Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy

Standard

Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy. / Serpa, Marco; Baier, Kurt; Cremers, Florian; Guckenberger, Matthias; Meyer, Juergen.

In: MED PHYS, Vol. 41, No. 3, 03.2014, p. 031702.

Research output: SCORING: Contribution to journalSCORING: Journal articleResearchpeer-review

Harvard

Serpa, M, Baier, K, Cremers, F, Guckenberger, M & Meyer, J 2014, 'Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy', MED PHYS, vol. 41, no. 3, pp. 031702. https://doi.org/10.1118/1.4863597

APA

Serpa, M., Baier, K., Cremers, F., Guckenberger, M., & Meyer, J. (2014). Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy. MED PHYS, 41(3), 031702. https://doi.org/10.1118/1.4863597

Vancouver

Bibtex

@article{d52a538f984f4f089d3955f395bc306d,
title = "Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy",
abstract = "PURPOSE: To maximize the benefits of respiratory gated radiotherapy (RGRT) of lung tumors real-time verification of the tumor position is required. This work investigates the feasibility of markerless tracking of lung tumors during beam-on time in electronic portal imaging device (EPID) images of the MV therapeutic beam.METHODS: EPID movies were acquired at ∼2 fps for seven lung cancer patients with tumor peak-to-peak motion ranges between 7.8 and 17.9 mm (mean: 13.7 mm) undergoing stereotactic body radiotherapy. The external breathing motion of the abdomen was synchronously measured. Both datasets were retrospectively analyzed in PortalTrack, an in-house developed tracking software. The authors define a three-step procedure to run the simulations: (1) gating window definition, (2) gated-beam delivery simulation, and (3) tumor tracking. First, an amplitude threshold level was set on the external signal, defining the onset of beam-on/-off signals. This information was then mapped onto a sequence of EPID images to generate stamps of beam-on/-hold periods throughout the EPID movies in PortalTrack, by obscuring the frames corresponding to beam-off times. Last, tumor motion in the superior-inferior direction was determined on portal images by the tracking algorithm during beam-on time. The residual motion inside the gating window as well as target coverage (TC) and the marginal target displacement (MTD) were used as measures to quantify tumor position variability.RESULTS: Tumor position monitoring and estimation from beam's-eye-view images during RGRT was possible in 67% of the analyzed beams. For a reference gating window of 5 mm, deviations ranging from 2% to 86% (35% on average) were recorded between the reference and measured residual motion. TC (range: 62%-93%; mean: 77%) losses were correlated with false positives incidence rates resulting mostly from intra-/inter-beam baseline drifts, as well as sudden cycle-to-cycle fluctuations in exhale positions. Both phenomena can lead to considerable deviations (with MTD values up to a maximum of 7.8 mm) from the intended tumor position, and in turn may result in a marginal miss. The difference between tumor traces determined within the gating window against ground truth trajectory maps was 1.1 ± 0.7 mm on average (range: 0.4-2.3 mm).CONCLUSIONS: In this retrospective analysis of motion data, it is demonstrated that the system is capable of determining tumor positions in the plane perpendicular to the beam direction without the aid of fiducial markers, and may hence be suitable as an online verification tool in RGRT. It may be possible to use the tracking information to enable on-the-fly corrections to intra-/inter-beam variations by adapting the gating window by means of a robotic couch.",
keywords = "Algorithms, Computer Simulation, False Positive Reactions, Humans, Incidence, Lung Neoplasms, Movement, Radiosurgery, Radiotherapy, Radiotherapy Planning, Computer-Assisted, Radiotherapy, Computer-Assisted, Reproducibility of Results, Retrospective Studies, Software",
author = "Marco Serpa and Kurt Baier and Florian Cremers and Matthias Guckenberger and Juergen Meyer",
year = "2014",
month = mar,
doi = "10.1118/1.4863597",
language = "English",
volume = "41",
pages = "031702",
journal = "MED PHYS",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "3",

}

RIS

TY - JOUR

T1 - Suitability of markerless EPID tracking for tumor position verification in gated radiotherapy

AU - Serpa, Marco

AU - Baier, Kurt

AU - Cremers, Florian

AU - Guckenberger, Matthias

AU - Meyer, Juergen

PY - 2014/3

Y1 - 2014/3

N2 - PURPOSE: To maximize the benefits of respiratory gated radiotherapy (RGRT) of lung tumors real-time verification of the tumor position is required. This work investigates the feasibility of markerless tracking of lung tumors during beam-on time in electronic portal imaging device (EPID) images of the MV therapeutic beam.METHODS: EPID movies were acquired at ∼2 fps for seven lung cancer patients with tumor peak-to-peak motion ranges between 7.8 and 17.9 mm (mean: 13.7 mm) undergoing stereotactic body radiotherapy. The external breathing motion of the abdomen was synchronously measured. Both datasets were retrospectively analyzed in PortalTrack, an in-house developed tracking software. The authors define a three-step procedure to run the simulations: (1) gating window definition, (2) gated-beam delivery simulation, and (3) tumor tracking. First, an amplitude threshold level was set on the external signal, defining the onset of beam-on/-off signals. This information was then mapped onto a sequence of EPID images to generate stamps of beam-on/-hold periods throughout the EPID movies in PortalTrack, by obscuring the frames corresponding to beam-off times. Last, tumor motion in the superior-inferior direction was determined on portal images by the tracking algorithm during beam-on time. The residual motion inside the gating window as well as target coverage (TC) and the marginal target displacement (MTD) were used as measures to quantify tumor position variability.RESULTS: Tumor position monitoring and estimation from beam's-eye-view images during RGRT was possible in 67% of the analyzed beams. For a reference gating window of 5 mm, deviations ranging from 2% to 86% (35% on average) were recorded between the reference and measured residual motion. TC (range: 62%-93%; mean: 77%) losses were correlated with false positives incidence rates resulting mostly from intra-/inter-beam baseline drifts, as well as sudden cycle-to-cycle fluctuations in exhale positions. Both phenomena can lead to considerable deviations (with MTD values up to a maximum of 7.8 mm) from the intended tumor position, and in turn may result in a marginal miss. The difference between tumor traces determined within the gating window against ground truth trajectory maps was 1.1 ± 0.7 mm on average (range: 0.4-2.3 mm).CONCLUSIONS: In this retrospective analysis of motion data, it is demonstrated that the system is capable of determining tumor positions in the plane perpendicular to the beam direction without the aid of fiducial markers, and may hence be suitable as an online verification tool in RGRT. It may be possible to use the tracking information to enable on-the-fly corrections to intra-/inter-beam variations by adapting the gating window by means of a robotic couch.

AB - PURPOSE: To maximize the benefits of respiratory gated radiotherapy (RGRT) of lung tumors real-time verification of the tumor position is required. This work investigates the feasibility of markerless tracking of lung tumors during beam-on time in electronic portal imaging device (EPID) images of the MV therapeutic beam.METHODS: EPID movies were acquired at ∼2 fps for seven lung cancer patients with tumor peak-to-peak motion ranges between 7.8 and 17.9 mm (mean: 13.7 mm) undergoing stereotactic body radiotherapy. The external breathing motion of the abdomen was synchronously measured. Both datasets were retrospectively analyzed in PortalTrack, an in-house developed tracking software. The authors define a three-step procedure to run the simulations: (1) gating window definition, (2) gated-beam delivery simulation, and (3) tumor tracking. First, an amplitude threshold level was set on the external signal, defining the onset of beam-on/-off signals. This information was then mapped onto a sequence of EPID images to generate stamps of beam-on/-hold periods throughout the EPID movies in PortalTrack, by obscuring the frames corresponding to beam-off times. Last, tumor motion in the superior-inferior direction was determined on portal images by the tracking algorithm during beam-on time. The residual motion inside the gating window as well as target coverage (TC) and the marginal target displacement (MTD) were used as measures to quantify tumor position variability.RESULTS: Tumor position monitoring and estimation from beam's-eye-view images during RGRT was possible in 67% of the analyzed beams. For a reference gating window of 5 mm, deviations ranging from 2% to 86% (35% on average) were recorded between the reference and measured residual motion. TC (range: 62%-93%; mean: 77%) losses were correlated with false positives incidence rates resulting mostly from intra-/inter-beam baseline drifts, as well as sudden cycle-to-cycle fluctuations in exhale positions. Both phenomena can lead to considerable deviations (with MTD values up to a maximum of 7.8 mm) from the intended tumor position, and in turn may result in a marginal miss. The difference between tumor traces determined within the gating window against ground truth trajectory maps was 1.1 ± 0.7 mm on average (range: 0.4-2.3 mm).CONCLUSIONS: In this retrospective analysis of motion data, it is demonstrated that the system is capable of determining tumor positions in the plane perpendicular to the beam direction without the aid of fiducial markers, and may hence be suitable as an online verification tool in RGRT. It may be possible to use the tracking information to enable on-the-fly corrections to intra-/inter-beam variations by adapting the gating window by means of a robotic couch.

KW - Algorithms

KW - Computer Simulation

KW - False Positive Reactions

KW - Humans

KW - Incidence

KW - Lung Neoplasms

KW - Movement

KW - Radiosurgery

KW - Radiotherapy

KW - Radiotherapy Planning, Computer-Assisted

KW - Radiotherapy, Computer-Assisted

KW - Reproducibility of Results

KW - Retrospective Studies

KW - Software

U2 - 10.1118/1.4863597

DO - 10.1118/1.4863597

M3 - SCORING: Journal article

C2 - 24593706

VL - 41

SP - 031702

JO - MED PHYS

JF - MED PHYS

SN - 0094-2405

IS - 3

ER -