Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters

Dowdell, S; Grassberger, Clemens; Sharp, G; Paganetti, Harald

doi:10.1088/0031-9155/58/12/4137

Cited by 129 publications

(174 citation statements)

References 41 publications

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“…As multiple beam paintings of four are clinically achievable, we believe that the dosimetric advantage of PBS treatment in this patient will be able to be maintained despite the interplay phenomenon. These observations are consistent with that reported by many researchers 4 , 18 , 19 , 20 , 21 . Because the breathing period and beam duration can vary from patient to patient, detailed assessment of the interplay effect for multiple patients and multiple motion mitigation strategies is the subject of current investigation within our group.…”

Section: Discussionsupporting

confidence: 91%

“… 18 , 19 , 20 , 21 In this study we demonstrate such an interplay phenomenon for a representative thoracic patient.…”

Section: Introductionsupporting

confidence: 53%

“…The method we used to evaluate beam interplay is similar to Zou et al (33) for conventional lung SBRT applications and other researchers for PBS applications 11 , 12 , 18 , 19 , 21 . A representative patient is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

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Beam‐specific planning target volumes incorporating 4D CT for pencil beam scanning proton therapy of thoracic tumors

Lin

Kang

Huang

et al. 2015

J Applied Clin Med Phys

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The purpose of this study is to determine whether organ sparing and target coverage can be simultaneously maintained for pencil beam scanning (PBS) proton therapy treatment of thoracic tumors in the presence of motion, stopping power uncertainties, and patient setup variations. Ten consecutive patients that were previously treated with proton therapy to 66.6/1.8 Gy (RBE) using double scattering (DS) were replanned with PBS. Minimum and maximum intensity images from 4D CT were used to introduce flexible smearing in the determination of the beam specific PTV (BSPTV). Datasets from eight 4D CT phases, using ±3% uncertainty in stopping power and ±3 mm uncertainty in patient setup in each direction, were used to create 8×12×10=960 PBS plans for the evaluation of 10 patients. Plans were normalized to provide identical coverage between DS and PBS. The average lung V20, V5, and mean doses were reduced from 29.0%, 35.0%, and 16.4 Gy with DS to 24.6%, 30.6%, and 14.1 Gy with PBS, respectively. The average heart V30 and V45 were reduced from 10.4% and 7.5% in DS to 8.1% and 5.4% for PBS, respectively. Furthermore, the maximum spinal cord, esophagus, and heart doses were decreased from 37.1 Gy, 71.7 Gy, and 69.2 Gy with DS to 31.3 Gy, 67.9 Gy, and 64.6 Gy with PBS. The conformity index (CI), homogeneity index (HI), and global maximal dose were improved from 3.2, 0.08, 77.4 Gy with DS to 2.8, 0.04, and 72.1 Gy with PBS. All differences are statistically significant, with p‐values <0.05, with the exception of the heart V45 (p=0.146). PBS with BSPTV achieves better organ sparing and improves target coverage using a repainting method for the treatment of thoracic tumors. Incorporating motion‐related uncertainties is essential.PACS number: 87.55.D

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Section: Discussionsupporting

confidence: 91%

“… 18 , 19 , 20 , 21 In this study we demonstrate such an interplay phenomenon for a representative thoracic patient.…”

Section: Introductionsupporting

confidence: 53%

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Beam‐specific planning target volumes incorporating 4D CT for pencil beam scanning proton therapy of thoracic tumors

Lin

Kang

Huang

et al. 2015

J Applied Clin Med Phys

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“…[3,4]) which did not actually treat patients with PBS. Due to its time structure, beam scanning is more susceptible to intra-fractional motion when compared with passive scattering [5]. However, PBS has the ability to conform to the target three-dimensionally.…”

Section: Introductionmentioning

confidence: 99%

Proton pencil beam scanning for mediastinal lymphoma: treatment planning and robustness assessment

et al. 2016

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Background: Modern radiotherapy (RT) for lymphoma is highly personalized. While advanced imaging is largely employed to define limited treatment volumes, the use of proton pencil beam scanning (PBS) for highly conformal lymphoma RT is still in its infancy. Here, we assess the dosimetric benefits and feasibility of PBS for mediastinal lymphoma (ML). Materials and methods: Ten patients were planned using PBS for involved-site RT. The initial plans were calculated on the average four-dimensional computed tomography (4D-CT). PBS plans were compared with 3D conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and proton double scattering (DS). In order to evaluate the feasibility of PBS and the plan robustness against interand intra-fractional uncertainties, the 4D dose was calculated on initial and verification CTs. The deviation of planned dose from delivered dose was measured. The same proton beamline was used for all patients, while another beamline with larger spots was employed for patients with large motion perpendicular to the beam. Results: PBS provided the lowest mean lung dose (MLD) and mean heart dose (MHD) for all patients in comparison with 3D-CRT, IMRT, and DS. For eight patients, internal target volume (ITV) D 98% was degraded by <3%; and the MLD and MHD deviated by <10% of prescription over the course of treatment when the PBS field was painted twice in each session. For one patient with target motion perpendicular to the beam (>5 mm), the degradation of ITV D 98% was 9%, which was effectively mitigated by employing large spots. One patient exhibited large dose degradation due to pericardial effusion, which required replanning across all modalities. Conclusions: This study demonstrates that PBS plans significantly reduce MLD and MHD relative to 3D-CRT, IMRT, and DS and identifies requirements for robust free-breathing ML PBS treatments, showing that PBS plan robustness can be maintained with repainting and/or large spots.

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“…Several previous studies have investigated motion and interplay effects in proton [4][5][6][7] and carbon ion therapy. [8][9][10] These investigations of the interplay effect in proton and ion therapy have typically used single-field uniform dose (SFUD) fields that each deliver homogeneous target doses.…”

Section: Introductionmentioning

confidence: 99%

Four‐dimensional Monte Carlo simulations demonstrating how the extent of intensity‐modulation impacts motion effects in proton therapy lung treatments

2013

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Purpose:To compare motion effects in intensity modulated proton therapy (IMPT) lung treatments with different levels of intensity modulation. Methods: Spot scanning IMPT treatment plans were generated for ten lung cancer patients for 2.5Gy(RBE) and 12Gy(RBE) fractions and two distinct energy-dependent spot sizes (σ ∼8-17 mm and ∼2-4 mm). IMPT plans were generated with the target homogeneity of each individual field restricted to <20% (IMPT 20% ). These plans were compared to full IMPT (IMPT full ), which had no restriction on the single field homogeneity. 4D Monte Carlo simulations were performed upon the patient 4DCT geometry, including deformable image registration and incorporating the detailed timing structure of the proton delivery system. Motion effects were quantified via comparison of the results of the 4D simulations (4D-IMPT 20% , 4D-IMPT full ) with those of a 3D Monte Carlo simulation (3D-IMPT 20% , 3D-IMPT full ) upon the planning CT using the equivalent uniform dose (EUD), V 95 and D 1 -D 99 . The effects in normal lung were quantified using mean lung dose (MLD) and V 90% . Results: For 2.5Gy(RBE), the mean EUD for the large spot size is 99.9% ± 2.8% for 4D-IMPT 20% compared to 100.1% ± 2.9% for 4D-IMPT full . The corresponding values are 88.6% ± 8.7% (4D-IMPT 20% ) and 91.0% ± 9.3% (4D-IMPT full ) for the smaller spot size. The EUD value is higher in 69.7% of the considered deliveries for 4D-IMPT full . The V 95 is also higher in 74.7% of the plans for 4D-IMPT full , implying that IMPT full plans experience less underdose compared to IMPT 20% . However, the target dose homogeneity is improved in the majority (67.8%) of plans for 4D-IMPT 20% . The higher EUD and V 95 suggests that the degraded homogeneity in IMPT full is actually due to the introduction of hot spots in the target volume, perhaps resulting from the sharper in-target dose gradients. The greatest variations between the IMPT 20% and IMPT full deliveries are observed for patients with the largest motion amplitudes. These patients would likely be treated using gating or another motion mitigation technique, which was not the focus of this study. Conclusions: For the treatment parameters considered in this study, the differences between IMPT full and IMPT 20% are only likely to be clinically significant for patients with large (>20 mm) motion amplitudes.

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Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters

Cited by 129 publications

References 41 publications

Beam‐specific planning target volumes incorporating 4D CT for pencil beam scanning proton therapy of thoracic tumors

Beam‐specific planning target volumes incorporating 4D CT for pencil beam scanning proton therapy of thoracic tumors

Proton pencil beam scanning for mediastinal lymphoma: treatment planning and robustness assessment

Four‐dimensional Monte Carlo simulations demonstrating how the extent of intensity‐modulation impacts motion effects in proton therapy lung treatments

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