Iterative least-squares (ILS) has been used in CT image reconstruction for many years and has also been successfully applied to fluence optimization in intensity-modulated radiation therapy. However, most optimization schemes use aperture optimization, where it is not so clear how to apply ILS. This study therefore proposes a method of using ILS for aperture optimization in volumetric modulated arc therapy (VMAT) and evaluates the performance by comparing with segment weight optimization. The AutoBeam inverse treatment planning system was used to optimize fluence, sequence the fluence into deliverable apertures and then optimize these apertures and their accompanying segment weights. ILS was used for both the fluence and aperture optimization stages. In the aperture optimization, if the dose beyond a multileaf collimator (MLC) leaf was too high, that leaf was closed up slightly, and if the dose underneath a leaf was too low, that leaf was opened up slightly. To evaluate this heuristic, five prostate and pelvic nodes patients were retrospectively planned. To evaluate the performance of the aperture optimization, these plans were compared to those produced using segment weight optimization alone after sequencing. Sinograms showing effective monitor units delivered by MLC leaf pairs over the course of beam delivery were used to elucidate the comparison. It was found that aperture optimization with ILS produced treatment plans which were conformal, with dose deposition easily controlled by a few clinical objectives. Sinogram analysis showed that aperture optimization with ILS produced less leaf motion and less monitor unit variation between control points than when using segment weight optimization only. By converting fluence corrections to aperture shape corrections, ILS can be used as a powerful method for VMAT aperture optimization. Sinogram analysis provides a clear insight into the behaviour of the heuristic.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1088/0031-9155/58/5/1235 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Revolutionizing Free-Space Optics: A Survey of Enabling Technologies, Challenges, Trends, and Prospects of Beyond 5G Free-Space Optical (FSO) Communication Systems.
Sensors (Basel)
December 2024
Instituto de Telecomunicações, University of Aveiro, 3810-193 Aveiro, Portugal.
As the demand for high-speed, low-latency communication continues to grow, free-space optical (FSO) communication has gained prominence as a promising solution for supporting the next generation of wireless networks, especially in the context of the 5G and beyond era. It offers high-speed, low-latency data transmission over long distances without the need for a physical infrastructure. However, the deployment of FSO systems faces significant challenges, such as atmospheric turbulence, weather-induced signal degradation, and alignment issues, all of which can impair performance.
View Article and Find Full Text PDFA Combined CNN-LSTM Network for Ship Classification on SAR Images.
Sensors (Basel)
December 2024
ENSTA Bretagne, Lab-STICC, UMR CNRS 6285, 29806 Brest, France.
Satellite SAR (synthetic aperture radar) imagery offers global coverage and all-weather recording capabilities, making it valuable for applications like remote sensing and maritime surveillance. However, its use in machine learning-based automatic target classification faces challenges, including the limited availability of SAR target training samples and the inherent constraints of SAR images, which provide less detailed features compared to natural images. These issues hinder the effective training of convolutional neural networks (CNNs) and complicate the transfer learning process due to the distinct imaging mechanisms of SAR and natural images.
View Article and Find Full Text PDFPortable astronomical observation system based on large-aperture concentric-ring metalens.
Light Sci Appl
January 2025
Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtzplatz 1, Eggenstein-Leopoldshafen, 76344, Germany.
The core advantage of metalenses over traditional bulky lenses lies in their thin volume and lightweight. Nevertheless, as the application scenarios of metalenses extend to the macro-scale optical imaging field, a contradiction arises between the increasing demand for large-aperture metalenses and the synchronous rise in design and processing costs. In response to the application requirements of metalens with diameter reaching the order of 10λ or even 10λ, this paper proposes a novel design method for fixed-height concentric-ring metalenses, wherein, under the constraints of the processing technology, a subwavelength 2D building unit library is constructed based on different topological structures, and the overall cross-section of the metalens is assembled.
View Article and Find Full Text PDFMeasurement distance effects on [Formula: see text]-symmetric Taylor patterns with optimal transition integer [Formula: see text] and with reduced inner sidelobes.
Sci Rep
December 2024
Radiating Systems Group, Department of Applied Physics, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain.
The following paper presents the findings of a study conducted on the distances at which the field generated by a ϕ-symmetric circular Taylor aperture distribution can be classified as far-field, and also the efficiency across various study parameters. The [Formula: see text] transition integers that produce a monotonic distribution, which have been traditionally used and analyzed, are compared with those that yield a peaked distribution, and offer greater efficiency. Additionally, modified circular Taylor [Formula: see text] distributions featuring synthesized patterns with one or two depressed inner sidelobes, which have not been previously explored, are also examined.
View Article and Find Full Text PDFTime-series InSAR measurement using ICOPS and estimation of along-track surface deformation using MAI during the 2021 eruption of Fagradalsfjall Volcano, Iceland.
Sci Rep
December 2024
Department of Science Education, Kangwon National University, 1 Gangwondaehak-gil, Chuncheon-si, 24341, Gangwon-do, Republic of Korea.
The eruption in Fagradalsfjall Volcano, located in Reykjanes Peninsula, Iceland, from several centuries' dormant states, occurred for the first time on March 19, 2021. Observations of Fagradalsfjall Volcano were conducted in 2021, and the eruption period lasted for six months until 18 September 2021. Six days pair of interferograms were generated from ninety synthetic aperture radar (SAR) data.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!