Navigator‐based slice tracking for kidney <scp>pCASL</scp> using spin‐echo <scp>EPI</scp> acquisition

Zhang, Ke; Triphan, Simon M. F.; Ziener, Christian H.; Jende, Johann M. E.; Kauczor, Hans‐Ulrich; Sedlaczek, Oliver; Kurz, Felix T.

doi:10.1002/mrm.29621

Cited by 4 publications

(1 citation statement)

References 27 publications

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“…Wang et al (2021) Use the short-period seismograph network to analyze the earthquake sequence. Zhang et al (2023) analyzed the spatiotemporal distribution characteristics of the Yangbi earthquake sequence. It is very necessary to use different methods and perspectives thinking angles to verify the results of the earthquake and supply new understandings.…”

Section: Introductionmentioning

confidence: 99%

Study on the sequence activities of the 2021 Yangbi MS 6.4 earthquake in Yunnan

Zheng

Zhang

et al. 2023

Front. Earth Sci.

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On 21 May 2021, the MS 6.4 earthquake struck Yangbi County, Dali City, Yunnan Province. Minor seismic activities were common both before and after the earthquake; the foreshock sequence activity characteristics of this earthquake were studied to gain a better understanding and more perspective. First, between May 18 and 5 July 2021, we collected data of the seismic events from the Yangbi MS 6.4 earthquake sequence, determined the minimum magnitude of completeness of the sequence based on the magnitude-frequency relationship, filtered out the more complete earthquake sequences, and performed double-difference earthquake relocation using the HypoDD method. Then, we improved the nearest-neighbor distance algorithm and used it in conjunction with the Gaussian mixed model fitting method to conduct a comprehensive multiple factor analysis of the Yangbi MS 6.4 earthquake sequence. The main findings of our preliminary analysis are as follows: 1) We distinguished the foreshocks, mainshocks, and aftershocks of the Yangbi earthquake sequence as well as their higher-order aftershocks, using the method described in this paper, and we can obtain clear intergenerational relationships between them. We identified eight “foreshocks” with statistically greater physical significance than the others and found that majority of the shocks occurred shortly after the mainshock were direct aftershocks, with secondary or higher-order aftershocks gradually increasing in the later stage of the sequence. 2) Combining the double-difference earthquake relocation and the event distribution on the fault plane, we found that the b-value of the Yangbi foreshock sequence was clearly on the lower end of the spectrum, with an obvious nonlinear amplification process, and can be divided into three foreshock sub-sequences: sub-sequence I with the lowest b-value and a concentrated spatial distribution, which is an F-value foreshock sequence; subsequence II with an overall shallower source depth and an obvious rebound in b-value, which is an explosive aftershock sequence; subsequence III with a lower b-value and a rapid rupture spread, which is a typical U-F-ρ foreshock. 3) We constructed a topological tree of the Yangbi foreshock sequence in Yunnan Province using the nearest-neighbor distance algorithm, combining the correlation between earthquake sequence type and fault rupture intensity. We analyzed the distribution and topology of the three sub-sequences (combined) of the Yangbi MS 6.4 foreshock sequence and found the following: the topology of subsequence I was more linear than the sequence II, each was the parent event of the subsequent event, and its rupture mode was similar to the fluid intrusion rupture in a specific channel; sequence II had a relatively simple topology, exhibiting a spray topology, and independently formed a main-aftershock mini-sequence, probably triggered by its shallow brittle rupture, which caused the fluid intrusion rupture to spread faster and eventually triggered the Yangbi MS6.4 mainshock.

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Section: Introductionmentioning

confidence: 99%

Study on the sequence activities of the 2021 Yangbi MS 6.4 earthquake in Yunnan

Zheng

Zhang

et al. 2023

Front. Earth Sci.

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Navigator‐based motion compensation for liver BOLD measurement with five‐echo SAGE EPI and breath‐hold task

Zhang,

Triphan,

Wielpütz

et al. 2024

NMR in Biomedicine

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PurposeThe purpose of this work is to apply multi‐echo spin‐ and gradient‐echo (SAGE) echo‐planar imaging (EPI) combined with a navigator‐based (NAV) prospective motion compensation method for a quantitative liver blood oxygen level dependent (BOLD) measurement with a breath‐hold (BH) task.MethodsA five‐echo SAGE sequence was developed to quantitatively measure T2 and T2* to depict function with sufficient signal‐to‐noise ratio, spatial resolution and sensitivity to BOLD changes induced by the BH task. To account for respiratory motion, a navigator was employed in the form of a single gradient‐echo projection readout, located at the diaphragm along the inferior–superior direction. Prior to each transverse imaging slice of the spin‐echo EPI‐based readouts, navigator acquisition and fat suppression were incorporated. Motion data was obtained from the navigator and transmitted back to the sequence, allowing real‐time adjustments to slice positioning. Six healthy volunteers and three patients with liver carcinoma were included in this study. Quantitative T2 and T2* were calculated at each time point of the BH task. Parameters of t value from first‐level analysis using a general linear model and hepatovascular reactivity (HVR) of Echo1, T2 and T2* were calculated.ResultsThe motion caused by respiratory activity was successfully compensated using the navigator signal. The average changes of T2 and T2* during breath‐hold were about 1% and 0.7%, respectively. With the help of NAV prospective motion compensation whole liver t values could be obtained without motion artifacts. The quantified liver T2 (34.7 ± 0.7 ms) and T2* (29 ± 1.2 ms) values agreed with values from literature. In healthy volunteers, the distribution of statistical t value and HVR was homogeneous throughout the whole liver. In patients with liver carcinoma, the distribution of t value and HVR was inhomogeneous due to metastases or therapy.ConclusionsThis study demonstrates the feasibility of using a NAV prospective motion compensation technique in conjunction with five‐echo SAGE EPI for the quantitative measurement of liver BOLD with a BH task.

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MR Perfusion Imaging for Kidney Disease

Wu,

Zhang

2024

Magnetic Resonance Imaging Clinics of North America

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Navigator‐based slice tracking for kidney pCASL using spin‐echo EPI acquisition

Cited by 4 publications

References 27 publications

Study on the sequence activities of the 2021 Yangbi MS 6.4 earthquake in Yunnan

Study on the sequence activities of the 2021 Yangbi MS 6.4 earthquake in Yunnan

Navigator‐based motion compensation for liver BOLD measurement with five‐echo SAGE EPI and breath‐hold task

MR Perfusion Imaging for Kidney Disease

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