Perturbation of water‐equivalent thickness as a surrogate for respiratory motion in proton therapy

Matney, Jason; Park, Peter C.; Li, Heng; Court, Laurence Edward; Zhu, X.R.; Dong, Lei; Liu, Wei; Mohan, Radhe

doi:10.1120/jacmp.v17i2.5795

Cited by 26 publications

(27 citation statements)

References 24 publications

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“…WET variation has the potential to produce a significantly different dose distribution for any defined sub‐portion of the respiratory cycle. Without motion management, movement of both the target and upstream normal tissues along the beam path (such as the diaphragm) can lead to unacceptable differences in planned vs delivered proton range . The severity of the effect is beam specific.…”

Section: Introductionmentioning

confidence: 99%

Clinical implementation of respiratory‐gated spot‐scanning proton therapy: An efficiency analysis of active motion management

Gelover

Deisher

Herman

et al. 2019

J Applied Clin Med Phys

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Purpose The aim of this work is to describe the clinical implementation of respiratory‐gated spot‐scanning proton therapy (SSPT) for the treatment of thoracic and abdominal moving targets. The experience of our institution is summarized, from initial acceptance and commissioning tests to the development of standard clinical operating procedures for simulation, motion assessment, motion mitigation, treatment planning, and gated SSPT treatment delivery. Materials and methods A custom respiratory gating interface incorporating the Real‐Time Position Management System (RPM, Varian Medical Systems, Inc., Palo Alto, CA, USA) was developed in‐house for our synchrotron‐based delivery system. To assess gating performance, a motion phantom and radiochromic films were used to compare gated vs nongated delivery. Site‐specific treatment planning protocols and conservative motion cutoffs were developed, allowing for free‐breathing (FB), breath‐holding (BH), or phase‐gating (Ph‐G). Room usage efficiency of BH and Ph‐G treatments was retrospectively evaluated using beam delivery data retrieved from our record and verify system and DICOM files from patient‐specific quality assurance (QA) procedures. Results More than 70 patients were treated using active motion management between the launch of our motion mitigation program in October 2015 and the end date of data collection of this study in January 2018. During acceptance procedures, we found that overall system latency is clinically‐suitable for Ph‐G. Regarding room usage efficiency, the average number of energy layers delivered per minute was <10 for Ph‐G, 10‐15 for BH and ≥15 for FB, making Ph‐G the slowest treatment modality. When comparing to continuous delivery measured during pretreatment QA procedures, the median values of BH treatment time were extended from 6.6 to 9.3 min (+48%). Ph‐G treatments were extended from 7.3 to 13.0 min (+82%). Conclusions Active motion management has been crucial to the overall success of our SSPT program. Nevertheless, our conservative approach has come with an efficiency cost that is more noticeable in Ph‐G treatments and should be considered in decision‐making.

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Section: Introductionmentioning

confidence: 99%

Clinical implementation of respiratory‐gated spot‐scanning proton therapy: An efficiency analysis of active motion management

Gelover

Deisher

Herman

et al. 2019

J Applied Clin Med Phys

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“…The range uncertainties are, therefore, closely coupled to the changes in the water equivalent path length (WEPL) of the proton pencil beams towards the target [13][14][15]. Robust optimization has been explored by several studies [6,12,[16][17][18]; however, only few studies have so far investigated the advantages of minimizing the WEPL in regard to beam angles for the purpose of identifying the most robust beam directions for proton therapy [13,[19][20][21][22]. In a previous study from our institution, Casarez-Magaz et al [13] investigated the correlation of WEPL variation with dose degradation on 4D-CT scans of lung cancer patients.…”

Section: Introductionmentioning

confidence: 99%

Beam angle evaluation to improve inter-fraction motion robustness in pelvic lymph node irradiation with proton therapy

et al. 2017

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“…Currently, it is difficult to evaluate the possible dosimetric error in advance of the treatment with enough temporal and spatial resolution. A novel technique to reconstruct cine‐4DCT[] with high‐temporal resolution may be applied to determine the gate size by evaluating the actual WEL variation according to the target location.…”

Section: Discussionmentioning

confidence: 99%

Dynamic gating window technique for the reduction of dosimetric error in respiratory‐gated spot‐scanning particle therapy: An initial phantom study using patient tumor trajectory data

Miyamoto

Kouhei

Sugiyama

et al. 2020

J Applied Clin Med Phys

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Spot-scanning particle therapy possesses advantages, such as high conformity to the target and efficient energy utilization compared with those of the passive scattering irradiation technique. However, this irradiation technique is sensitive to target motion. In the current clinical situation, some motion management techniques, such as respiratory-gated irradiation, which uses an external or internal surrogate, have been clinically applied. In surrogate-based gating, the size of the gating window is fixed during the treatment in the current treatment system. In this study, we propose a dynamic gating window technique, which optimizes the size of gating window for each spot by considering a possible dosimetric error. The effectiveness of the dynamic gating window technique was evaluated by simulating irradiation using a moving target in a water phantom. In dosimetric characteristics comparison, the dynamic gating window technique exhibited better performance in all evaluation volumes with different effective depths compared with that of the fixed gate approach. The variation of dosimetric characteristics according to the target depth was small in dynamic gate compared to fixed gate. These results suggest that the dynamic gating window technique can maintain an acceptable dose distribution regardless of the target depth. The overall gating efficiency of the dynamic gate was approximately equal or greater than that of the fixed gating window. In dynamic gate, as the target depth becomes shallower, the gating efficiency will be reduced, although dosimetric characteristics will be maintained regardless of the target depth.The results of this study suggest that the proposed gating technique may potentially improve the dose distribution. However, additional evaluations should be undertaken in the future to determine clinical applicability by assuming the specifications of the treatment system and clinical situation.

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Perturbation of water‐equivalent thickness as a surrogate for respiratory motion in proton therapy

Cited by 26 publications

References 24 publications

Clinical implementation of respiratory‐gated spot‐scanning proton therapy: An efficiency analysis of active motion management

Clinical implementation of respiratory‐gated spot‐scanning proton therapy: An efficiency analysis of active motion management

Beam angle evaluation to improve inter-fraction motion robustness in pelvic lymph node irradiation with proton therapy

Dynamic gating window technique for the reduction of dosimetric error in respiratory‐gated spot‐scanning particle therapy: An initial phantom study using patient tumor trajectory data

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