Velocity mapping of the aortic flow at 9.4 T in healthy mice and mice with induced heart failure using time-resolved three-dimensional phase-contrast MRI (4D PC MRI).

Philipp Rene Bovenkamp,Tobias Brix,Richard Holtmeier,Jörg Stypmann,Michael T Kuhlmann,Verena Hoerr,Gustav J Strijkers,Klaus H Hinrichs,Desiree Abdurrachim,Florian Lindemann

doi:10.1007/s10334-014-0466-z

Abstract

ObjectivesIn this study, we established and validated a time-resolved three-dimensional phase-contrast magnetic resonance imaging method (4D PC MRI) on a 9.4 T small-animal MRI system. Herein we present the feasibility of 4D PC MRI in terms of qualitative and quantitative flow pattern analysis in mice with transverse aortic constriction (TAC).Materials and methods4D PC FLASH images of a flow phantom and mouse heart were acquired at 9.4 T using a four-point phase-encoding scheme. The method was compared with slice-selective PC FLASH and ultrasound using Bland–Altman analysis. Advanced 3D streamlines were visualized utilizing Voreen volume-rendering software.ResultsIn vitro, 4D PC MRI flow profiles showed the transition between laminar and turbulent flow with increasing velocities. In vivo, 4D PC MRI data of the ascending aorta and the pulmonary artery were confirmed by ultrasound, resulting in linear regressions of R 2 > 0.93. Magnitude- and direction-encoded streamlines differed substantially pre- and post-TAC surgery.Conclusions4D PC MRI is a feasible tool for in vivo velocity measurements on high-field small-animal scanners. Similar to clinical measurement, this method provides a complete spatially and temporally resolved dataset of the murine cardiovascular blood flow and allows for three-dimensional flow pattern analysis.Electronic supplementary materialThe online version of this article (doi:10.1007/s10334-014-0466-z) contains supplementary material, which is available to authorized users.

Highlights

Pathologies of the heart and cardiovascular system are among the major diseases of our time
To evaluate the accuracy of flow calculations based on 4D PC FLASH data, 4D velocity measurements (SNR = 58.5 ± 3.7, 3 averages, vmax = 120 cm/s) were validated against an established slice-selective 2D PC method (SNR = 61.6 ± 2.9, 10 averages, vmax = 120 cm/s) for different velocities on a flow phantom
Flow measurements with our established 4D PC FLASH method, both in vitro and in vivo (Figs. 2, 3, 4; Table 1), showed good agreement with the results obtained by sliceselective 2D phase-contrast magnetic resonance imaging (PC MRI) and US, which confirmed the accuracy of the 4D method on a small-animal scanner

Summary

Introduction

Pathologies of the heart and cardiovascular system are among the major diseases of our time. Time-resolved phase-contrast techniques combined with three-dimensional volume acquisition—the so-called 4D PC MRI methods—have been developed to investigate the cardiovascular system in three-dimensional velocity vector graphs [7,8,9,10,11]. Both slice-selective PC MRI and optical methods have been used to verify the accuracy of 4D flow velocity measurements [11, 12]. Streamlines visualized as tangential traces to three-dimensional velocity fields are especially powerful for the analysis of different flow patterns [8, 9]

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Discussion

Conclusion