0.04-0.07 and 0.04-0.12). The maximum absolute difference for flatness and symmetry for maximum and minimum speed were 0.16% and 0.34%.However, for scanning speeds from 0.5-1cm/s, results were almost identical with maximum SD 0.03 for both flatness and symmetry. Use of different scanning speeds did not influence penumbra; SD was 0 for all measurements. This study reveals small influence of scanning speed within predefined range. Consequently, difference in measurements does not have clinical significance

Consistency and Lyapunov Stability of Linear Singular Time Delay Systems: a Geometric Approach

When we consider the control design of practical systems (chemical engineering systems, lossless transmission lines, large-scale electric network control, aircraft attitude control, flexible arm control of robots, etc.), time-delay often appears in many situations. Singular time delayed systems are the dynamic systems described by a mixture of algebraic and differential equations with retarded argument. This paper investigates the geometric description of initial conditions that generate smooth solutions to such problems and the construction of the Lyapunov stability theory to bound the rates of decay of such solutions. The new delay dependent conditions for asymptotic stability for the class of systems under consideration were derived. Moreover, the result is expressed in terms of only systems matrices that naturally occur in the model, therefore avoiding the need to introduce algebraic transformations into the statement of the main theorem.На практике при рассмотрении различных систем с управлением (химические инженерные системы, линии передачи без потерь, крупномасштабное управление электрической сетью, управление ориентацией самолета, гибкое управление руками роботов и т.д.) часто во многих ситуациях мы можем наблюдать наличие временного запаздывания. Вырожденные системы с запаздыванием являются динамическими системами, описываемыми взаимосвязанными алгебраическими и дифференциальными уравнениями. В данной работе исследуются геометрические представления начальных данных, которые обеспечивают гладкость решений рассматриваемых задач. Также изучается построение теории устойчивости Ляпунова для ограничения скорости убывания решений. Для одного класса изучаемых систем получены новые условия асимптотической устойчивости, зависящие от запаздывания. Более того, результат выражается в терминах матриц, которые задают систему и естественным образом возникают при моделировании, однако при этом отсутствует необходимость введения алгебраических преобразований в утверждение основной теоремы