Investigation of undersampling and reconstruction algorithm dependence on respiratory correlated 4D-MRI for online MR-guided radiation therapy

Mickevicius, Nikolai J.; Paulson, E.S.

doi:10.1088/1361-6560/aa54f2

Cited by 51 publications

(75 citation statements)

References 29 publications

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“…Stemkens et al used a stack of stars trajectory to generate a respiratory correlated 4D-MRI with linear phase binning [7]. Several authors have also demonstrated the feasibility of an online constructed 4D-MRI using a stack of stars trajectory similar to the sequence presented here [7,22]. Online 4D-MRI using "pre beam" 4D-MRI and online 2D-cine has shown encouraging results [23].…”

Section: Discussionmentioning

confidence: 98%

Comparison of four dimensional computed tomography and magnetic resonance imaging in abdominal radiotherapy planning

Oar

Liney

Rai

et al. 2018

Physics and Imaging in Radiation Oncology

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Background and Purpose: Four-dimensional (4D) computed tomography (CT) is widely used in radiotherapy (RT) planning and remains the current standard for motion evaluation. We assess a 4D magnetic resonance imaging (MRI) sequence in terms of motion and image quality in a phantom, healthy volunteers and patients undergoing RT. Materials and Methods: The 4D-MRI sequence is a prototype T1-weighted 3D gradient echo with radial acquisition with self-gating. The accuracy of the 4D-MRI respiratory sorting based method was assessed using a MRI-CT compatible respiratory simulation phantom. In volunteers, abdominal viscera were evaluated for artefact, noise, structure delineation and overall image quality using a previously published four-point scoring system. In patients undergoing abdominal RT, the tumour (or a surrogate) was utilized to assess the range of motion on both 4D-CT and 4D-MRI. Furthermore, imaging quality was evaluated for both 4D-CT and 4D-MRI. Results: In phantom studies 4D-MRI demonstrated amplitude of motion error of less than 0.2 mm for five, seven and ten bins. 4D-MRI provided excellent image quality for liver, kidney and pancreas. In patients, the median amplitude of motion seen on 4D-CT and 4D-MRI was 11.2 mm (range 2.8-20.3 mm) and 10.1 mm (range 0.7-20.7 mm) respectively. The median difference in amplitude between 4D-CT and 4D-MRI was −0.6 mm (range −3.4-5.2 mm). 4D-MRI demonstrated superior edge detection (median score 3 versus 1) and overall image quality (median score 2 versus 1) compared to 4D-CT. Conclusions: The prototype 4D-MRI sequence demonstrated promising results and may be used in abdominal targeting, motion gating, and towards implementing MRI-based adaptive RT.

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Section: Discussionmentioning

confidence: 98%

Comparison of four dimensional computed tomography and magnetic resonance imaging in abdominal radiotherapy planning

Oar

Liney

Rai

et al. 2018

Physics and Imaging in Radiation Oncology

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“…It may be tempting to consider using the 4D-SOPI method to construct motion models for use in treatment planning (i.e., during MR simulation). While this is a possibility, higher quality 4D-MR images may be obtained with dedicated 3D approaches in shorter scan durations [17], [34]. The main benefit of 4D-SOPI is the simultaneous realtime imaging and construction of serial, self-navigated 4D-MR epochs for dose reconstruction for abdominal and thoracic MR-gRT.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous motion monitoring and truth-in-delivery analysis imaging framework for MR-guided radiotherapy

Mickevicius¹,

Chen²,

Boyd³

et al. 2018

Phys. Med. Biol.

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Intrafraction motion (i.e., motion occurring during a treatment session) can play a pivotal role in the success of abdominal and thoracic radiation therapy. Hybrid magnetic resonance-guided radiotherapy systems have the potential to control for intrafraction motion. Recently, we introduced an MRI sequence capable of acquiring real-time cine imaging in two orthogonal planes (SOPI). We extend SOPI here to permit dynamic updating of slice positions in one plane while keeping the other plane position fixed. In this implementation, cine images from the static plane are used for motion monitoring and as image navigators to sort stepped images in the other plane, producing dynamic 4D image volumes for use in dose reconstruction. A custom 3D-printed target, designed to mimic the pancreas and duodenum and filled with radiochromic FXG gel, was interfaced to the dynamic motion phantom. 4D-SOPI was acquired in a dynamic motion phantom driven by an actual patient respiratory waveform displaying amplitude/frequency variations and drifting and in a healthy volunteer. Unique 4D-MRI epochs were reconstructed from a time series of phantom motion. Dose from a static 4cmx15cm field was calculated on each 4D respiratory phase bin and epoch image, scaled by the time spent in each bin, and then rigidly accumulated. The phantom was then positioned on an Elekta MR Linac and irradiated while moving. Following irradiation, actual dose deposited to the FXG gel was determined by applying a R1 versus dose calibration curve to R1 maps of the phantom. The 4D-SOPI cine images produced a respiratory motion navigator that was highly correlated with the actual phantom motion (CC=0.9981). The mean difference between the accumulated and measured dose inside the target was 4.4% of the maximum prescribed dose. These results provide early validation that 4D-SOPI simultaneously enables real-time motion monitoring and truth-in-delivery analysis for integrated MRguided radiation therapy (MR-gRT) systems.

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“…Focusing on the lesions will decrease the volume and hence registration time. The increasing use of image registration in different applications in the context of MR guided radiotherapy [33][34][35][36], registration algorithms capable of parallel computing [37] and the use of different parallel imaging reconstructions will lead to further time reductions [38]. The physician should decide if registration in case of expiration is necessary or not and if nn-Reg should be preferred because of shorter reconstruction times if image quality is supposed to be not significantly lower compared to dir-Reg Another requirement would be the same patient positioning in the CT and the MR to avoid inaccuracies in image fusion.…”

Section: Discussionmentioning

confidence: 99%

Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors

et al. 2020

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Background: To increase the image quality of end-expiratory and end-inspiratory phases of retrospective respiratory self-gated 4D MRI data sets using non-rigid image registration for improved target delineation of moving tumors. Methods: End-expiratory and end-inspiratory phases of volunteer and patient 4D MRI data sets are used as targets for non-rigid image registration of all other phases using two different registration schemes: In the first, all phases are registered directly (dir-Reg) while next neighbors are successively registered until the target is reached in the second (nn-Reg). Resulting data sets are quantitatively compared using diaphragm and tumor sharpness and the coefficient of variation of regions of interest in the lung, liver, and heart. Qualitative assessment of the patient data regarding noise level, tumor delineation, and overall image quality was performed by blinded reading based on a 4 point Likert scale. Results: The median coefficient of variation was lower for both registration schemes compared to the target. Median dir-Reg coefficient of variation of all ROIs was 5.6% lower for expiration and 7.0% lower for inspiration compared with nn-Reg. Statistical significant differences between the two schemes were found in all comparisons. Median sharpness in inspiration is lower compared to expiration sharpness in all cases. Registered data sets were rated better compared to the targets in all categories. Over all categories, mean expiration scores were 2.92 ± 0.18 for the target, 3.19 ± 0.22 for nn-Reg and 3.56 ± 0.14 for dir-Reg and mean inspiration scores 2.25 ± 0.12 for the target, 2.72 ± 215 0.04 for nn-Reg and 3.78 ± 0.04 for dir-Reg. Conclusions: In this work, end-expiratory and inspiratory phases of a 4D MRI data sets are used as targets for nonrigid image registration of all other phases. It is qualitatively and quantitatively shown that image quality of the targets can be significantly enhanced leading to improved target delineation of moving tumors.

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Investigation of undersampling and reconstruction algorithm dependence on respiratory correlated 4D-MRI for online MR-guided radiation therapy

Cited by 51 publications

References 29 publications

Comparison of four dimensional computed tomography and magnetic resonance imaging in abdominal radiotherapy planning

Comparison of four dimensional computed tomography and magnetic resonance imaging in abdominal radiotherapy planning

Simultaneous motion monitoring and truth-in-delivery analysis imaging framework for MR-guided radiotherapy

Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors

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