| 1. |
- Abdollahi, Sara, et al.
(författare)
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A dose planning study for cardiac and lung dose sparing techniques in left breast cancer radiotherapy : Can free breathing helical tomotherapy be considered as an alternative for deep inspiration breath hold?
- 2023
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Ingår i: Technical Innovations and Patient Support in Radiation Oncology. - : Elsevier BV. - 2405-6324. ; 25
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the possibility to be able to offer left sided breast cancer patients, not suitable for DIBH, an organ at risk saving treatment. Materials and Methods: Twenty patients receiving radiotherapy for left breast cancer in DIBH were enrolled in the study. Planning CT scans were acquired in the same supine treatment position in FB and DIBH. 3DCRT_DIBH plans were designed and optimized using two parallel opposed tangent beams (with some additional segments) for the breast and chest wall and anterior-posterior fields for regional lymph nodes irradiation. Additionally, FB helical tomotherapy plans were optimized to minimize heart and lung dose. All forty plans were optimized with at least 95% of the total CTV covered by the 95% of prescribed dose of 50 Gy in 25 fractions. Results: HT_FB plans showed significantly better dose homogeneity and conformity compared to the 3DCRT_DIBH specially for regional nodal irradiation. The heart mean dose was almost comparable in 3DCRT_DIBH and HT_FB while the volume (%) of the heart receiving 25 Gy had a statistically significant reduction from 7.90 ± 3.33 in 3DCRT_DIBH to 0.88 ± 0.66 in HT_FB. HT_FB was also more effective in left descending artery (LAD) mean dose reduction about 100% from 30.83 ± 9.2 Gy to 9.7 ± 3.1. The ipsilateral lung volume receiving 20 Gy has a further reduction of 43 % in HT_FB compared with 3DCRT_DIBH. For low dose comparison, 3DCRT_DIBH was superior for contralateral organ sparing compared to the HT_FB due to the limited angle for dose delivery. Conclusion: For patients who cannot be a candidate for DIBH for any reason, HT in free breathing may be a good alternative and provides heart and ipsilateral lung dose sparing, however with the cost of increased dose to contralateral breast and lung.
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| 2. |
- Abdollahi, Sara, et al.
(författare)
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Surface guided 3DCRT in deep-inspiration breath-hold for left sided breast cancer radiotherapy : implementation and first clinical experience in Iran
- 2022
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Ingår i: Reports of Practical Oncology and Radiotherapy. - 1507-1367. ; 27:5, s. 881-896
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Tidskriftsartikel (refereegranskat)abstract
- Background: The aim of the study is to evaluate the overall accuracy of the surface-guided radiotherapy (SGRT) workflow through a comprehensive commissioning and quality assurance procedures and assess the potential benefits of deep-inspiration breath-hold (DIBH) radiotherapy as a cardiac and lung dose reduction approach for left-sided breast cancer irradiation. Materials and methods: Accuracy and reproducibility of the optical surface scanner used for DIBH treatment were evaluated using different phantoms. Patient positioning accuracy and reproducibility of DIBH treatment were evaluated. Twenty patients were studied for treatment plan quality in target dose coverage and healthy organ sparing for the two different treatment techniques. Results: Reproducibility tests for the surface scanner showed good stability within 1 mm in all directions. The maximum position variation between applied shifts on the couch and the scanner measured offsets is 1 mm in all directions. The clinical study of 200 fractions showed good agreement between the surface scanner and portal imaging with the isocenter position deviation of less than 3 mm in each lateral, longitudinal, and vertical direction. The standard deviation of the DIBH level showed a value of < 2 mm during all evaluated DIBHs. Compared to the free breathing (FB) technique, DIBH showed significant reduction of 48% for heart mean dose, 43% for heart V25, and 20% for ipsilateral lung V20. Conclusion: Surface-guided radiotherapy can be regarded as an accurate tool for patient positioning and monitoring in breast radiotherapy. DIBH treatment are considered to be effective techniques in heart and ipsilateral lung dose reductions for left breast radiotherapy.
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| 3. |
- Aberer, Karl, et al.
(författare)
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The Essence of P2P : A Reference Architecture for Overlay Networks
- 2005
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Ingår i: Fifth IEEE International Conference on Peer-to-Peer Computing, Proceedings. - 0769523765 ; , s. 11-20
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Konferensbidrag (refereegranskat)abstract
- The success of the P2P idea has created a huge diversity of approaches, among which overlay networks, for example, Gnutella, Kazaa, Chord, Pastry, Tapestry, P-Grid, or DKS, have received specific attention from both developers and researchers. A wide variety of algorithms, data structures, and architectures have been proposed. The terminologies and abstractions used, however have become quite inconsistent since the P2P paradigm has attracted people from many different communities, e.g., networking, databases, distributed systems, graph theory, complexity theory, biology, etc. In this paper we propose a reference model for overlay networks which is capable of modeling different approaches in this domain in a generic manner It is intended to allow researchers and users to assess the properties of concrete systems, to establish a common vocabulary for scientific discussion, to facilitate the qualitative comparison of the systems, and to serve as the basis for defining a standardized API to make overlay networks interoperable.
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| 4. |
- Alima, Luc Onana, et al.
(författare)
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A Framework for Structured Peer-to-Peer Overlay Networks
- 2004. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Structured peer-to-peer overlay networks have recently emerged as good candidate infrastructure for building novel large-scale and robust Internet applications in which participating peers share computing resources as equals. In the past three year, various structured peer-to-peer overlay networks have been proposed, and probably more are to come. We present a framework for understanding, analyzing and designing structured peer-to-peer overlay networks. The main objective of the paper is to provide practical guidelines for the design of structured overlay networks by identifying a fundamental element in the construction of overlay networks: the embedding of k-ary trees. Then, a number of effective techniques for maintaining these overlay networks are discussed. The proposed framework has been effective in the development of the DKS system.
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| 5. |
- Ananthanarayanan, G., et al.
(författare)
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PACMan : Coordinated memory caching for parallel jobs
- 2012
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Ingår i: Proceedings of NSDI 2012. - : USENIX Association. ; , s. 267-280
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Konferensbidrag (refereegranskat)abstract
- Data-intensive analytics on large clusters is important for modern Internet services. As machines in these clusters have large memories, in-memory caching of inputs is an effective way to speed up these analytics jobs. The key challenge, however, is that these jobs run multiple tasks in parallel and a job is sped up only when inputs of all such parallel tasks are cached. Indeed, a single task whose input is not cached can slow down the entire job. To meet this "all-or-nothing" property, we have built PACMan, a caching service that coordinates access to the distributed caches. This coordination is essential to improve job completion times and cluster efficiency. To this end, we have implemented two cache replacement policies on top of PACMan's coordinated infrastructure fb-LIFE that minimizes average completion time by evicting large incomplete inputs, and LFU-F that maximizes cluster efficiency by evicting less frequently accessed inputs. Evaluations on production workloads from Facebook and Microsoft Bing show that PACMan reduces average completion time of jobs by 56% and 51% (small interactive jobs improve by 77%), and improves efficiency of the cluster by 47% and 54%, respectively.
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| 6. |
- Arad, Cosmin, et al.
(författare)
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GODS: Global Observatory for Distributed Systems
- 2007. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We propose GODS, an ecosystem for the evaluation and study of world-wide distributed and dynamic systems under a realistic emulated network environment. GODS allows the evaluation of a system's actual implementation in reproducible experiments, collecting global knowledge about the system state. Furthermore, GODS addresses the problems of debugging distributed algorithms, performance tuning, measuring bandwidth consumption, regression testing, and benchmarking similar systems, thus offering a complete evaluation environment for distributed applications. Our framework uses ModelNet for the network emulation and enhances that by (1) adding dynamism by varying link properties, partitioning the network and emulating churn, (2) offering global knowledge about the observed system by gathering statistics and events and (3) enabling the user to easily deploy, manage and monitor complex, large-scale distributed systems.
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| 7. |
- Bailis, P., et al.
(författare)
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Bolt-on causal consistency
- 2013
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Ingår i: SIGMOD '13 Proceedings of the 2013 ACM SIGMOD International Conference on Management of Data. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450320375 ; , s. 761-772
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of separating consistency-related safety properties from availability and durability in distributed data stores via the application of a "bolt-on" shim layer that upgrades the safety of an underlying general-purpose data store. This shim provides the same consistency guarantees atop a wide range of widely deployed but often inflexible stores. As causal consistency is one of the strongest consistency models that remain available during system partitions, we develop a shim layer that upgrades eventually consistent stores to provide convergent causal consistency. Accordingly, we leverage widely deployed eventually consistent infrastructure as a common substrate for providing causal guarantees. We describe algorithms and shim implementations that are suitable for a large class of application-level causality relationships and evaluate our techniques using an existing, production-ready data store and with real-world explicit causality relationships.
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| 8. |
- Bailis, Peter, et al.
(författare)
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Eventual Consistency Today : Limitations, Extensions, and Beyond
- 2013
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Ingår i: Communications of the ACM. - : Association for Computing Machinery (ACM). - 0001-0782 .- 1557-7317. ; 56:5, s. 55-63
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Tidskriftsartikel (refereegranskat)abstract
- Brewer's conjecture'based on his experiences building infrastructure for some of the first Internet search engines at Inktomi'states that distributed systems requiring always on, highly available operation cannot guarantee the illusion of coherent, consistent single-system operation in the presence of network partitions, which cut communication between active servers. Moreover, even without partitions, a system that chooses availability over consistency enjoys benefits of low latency. If a server can safely respond to a user's request when it is partitioned from all other servers, then it can also respond to a user's request without contacting other servers even when it is able to do so. Eventual consistency as an available alternative. Given the CAP impossibility result, distributed-database designers sought weaker consistency models that would enable both availability and high performance.
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| 9. |
- Bailis, P., et al.
(författare)
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HAT, not CAP : Towards highly available transactions
- 2013
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Ingår i: 14th Workshop on Hot Topics in Operating Systems, HotOS 2013. - : USENIX Association.
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Konferensbidrag (refereegranskat)abstract
- While the CAP Theorem is often interpreted to preclude the availability of transactions in a partition-prone environment, we show that highly available systems can provide useful transactional semantics, often matching those of today's ACID databases. We propose Highly Available Transactions (HATs) that are available in the presence of partitions. HATs support many desirable ACID guarantees for arbitrary transactional sequences of read and write operations and permit low-latency operation.
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| 10. |
- Bailis, P., et al.
(författare)
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The potential dangers of causal consistency and an explicit solution
- 2012
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Ingår i: Proceedings of the 3rd ACM Symposium on Cloud Computing, SoCC 2012. - New York, NY, USA : ACM. - 9781450317610
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Konferensbidrag (refereegranskat)abstract
- Causal consistency is the strongest consistency model that is available in the presence of partitions and provides useful semantics for human-facing distributed services. Here, we expose its serious and inherent scalability limitations due to write propagation requirements and traditional dependency tracking mechanisms. As an alternative to classic potential causality, we advocate the use of explicit causality, or application-defined happens-before relations. Explicit causality, a subset of potential causality, tracks only relevant dependencies and reduces several of the potential dangers of causal consistency.
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