Self‐adapting cyclic registration for motion‐compensated cone‐beam CT in image‐guided radiation therapy

Brehm, Marcus; Paysan, Pascal; Oelhafen, Markus; Kunz, Patrik; Kachelrieß, Marc

doi:10.1118/1.4766435

Cited by 46 publications

(66 citation statements)

References 39 publications

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“…There are other approaches that have been published in the literature to improve image quality with the most common approaches using iterative reconstruction techniques after the raw data has been acquired, see (Bian et al 2010), (Bergner et al 2009), (Bergner et al 2010), (Leng et al 2008), (Li et al 2007), (Brehm et al 2012), (Brehm et al 2013), and (Mckinnon & Bates 1981) or techniques that attempt to reconstruct 4DCBCT from a one minute 3DCBCT (Yan et al 2014). RMG-4DCBCT can be used in conjunction with these approaches but it has the added benefit that it is the only technique that addresses image quality and imaging dose issues at the source of the problem; i.e., during image acquisition.…”

Section: Discussionmentioning

confidence: 99%

Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

O’Brien¹,

Stankovic²,

Sonke³

et al. 2017

Phys. Med. Biol.

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Abstract. Four dimensional cone beam computed tomography (4DCBCT) uses a constant gantry speed and imaging frequency that are independent of the patient's breathing rate. Using a technique called Respiratory Motion Guided 4DCBCT (RMG-4DCBCT), we have previously demonstrated that by varying the gantry speed and imaging frequency, in response to changes in the patient's real-time respiratory signal, the imaging dose can be reduced by 50-70%. RMG-4DCBCT optimally computes a patient specific gantry trajectory to eliminate streaking artefacts and projection clustering that is inherent in 4DCBCT imaging. The gantry trajectory is continuously updated as projection data is acquired and the patient's breathing changes. The aim of this study was to realise RMG-4DCBCT for the first time on a linear accelerator.To change the gantry speed in real-time a potentiometer under microcontroller control was used to adjust the current supplied to an Elekta Synergy's gantry motor. A real-time feedback loop was developed on the microcontroller to modulate the gantry speed and projection acquisition in response to the real-time respiratory signal so that either 40, RMG-4DCBCT 40 , or 60, RMG-4DCBCT 60 , uniformly spaced projections were acquired in 10 phase bins. Images of the CIRS dynamic Thorax phantom were acquired with sinusoidal breathing periods ranging from 2s to 8s together with two breathing traces from lung cancer patients. Image quality was assessed using the contrast to noise ratio (CNR) and edge response width (ERW).For the average patient, with a 3.8s breathing period, the imaging time and image dose were reduced by 37% and 70% respectively. Across all respiratory rates, RMG-4DCBCT 40 had a CNR in the range of 6.5 to 7.5, and RMG-4DCBCT 60 had a CNR between 8.7 and 9.7, indicating that RMG-4DCBCT allows consistent and controllable CNR. In comparison, the CNR for conventional 4DCBCT drops from 20.4 to 6.2 as the breathing rate increases from 2s to 8s. With RMG-4DCBCT, the ERW in the direction of motion of the imaging insert decreases from 2.1mm to 1.1mm as the breathing rate increases from 2s to 8s while for conventional 4DCBCT the ERW increases from 1.9mm to 2.5mm.Image quality can be controlled during 4DCBCT acquisition by varying the gantry speed and the projection acquisition in response to the patient's real-time respiratory signal. However, although the image sharpness, i.e., ERW, is improved with RMG-4DCBCT, the ERW depends on the patient's breathing rate and breathing regularity.

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Section: Discussionmentioning

confidence: 99%

Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

O’Brien¹,

Stankovic²,

Sonke³

et al. 2017

Phys. Med. Biol.

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“…There we found that our artifact-specific cyclic registration and motion compensation (acMoCo) algorithms are extremely successful for slowly rotating CBCT systems. 6,7 In analogy to the 4D MoCo reconstruction we can formulate a 5D MoCo reconstruction:…”

Section: Methodsmentioning

confidence: 99%

“…In a first step for 5D motion estimation, our previously published 4D MoCo approach is applied to compensate for the respiratory patient motion, thus leading to high fidelity 4D CBCT images. 6,7 The main outcome of this approach are 4D MVFs denoted before as D r2 r1 , that accurately describe the lung motion between two adjacent phases as a function of the respiratory phase. In detail, and based on the wellknown FDK 20 filtered backprojection algorithm, phase-correlated, i.e.…”

Section: Methodsmentioning

confidence: 99%

Five-dimensional motion compensation for respiratory and cardiac motion with cone-beam CT of the thorax region

et al. 2016

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We propose an adapted method of our previously published five-dimensional (5D) motion compensation (MoCo) algorithm 1 , developed for micro-CT imaging of small animals, to provide for the first time motion artifact-free 5D cone-beam CT (CBCT) images from a conventional flat detector-based CBCT scan of clinical patients. Image quality of retrospectively respiratory-and cardiac-gated volumes from flat detector CBCT scans is deteriorated by severe sparse projection artifacts. These artifacts further complicate motion estimation, as it is required for MoCo image reconstruction. For high quality 5D CBCT images at the same x-ray dose and the same number of projections as todays 3D CBCT we developed a double MoCo approach based on motion vector fields (MVFs) for respiratory and cardiac motion. In a first step our already published four-dimensional (4D) artifact-specific cyclic motion-compensation (acMoCo) approach is applied to compensate for the respiratory patient motion. With this information a cyclic phase-gated deformable heart registration algorithm is applied to the respiratory motion-compensated 4D CBCT data, thus resulting in cardiac MVFs. We apply these MVFs on double-gated images and thereby respiratory and cardiac motion-compensated 5D CBCT images are obtained. Our 5D MoCo approach processing patient data acquired with the TrueBeam 4D CBCT system (Varian Medical Systems). Our double MoCo approach turned out to be very efficient and removed nearly all streak artifacts due to making use of 100% of the projection data for each reconstructed frame. The 5D MoCo patient data show fine details and no motion blurring, even in regions close to the heart where motion is fastest.

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“…We address this problem by using an artifact model, which predicts the shape and magnitude of the streak artifacts, combined with a deformable registration based on the Demons algorithm and a cyclic regularization [13], [14]. The first step (Fig.…”

Section: B Estimation Of Motion Vector Fieldsmentioning

confidence: 99%

Artifact model-based respiratory motion compensation (MoCo) for simultaneous PET/MR based on strongly undersampled radial MR data

Rank

Heuber

Brehm

et al. 2014

2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)

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We propose a new method for PET/MR respiratory motion compensation, which is based on strongly undersampled MR data. In our simulation study, we applied a 3D encoded radial stack-of-stars sampling scheme with 160 radial spokes per slice and an acquisition time of 38 s for MR data acquisition. Based on gated but strongly undersampled and thus streak artifact-contaminated 4D MR images, high-fidelity motion vector fields were estimated applying our newly-developed artifact model-based registration framework. Subsequently, MoCo 4D PET images of a simulated breathing thorax were reconstructed. Evaluation of eight artificial hot lesions in the lungs and upper abdomen showed a significant visual as well as a quantitative improvement in terms of SUVmean values, lesion size and localization for MoCo 4D PET images compared to 3D and 4D gated reconstructions especially for small lesion sizes.

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Self‐adapting cyclic registration for motion‐compensated cone‐beam CT in image‐guided radiation therapy

Cited by 46 publications

References 39 publications

Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

Five-dimensional motion compensation for respiratory and cardiac motion with cone-beam CT of the thorax region

Artifact model-based respiratory motion compensation (MoCo) for simultaneous PET/MR based on strongly undersampled radial MR data

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