Anisotropy of dose contributions—An instrument to upgrade real time IMRT and VMAT adaptation?

Bratengeier, Klaus; Holubyev, Kostyantyn

doi:10.1118/1.4963806

Cited by 2 publications

(6 citation statements)

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“…Brahme predicted a necessary fluence profile with a

F false(r false) \propto r^{- \frac{1}{2}}

inside the PTV adjacent to the

OAR

. In the vicinity of an OAR, it is approximately proportional to the anisotropy . Anisotropy profiles in a cross‐section through the isocenter show curves with similar scaling law throughout the PTV, to a certain range independent from the treatment technique.…”

Section: Discussionmentioning

confidence: 99%

“…Then, deforming the anisotropy distribution will result in special rules for the segment adaptation along the new structures. Both steps have been performed quantitatively for a cylindrical symmetric situation and qualitatively for prostate and head and neck cases . For the cylindrical symmetric situation, a strong correlation of anisotropy and segment shape has been shown.…”

Section: Discussionmentioning

confidence: 99%

“…Bratengeier et al 14 introduced a definition of an anisotropy field, which is given in Eqs. (1) and (2).…”

Section: A Anisotropy Of Dose Contributionsmentioning

confidence: 99%

“…It can avoid the problem of inadequate fluence grid warping, however, at the cost of increasing plan complexity and numbers of arc rotations Therefore, an indicator for the relevant 3D information that ideally may be applied to any treatment technique would be preferable. For this purpose, Bratengeier and Holubyev have suggested to use the anisotropy of dose contributions, which is closely related to the two‐step method. The anisotropy field has been analyzed in idealized geometries — a cylindrical OAR surrounded by a hollow cylindrical planning treatment volume (PTV).…”

Section: Introductionmentioning

confidence: 99%

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Properties of the anisotropy of dose contributions: A planning study on prostate cases

et al. 2018

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Purpose To characterize the static properties of the anisotropy of dose contributions for different treatment techniques on real patient data (prostate cases). From this, we aim to define a class of treatment techniques with invariant anisotropy distribution carrying information of target coverage and organ‐at‐risk (OAR) sparing. The anisotropy presumably is a helpful quantity for plan adaptation problems. Methods The anisotropy field is analyzed for different intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for a total of ten planning CTs of prostate cases. Primary irradiation directions ranged from 5 to 15. The uniqueness of anisotropy was explored: In particular, the anisotropy distribution inside the planning treatment volume (PTV) and in its vicinity was investigated. Furthermore, deviations of the anisotropy under beam rotations were explored by direct plan comparison as an indicating the susceptibility of each planned technique to changes in the geometric plan configuration. In addition, plan comparisons enabled the categorization of treatment techniques in terms of their anisotropy distribution. Results The anisotropy profile inside the PTV and in the transition between OAR and PTV is independent of the treatment technique as long as a sufficient number of beams contribute to the dose distribution. Techniques with multiple beams constitute a class of almost identical and technique‐independent anisotropy distribution. For this class of techniques, substructures of the anisotropy are particularly pronounced in the PTV, thus offering good options for applying adaptation rules. Additionally, the techniques forming the mentioned class fortunately allow a better OAR sparing at constant PTV coverage. Besides the characterization of the distribution, a pairwise plan comparison reveals each technique's susceptibility to deviations which decreases for an increasing number of primary irradiation directions. Conclusions Techniques using many irradiation directions form a class of almost identical anisotropy distributions which are assumed to provide a basis for improved adaptation procedures. Encouragingly, these techniques deliver quite invariant anisotropy distributions with respect to rotations correlated with good plan qualities than techniques using few gantry angles. The following will be the next steps toward anisotropy‐based adaptation: first, the quantification of anisotropy regarding organ deformations; and second, establishing the interrelation between the anisotropy and beam shaping.

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“…Brahme predicted a necessary fluence profile with a

F false(r false) \propto r^{- \frac{1}{2}}

inside the PTV adjacent to the

OAR

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Bratengeier et al 14 introduced a definition of an anisotropy field, which is given in Eqs. (1) and (2).…”

Section: A Anisotropy Of Dose Contributionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Properties of the anisotropy of dose contributions: A planning study on prostate cases

et al. 2018

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“…It was stated that adaptation was dominated by offline re-planning or re-optimization [ 17 ]. An offline- re-planning strategy was presented by Bratengeier et al The technique adapts step and shoot intensity modulated radiotherapy plans by modifying only the segment shapes and preserving the monitor units [ 18 , 19 ]. Another approach would be to generate motion robust treatment plans that are robust against interfraction and intrafraction motion [ 20 , 21 ].…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a software module for adaptive treatment planning and re-irradiation

et al. 2017

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BackgroundThe aim of this work is to validate the Dynamic Planning Module in terms of usability and acceptance in the treatment planning workflow.MethodsThe Dynamic Planning Module was used for decision making whether a plan adaptation was necessary within one course of radiation therapy. The Module was also used for patients scheduled for re-irradiation to estimate the dose in the pretreated region and calculate the accumulated dose to critical organs at risk. During one year, 370 patients were scheduled for plan adaptation or re-irradiation. All patient cases were classified according to their treated body region. For a sub-group of 20 patients treated with RT for lung cancer, the dosimetric effect of plan adaptation during the main treatment course was evaluated in detail. Changes in tumor volume, frequency of re-planning and the time interval between treatment start and plan adaptation were assessed.ResultsThe Dynamic Planning Tool was used in 20% of treated patients per year for both approaches nearly equally (42% plan adaptation and 58% re-irradiation). Most cases were assessed for the thoracic body region (51%) followed by pelvis (21%) and head and neck cases (10%). The sub-group evaluation showed that unintended plan adaptation was performed in 38% of the scheduled cases. A median time span between first day of treatment and necessity of adaptation of 17 days (range 4–35 days) was observed. PTV changed by 12 ± 12% on average (maximum change 42%). PTV decreased in 18 of 20 cases due to tumor shrinkage and increased in 2 of 20 cases. Re-planning resulted in a reduction of the mean lung dose of the ipsilateral side in 15 of 20 cases.ConclusionThe experience of one year showed high acceptance of the Dynamic Planning Module in our department for both physicians and medical physicists. The re-planning can potentially reduce the accumulated dose to the organs at risk and ensure a better target volume coverage. In the re-irradiation situation, the Dynamic Planning Tool was used to consider the pretreatment dose, to adapt the actual treatment schema more specifically and to review the accumulated dose.

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Anisotropy of dose contributions—An instrument to upgrade real time IMRT and VMAT adaptation?

Cited by 2 publications

References 22 publications

Properties of the anisotropy of dose contributions: A planning study on prostate cases

Properties of the anisotropy of dose contributions: A planning study on prostate cases

Evaluation of a software module for adaptive treatment planning and re-irradiation

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