Daily dose evaluation based on corrected CBCTs for breast cancer patients: accuracy of dose and complication risk assessment

Hamming, Vincent C; Andersson, Sean B.; Maduro, John H.; Langendijk, Johannes A.; Both, Stefan; Sijtsema, N.M.

doi:10.1186/s13014-022-02174-4

Cited by 6 publications

(5 citation statements)

References 49 publications

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“…The cCBCT method has been described by Thing et al 13 . and Hamming et al., 14 where the authors performed the daily dose evaluation for the breast, thorax, and pelvis with PBS. The algorithm works in two steps: First, a CBCT‐CT joint 2D histogram is created to generate a conversion function by minimizing the joint entropy between the two images.…”

Section: Methodsmentioning

confidence: 99%

Generation and evaluation of anatomy‐preserving virtual CT for online adaptive proton therapy

Kaushik,

Ödén,

Sharma

et al. 2024

Medical Physics

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BackgroundDaily CTs generated by CBCT correction are required for daily replanning in online‐adaptive proton therapy (APT) to effectively deal with inter‐fractional changes. Out of the currently available methods, the suitability of a daily CT generation method for proton dose calculation also depends on the anatomical site.PurposeWe propose an anatomy‐preserving virtual CT (APvCT) method as a hybrid method of CBCT correction, which is especially suitable for large anatomy deformations. The accuracy of the hybrid method was assessed by comparison with the corrected CBCT (cCBCT) and virtual CT (vCT) methods in the context of online APT.MethodsSeventy‐one daily CBCTs of four prostate cancer patients treated with intensity modulated proton therapy (IMPT) were converted to daily CTs using cCBCT, vCT, and the newly proposed APvCT method. In APvCT, planning CT (pCT) were mapped to CBCT geometry using deformable image registration with boundary conditions on controlling regions of interest (ROIs) created with deep learning segmentation on cCBCT. The relative frequency distribution (RFD) of HU, mass density and stopping power ratio (SPR) values were assessed and compared with the pCT. The ROIs in the APvCT and vCT were compared with cCBCT in terms of Dice similarity coefficient (DSC) and mean distance‐to‐agreement (mDTA). For each patient, a robustly optimized IMPT plan was created on the pCT and subsequent daily adaptive plans on daily CTs. For dose distribution comparison on the same anatomy, the daily adaptive plans on cCBCT and vCT were recalculated on the corresponding APvCT. The dose distributions were compared in terms of isodose volumes and 3D global gamma‐index passing rate (GPR) at γ(2%, 2 mm) criterion.ResultsFor all patients, no noticeable difference in RFDs was observed amongst APvCT, vCT, and pCT except in cCBCT, which showed a noticeable difference. The minimum DSC value was 0.96 and 0.39 for contours in APvCT and vCT respectively. The average value of mDTA for APvCT was 0.01 cm for clinical target volume and ≤0.01 cm for organs at risk, which increased to 0.18 cm and ≤0.52 cm for vCT. The mean GPR value was 90.9%, 64.5%, and 67.0% for APvCT versus cCBCT, vCT versus cCBCT, and APvCT versus vCT, respectively. When recalculated on APvCT, the adaptive cCBCT and vCT plans resulted in mean GPRs of 89.5 ± 5.1% and 65.9 ± 19.1%, respectively. The mean DSC values for 80.0%, 90.0%, 95.0%, 98.0%, and 100.0% isodose volumes were 0.97, 0.97, 0.97, 0.95, and 0.91 for recalculated cCBCT plans, and 0.89, 0.88, 0.87, 0.85, and 0.81 for recalculated vCT plans. Hausdorff distance for the 100.0% isodose volume in some cases of recalculated cCBCT plans on APvCT exceeded 1.00 cm.ConclusionsAPvCT contours showed good agreement with reference contours of cCBCT which indicates anatomy preservation in APvCT. A vCT with erroneous anatomy can result in an incorrect adaptive plan. Further, slightly lower values of GPR between the APvCT and cCBCT‐based adaptive plans can be explained by the difference in the cCBCT's SPR RFD from the pCT.

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Section: Methodsmentioning

confidence: 99%

Generation and evaluation of anatomy‐preserving virtual CT for online adaptive proton therapy

Kaushik,

Ödén,

Sharma

et al. 2024

Medical Physics

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“…When comparing the gamma pass rates for the corrCBCT and virtCT, Thing et al found the virtCT to have significantly (p < 0.05) higher pass rates than the corrCBCT for breast, prostate, and anal/rectal sites but did not show the significance for lungs. Hamming et al [42] investigated the methods for plan recalculation for breast cancer patients treated with VMAT, and found the corrCBCT (called CBCT CC in their study) performed very similarly to the virtCT (called CT V in their study), and both were adequate for dose recalculation on breast plans. Hamming et al did note that the virtCT and its correction methods are not particularly useful for breast cancer patients, as the treated site is mostly uniform soft tissue with very few opportunities for low-density overrides.…”

Section: Image Accuracymentioning

confidence: 99%

CBCT-Based Dose Monitoring and Adaptive Planning Triggers in Head and Neck PBS Proton Therapy

Reiners

Dagan

Holtzman

et al. 2023

Cancers

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Purpose: To investigate the feasibility of using cone-beam computed tomography (CBCT)-derived synthetic CTs to monitor the daily dose and trigger a plan review for adaptive proton therapy (APT) in head and neck cancer (HNC) patients. Methods: For 84 HNC patients treated with proton pencil-beam scanning (PBS), same-day CBCT and verification CT (vfCT) pairs were retrospectively collected. The ground truth CT (gtCT) was created by deforming the vfCT to the same-day CBCT, and it was then used as a dosimetric baseline and for establishing plan review trigger recommendations. Two different synthetic CT algorithms were tested; the corrected CBCT (corrCBCT) was created using an iterative image correction method and the virtual CT (virtCT) was created by deforming the planning CT to the CBCT, followed by a low-density masking process. Clinical treatment plans were recalculated on the image sets for evaluation. Results: Plan review trigger criteria for adaptive therapy were established after closely reviewing the cohort data. Compared to the vfCT, the corrCBCT and virtCT reliably produced dosimetric data more similar to the gtCT. The average discrepancy in D99 for high-risk clinical target volumes (CTV) was 1.1%, 0.7%, and 0.4% and for standard-risk CTVs was 1.8%, 0.5%, and 0.5% for the vfCT, corrCBCT, and virtCT, respectively. Conclusion: Streamlined APT has been achieved with the proposed plan review criteria and CBCT-based synthetic CT workflow.

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“…Additionally, the algorithm employs a stitching technique to simulate missing tissue outside the eld of view (FOV) of the CBCT by attaching the pCT outside the FOV [20,21,24]. Early versions of the algorithm using the scripting interface of the TPS have been tested have been tested by other groups [21][22][23]. The output of the algorithm is a so called corrected CBCT (CBCT c ) which can be used for dose calculation using the CT to mass-density conversion curve of the pCT.…”

Section: Algorithmsmentioning

confidence: 99%

“…The image quality of CBCT is often lower compared to fan-beam CT and the Houns eld Units (HU) to mass-or electron density conversion cannot be directly converted between these two modalities due to the different amount of scattered radiation and the projection geometry [11,12]. Several groups have investigated different strategies to overcome this limitation of the CBCT images and showed that accurate dose calculation is feasible [13][14][15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a novel CBCT conversion method implemented in a treatment planning system

Lechner

Kanalas

Haupt

et al. 2023

Preprint

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Background: To evaluate a novel CBCT conversion algorithm for dose calculation implemented in a research version of a treatment planning system (TPS). Methods: The algorithm was implemented in a research version of RayStation (v. 11B-DTK, RaySearch, Stockholm, Sweden). CBCTs acquired for each ten head and neck (HN), gynecology (GYN) and lung cancer (LNG) patients were collected and converted using the new algorithm (CBCTc). A bulk density overriding technique implemented in the same version of the TPS was used for comparison (CBCTb). A deformed CT (dCT) was created by using deformable image registration of the planning CT (pCT) to the CBCT to reduce anatomical changes. All treatment plans were recalculated on the pCT, dCT, CBCTc and the CBCTb. The resulting dose distributions were analyzed using the MICE toolkit (NONPIMedical AB Sweden, Umeå) with local gamma analysis, with 1% dose difference and 1 mm distance to agreement criteria. A Wilcoxon paired rank sum test was applied to test the differences in gamma pass rates (GPRs). A p-value smaller than 0.05 considered statistically significant. Results: The GPRs for the CBCTb method were systematically lower compared to the CBCTc method. Using the 10% dose threshold and the dCT as reference the median GPRs were for the CBCTc method were 100% and 99.8% for the HN and GYN cases, respectively. Compared to that the GPRs of the CBCTb method were lower with values of 99.8% and 98.0%, for the HN and GYN cases, respectively. The GPRs of the LNG cases were 99.9% and 97.5% for the CBCTc and CBCTb method, respectively. These differences were statistically significant. The main differences between the dose calculated on the CBCTs and the pCTs were found in regions near air/tissue interfaces, which are also subject to anatomical variations. Conclusion: The dose distribution calculated using the new CBCTc method showed excellent agreement with the dose calculated using dCT and pCT and was superior to the CBCTb method. The main reasons for deviations of the calculated dose distribution were caused by anatomical variations between the pCT and the corrected CBCT.

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Daily dose evaluation based on corrected CBCTs for breast cancer patients: accuracy of dose and complication risk assessment

Cited by 6 publications

References 49 publications

Generation and evaluation of anatomy‐preserving virtual CT for online adaptive proton therapy

Generation and evaluation of anatomy‐preserving virtual CT for online adaptive proton therapy

CBCT-Based Dose Monitoring and Adaptive Planning Triggers in Head and Neck PBS Proton Therapy

Evaluation of a novel CBCT conversion method implemented in a treatment planning system

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