Respiratory triggered 4D cone‐beam computed tomography: A novel method to reduce imaging dose

Cooper, Benjamin J; O’Brien, Ricky; Balik, Salim; Hugo, Geoffrey D.; Keall, Paul J.

doi:10.1118/1.4793724

Cited by 26 publications

(28 citation statements)

References 29 publications

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“…More importantly, we showed that by optimizing the imaging frequency for each individual respiratory phase, projections and thus imaging dose can be evenly spread over all respiratory phases. Cooper et al 15 already showed in a simulation study that this new acquisition technique allows for dose savings of the order of 50%, a result which is broadly in line with our measurements. The remaining small imbalance in the number of projections between the respiratory phases can be explained based on two factors: first, for the 3.5 s breathing period, the time spent in the early-inhale and lateinhale respiratory phases was of the same order as the minimum time between two projections (160 ms).…”

Section: Discussionsupporting

confidence: 91%

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Actively triggered 4d cone‐beam CT acquisition

et al. 2013

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Section: Discussionsupporting

confidence: 91%

“…Because on-the-fly adaptation of the gantry velocity was not available on our linac platform at the time of the experiments, we were limited to the imaging frequency as optimization parameter. Cooper et al 15 have recently reported on the positive impact of a variable imaging frequency on the total imaging dose in a simulation study.…”

Section: Introductionmentioning

confidence: 99%

Actively triggered 4d cone‐beam CT acquisition

et al. 2013

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“…3.C.2). This also justifies image acquisition techniques such as respiratory triggered-4DCBCT, 26 which reduces additional imaging dose that might otherwise cause projection clustering.…”

Section: D Projection Angular Spacingmentioning

confidence: 90%

Image quality in thoracic 4D cone‐beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

et al. 2014

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Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT. Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp-Davis-Kress (FDK), McKinnon-Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-meansquared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR values were found to increase with decreasing RMSE values of projection angular gaps with strong correlations (r ≈ −0.7) regardless of the reconstruction algorithm used. Conclusions: Based on the authors' results, displacement-based binning methods, better reconstruction algorithms, and the acquisition of even projection angular views are the most important factors to consider for improving thoracic 4D-CBCT image quality. In view of the practical issues with displacement-based binning and the fact that projection angular spacing is not currently directly controllable, development of better reconstruction algorithms represents the most effective strategy for improving image quality in thoracic 4D-CBCT for IGRT applications at the current stage.

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“…The standard deviations are non-negligible compared to the average sampling interval, which are caused by the ‘clustering’ and ‘gap’ [29] seen in the phase-binned slow-gantry projections. The step-and-shoot technique [11], which acquires fluoroscopy for over a respiratory cycle at preselected scan angles, is an acquisition technique that can avoid the ‘clustering’ and ‘gap’ to achieve evenly spaced projections.…”

Section: Methodsmentioning

confidence: 99%

“…However, step-and-shoot technique is not used in this study, because the current developer mode of Varian TrueBeam machines does not support very low frame rate acquisition (below 3 fps), which makes the dose of step-and-shoot technique much higher than the slow-gantry technique. Besides the step-and-shoot technique, recently developed active acquisition technique triggered by tracked tumor motion [29–31] can also achieve more evenly-spaced projections through adjusting gantry rotation speed/acquisition frame rate or dropping excessive projections. Due to the lack of supporting hardware and software, they were not used in this study either.…”

Section: Methodsmentioning

confidence: 99%

Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections

You

Yin

Pan

et al. 2015

Radiotherapy and Oncology

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Background and Purpose A new technique has been previously reported to estimate high-quality 4D-CBCT using prior information and limited-angle projections. This study is to investigate its clinical feasibility through both phantom and patient studies. Materials and Methods The new technique used to estimate 4D-CBCT is called MMFD-NCC. It is based on the previously reported motion-modeling and free-form deformation (MMFD) method, with the introduction of normalized-cross-correlation (NCC) as a new similarity metric. The clinical feasibility of this technique was evaluated by assessing the accuracy of estimated anatomical structures in comparison to those in the ‘ground-truth’ reference 4D-CBCT, using data obtained from a physical phantom and three lung cancer patients. Both volume percentage error (VPE) and center-of-mass error (COME) of the estimated tumor volume were used as the evaluation metrics. Results The average VPE/COME of the tumor in the prior image was 257.1%/10.1 mm for the phantom study and 55.6%/3.8 mm for the patient study. Using only orthogonal-view 30° projections, the MMFD-NCC has reduced the corresponding values to 7.7% /1.2 mm and 9.6%/1.1 mm, respectively. Conclusions The MMFD-NCC technique is able to estimate 4D-CBCT images with geometrical accuracy of the tumor within 10% VPE and 2 mm COME, which can be used to improve the localization accuracy of radiotherapy.

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Respiratory triggered 4D cone‐beam computed tomography: A novel method to reduce imaging dose

Abstract: Simulation studies have shown that RT 4D CBCT reduces imaging dose while maintaining comparable image quality for phase based 4D CBCT; image quality is degraded for displacement based RT 4D CBCT in its current implementation.

Cited by 26 publications

References 29 publications

Actively triggered 4d cone‐beam CT acquisition

Actively triggered 4d cone‐beam CT acquisition

Image quality in thoracic 4D cone‐beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

Preliminary clinical evaluation of a 4D-CBCT estimation technique using prior information and limited-angle projections

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