Image‐based retrospective 4D <scp>MRI</scp> in external beam radiotherapy: A comparative study with a digital phantom

Paganelli, Chiara; Kipritidis, John; Lee, Danny; Baroni, Guido; Keall, Paul J.; Riboldi, Marco

doi:10.1002/mp.12965

Cited by 22 publications

(25 citation statements)

References 39 publications

(114 reference statements)

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“…The validation on the digital phantom highlighted better performance of the internal multiple/single point surrogates with respect to the external surrogate. Internal multiple/single point surrogates produced errors comparable to the ones of current state-of-the-art image-based retrospective sorting [30], confirming the capability of the proposed approach to derive accurate 4D MRI. Due to the lack of a ground truth 4D MRI for the patient dataset, the mutual information approach [17] was adopted as a reference to compare 4D MRI volumes reconstructed with surrogates which differed in dimensionality (single vs. multiple) and location (internal vs. external).…”

Section: Discussionsupporting

confidence: 61%

“…Other state-of-the-art techniques, such as those based on body area, navigator slice or k-space surrogates were not investigated. During the separate acquisitions required for these techniques [30], different breathing patterns would occur, introducing uncertainty in the comparison of 4D MRI reconstructions.…”

Section: Discussionmentioning

confidence: 99%

“…The proposed approach was first validated (see Supplementary Material) in an in-silico framework [30], that provided a ground truth mean cycle as well as a direct comparison with the methods proposed in the literature.…”

Section: D Mri Reconstruction Evaluationmentioning

confidence: 99%

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A clustering approach to 4D MRI retrospective sorting for the investigation of different surrogates

et al. 2019

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In retrospective 4-Dimensional Magnetic Resonance Imaging (4D MRI) sorting, respiratory surrogate selection affects the image quality of reconstructed volumes. We propose a method for retrospective 4D MRI sorting based on clustering, which allowed us to compare the performance of single or multiple internal surrogates vs. a conventional external signal. Methods: A k-medoids clustering algorithm was exploited for sorting 2D MRI into 4D MRI, relying on (A) multiple or (B) single automatically tracked internal landmarks or (C) respiratory belt signal. 4D MRI reconstructions for seven liver cancer patients were compared to those of the state-of-the-art mutual information (MI) approach. Sorting artifacts were measured by the root mean square error (RMSE) between the diaphragm profile and a fitted second order curve. Diaphragm and tumor motions were evaluated. Results: The median RMSEs ranged 0.97-1.66 mm, 1.24-1.89 mm, 1.43-2.27 mm, 1.74-3.72 mm for the MI, (A), (B) and (C) methods, respectively. Significant differences (Friedman, α = 5%) were found between (C) and all other methods, and between (B) and MI approaches. The discrepancies between (A) and MI approaches ranged 1.1-6.2 mm and 0.7-5.3 mm respectively in diaphragm and tumor motions. Methods (A) and (B) showed similar ranges of motion. Conclusion: With multiple internal points, our method yielded the description of a higher range of motion and similar image quality with respect to the MI approach. The single point method led to more artifacts, suggesting the superior suitability of multiple internal surrogates for retrospective 4D MRI sorting. Considering internal rather than external information favored superior performance.

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Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

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A clustering approach to 4D MRI retrospective sorting for the investigation of different surrogates

et al. 2019

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“…In addition, 4DMRI allows utilizing an internal navigator as a respiratory surrogate, eliminating the uncertainty from an assumed external–internal motion correlation of an external surrogate used in the 4DCT acquisition. Thus, a navigator‐triggered/binned 4DMRI has higher image quality with fewer and less severe binning artifacts . Furthermore, MRI provides the option of the nonaxial scanning direction, such as sagittal or coronal scans, which are more desirable for characterizing tumor/organ respiratory motion .…”

Section: Introductionmentioning

confidence: 99%

Clinical evaluation of 4D MRI in the delineation of gross and internal tumor volumes in comparison with 4DCT

Zhang

Srivastava

Wang

et al. 2019

J Applied Clin Med Phys

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Purpose To evaluate clinical utility of respiratory‐correlated (RC) four‐dimensional magnetic resonance imaging (4DMRI) for lung tumor delineation and motion assessment, in comparison with the current clinical standard of 4D computed tomography (4DCT). Methods and Materials A prospective T2‐weighted (T2w) RC‐4DMRI technique was applied to acquire coronal 4DMRI images for 14 lung cancer patients (16 lesions) during free breathing (FB) under an IRB‐approved protocol, together with a breath‐hold (BH) T1w 3DMRI and axial 4DMRI. Clinical simulation CT and 4DCT were acquired within 2 h. An internal navigator was applied to trigger amplitude‐binned 4DMRI acquisition whereas a bellows or real‐time position management (RPM) was used in the 4DCT reconstruction. Six radiation oncologists manually delineated the gross and internal tumor volumes (GTV and ITV) in 399 3D images using programmed clinical workflows under a tumor delineation guideline. The ITV was the union of GTVs within the breathing cycle without margin. Average GTV and motion range were assessed and ITV variation between 4DMRI and 4DCT was evaluated using the Dice similarity index, mean distance agreement (MDA), and volume difference. Results The mean tumor volume is similar between 4DCT (GTV4DCT = 1.0, as the reference) and T2w‐4DMRI (GTVT2wMR = 0.97), but smaller in T1w MRI (GTVT1wMR = 0.76), suggesting possible peripheral edema around the tumor. Average GTV variation within the breathing cycle (22%) in 4DMRI is slightly greater than 4DCT (17%). GTV motion variation (−4 to 12 mm) and ITV variation (∆VITV=−25 to 95%) between 4DCT and 4DMRI are large, confirmed by relatively low ITV similarity (Dice = 0.72 ± 0.11) and large MDA = 2.9 ± 1.5 mm. Conclusion Average GTVs are similar between T2w‐4DMRI and 4DCT, but smaller by 25% in T1w BH MRI. Physician training and breathing coaching may be necessary to reduce ITV variability between 4DMRI and 4DCT. Four‐dimensional magnetic resonance imaging is a promising and viable technique for clinical lung tumor delineation and motion assessment.

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“…Visual biofeedback was compared against a free-breathing acquisition (To et al 2016b), whereas a direct comparison of an internal surrogate (1D navigator) with a concurrently acquired external surrogate was reported (Li et al 2016). Multi-slice 2D acquisition based on navigator approaches can substantially reduce image artefacts compared with some of the image-derived approaches (Paganelli et al 2018) and could describe intra-cycle variations more effectively (Von Siebenthal et al 2007). One limitation of the navigator methods, however, is that they would require sequence modification and may result in longer acquisition time, which is instead overcome by image-based approaches exploiting slice acquisition modality without a navigator.…”

Section: Respiratory-correlated (4d) Mrimentioning

confidence: 99%

MRI-guidance for motion management in external beam radiotherapy: current status and future challenges

et al. 2018

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Image‐based retrospective 4D MRI in external beam radiotherapy: A comparative study with a digital phantom

Abstract: A comparison between three different image-based retrospective sorting methods for 4D MRI is proposed, providing guidelines for benchmark definition in MRI-guided radiotherapy.

Cited by 22 publications

References 39 publications

A clustering approach to 4D MRI retrospective sorting for the investigation of different surrogates

A clustering approach to 4D MRI retrospective sorting for the investigation of different surrogates

Clinical evaluation of 4D MRI in the delineation of gross and internal tumor volumes in comparison with 4DCT

MRI-guidance for motion management in external beam radiotherapy: current status and future challenges

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