Dosimetric Changes Resulting From Patient Rotational Setup Errors in Proton Therapy Prostate Plans

Sejpal, Samir; Amos, R.; Bluett, J.; Levy, Lawrence B.; Kudchadker, Rajat J.; Johnson, Jennifer L.; Choi, Seungtaek; Lee, Andrew K.

doi:10.1016/j.ijrobp.2008.08.042

Cited by 25 publications

(20 citation statements)

References 14 publications

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“…However, the clinical signi icance of rotational error depends on disease site and treatment technique. As reported by Sejpal et al [22], the impact of rotational error of 3° and 5° for passive scattering proton therapy of prostate did not signi icantly change the dose to target coverage and critical organs; however, a rotational error of 2° or more would lead to substantial target under coverage for lung cancer treatment using intensity modulated proton therapy as reported by Suresh et al [23]. Note that while more freedom of correction such as 5D or 6D registration would allow more accurate patient positioning, it could also add additional complexity in image registration, leading potential larger interobserver variability.…”

Section: Discussionsupporting

confidence: 53%

Inter-Observer Variability of a Commercial Patient Positioning and Verification System in Proton Therapys

Zheng¹

2017

J Radiol Oncol

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Purpose: Accurate patient positioning is crucial in radiation therapy. To fully benefi t from the preciseness of proton therapy, image guided patient positioning and verifi cation system is typically utilized in proton therapy. The purpose of this study is to evaluate the inter-observer variability of image alignment using a commercially available patient positioning and verifi cation system in proton therapy. Methods:The VeriSuite patient positioning and verifi cation system (MedCom GmbH, Darmstadt, Germany) provides a six degrees of freedom correction vector by registering two orthogonal x-ray images to digitally reconstructed radiograph (DRR) images that are rendered in real time from the planning computed tomography (CT) images. Six cases of various disease sites, including brain, head & neck, lung, prostate, pelvis, and bladder, were used in this study. For each case, the planning CT images and a daily orthogonal x-ray portal image pair were loaded into the VeriSuite system. The same set of x-ray images and CT images for each case were reviewed and aligned separately by each of the 10 radiation therapist, following the clinical procedure for the corresponding disease site. The resulting correction vectors were then recorded and analyzed.Results: Our study shows that the inter-observer variation (One standard deviation) in image alignment using the VeriSuite system ranged from 1.2 to 2.0 mm for translational correction and from 0.6 to 1.3 degrees for rotational correction for the six cases. The use of fi ducial markers for prostate patient alignment achieved the least inter-observer variation while the bladder case produced the largest. Conclusions:Inter-observer variation in image alignment could be relatively large, depending on the complexity of patient anatomy, image alignment approach, and user experience and software limitations. Automatic registration and fi ducial markers could potentially be used to align patient more accurately and consistently. To ensure adequate tumor coverage in proton therapy, inter-observer variability in patient alignment should be carefully evaluated and accounted for in patient setup uncertainty analysis and treatment planning margin determination.

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Section: Discussionsupporting

confidence: 53%

Inter-Observer Variability of a Commercial Patient Positioning and Verification System in Proton Therapys

Zheng¹

2017

J Radiol Oncol

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“…A wide range of online position correction dosimetric effects have been observed and it is increasingly becoming a field of interest 10 , 11 , 12 , 13 , 14 . Several authors studied the target coverage of the prostate after applying translational position correction.…”

Section: Introductionmentioning

confidence: 99%

Adaptive optimization by 6 DOF robotic couch in prostate volumetric IMRT treatment: rototranslational shift and dosimetric consequences

Chiesa

Placidi

Azario

et al. 2015

J Applied Clin Med Phys

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The purpose of this study was to investigate the magnitude and dosimetric relevance of translational and rotational shifts on IGRT prostate volumetric‐modulated arc therapy (VMAT) using Protura six degrees of freedom (DOF) Robotic Patient Positioning System. Patients with cT3aN0M0 prostate cancer, treated with VMAT simultaneous integrated boost (VMAT‐SIB), were enrolled. PTV2 was obtained adding 0.7 cm margin to seminal vesicles base (CTV2), while PTV1 adding to prostate (CTV1) 0.7 cm margin in all directions, except 1.2 cm, as caudal margin. A daily CBCT was acquired before dose delivery. The translational and rotational displacements were corrected through Protura Robotic Couch, collected and applied to the simulation CT to obtain a translated CT (tCT) and a rototranslated CT (rtCT) on which we recalculated the initial treatment plan (TP). We analyzed the correlation between dosimetric coverage, organs at risk (OAR) sparing, and translational or rotational displacements. The dosimetric impact of a rototranslational correction was calculated. From October 2012 to September 2013, a total of 263 CBCT scans from 12 patients were collected. Translational shifts were <5mm in 81% of patients and the rotational shifts were <2∘ in 93% of patient scans. The dosimetric analysis was performed on 172 CBCT scans and calculating 344 VMAT‐TP. Two significant linear correlations were observed between yaw and the V20 femoral heads and between pitch rotation and V50 rectum (p<0.001); rototranslational correction seems to impact more on PTV2 than on PTV1, especially when margins are reduced. Rotational errors are of dosimetric significance in sparing OAR and in target coverage. This is relevant for femoral heads and rectum because of major distance from isocenter, and for seminal vesicles because of irregular shape. No correlation was observed between translational and rotational errors. A study considering the intrafractional error and the deformable registration is ongoing.PACS number: 87.55.de

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“…The literature does not show evidence justifying the use of 6DOF for extracranial treatments. Several studies have demonstrated that rotational errors have an insignificant effect on target coverage of the prostate . Mancosu et al .…”

Section: For the Proposition: Christopher F Njeh Phdmentioning

confidence: 99%

The use of six degrees of freedom couch is only clinically beneficial in stereotactic radio surgery

2019

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Dosimetric Changes Resulting From Patient Rotational Setup Errors in Proton Therapy Prostate Plans

Cited by 25 publications

References 14 publications

Inter-Observer Variability of a Commercial Patient Positioning and Verification System in Proton Therapys

Inter-Observer Variability of a Commercial Patient Positioning and Verification System in Proton Therapys

Adaptive optimization by 6 DOF robotic couch in prostate volumetric IMRT treatment: rototranslational shift and dosimetric consequences

The use of six degrees of freedom couch is only clinically beneficial in stereotactic radio surgery

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