Validation of the collapsed cone algorithm for HDR liver brachytherapy against Monte Carlo simulations

Duque, Anna Sophie; Wagenberg, T. van; Seidensticker, Max; Streitparth, Florian; Walter, Franziska; Parodi, Katia; Verhaegen, Frank; Ricke, Jens; Belka, Claus; Fonseca, Gabriel Paiva; Corradini, Stefanie; Landry, Guillaume

doi:10.1016/j.brachy.2021.03.018

Cited by 2 publications

(1 citation statement)

References 35 publications

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“…We included a considerable number of patients with metastases in less-favorable localizations (close to OARs, central lesions). Therefore, a number of lesions could not be treated with the prescribed dose, but had a compromised dose to spare adjacent risk structures or to reduce overall liver exposure [ 36 , 37 ]. We conducted a sub-group analysis in patients with CRC that received a minimal dose of 20 Gy (D100) in all treated lesions in each individual fraction and compared it to patients with compromised dose coverage.…”

Section: Discussionmentioning

confidence: 99%

Interstitial High-Dose-Rate Brachytherapy of Liver Metastases in Oligometastatic Patients

Walter

Rottler

Nierer

et al. 2021

Cancers

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Local ablative treatments have emerged as a promising treatment strategy for patients with oligometastatic disease. Among others, interstitial brachytherapy (iBT) is an upcoming treatment option for unresectable liver metastases. We report the feasibility and oncologic outcome of iBT of oligometastatic liver metastases performed in patients with limited tumor burdens in a high-volume center. Patients undergoing iBT between August 2017and March 2019 were included. A retrospective analysis of patient outcomes and treatment complications was performed. Patients treated for metastatic colorectal carcinoma (CRC) were compared to other histologies. A total of 141 iBT procedures were performed in 106 patients (male:52; female:54) and 244 liver metastases. Overall, 51% (54/106) of patients had a diagnosis of metastatic CRC. The median follow-up was 9 months, and overall survival (OS) was 92.3% at 6 months and 76.3% at 12 months. Local-relapse-free survival (LRFS) was 88.4% at 6 months and 71.5% at 12 months, with a significant difference between patients with CRC (84.1% and 50.6%) versus other histologies (92.4% and 92.4%, p < 0.001). A sub-group analysis showed a significant advantage in patients with CRC receiving a minimal dose (D100) of 20 Gy to the planning target volume. Treatments of smaller total liver-tumor volumes (<18 ccm) resulted in better LRFS rates. iBT is a safe and effective treatment approach for oligometastatic liver disease. A higher treatment dose is needed for patients with CRC. Moreover, lower metastatic burdens may be favorable for LRFS. Prospective studies are needed to assess the role of iBT in the oligometastatic setting as an alternative to other local ablative treatment approaches in patients with liver metastases.

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Section: Discussionmentioning

confidence: 99%

Interstitial High-Dose-Rate Brachytherapy of Liver Metastases in Oligometastatic Patients

Walter

Rottler

Nierer

et al. 2021

Cancers

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Improved heterogeneity handling in the collapsed cone dose engine for brachytherapy

Alpsten,

van Veelen,

Valdes‐Cortez

et al. 2024

Medical Physics

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BackgroundModel‐based dose calculation algorithms (MBDCA), such as the Advanced Collapsed cone Engine (ACE) in Oncentra Brachy® can be used to overcome the limitations of the TG‐43 formalism. ACE is a point kernel superposition algorithm that calculates the total dose separated into primary, first‐scatter, and multiple‐scatter dose. Albeit ACE yields accurate results under most circumstances, several studies have reported underestimations of the dose to cortical bone. These underestimations are likely caused by approximations in the handling of multiple‐scatter dose for non‐water media. Such would result in noticeable deviations where the multiple‐scatter is a considerable fraction of the total dose, that is, at greater distances from the source.PurposeTo improve and test the accuracy of the multiple‐scatter dose component in the ACE algorithm to remedy its inaccuracy for non‐water geometries.MethodsA careful analysis of the transport and absorption of the multiple‐scatter energy fluence revealed an inconsistency in the scaling of energy absorption ratios for non‐water media of the multiple‐scatter kernel. We implemented an updated algorithm version, ACEcorr, and tested it for three different geometries. All had a single 192Ir‐source at the center of a cubic water phantom with a box‐shaped heterogeneity of either cortical bone or air, positioned at different distances from the source. Dose distributions for the three cases were calculated with ACE and ACEcorr and compared to Monte Carlo simulations, using the percentage dose difference ratio as figure‐of‐merit. All dose calculation methods scored separately the dose deposited by primary, first‐scattered, and multiple‐scattered photons.ResultsThe accuracy of the updated algorithm ACEcorr was superior to ACE. In the cortical bone heterogeneity, the mean percentage dose difference ratio for the total dose improved from to (in the worst case) by our update. Less impact was seen in the air heterogeneity, where both ACE and ACEcorr deviated less than 2% from the Monte Carlo results. The algorithm update mainly concerns the multiple‐scattered dose component, but an accompanying data processing update also had a small effect (0.5% difference) on the primary and first‐scattered dose. The calculation times were not affected.ConclusionsThe updates to ACE improved the accuracy of multiple‐scatter dose calculation for non‐water media, without increasing calculation times.

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Validation of the collapsed cone algorithm for HDR liver brachytherapy against Monte Carlo simulations

Cited by 2 publications

References 35 publications

Interstitial High-Dose-Rate Brachytherapy of Liver Metastases in Oligometastatic Patients

Interstitial High-Dose-Rate Brachytherapy of Liver Metastases in Oligometastatic Patients

Improved heterogeneity handling in the collapsed cone dose engine for brachytherapy

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