Anatomically robust proton therapy using multiple planning computed tomography scans for locally advanced prostate cancer

Busch, Kia; Dahl, Benjamin A.; Petersen, Steffen; Rønde, H.S.; Bentzen, L.; Pilskog, Sara; Muren, L.P.

doi:10.1080/0284186x.2021.1892181

Cited by 2 publications

(3 citation statements)

References 36 publications

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“…Two experienced radiation oncologists contoured the targets and relevant organs at risk (OARs) on pCTs and rCTs using the Eclipse TPS. The lymph node target and bowel contouring are described in Busch et al [19]. Additional details are described by Thörnqvist et al [18].…”

Section: Patient Cohortmentioning

confidence: 99%

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations

Busch

Andersen

Petersen

et al. 2022

Biomed. Phys. Eng. Express

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Introduction: Internal organ motion and deformations may cause dose degradations in proton therapy (PT) that are challenging to resolve using conventional image-guidance strategies. This study aimed to investigate the potential of range guidance using water-equivalent path length (WEPL) calculations to detect dose degradations occurring in PT. Materials and methods: Proton ranges were estimated using WEPL calculations. Field-specific isodose surfaces in the planning CT (pCT), from robustly optimised five-field proton plans (opposing lateral and three posterior/posterior oblique beams) for locally advanced prostate cancer patients, were used as starting points. WEPLs to each point on the field-specific isodoses in the pCT were calculated. The corresponding range for each point was found in the repeat CTs (rCTs). The spatial agreement between the resulting surfaces in the rCTs (hereafter referred to as iso-WEPLs) and the isodoses re-calculated in rCTs was evaluated for different dose levels and Hausdorff thresholds (2-5 mm). Finally, the sensitivity and specificity of detecting target dose degradation (V95%<95%) using spatial agreement measures between the iso-WEPLs and isodoses in the pCT was evaluated. Results: The spatial agreement between the iso-WEPLs and isodoses in the rCTs depended on the Hausdorff threshold. The agreement was 65-88% for a 2 mm threshold, 83-96% for 3 mm, 90-99% for 4 mm, and 94-99% for 5 mm, across all fields and isodose levels. Minor differences were observed between the different isodose levels investigated. Target dose degradations were detected with 82-100% sensitivity and 75-80% specificity using a 2 mm Hausdorff threshold for the lateral fields. Conclusion: Iso-WEPLs were comparable to isodoses re-calculated in the rCTs. The proposed strategy could detect target dose degradations occurring in the rCTs and could be an alternative to a fully-fledged dose re-calculation to detect anatomical variations severely influencing the proton range.

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Section: Patient Cohortmentioning

confidence: 99%

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations

Busch

Andersen

Petersen

et al. 2022

Biomed. Phys. Eng. Express

View full text Add to dashboard Cite

show abstract

“…One approach to address these problems is to include uncertainties during plan optimization, 4 and several studies have improved robust optimization to include specific anatomical changes. Nevertheless, large anatomical changes reduce plan quality if the changes exceed the robustness assumed during the optimization process 5 …”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, large anatomical changes reduce plan quality if the changes exceed the robustness assumed during the optimization process. 5 Online adaptive radiotherapy (OART) can account for inter-fractional anatomical changes as patient images are acquired daily, using either an in-room CT or gantry-mounted cone-beam CT (CBCT) to monitor daily changes in anatomy. A new plan (adapted plan) is created online if these changes affect treatment quality.…”

Section: Introductionmentioning

confidence: 99%

Deformed dose restoration to account for tumor deformation and position changes for adaptive proton therapy

et al. 2022

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Background Online adaptation during intensity‐modulated proton therapy (IMPT) can minimize the effect of inter‐fractional anatomical changes, but remains challenging because of the complex workflow. One approach for fast and automated online IMPT adaptation is dose restoration, which restores the initial dose distribution on the updated anatomy. However, this method may fail in cases where tumor deformation or position changes occur. Purpose To develop a fast and robust IMPT online adaptation method named “deformed dose restoration (DDR)” that can adjust for inter‐fractional tumor deformation and position changes. Methods The DDR method comprises two steps: (1) calculation of the deformed dose distribution, and (2) restoration of the deformed dose distribution. First, the deformable image registration (DIR) between the initial clinical target volume (CTV) and the new CTV were performed to calculate the vector field. To ensure robustness for setup and range uncertainty and the ability to restore the deformed dose distribution, an expanded CTV‐based registration to maintain the dose gradient outside the CTV was developed. The deformed dose distribution was obtained by applying the vector field to the initial dose distribution. Then, the voxel‐by‐voxel dose difference optimization was performed to calculate beam parameters that restore the deformed dose distribution on the updated anatomy. The optimization function was the sum of total dose differences and dose differences of each field to restore the initial dose overlap of each field. This method only requires target contouring, which eliminates the need for organs at risk (OARs) contouring. Six clinical cases wherein the tumor deformation and/or position changed on repeated CTs were selected. DDR feasibility was evaluated by comparing the results with those from three other strategies, namely, not adapted (continuing the initial plan), adapted by previous dose restoration, and fully optimized. Results In all cases, continuing the initial plan was largely distorted on the repeated CTs and the dose‐volume histogram (DVH) metrics for the target were reduced due to the tumor deformation or position changes. On the other hand, DDR improved DVH metrics for the target to the same level as the initial dose distribution. Dose increase was seen for some OARs because tumor growth had reduced the relative distance between CTVs and OARs. Robustness evaluation for setup and range uncertainty (3 mm/3.5%) showed that deviation in DVH‐bandwidth for CTV D95% from the initial plan was 0.4% ± 0.5% (Mean ± S.D.) for DDR. The calculation time was 8.1 ± 6.4 min. Conclusions An online adaptation algorithm was developed that improved the treatment quality for inter‐fractional anatomical changes and retained robustness for intra‐fractional setup and range uncertainty. The main advantage of this method is that it only requires target contouring alone and saves the time for OARs contouring. The fast and robust adaptation method for tumor deformation and position changes described h...

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Anatomically robust proton therapy using multiple planning computed tomography scans for locally advanced prostate cancer

Cited by 2 publications

References 36 publications

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations

Deformed dose restoration to account for tumor deformation and position changes for adaptive proton therapy

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