Investigation of sagittal image acquisition for 4D‐MRI with body area as respiratory surrogate

Purpose: T2-weighted MRI provides excellent tumor-to-tissue contrast for target volume delineation in radiation therapy treatment planning. This study aims at developing a novel T2-weighted retrospective four dimensional magnetic resonance imaging (4D-MRI) phase sorting technique for imaging organ/tumor respiratory motion. Methods: A 2D fast T2-weighted half-Fourier acquisition single-shot turbo spin-echo MR sequence was used for image acquisition of 4D-MRI, with a frame rate of 2-3 frames/s. Respiratory motion was measured using an external breathing monitoring device. A phase sorting method was developed to sort the images by their corresponding respiratory phases. Besides, a result-driven strategy was applied to effectively utilize redundant images in the case when multiple images were allocated to a bin. This strategy, selecting the image with minimal amplitude error, will generate the most representative 4D-MRI. Since we are using a different image acquisition mode for 4D imaging (the sequential image acquisition scheme) with the conventionally used cine or helical image acquisition scheme, the 4D dataset sufficient condition was not obviously and directly predictable. An important challenge of the proposed technique was to determine the number of repeated scans (N R ) required to obtain sufficient phase information at each slice position. To tackle this challenge, the authors first conducted computer simulations using real-time position management respiratory signals of the 29 cancer patients under an IRB-approved retrospective study to derive the relationships between N R and the following factors: number of slices (N S ), number of 4D-MRI respiratory bins (N B ), and starting phase at image acquisition (P 0 ). To validate the authors' technique, 4D-MRI acquisition and reconstruction were simulated on a 4D digital extended cardiac-torso (XCAT) human phantom using simulation derived parameters. Twelve healthy volunteers were involved in an IRB-approved study to investigate the feasibility of this technique. Results: 4D data acquisition completeness (C p ) increases as NR increases in an inverse-exponential fashion (C p = 100 − 99 × exp(−0.18 × N R ), when N B = 6, fitted using 29 patients' data). The N R required for 4D-MRI reconstruction (defined as achieving 95% completeness, C p = 95%, N R = N R,95 ) is proportional to N B (N R,95 ∼ 2.86 × N B , r = 1.0), but independent of N S and P 0 . Simulated XCAT 4D-MRI showed a clear pattern of respiratory motion. Tumor motion trajectories measured on 4D-MRI were comparable to the average input signal, with a mean relative amplitude error of 2.7% ± 2.9%. Reconstructed 4D-MRI for healthy volunteers illustrated clear respiratory motion on three orthogonal planes, with minimal image artifacts. The artifacts were presumably caused by breathing irregularity and incompleteness of data acquisition (95% acquired only). The mean relative amplitude error between critical structure trajectory and average breathing curve for 12 healthy volunteers is 2.5 ± 0.3 mm in superior-...

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“…We have done MRI studies on other planes. 30 Applying our technique on other planes is in our future investigation plan.…”

Section: Discussionmentioning

confidence: 99%

T2‐weighted four dimensional magnetic resonance imaging with result‐driven phase sorting

et al. 2015

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“…Sagittal slices are used because respiratory motion then is mostly in-plane, which leads to less space-dependent phase shift [27]. N ∈ {17 , … , 20} is chosen such that the slices cover the region of interest.…”

Section: Methodsmentioning

confidence: 99%

“…In 4-D MR imaging, many different sources of respiratory signals have been proposed, including external devices [28], [30], the center of k-space [18], [19], [23], [26], the body area [25], [27], body boundary [26], navigator signals [20], and navigator slices [29]. Recently, dimensionality reduction has become popular in MR [17], [31], [32] and other applications [32], [33].…”

Section: Introductionmentioning

confidence: 99%

An MR-Based Model for Cardio-Respiratory Motion Compensation of Overlays in X-Ray Fluoroscopy

Fischer

Faranesh

Pohl

et al. 2018

IEEE Trans. Med. Imaging

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In X-ray fluoroscopy, static overlays are used to visualize soft tissue. We propose a system for cardiac and respiratory motion compensation of these overlays. It consists of a 3-D motion model created from real-time MR imaging. Multiple sagittal slices are acquired and retrospectively stacked to consistent 3-D volumes. Slice stacking considers cardiac information derived from the ECG and respiratory information extracted from the images. Additionally, temporal smoothness of the stacking is enhanced. Motion is estimated from the MR volumes using deformable 3-D/3-D registration. The motion model itself is a linear direct correspondence model using the same surrogate signals as slice stacking. In X-ray fluoroscopy, only the surrogate signals need to be extracted to apply the motion model and animate the overlay in real time. For evaluation, points are manually annotated in oblique MR slices and in contrast-enhanced X-ray images. The 2-D Euclidean distance of these points is reduced from 3.85 mm to 2.75 mm in MR and from 3.0 mm to 1.8 mm in X-ray compared to the static baseline. Furthermore, the motion-compensated overlays are shown qualitatively as images and videos.

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“…9 Stemkens B, et al compared 2 surrogate signals (external bellows and internal navigator) and 2 MR sampling strategies (Cartesian and radial) and constructed 4D-MRI by resorting 2D K-space data. 10 All of these 4D-MRI methods have adopted similar concept used in 4D-CT and have shown promise in capturing more comprehensive anatomical information, however they have also inherited the same stitching artifacts resulted from 2D imaging-space resorting [7][8][9][10][11] . Another significant limitation is the anisotropic resolution due to the large slice thickness of cine 2D-MRI.…”

Section: Introductionmentioning

confidence: 99%

Four Dimensional Magnetic Resonance Imaging With 3D Radial Sampling and Self-gating Based K-space Sorting: Early Clinical Experience on Pancreatic Cancer Patients

Yang

Fan

Tuli

et al. 2015

International Journal of Radiation Oncology*Biology*Physics

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Purpose-Dynamic magnetic resonance imaging (MRI) has been used to characterize internal organ motion but real time acquisition is typically limited to 2 dimensions. Methods have been developed to reconstruct four dimensional MRI (4D-MRI) based on time-stamped 2D images or 2D K-space data. These methods suffer from anisotropic resolution and rebinning artifacts. We applied a novel self-gating K-space sorted 4D-MRI (SG-KS-4D-MRI) method to overcome these limitations and to monitor pancreatic tumor motion.Methods and Material-Ten patients were imaged using 4D-CT, cine 2D-MRI and the SG-KS-4D-MRI, which is a spoiled gradient recalled echo (GRE) sequence with 3D radial-sampling K-space projections and 1D projection-based self-gating. Tumor volumes were defined on all phases in both 4D-MRI and 4D-CT and then compared.Results-An isotropic resolution of 1.56 mm was achieved in the SG-KS-4D-MRI images, which showed superior soft tissue contrast to 4D-CT and appeared to be free of visible rebinning artifacts. The tumor motion trajectory cross-correlations between SG-KS-4D-MRI and cine 2D-MRI in SI, AP and ML directions were 0.93±0.03, 0.83±0.10 and 0.74±0.18, respectively. The tumor motion trajectories cross-correlations between SG-KS-4D-MRI and 4D-CT in SI, AP and ML directions were 0.91±0.06, 0.72±0.16 and 0.44±0.24, respectively. The average standard deviation of GTV volume (GTV_σ) calculated from the ten breathing phases were 0.81 cc and 1.02 cc for SG-KS-4D-MRI and 4D-CT (p=0.012). *Corresponding author: Wensha Yang, PhD, Department of Radiation Oncology, Cedars Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048, wensha.yang@cshs.org. Conflicts of interest: nonePublisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptConclusions-A novel SG-KS-4D-MRI acquisition method capable of reconstructing rebinning artifact free high resolution 4D-MRI images was used to quantify pancreas tumor motion. The resultant pancreatic tumor motion trajectories agreed well with 2D-cine-MRI and 4D-CT. The pancreatic tumor volumes shown in the different phases for the SG-KS-4D-MRI were statistically significantly more consistent than those in the 4D-CT.

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Investigation of sagittal image acquisition for 4D‐MRI with body area as respiratory surrogate

Cited by 48 publications

References 41 publications

T2‐weighted four dimensional magnetic resonance imaging with result‐driven phase sorting

T2‐weighted four dimensional magnetic resonance imaging with result‐driven phase sorting

An MR-Based Model for Cardio-Respiratory Motion Compensation of Overlays in X-Ray Fluoroscopy

Four Dimensional Magnetic Resonance Imaging With 3D Radial Sampling and Self-gating Based K-space Sorting: Early Clinical Experience on Pancreatic Cancer Patients

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