WE‐AB‐207A‐08: BEST IN PHYSICS (IMAGING): Advanced Scatter Correction and Iterative Reconstruction for Improved Cone‐Beam CT Imaging On the TrueBeam Radiotherapy Machine

Wang, A; Paysan, Pascal; Brehm, Marcus; Maslowski, Alexander; Lehmann, Mathias; Messmer, Philippe; Munro, Peter; Yoon, Sung Ho; Star‐Lack, Josh; Seghers, Dieter

doi:10.1118/1.4957761

Cited by 6 publications

(6 citation statements)

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“…This commercially available iterative_CBCT algorithm presented here is different from other approaches focused on improving image quality of low-dose CBCT scans 17,28,31,44 in that it uses the same raw projection data from standard Truebeam CBCT acquisitions and applies software-only methods to improve low-contrast detection and soft-tissue visibility. 40,45,46 Consistent with results in the literature, 7 -10,13,17,23,30 -33,47 -49 iterative reconstruction uses physical constraints, such as regularization penalty terms to improve image quality by reducing image noise and enhancing CNR. This iterative reconstruction algorithm reduces noise and enhances low-contrast detection while maintaining spatial resolution relative to the standard (FDK-based) approach.…”

Section: Discussionsupporting

confidence: 64%

Evaluation and Clinical Application of a Commercially Available Iterative Reconstruction Algorithm for CBCT-Based IGRT

Mao

Liu

Gardner

et al. 2019

Technol Cancer Res Treat

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Purpose:We have quantitatively evaluated the image quality of a new commercially available iterative cone-beam computed tomography reconstruction algorithm over standard cone-beam computed tomography image reconstruction results.Methods:This iterative cone-beam computed tomography reconstruction pipeline uses a finite element solver (AcurosCTS)-based scatter correction and a statistical (iterative) reconstruction in addition to a standard kernel-based correction followed by filtered back-projection-based Feldkamp-Davis-Kress cone-beam computed tomography reconstruction. Standard full-fan half-rotation Head, half-fan full-rotation Head, and standard Pelvis cone-beam computed tomography protocols have been investigated to scan a quality assurance phantom via the following image quality metrics: uniformity, HU constancy, spatial resolution, low contrast detection, noise level, and contrast-to-noise ratio. An anthropomorphic head phantom was scanned for verification of noise reduction. Clinical patient image data sets for 5 head/neck patients and 5 prostate patients were qualitatively evaluated.Results:Quality assurance phantom study results showed that relative to filtered back-projection-based cone-beam computed tomography, noise was reduced from 28.8 ± 0.3 HU to a range between 18.3 ± 0.2 and 5.9 ± 0.2 HU for Full-Fan Head scans, from 14.4 ± 0.2 HU to a range between 12.8 ± 0.3 and 5.2 ± 0.3 HU for Half-Fan Head scans, and from 6.2 ± 0.1 HU to a range between 3.8 ± 0.1 and 2.0 ± 0.2 HU for Pelvis scans, with the iterative cone-beam computed tomography algorithm. Spatial resolution was marginally improved while results for uniformity and HU constancy were similar. For the head phantom study, noise was reduced from 43.6 HU to a range between 24.8 and 13.0 HU for a Full-Fan Head and from 35.1 HU to a range between 22.9 and 14.0 HU for a Half-Fan Head scan. The patient data study showed that artifacts due to photon starvation and streak artifacts were all reduced, and image noise in specified target regions were reduced to 62% ± 15% for 10 patients.Conclusion:Noise and contrast-to-noise ratio image quality characteristics were significantly improved using the iterative cone-beam computed tomography reconstruction algorithm relative to the filtered back-projection-based cone-beam computed tomography method. These improvements will enhance the accuracy of cone-beam computed tomography-based image-guided applications.

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Section: Discussionsupporting

confidence: 64%

Evaluation and Clinical Application of a Commercially Available Iterative Reconstruction Algorithm for CBCT-Based IGRT

Mao

Liu

Gardner

et al. 2019

Technol Cancer Res Treat

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“…This is most common in abdominal cases without fiducials that are located far from the diaphragm. For these cases, the iterative CBCT reconstruction algorithm, 23 an additional add‐on TrueBeam imaging feature, has been useful to improve image quality and target visibility on the amplitude‐gated CBCT. For the latter two instances where the target is not visible on fluoroscopy and the amplitude gate thresholds are estimated from either 4DCBCT motion analysis or the planning phases, the phase dial in the TrueBeam software can be used to correlate the current respiratory trace with phase.…”

Section: Discussionmentioning

confidence: 99%

“…This is most common in abdominal cases without fiducials that are located far from the diaphragm. For these cases, the iterative CBCT reconstruction algorithm, 23 The use of 4DCBCT and fluoroscopy in the daily pretreatment imaging process leads to an increase in patient imaging dose compared to non-gated treatments. However, the trade-off between imaging dose and the decreased treatment volumes achievable with accurately delivered gated treatments must be considered.…”

Section: B3 | Robustness To Irregular Breathingmentioning

confidence: 99%

“…This is most common in abdominal cases without fiducials that are located far from the diaphragm. For these cases, the iterative CBCT reconstruction algorithm, 23 | 127 consistent with the planning CT. If anatomy appears enlarged or blurred compared to the planning CT, this indicates that the amplitude gate is too wide and the gate thresholds are adjusted.…”

Section: B3 | Robustness To Irregular Breathingmentioning

confidence: 99%

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Implementation of free breathing respiratory amplitude‐gated treatments

Hickling

Veres

Moseley

et al. 2021

J Applied Clin Med Phys

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The purpose of this study was to provide guidance in developing and implementing a process for the accurate delivery of free breathing respiratory amplitude-gated treatments.Methods: A phase-based 4DCT scan is acquired at time of simulation and motion is evaluated to determine the exhale phases that minimize respiratory motion to an acceptable level. A phase subset average CT is then generated for treatment planning and a tracking structure is contoured to indicate the location of the target or a suitable surrogate over the planning phases. Prior to treatment delivery, a 4DCBCT is acquired and a phase subset average is created to coincide with the planning phases for an initial match to the planning CT. Fluoroscopic imaging is then used to set amplitude gate thresholds corresponding to when the target or surrogate is in the tracking structure. The final imaging prior to treatment is an amplitude-gated CBCT to verify both the amplitude gate thresholds and patient positioning. An amplitude-gated treatment is then delivered. This technique was commissioned using an in-house lung motion phantom and film measurements of a simple two-field 3D plan.Results: The accuracy of 4DCBCT motion and target position measurements were validated relative to 4DCT imaging. End to end testing showed strong agreement between planned and film measured dose distributions. Robustness to interuser variability and changes in respiratory motion were demonstrated through film measurements. Conclusions:The developed workflow utilizes 4DCBCT, respiratory-correlated fluoroscopy, and gated CBCT imaging in an efficient and sequential process to ensure the accurate delivery of free breathing respiratory-gated treatments. | INTRODUCTIONRespiratory motion management is an important strategy to account for breathing-induced target motion during radiation therapy. 1 If not considered during both the treatment planning and delivery processes, respiratory motion can lead to artifacts and target volumes that do not adequately encompass the target. Active respiratory motion management techniques can be used to minimize target motion during treatment delivery, allowing for a reduction in target volumes and improved normal tissue sparing. Such techniques include abdominal compression, 2 breath hold, 3 and free breathing phase or amplitude gating. 4 Many thoracic and abdominal sites are susceptible to substantial motion, with abdominal and lower lung lesion motion often measured to be greater than 1 cm. 5,6 Inter-and intrafraction changes in target motion magnitude greater than 5 mm have been

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“…During treatment of HNSCC, CBCT imaging is commonly obtained daily or weekly for setup veri cation and to monitor for changes in patient anatomy due to tumor response or weight loss. Over the past decade, innovations including Varian's Iterative CBCT have tremendously improved the resolution and quality of cone beam computed tomography (CBCT) such that discrete masses and lymph node conglomerates are readily discernable [5][6][7]. However, this large dataset of CT information has not been routinely used to monitor treatment responses largely because of the low resolution of CBCT in the past.…”

Section: Introductionmentioning

confidence: 99%

End of Treatment Cone-Beam Computed Tomography (CBCT) is Predictive of Radiation Response and Overall Survival in Head and Neck Cancer

Sumner

Kim

Vitzthum

et al. 2021

Preprint

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Background: Image guidance in radiation oncology has resulted in significant improvements in the accuracy and precision of radiation therapy (RT). Recently, the resolution and quality of cone beam computed tomography (CBCT) for image guidance has increased so that tumor masses and lymph nodes are readily detectable and measurable. During treatment of head and neck squamous cell carcinoma (HNSCC), on-board CBCT setup imaging is routinely obtained; however, this CBCT imaging data has not been utilized to predict patient outcomes. Here, we analyzed whether changes in CBCT measurements obtained during a course of radiation therapy correlate with responses on routine 3-month follow-up diagnostic imaging and overall survival (OS). Materials/Methods: Patients with oropharyngeal primary tumors who received radiation therapy between 2015 and 2018 were included. Anatomical measurements were collected of the primary tumor and largest nodal conglomerate (LNC) at CT simulation, end of radiation treatment (EOT CBCT), and routine 3-month post-RT imaging. At each timepoint anteroposterior (AP), mediolateral (ML) and craniocaudal (CC) measurements were obtained and used to create a 2-dimensional (2D) maximum. Results: CBCT data from 64 node positive patients were analyzed. The largest nodal 2D maximum and CC measurements on EOT CBCT showed a statistically significant correlation with complete response on 3-month post-RT imaging (r=0.313, p=0.02 and r=0.318, p=0.02, respectively). Furthermore, patients who experienced a 30% or greater reduction in the CC dimension had improved OS (continuous HR 1.07, 95% CI 1.02-1.15, p=0.045). Conclusion: Decreased size of pathologic lymph nodes measured using CBCT setup imaging during a radiation course correlates with long term therapeutic response and overall survival of HNSCC patients. These results indicate that CBCT setup imaging may have utility as an early predictor of treatment response in oropharyngeal HNSCC and could ultimately help guide management.

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WE‐AB‐207A‐08: BEST IN PHYSICS (IMAGING): Advanced Scatter Correction and Iterative Reconstruction for Improved Cone‐Beam CT Imaging On the TrueBeam Radiotherapy Machine

Cited by 6 publications

References 0 publications

Evaluation and Clinical Application of a Commercially Available Iterative Reconstruction Algorithm for CBCT-Based IGRT

Evaluation and Clinical Application of a Commercially Available Iterative Reconstruction Algorithm for CBCT-Based IGRT

Implementation of free breathing respiratory amplitude‐gated treatments

End of Treatment Cone-Beam Computed Tomography (CBCT) is Predictive of Radiation Response and Overall Survival in Head and Neck Cancer

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