Target margins in radiotherapy of prostate cancer

Yartsev, Slav

doi:10.1259/bjr.20160312

Cited by 40 publications

(43 citation statements)

References 128 publications

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“…[15][16][17][18][19][20] The magnitude of margins has been shown to depend on the modality used for image guidance. 21,22 Margins are anticipated to continue to adapt to and improve with advances in image guided radiation therapy techniques, such as real-time fiducial tracking 19 and advanced anatomic imaging. 20 The safety margin paradigm for photons cannot be directly extended to protons.…”

Section: Addressing Uncertainties In Treatment Planningmentioning

confidence: 99%

Robustness Analysis for External Beam Radiation Therapy Treatment Plans: Describing Uncertainty Scenarios and Reporting Their Dosimetric Consequences

Yock

Mohan

Flampouri

et al. 2019

Practical Radiation Oncology

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Purpose: With external beam radiation therapy, uncertainties in treatment planning and delivery can result in an undesirable dose distribution delivered to the patient that can compromise the benefit of treatment. Techniques including geometric margins and probabilistic optimization have been used effectively to mitigate the effects of uncertainties. However, their broad application is inconsistent and can compromise the conclusions derived from cross-technique and cross-modality comparisons. Methods and Materials: Conventional methods to deal with treatment planning and delivery uncertainties are described, and robustness analysis is presented as a framework that is applicable across treatment techniques and modalities. Results: This report identifies elements that are imperative to include when conducting a robustness analysis and describing uncertainties and their dosimetric effects.NotedEarn CME credit by taking a brief online assessment at https://academy.astro.org.Conclusion: The robustness analysis approach described here is presented to promote reliable plan evaluation and dose reporting, particularly during clinical trials conducted across institutions and treatment modalities.

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Section: Addressing Uncertainties In Treatment Planningmentioning

confidence: 99%

Robustness Analysis for External Beam Radiation Therapy Treatment Plans: Describing Uncertainty Scenarios and Reporting Their Dosimetric Consequences

Yock

Mohan

Flampouri

et al. 2019

Practical Radiation Oncology

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“…There are many references to the PTV margin associated with CBCT [ 14 ], but some reports suggested values for the PTV margin that cannot be guaranteed with validity. One reason for this might come from the fact that guidelines for PTV margin definition based on kV-CBCT have not been adopted.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, markerless kV-CBCT techniques have uncertainty for recognizing prostate positioning, and it is assumed that the clinical target volume (CTV)-to-planning target volume (PTV) margin calculated from markerless kV-CBCT will become larger than the PTV margin from kV-OBI with FMs. However in IG-IMRT with markerless kV-CBCT, there is no guideline for the method of calculating the PTV margin, and various sizes for the PTV margin are recommended based on some reports with more or less assumptions by each researcher [ 14 ]. Although the methodology for calculating the PTV margin for IG-IMRT with markerless kV-CBCT has been continuously discussed, it has not yet been finalized.…”

Section: Introductionmentioning

confidence: 99%

“…Although the methodology for calculating the PTV margin for IG-IMRT with markerless kV-CBCT has been continuously discussed, it has not yet been finalized. For this reason, the differences between kV-CBCT and other techniques, such as CT-on-rails, megavoltage (MV) CBCT, or MVCT integrated with tomotherapy, are confused even in some review articles [ 14 ]. Nonetheless, because FM implantation is time- and staff-consuming and requires invasive surgery, markerless CBCT without FMs is becoming the mainstream method of IG-IMRT.…”

Section: Introductionmentioning

confidence: 99%

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The potential failure risk of the cone-beam computed tomography-based planning target volume margin definition for prostate image-guided radiotherapy based on a prospective single-institutional hybrid analysis

et al. 2018

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BackgroundThe purpose of this study was to evaluate the impact of markerless on-board kilovoltage (kV) cone-beam computed tomography (CBCT)-based positioning uncertainty on determination of the planning target volume (PTV) margin by comparison with kV on-board imaging (OBI) with gold fiducial markers (FMs), and to validate a methodology for the evaluation of PTV margins for markerless kV-CBCT in prostate image-guided radiotherapy (IGRT).MethodsA total of 1177 pre- and 1177 post-treatment kV-OBI and 1177 pre- and 206 post-treatment kV-CBCT images were analyzed in 25 patients who received prostate IGRT with daily localization by implanted FMs. Intrafractional motion of the prostate was evaluated between each pre- and post-treatment image with these two different techniques. The differences in prostate deviations and intrafractional motions between matching by FM in kV-OBI (OBI-FM) and matching by soft tissues in kV-CBCT (CBCT-ST) were compared by Bland-Altman limits of agreement. Compensated PTV margins were determined and compensated by references.ResultsMean differences between OBI-FM and CBCT-ST in the anterior to posterior (AP), superior to inferior (SI), and left to right (LR) directions were − 0.43 ± 1.45, − 0.09 ± 1.65, and − 0.12 ± 0.80 mm, respectively, with R2 = 0.85, 0.88, and 0.83, respectively. Intrafractional motions obtained from CBCT-ST were 0.00 ± 1.46, 0.02 ± 1.49, and 0.15 ± 0.64 mm, respectively, which were smaller than the results from OBI-FM, with 0.43 ± 1.90, 0.12 ± 1.98, and 0.26 ± 0.80 mm, respectively, with R2 = 0.42, 0.33, and 0.16, respectively. Bland-Altman analysis showed a significant proportional bias. PTV margins of 1.5 mm, 1.4 mm, and 0.9 mm for CBCT-ST were calculated from the values of CBCT-ST, which were also smaller than the values of 3.15 mm, 3.66 mm, and 1.60 mm from OBI-FM. The practical PTV margin for CBCT-ST was compensated with the values from OBI-FM as 4.1 mm, 4.8 mm, and 2.2 mm.ConclusionsPTV margins calculated from CBCT-ST might be underestimated compared to the true PTV margins. To determine a reliable CBCT-ST-based PTV margin, at least the systemic error Σ and the random error σ for on-line matching errors need to be investigated by supportive preliminary FM evaluation at least once.

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“…Thereby, the therapists/clinicians can objectively align the tumors using image registration. For the simplicity of implementation and the reduction of X-ray imaging times, a hybrid system (combining infrared [IR] camera and X-ray imaging technique), such as ExacTrac/Novalis Body system, 16 – 20 is developed. The IR camera technique is used for an initial patient setup and the target is accurately located by an X-ray imaging system.…”

Section: Introductionmentioning

confidence: 99%

A Noninvasive Body Setup Method for Radiotherapy by Using a Multimodal Image Fusion Technique

Zhang

Chen

et al. 2017

Technol Cancer Res Treat

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Purpose:To minimize the mismatch error between patient surface and immobilization system for tumor location by a noninvasive patient setup method.Materials and Methods:The method, based on a point set registration, proposes a shift for patient positioning by integrating information of the computed tomography scans and that of optical surface landmarks. An evaluation of the method included 3 areas: (1) a validation on a phantom by estimating 100 known mismatch errors between patient surface and immobilization system. (2) Five patients with pelvic tumors were considered. The tumor location errors of the method were measured using the difference between the proposal shift of cone-beam computed tomography and that of our method. (3) The collected setup data from the evaluation of patients were compared with the published performance data of other 2 similar systems.Results:The phantom verification results showed that the method was capable of estimating mismatch error between patient surface and immobilization system in a precision of <0.22 mm. For the pelvic tumor, the method had an average tumor location error of 1.303, 2.602, and 1.684 mm in left–right, anterior–posterior, and superior–inferior directions, respectively. The performance comparison with other 2 similar systems suggested that the method had a better positioning accuracy for pelvic tumor location.Conclusion:By effectively decreasing an interfraction uncertainty source (mismatch error between patient surface and immobilization system) in radiotherapy, the method can improve patient positioning precision for pelvic tumor.

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Target margins in radiotherapy of prostate cancer

Cited by 40 publications

References 128 publications

Robustness Analysis for External Beam Radiation Therapy Treatment Plans: Describing Uncertainty Scenarios and Reporting Their Dosimetric Consequences

Robustness Analysis for External Beam Radiation Therapy Treatment Plans: Describing Uncertainty Scenarios and Reporting Their Dosimetric Consequences

The potential failure risk of the cone-beam computed tomography-based planning target volume margin definition for prostate image-guided radiotherapy based on a prospective single-institutional hybrid analysis

A Noninvasive Body Setup Method for Radiotherapy by Using a Multimodal Image Fusion Technique

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