Abdominal Applications of 4D Flow MRI

Riedel, Christoph; Lenz, Alexander; Fischer, Lutz; Li, Jun; Piecha, F; Kluwe, Johannes; Adam, Gerhard; Bannas, Peter

doi:10.1055/a-1271-7405

Cited by 12 publications

(6 citation statements)

References 68 publications

(124 reference statements)

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“…Another patient‐friendly option would be to add respiratory binning, 69 allowing free breathing and therefore

{\mathrm{B}}_1^{+}

mapping flexibility. Calculating respiration‐robust k T ‐points, possibly universal, pulses based on these respiration‐resolved

{\mathrm{B}}_1^{+}

maps as in Aigner et al 70 would make the proposed method suitable for numerous other abdominal applications such as Dixon, 71 dynamic contrast enhancement, 72 and 4D Flow 73 …”

Section: Discussionmentioning

confidence: 99%

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Runderkamp,

Roos,

van der Zwaag

et al. 2023

Magnetic Resonance in Med

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PurposeTo obtain homogeneous signal throughout the human liver at 7 T. Flip angle (FA) shimming in 7T whole‐liver imaging was performed through parallel‐transmit kT‐point pulses based on subject‐specific multichannel absolute maps from Fourier phase‐encoded dual refocusing echo acquisition mode (PE‐DREAM).MethodsThe optimal number of Fourier phase‐encoding steps for PE‐DREAM mapping was determined for a 7T eight‐channel parallel‐transmission system. FA shimming experiments were performed in the liver of 7 healthy subjects with varying body mass index. In these subjects, first shimming and Fourier PE‐DREAM mapping were performed. Subsequently, three small‐flip‐angle 3D gradient‐echo scans were acquired, comparing a circularly polarized (CP) mode, a phase shim, and a kT‐point pulse. Resulting homogeneity was assessed and compared with estimated FA maps and distributions.ResultsFourier PE‐DREAM with 13 phase‐encoding steps resulted in a good tradeoff between accuracy and scan time. Lower coefficient of variation values (average [min‐max] across subjects) of the estimated FA in the volume of interest were observed using kT‐points (7.4 [6.6%–8.0%]), compared with phase shimming (18.8 [12.9%–23.4%], p < 0.001) and CP (43.2 [39.4%–47.1%], p < 0.001). kT‐points delivered whole‐liver images with the nominal FA and the highest degree of homogeneity. CP and phase shimming resulted in either inaccurate or imprecise FA distributions. Here, locations having suboptimal FA in the estimated FA maps corresponded to liver areas suffering from inconsistent signal intensity and T1‐weighting in the gradient‐echo scans.ConclusionHomogeneous whole‐liver 3D gradient‐echo acquisitions at 7 T can be obtained with eight‐channel kT‐point pulses calculated based on subject‐specific multichannel absolute Fourier PE‐DREAM maps.

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“…Another patient‐friendly option would be to add respiratory binning, 69 allowing free breathing and therefore

{\mathrm{B}}_1^{+}

mapping flexibility. Calculating respiration‐robust k T ‐points, possibly universal, pulses based on these respiration‐resolved

{\mathrm{B}}_1^{+}

maps as in Aigner et al 70 would make the proposed method suitable for numerous other abdominal applications such as Dixon, 71 dynamic contrast enhancement, 72 and 4D Flow 73 …”

Section: Discussionmentioning

confidence: 99%

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Runderkamp,

Roos,

van der Zwaag

et al. 2023

Magnetic Resonance in Med

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“…4D flow CMR does not only allow quantification of flow velocities and flow rates but also three-dimensional visualization of complex blood flow patterns in complex anatomical structures such as collaterals and varices [ 17 ]. Further, 4D flow CMR allows retrospective evaluation of these flow patterns off-line during post-processing [ 18 ].…”

Section: Discussionmentioning

confidence: 99%

Validation of 4D flow cardiovascular magnetic resonance in TIPS stent grafts using a 3D-printed flow phantom

Riedel

Ristow

Lenz

et al. 2023

Journal of Cardiovascular Magnetic Resonance

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Background Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is feasible for portal blood flow evaluation after placement of transjugular intrahepatic portosystemic shunts (TIPS) in patients with liver cirrhosis. However, clinical acceptance of 4D flow CMR in TIPS patients is limited due to the lack of validation studies. The purpose of this study was to validate 4D flow CMR-derived measurements in TIPS stent grafts using a three-dimensional (3D)-printed flow phantom. Methods A translucent flow phantom of the portal vasculature was 3D-printed. The phantom consisted of the superior mesenteric vein and the splenic vein draining into the portal vein, the TIPS-tract, and the hepatic vein. A TIPS stent graft (Gore® Viatorr®) was positioned within the TIPS-tract. Superior mesenteric vein and splenic vein served as inlets for blood-mimicking fluid. 4D flow CMR acquisitions were performed at 3T at preset flow rates of 0.8 to 2.8 l/min using velocity encoding of both 1.0 and 2.0 m/s. Flow rates and velocities were measured at predefined levels in the portal vasculature and within the stent graft. Accuracy of 4D flow CMR was assessed through linear regression with reference measurements obtained by flow sensors and two-dimensional (2D) phase contrast (PC) CMR. Intra- and interobserver agreement were assessed through Bland–Altman analyses. Results At a velocity encoding of 2.0 m/s, 4D flow CMR-derived flow rates and velocities showed an excellent correlation with preset flow rates and 2D PC CMR-derived flow velocities at all vascular levels and within the stent graft (all r ≥ 0.958, p ≤ 0.003). At a velocity encoding of 1.0 m/s, aliasing artifacts were present within the stent graft at flow rates ≥ 2.0 l/min. 4D flow CMR-derived measurements revealed high intra- and interobserver agreement. Conclusions The in vitro accuracy and precision of 4D flow CMR is unaffected by the presence of TIPS stent grafts, suggesting that 4D flow CMR may be used to monitor TIPS patency in patients with liver cirrhosis.

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“…Four-dimensional (4D) flow MRI is a noninvasive functional imaging technique that makes it possible to obtain time-resolved information on human blood flow dynamics [68][69][70][71][72]. This technique is based on phase contrast imaging, an MRI technique that allows simultaneous co-registration of morphological images and velocity data.…”

Section: Emerging Imaging Techniques and Technical Applicationsmentioning

confidence: 99%

Current Imaging Strategies in Patients with Abdominal Aortic Aneurysms

Ristow,

Riedel,

Lenz

et al. 2023

Rofo

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Background An abdominal aortic aneurysm (AAA) is defined as a localized dilatation of the abdominal aorta of ≥ 3 cm. With a prevalence of 4–8 %, AAA is one of the most common vascular diseases in Western society. Radiological imaging is an elementary component in the diagnosis, monitoring, and treatment planning of AAA patients. Method This is a narrative review article on preoperative imaging strategies of AAA, incorporating expert opinions based on the current literature and standard-of-care practices from our own center. Examples are provided to illustrate clinical cases from our institution. Results and Conclusion Radiological imaging plays a pivotal role in the initial diagnosis and monitoring of patients with AAA. Ultrasound is the mainstay imaging modality for AAA screening and surveillance. Contrast-enhanced CT angiography is currently considered the gold standard for preoperative imaging and image-based treatment planning in AAA repair. New non-contrast MR angiography techniques are robustly applicable and allow precise determination of aortic diameters, which is of critical importance, particularly with regard to current diameter-based surgical treatment guidelines. 3D imaging with multiplanar reformation and automatic centerline positioning enables more accurate assessment of the maximum aortic diameter. Modern imaging techniques such as 4D flow MRI have the potential to further improve individualized risk stratification in patients with AAA. Key points:

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Abdominal Applications of 4D Flow MRI

Cited by 12 publications

References 68 publications

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Validation of 4D flow cardiovascular magnetic resonance in TIPS stent grafts using a 3D-printed flow phantom

Current Imaging Strategies in Patients with Abdominal Aortic Aneurysms

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Abdominal Applications of 4D Flow MRI

Cited by 12 publications

References 68 publications

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit kT‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit kT‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Validation of 4D flow cardiovascular magnetic resonance in TIPS stent grafts using a 3D-printed flow phantom

Current Imaging Strategies in Patients with Abdominal Aortic Aneurysms

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Product

Resources

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Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping