| 1. |
- Anastasi, Gail, et al.
(författare)
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Patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) part I : Intra-fraction breathing motion management
- 2020
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Ingår i: Radiotherapy and Oncology. - : ELSEVIER IRELAND LTD. - 0167-8140 .- 1879-0887. ; 153, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The POP-ART RT study aims to determine to what extent and how intra-fractional real-time respiratory motion management (RRMM) and plan adaptation for inter-fractional anatomical changes (ART), are used in clinical practice and to understand barriers to implementation. Here we report on part I: RRMM. Material and methods: A questionnaire was distributed worldwide to assess current clinical practice, wishes for expansion or new implementation and barriers to implementation. RRMM was defined as inspiration/expiration gating in free-breathing or breath-hold, or tracking where the target and the beam are continuously realigned. Results: The questionnaire was completed by 200 centres from 41 countries. RRMM was used by 68% of respondents ('users') for a median (range) of 2 (1-6) tumour sites. Eighty-one percent of users applied inspiration breath-hold in at least one tumour site (breast: 96%). External marker was used to guide RRMM by 61% of users. KV/MV imaging was frequently used for liver and pancreas (with fiducials) and for lung (with or without fiducials). Tracking was mainly performed on robotic linacs with hybrid internal-external monitoring. For breast and lung, approximately 75% of respondents used or wished to implement RRMM, which was lower for liver (44%) and pancreas (27%). Seventy-one percent of respondents wished to implement RRMM for a new tumour site. Main barriers were human/financial resources and capacity on the machine. Conclusion: Sixty-eight percent of respondents used RRMM and 71% wished to implement RRMM for a new tumour site. The main barriers to implementation were human/financial resources and capacity on treatment machines. (C) 2020 The Authors. Published by Elsevier B.V.
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| 2. |
- Bertholet, Jenny, et al.
(författare)
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Patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) part II : Offline and online plan adaption for interfractional changes
- 2020
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Ingår i: Radiotherapy and Oncology. - : ELSEVIER IRELAND LTD. - 0167-8140 .- 1879-0887. ; 153, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The POP-ART RT study aims to determine to what extent and how intrafractional real-time respiratory motion management (RRMM), and plan adaptation for interfractional anatomical changes (ART) are used in clinical practice and to understand barriers to implementation. Here we report on part II: ART using more than one plan per target per treatment course. Materials and methods: A questionnaire on the current practice of ART, wishes for expansion or implementation, and barriers to implementation was distributed worldwide. Four types of ART were discriminated: daily online replanning, online plan library, protocolled offline replanning (all three based on a protocol), and ad-hoc offline replanning. Results: The questionnaire was completed by 177 centres from 40 countries. ART was used by 61% of respondents (31% with protocol) for a median (range) of 3 (1-8) tumour sites. CBCT/MVCT was the main imaging modality except for online daily replanning (11 users) where 10 users used MR. Two thirds of respondents wished to implement ART for a new tumour site; 40% of these had plans to do it in the next 2 years. Human/material resources and technical limitations were the main barriers to further use and implementation. Conclusions: ART was used for a broad range of tumour sites, mainly with ad-hoc offline replanning and for a median of 3 tumour sites. There was a large interest in implementing ART for more tumour sites, mainly limited by human/material resources and technical limitations. Daily online replanning was primarily performed on MR-linacs. (C) 2020 The Authors. Published by Elsevier B.V.
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| 3. |
- Colvill, Emma, et al.
(författare)
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A dosimetric comparison of real-time adaptive and non-adaptive radiotherapy : A multi-institutional study encompassing robotic, gimbaled, multileaf collimator and couch tracking
- 2016
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140. ; 119:1, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- Purpose A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion. Methods and materials Ten institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan was delivered twice to a moving dosimeter; with and without real-time adaptation. Each measurement was compared to a static measurement and the percentage of failed points for γ-tests recorded. Results For all lung traces all measurement sets show improved dose accuracy with a mean 2%/2 mm γ-fail rate of 1.6% with adaptation and 15.2% without adaptation (p < 0.001). For all prostate the mean 2%/2 mm γ-fail rate was 1.4% with adaptation and 17.3% without adaptation (p < 0.001). The difference between the four systems was small with an average 2%/2 mm γ-fail rate of <3% for all systems with adaptation for lung and prostate. Conclusions The investigated systems all accounted for realistic tumor motion accurately and performed to a similar high standard, with real-time adaptation significantly outperforming non-adaptive delivery methods.
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| 4. |
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| 5. |
- Mu, Xiangkui, et al.
(författare)
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Does electron and proton therapy reduce the risk of radiation induced cancer after spinal irradiation for childhood medulloblastoma? A comparative treatment planning study.
- 2005
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Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 44:6, s. 554-62
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this treatment planning comparison study was to explore different spinal irradiation techniques with respect to the risk of late side-effects, particularly radiation-induced cancer. The radiotherapy techniques compared were conventional photon therapy, intensity modulated x-ray therapy (IMXT), conventional electron therapy, intensity/energy modulated electron therapy (IMET) and proton therapy (IMPT).CT images for radiotherapy use from five children, median age 8 and diagnosed with medulloblastoma, were selected for this study. Target volumes and organs at risk were defined in 3-D. Treatment plans using conventional photon therapy, IMXT, conventional electron therapy, IMET and IMPT were set up. The probability of normal tissue complication (NTCP) and the risk of cancer induction were calculated using models with parameters-sets taken from published data for the general population; dose data were taken from dose volume histograms (DVH).Similar dose distributions in the targets were achieved with all techniques but the absorbed doses in the organs-at-risk varied significantly between the different techniques. The NTCP models based on available data predicted very low probabilities for side-effects in all cases. However, the effective mean doses outside the target volumes, and thus the predicted risk of cancer induction, varied significantly between the techniques. The highest lifetime risk of secondary cancers was estimated for IMXT (30%). The lowest risk was found with IMPT (4%). The risks associated with conventional photon therapy, electron therapy and IMET were 20%, 21% and 15%, respectively.This model study shows that spinal irradiation of young children with photon and electron techniques results in a substantial risk of radiation-induced secondary cancers. Multiple beam IMXT seems to be associated with a particularly high risk of secondary cancer induction. To minimise this risk, IMPT should be the treatment of choice. If proton therapy is not available, advanced electron therapy may provide a better alternative.
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| 6. |
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| 7. |
- Olofsson, Lennart, et al.
(författare)
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Intensity modulated radiation therapy with electrons using algorithm based energy/range selection methods.
- 2004
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 73:2, s. 223-231
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: In recent years photon intensity modulated radiation therapy (IMRT) has gained attention due to its ability to improve conformity of dose distributions. A potential advantage of electron-IMRT is that the dose fall off in the depth dose curve makes it possible to modulate the dose distribution in the direction of the beam by selecting different electron energies. This paper examines the use of a computer based energy selection in combination with the IMRT technique to optimise the electron dose distribution. MATERIALS AND METHODS: One centimetre square electron beamlets ranging from 2.5 to 50 MeV were pre-calculated in water using Monte Carlo methods. A modified IMRT optimisation tool was then used to find an optimum mix of electron energies and intensities. The main principles used are illustrated in some simple geometries and tested on two clinical cases of post-operated ca. mam. RESULTS: It is clearly illustrated that the energy optimisation procedure lowers the dose to lung and heart and makes the dose in the target more homogeneous. Increasing the energy at steep gradients compensates for lack of target coverage at beam edges and steep gradients. Comparison with a clinically acceptable four segment plan indicates the advantage of the used electron IMRT technique. CONCLUSIONS: Using an intensity optimised mix of computer selected electron energies has the potential to improve electron treatments for mastectomy patients with good target coverage and reduced dose to normal tissue such as lung and heart.
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| 8. |
- Taheri-Kadkhoda, Zahra, 1969, et al.
(författare)
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Intensity-modulated radiotherapy of nasopharyngeal carcinoma: a comparative treatment planning study of photons and protons.
- 2008
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Ingår i: Radiation oncology (London, England). - 1748-717X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The aim of this treatment planning study was to investigate the potential advantages of intensity-modulated (IM) proton therapy (IMPT) compared with IM photon therapy (IMRT) in nasopharyngeal carcinoma (NPC). METHODS: Eight NPC patients were chosen. The dose prescriptions in cobalt Gray equivalent (GyE) for gross tumor volumes of the primary tumor (GTV-T), planning target volumes of GTV-T and metastatic (PTV-TN) and elective (PTV-N) lymph node stations were 72.6 GyE, 66 GyE, and 52.8 GyE, respectively. For each patient, nine coplanar fields IMRT with step-and-shoot technique and 3D spot-scanned three coplanar fields IMPT plans were prepared. Both modalities were planned in 33 fractions to be delivered with a simultaneous integrated boost technique. All plans were prepared and optimized by using the research version of the inverse treatment planning system KonRad (DKFZ, Heidelberg). RESULTS: Both treatment techniques were equal in terms of averaged mean dose to target volumes. IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3. The low-to-medium dose volumes (0.33-13.2 GyE) were more than doubled by IMRT plans. CONCLUSION: In radiotherapy of NPC patients, three-field IMPT has greater potential than nine-field IMRT with respect to tumor coverage and reduction of the integral dose to OARs and non-specific normal tissues. The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale.
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| 9. |
- Tilly, David, 1974-
(författare)
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Probabilistic treatment planning based on dose coverage : How to quantify and minimize the effects of geometric uncertainties in radiotherapy
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Traditionally, uncertainties are handled by expanding the irradiated volume to ensure target dose coverage to a certain probability. The uncertainties arise from e.g. the uncertainty in positioning of the patient at every fraction, organ motion and in defining the region of interests on the acquired images. The applied margins are inherently population based and do not exploit the geometry of the individual patient. Probabilistic planning on the other hand incorporates the uncertainties directly into the treatment optimization and therefore has more degrees of freedom to tailor the dose distribution to the individual patient. The aim of this thesis is to create a framework for probabilistic evaluation and optimization based on the concept of dose coverage probabilities. Several computational challenges for this purpose are addressed in this thesis.The accuracy of the fraction by fraction accumulated dose depends directly on the accuracy of the deformable image registration (DIR). Using the simulation framework, we could quantify the requirements on the DIR to 2 mm or less for a 3% uncertainty in the target dose coverage.Probabilistic planning is computationally intensive since many hundred treatments must be simulated for sufficient statistical accuracy in the calculated treatment outcome. A fast dose calculation algorithm was developed based on the perturbation of a pre-calculated dose distribution with the local ratio of the simulated treatment’s fluence and the fluence of the pre-calculated dose. A speedup factor of ~1000 compared to full dose calculation was achieved with near identical dose coverage probabilities for a prostate treatment.For some body sites, such as the cervix dataset in this work, organ motion must be included for realistic treatment simulation. A statistical shape model (SSM) based on principal component analysis (PCA) provided the samples of deformation. Seven eigenmodes from the PCA was sufficient to model the dosimetric impact of the interfraction deformation.A probabilistic optimization method was developed using constructs from risk management of stock portfolios that enabled the dose planner to request a target dose coverage probability. Probabilistic optimization was for the first time applied to dataset from cervical cancer patients where the SSM provided samples of deformation. The average dose coverage probability of all patients in the dataset was within 1% of the requested.
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