Intrafraction tumor motion monitoring and dose reconstruction for liver pencil beam scanning proton therapy

Frontiers in Oncology

Oncology

Jakob Borup Thomsen¹  Morten Høyer¹  Hanna Rahbek Mortensen¹  Line Bjerregaard Stick¹  Saber Nankali²  Britta Weber³  Per Rugaard Poulsen³  Esben Schjødt Worm⁴  Jenny Bertholet⁵ 

[1] Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark;Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark;Department of Clinical Medicine, Aarhus University, Aarhus, Denmark;Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark;Department of Oncology, Aarhus University Hospital, Aarhus, Denmark;Department of Oncology, Aarhus University Hospital, Aarhus, Denmark;Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland;

关键词: proton therapy;    pencil beam scanning;    dose reconstruction;    liver cancer;    motion management;    respiratory gating;    tumor motion monitoring (Min.5-Max. 8);   

DOI  :  10.3389/fonc.2023.1112481

 received in 2022-11-30, accepted in 2023-02-13,  发布年份 2023

来源: Frontiers

【 摘 要 】

BackgroundPencil beam scanning (PBS) proton therapy can provide highly conformal target dose distributions and healthy tissue sparing. However, proton therapy of hepatocellular carcinoma (HCC) is prone to dosimetrical uncertainties induced by respiratory motion. This study aims to develop intra-treatment tumor motion monitoring during respiratory gated proton therapy and combine it with motion-including dose reconstruction to estimate the delivered tumor doses for individual HCC treatment fractions.MethodsThree HCC-patients were planned to receive 58 GyRBE (n=2) or 67.5 GyRBE (n=1) of exhale respiratory gated PBS proton therapy in 15 fractions. The treatment planning was based on the exhale phase of a 4-dimensional CT scan. Daily setup was based on cone-beam CT (CBCT) imaging of three implanted fiducial markers. An external marker block (RPM) on the patient’s abdomen was used for exhale gating in free breathing. This study was based on 5 fractions (patient 1), 1 fraction (patient 2) and 6 fractions (patient 3) where a post-treatment control CBCT was available. After treatment, segmented 2D marker positions in the post-treatment CBCT projections provided the estimated 3D motion trajectory during the CBCT by a probability-based method. An external-internal correlation model (ECM) that estimated the tumor motion from the RPM motion was built from the synchronized RPM signal and marker motion in the CBCT. The ECM was then used to estimate intra-treatment tumor motion. Finally, the motion-including CTV dose was estimated using a dose reconstruction method that emulates tumor motion in beam’s eye view as lateral spot shifts and in-depth motion as changes in the proton beam energy. The CTV homogeneity index (HI) The CTV homogeneity index (HI) was calculated as D2% − D98%D50% ×100%.ResultsThe tumor position during spot delivery had a root-mean-square error of 1.3 mm in left-right, 2.8 mm in cranio-caudal and 1.7 mm in anterior-posterior directions compared to the planned position. On average, the CTV HI was larger than planned by 3.7%-points (range: 1.0-6.6%-points) for individual fractions and by 0.7%-points (range: 0.3-1.1%-points) for the average dose of 5 or 6 fractions.ConclusionsA method to estimate internal tumor motion and reconstruct the motion-including fraction dose for PBS proton therapy of HCC was developed and demonstrated successfully clinically.

【 授权许可】

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Copyright © 2023 Nankali, Worm, Thomsen, Stick, Bertholet, Høyer, Weber, Mortensen and Poulsen