Validation of the mid-position strategy for lung tumors in helical TomoTherapy

Wanet, Marie; Sterpin, Edmond; Janssens, Guillaume; Delor, Antoine; Lee, John A.; Geets, Xavier

doi:10.1016/j.radonc.2013.10.025

Cited by 35 publications

(33 citation statements)

References 54 publications

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“…The optimal PTV could be defined as the volume that maintains the smallest margins as prudently possible without sacrificing target coverage [7]. As expected, the ITV-based PTV boundaries using a 5 mm Previous studies reported that a MidV approach could significantly reduce PTVs and therefore reduce lung tissue exposure compared to an ITV-based PTV using a 5 mm margin [6,11,12,16,17]. In the present work, the PTV MidV was on average 16% smaller than PTV ITV + 5mm , which is similar to the study results of Wanet et al [16].…”

Section: Discussionmentioning

confidence: 76%

“…The actual respiration-correlated 4D positions of the target during beam delivery were therefore considered. To the best of our knowledge, all previous studies comparing respiratory motion management strategies in lung SBRT were performed exclusively with pretreatment data [6,16,17]. In our study, the evaluation incorporated all residual localization errors and account for the effective breathing patterns of the patient during treatment.…”

Section: Discussionmentioning

confidence: 99%

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ITV versus mid-ventilation for treatment planning in lung SBRT: a comparison of target coverage and PTV adequacy by using in-treatment 4D cone beam CT

et al. 2020

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Background: The internal target volume (ITV) approach and the mid-ventilation (MidV) concept are the two main respiratory motion-management strategies under free breathing. The purpose of this work was to compare the actual in-treatment target coverage during volumetric modulated arctherapy (VMAT) delivered through both ITVbased and MidV-based planning target volume (PTV) and to provide knowledge in choosing the optimal PTV for stereotactic body radiotherapy (SBRT) for lung lesions. Methods and materials: Thirty-two lung cancer patients treated by a VMAT technique were included in the study. For each fraction, the mean time-weighted position of the target was localized by using a 4-dimensional conebeam CT (4D-CBCT)-based image guidance procedure. The respiratory-correlated location of the gross tumor volume (GTV) during treatment delivery was determined for each fraction by using in-treatment 4D-CBCT images acquired concurrently with VMAT delivery (4D-CBCT in-treat ). The GTV was delineated from each of the ten respiratory phase-sorted 4D-CBCT in-treat datasets for each fraction. We defined target coverage as the average percentage of the GTV included within the PTV during the patient's breathing cycle averaged over the treatment course. Target coverage and PTVs were reported for a MidV-based PTV (PTV MidV ) using dose-probabilistic margins and three ITVbased PTVs using isotropic margins of 5 mm (PTV ITV + 5mm ), 4 mm (PTV ITV + 4mm ) and 3 mm (PTV ITV + 3mm ). The intreatment baseline displacements and target motion amplitudes were reported to evaluate the impact of both parameters on target coverage. Results: Overall, 100 4D-CBCT in-treat images were analyzed. The mean target coverage was 98.6, 99.6, 98.9 and 97.2% for PTV MidV , PTV ITV + 5mm , PTV ITV + 4mm and PTV ITV + 3mm , respectively. All the PTV margins led to a target coverage per treatment higher than 95% in at least 90% of the evaluated cases. Compared to PTV ITV + 5mm , PTV MidV , PTV ITV + 4mm and PTV ITV + 3mm had mean PTV reductions of 16, 19 and 33%, respectively.Conclusion: When implementing VMAT with 4D-CBCT-based image guidance, an ITV-based approach with a tighter margin than the commonly used 5 mm margin remains an alternative to the MidV-based approach for reducing healthy tissue exposure in lung SBRT. Compared to PTV MidV , PTV ITV + 3mm significantly reduced the PTV while still maintaining an adequate in-treatment target coverage.

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Section: Discussionmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

ITV versus mid-ventilation for treatment planning in lung SBRT: a comparison of target coverage and PTV adequacy by using in-treatment 4D cone beam CT

et al. 2020

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“…The analysis of organ motion via positional extremes, as shown in this work, is integral to margin determination 10, 18. A MidP strategy, which uses the mean position of an organ throughout the respiratory cycle as the planning volume, margin has been studied in lung volumes and has been found to result in smaller volumes and less therapeutic radiation dose 19. This finding is encouraging, especially given the significantly higher doses of radiation that accompany the use of 4DCT imaging 20.…”

Section: Discussionmentioning

confidence: 99%

Organ motion in pediatric high‐risk neuroblastoma patients using four‐dimensional computed tomography

Kannan

Teo

Solberg

et al. 2016

J Applied Clin Med Phys

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Purpose/objective(s)High‐risk neuroblastoma (HR‐NBL) requires multimodality treatment, including external beam radiation of the primary tumor site following resection. Radiotherapy planning must take into account motion of the target and adjacent normal anatomy, both of which are poorly understood in the pediatric population, and which may differ significantly from those in adults.Methods/materialsWe examined 4DCT scans of 15 consecutive pediatric patients treated for HR‐NBL, most with tumors in the abdominal cavity. The diaphragm and organs at risk were contoured at full inhale, full exhale, and on free‐breathing scans. Maximum displacement of organs between full inhale and full exhale was measured in the anterior, posterior, superior, inferior, left, and right directions, as was displacement of centroids in the A/P, S/I, and L/R axes. Contours on free‐breathing scans were compared to those on 4D scans.ResultsMaximum displacement was along the S/I axis, with the superior aspects of organs moving more than the inferior, implying organ compression with respiration. Liver and spleen exhibited the largest motion, which correlated strongly with the S/I motion of the diaphragm. The maximum organ motion observed in the abdomen and thorax were 4.5 mm and 7.4 mm, respectively, while maximum diaphragm displacement was 5.7 mm. Overall findings mirrored observations in adults, but with smaller magnitudes, as expected. No consistent margins could be added to the free‐breathing scans to encompass the motion determined using 4DCT.ConclusionsOrgan motion within the pediatric abdomen and pelvis is similar to that observed in adults, but with smaller magnitude. Precise margins to accommodate motion are patient‐specific, underscoring the need for 4DCT scanning when possible.

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“…Treatment plan optimization is performed with the 4D‐robust optimization algorithm of the TPS RayStation research version v7.99 (RaySearch Laboratories, Stockholm, Sweden). The time‐averaged mid‐position CT is used as the nominal planning CT which was created with the open‐source platform OpenReggui . OpenReggui calculates the mid‐position CT by computing the mean position over the respiratory cycle after deformable registration between all phases of the 4D‐CT image set.…”

Section: Methodsmentioning

confidence: 99%

Towards fast and robust 4D optimization for moving tumors with scanned proton therapy

et al. 2019

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Purpose Robust optimization is becoming the gold standard for generating robust plans against various kinds of treatment uncertainties. Today, most robust optimization strategies use a pragmatic set of treatment scenarios (the so‐called uncertainty set) consisting of combinations of maximum errors, of each considered uncertainty source (such as tumor motion, setup and image‐conversion errors). This approach presents two key issues. First, a subset of considered scenarios is unnecessarily improbable which could potentially compromise the plan quality. Second, the resulting large uncertainty set leads to long plan computation times, which limits the potential for robust optimization as a standard clinical tool. In order to address these issues, a method is introduced which is able to preselect a limited set of relevant treatment error scenarios. Methods Uncertainties due to systematic setup errors, image‐conversion errors and respiratory tumor motion are considered. A four‐dimensional (4D)‐equiprobability hypersurface is defined, which takes into account the joint probabilities of the above‐mentioned uncertainty sources. Only scenarios that lie on the predefined 4D hypersurface are considered, guaranteeing statistical consistency of the uncertainty set. In this regard, twelve scenarios are selected that cover maximum spatial displacements of the tumor during breathing. Subsequently, additional scenarios are considered (sampled from the aforementioned 4D hypersurface) in order to cover any estimated residual range errors. Two different scenario‐selection procedures were tested: (a) the maximum displacements (MD) method that only considers twelve scaled maximum displacement scenarios and (b) maximum displacements and residual range (MDR) method which, in addition to the scaled maximum displacement scenarios, considers additional maximum range uncertainty scenarios. The methods were tested for five lung cancer patients by performing comprehensive Monte Carlo robustness evaluations. Results A plan computation time gain of 78% is achieved by applying the MD method, whilst obtaining a target robustness of D95 larger than 95% of the prescribed dose, for the worst‐case scenario. Additionally, the MD method has the potential to be fully automatic which makes it a promising candidate for fast automatic planning workflows. The MDR method produced plans with excellent target robustness (D99 larger than 95% of the prescribed dose, even for the worst‐case scenario), whilst still obtaining a significant plan computation time gain of 57%. Conclusions Two scenario‐selection procedures were developed which achieved significant reduction of plan computation time and memory consumption, without compromising plan quality or robustness.

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Validation of the mid-position strategy for lung tumors in helical TomoTherapy

Cited by 35 publications

References 54 publications

ITV versus mid-ventilation for treatment planning in lung SBRT: a comparison of target coverage and PTV adequacy by using in-treatment 4D cone beam CT

ITV versus mid-ventilation for treatment planning in lung SBRT: a comparison of target coverage and PTV adequacy by using in-treatment 4D cone beam CT

Organ motion in pediatric high‐risk neuroblastoma patients using four‐dimensional computed tomography

Towards fast and robust 4D optimization for moving tumors with scanned proton therapy

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