Clinical translation of a new flat-panel detector for beam’s-eye-view imaging

Harris, Thomas C.; Seco, Joao; Ferguson, D.; Lehmann, Mathias; Huber, Pascal; Shi, Mengze; Jacobson, M.; Lozano, Ingrid Valencia; Myronakis, Marios; Baturin, Paul; Fueglistaller, Rony; Morf, Daniel; Berbeco, R.

doi:10.1088/1361-6560/abb571

Cited by 6 publications

(15 citation statements)

References 41 publications

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“…However, DE image contrast may be inferior using this approach since the mean energy separation between the two images is small. [79][80][81] More recently, there has been interest in the use of photon counting detectors to provide spectral separation which may be used to remove overlaying bone on kV-projections. [82][83][84][85][86] Furthermore, machine learning approaches, especially deep learning approaches, have been applied to segment kVprojections.…”

Section: F I G U R Ementioning

confidence: 99%

The markerless lung target tracking AAPM Grand Challenge (MATCH) results

et al. 2021

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Purpose: Lung stereotactic ablative body radiotherapy (SABR) is a radiation therapy success story with level 1 evidence demonstrating its efficacy. To provide real-time respiratory motion management for lung SABR, several commercial and preclinical markerless lung target tracking (MLTT) approaches have been developed. However, these approaches have yet to be benchmarked using a common measurement methodology. This knowledge gap motivated the MArkerless lung target Tracking CHallenge (MATCH). The aim was to localize lung targets accurately and precisely in a retrospective in silico study and a prospective experimental study. Methods: MATCH was an American Association of Physicists in Medicine sponsored Grand Challenge. Common materials for the in silico and experimental studies were the experiment setup including an anthropomorphic thorax phantom with two targets within the lungs, and a lung SABR planning protocol. The phantom was moved rigidly with patient-measured lung target motion traces, which also acted as ground truth motion. In the retrospective in silico study a volumetric modulated arc therapy treatment was simulated and a dataset consisting of treatment planning data and intra-treatment kilovoltage (kV) and megavoltage (MV) images for four blinded lung motion traces was provided to the participants. The participants used their MLTT approach to localize the moving target based on the dataset. In the experimental study, the participants received the phantom experiment setup and five patient-measured lung motion traces. The participants used their MLTT approach to localize the moving target during an experimental SABR phantom treatment. The challenge was open to any participant, and participants could complete either one or both parts of the challenge. For both the in silico and experimental studies the MLTT results were

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Section: F I G U R Ementioning

confidence: 99%

The markerless lung target tracking AAPM Grand Challenge (MATCH) results

et al. 2021

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“…It is anticipated that the CNR versus dose relationship could be further improved in all of these acquisition modes through the integration of a high-efficiency multilayer detector in the 2.5 MV sintered diamond target beamline. 3,7…”

Section: Discussionmentioning

confidence: 99%

“…Despite the low DQE of the standard as1000 flat‐panel detector in the 2.5 MV beamline, current and previous results combined demonstrate improved CNR versus dose characteristics in planar, CBCT and VOI CBCT imaging compared to the commercial beam. It is anticipated that the CNR versus dose relationship could be further improved in all of these acquisition modes through the integration of a high‐efficiency multi‐layer detector in the 2.5 MV sintered diamond target beamline 3,7 …”

Section: Discussionmentioning

confidence: 99%

“…In the thin phantom, the 2.5 MV diamond CNR was greater than the commercial imaging beam by factors of up to 1.3 and 1.7 times for the lung and bone 800 mg/cm 3 inserts, respectively, at doses of approximately 2 cGy, for example. At doses beyond 5 cGy, 3) bone (800 mg/cm 3 ), ( 4) lung (inhale), ( 5) bone (200 mg/cm 3 ) this CNR improvement factor reduced to between 1.15 and 1.25 for the lung and bone 800 mg/ cm 3 materials. While the 2.5 MV diamond target beam displays superior CNR compared to the commercial copper target beam, all of the kV acquired CBCTs demonstrated CNR values much higher than what was acquired with the MV beams for a small fraction of the dose (i.e.,mGy vs.cGy).…”

Section: Diamond Target Beam Cone Beam Ct Image Qualitymentioning

confidence: 93%

“…Kilovoltage x-ray image guidance offers favorable image quality and dose characteristics, but kV onboard imaging incurs increased cost, maintenance, and introduces its own uncertainties 1 ;while for planar imaging,lacks the advantageous perspective of the treatment beams-eyeview. 2 Numerous efforts have focused on improvement of MV imaging systems with regard to both detectors and beam production, including the ongoing development of efficient multilayer detectors 3,4 and the recent installation of the 2.5 MV imaging beam on the modern TrueBeam (Varian Medical Systems, Palo Alto, CA) treatment unit.…”

Section: Introductionmentioning

confidence: 99%

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Improving image quality and reducing dose with 2.5 MV diamond target volume‐of‐interest cone beam CT imaging

2022

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Purpose Over the past decades, continuous efforts have been made to improve megavoltage (MV) image quality versus dose characteristics, including the implementation of low atomic number (Z) targets in MV beamlines and the development of more efficient detectors. Recently, a diamond target beam within a commercial radiotherapy treatment platform demonstrated improved planar contrast‐to‐noise‐ratio (CNR) per unit dose using a novel 2.5 MV sintered diamond target beam, which enabled image acquisition on the order of mGy. The present work assesses cone beam CT (CBCT) image quality characteristics for the novel 2.5 MV diamond target beam and the effects of volume‐of‐interest (VOI) collimation on the image quality and imaging dose distribution. Methods A sintered diamond target was incorporated into the target arm of the linear accelerator, replacing the 2.5 MV commercial copper imaging target. CBCT image quality was evaluated against the commercial imaging beam with regard to spatial resolution and CNR versus dose. In addition to full‐field acquisitions, we investigated VOI techniques that collimate the imaging beam to preselected anatomy, to determine potential image quality improvements and dose sparing capacity. Using an anthropomorphic phantom, VOI regions were defined to encompass the maxillary and ethmoid sinuses and ranged in dimension from 3 cm to 4.85 cm equivalent radius. The MLC was fit to each VOI structure throughout a full CBCT arc and the corresponding MLC sequences were produced as XML scripts for acquisition. Calibrated radiochromic film was used in phantom to measure cumulative axial dose distributions during each CBCT acquisition. Results In full‐field CBCT, the 2.5 MV diamond target beam demonstrated improved CNR versus dose compared to the commercial imaging beam, by factors of up to 1.7. The calculated modulation transfer function (MTF) displayed an increase of nearly 30% in f50 for the 2.5 MV diamond target beam compared to the commercial beam. Using VOI techniques, CNR increased monotonically as a function of equivalent radius at the bone–tissue interface. At the bone–sinus interface, the CNR for the full‐field case was slightly decreased compared to the largest VOI case. Imaging dose in the anteroposterior direction increased with increasing VOI equivalent radius. Conclusion The novel 2.5 MV sintered diamond target beam presents a simple modification to the commercial imaging beam which provides improved image quality in full‐field CBCT and the potential for simultaneous dose sparing and CNR improvement at high‐contrast interfaces using VOI acquisition techniques.

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Improvements in beam’s eye view fiducial tracking using a novel multilayer imager

Harris¹,

Seco²,

Ferguson³

et al. 2021

Phys. Med. Biol.

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Purpose. Electronic portal image devices (EPIDs) have been investigated previously for beams-eye view (BEV) applications such as tumor tracking but are limited by low contrast-to-noise ratio and detective quantum efficiency. A novel multilayer imager (MLI), consisting of four stacked flat-panels was used to measure improvements in fiducial tracking during liver stereotactic body radiation therapy (SBRT) procedures compared to a single layer EPID. Methods. The prototype MLI was installed on a clinical TrueBeam linac in place of the conventional DMI single-layer EPID. The panel was extended during volumetric modulated arc therapy SBRT treatments in order to passively acquire data during therapy. Images were acquired for six patients receiving SBRT to liver metastases over two fractions each, one with the MLI using all 4 layers and one with the MLI using the top layer only, representing a standard EPID. The acquired frames were processed by a previously published tracking algorithm modified to identify implanted radiopaque fiducials. Truth data was determined using respiratory traces combined with partial manual tracking. Results for 4- and 1-layer mode were compared against truth data for tracking accuracy and efficiency. Tracking and noise improvements as a function of gantry angle were determined. Results. Tracking efficiency with 4-layers improved to 82.8% versus 58.4% for the 1-layer mode, a relative improvement of 41.7%. Fiducial tracking with 1-layer returned a root mean square error (RMSE) of 2.1 mm compared to 4-layer RMSE of 1.5 mm, a statistically significant (p < 0.001) improvement of 0.6 mm. The reduction in noise correlated with an increase in successfully tracked frames (r = 0.913) and with increased tracking accuracy (0.927). Conclusion. Increases in MV photon detection efficiency by utilization of a MLI results in improved fiducial tracking for liver SBRT treatments. Future clinical applications utilizing BEV imaging may be enhanced by including similar noise reduction strategies.

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Clinical translation of a new flat-panel detector for beam’s-eye-view imaging

Cited by 6 publications

References 41 publications

The markerless lung target tracking AAPM Grand Challenge (MATCH) results

The markerless lung target tracking AAPM Grand Challenge (MATCH) results

Improving image quality and reducing dose with 2.5 MV diamond target volume‐of‐interest cone beam CT imaging

Improvements in beam’s eye view fiducial tracking using a novel multilayer imager

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