Fast myocardial perfusion mapping in mice using heart cycle dependent data weighting
Fabian Tobias Gutjahr1, Thomas Kampf1, Stephan Michael Guenster1, Volker Herold1, Patrick Winter1, Xavier Helluy2, Wolfgang Bauer3, and Peter Jakob1

1Experimental Physics V, University of Wuerzburg, Wuerzburg, Germany, 2NeuroImaging Centre, Ruhr University, Bochum, Germany, 3Department of Internal Medicine 1, Universitaetsklinikum W├╝rzburg, Wuerzburg, Germany

Synopsis

A fast method for the measurement of myocardial perfusion in mice is presented. Using an efficient retrospective data selection and weighting process in combination with a model based reconstruction perfusion maps can be acquired within 3.5min.

Purpose

T1 based arterial spin labeling (ASL) perfusion measurements have become the de facto (1-2) standard for myocardial perfusion mapping in mice. Yet there has been an increased interest in first pass perfusion measurements (3-4) due to the high acquisition speed. In this work we want to demonstrate an ASL method that is nearly as fast as first pass measurements while retaining the advantages of ASL measurements.

Methods

In (5) a retrospectively triggered method using a model based reconstruction has been demonstrated. Retrospective triggering and breath gating leads to undersampling. A model based method is used to extrapolate missing data directly in k-space. Data acquired during a 30% window around the desired position in the cardiac cycle is accepted for reconstruction. In order to use the acquired data more efficiently, data further away from the desired position in the cardiac cycle can be used to improve the reconstruction. To prevent smeared images, data are weighted before the interpolation. Weighting is done in dependence of the position in k-space and in the cardiac cycle. A proposed weighting scheme can be seen in Fig. 1. In the k-space center the selection is more strict so intensity variations due to blood flow and cardiac motion do not influence the image intensity, which would lead to incorrect T1 fits. Using a numerical phantom the sharpness of the acquired images was assessed. The gain in accepted data can be used to shorten the measurement time significantly.

Results

Data from a wider range of the heart cycle are used for reconstruction. Perfusion measurements of murine myocardium were acquired in less than 3.5 minutes with a native inplane resolution of (230µm)2. A comparison of the results from the reconstruction with a fixed 30% window and the weighted selection can be seen in Fig. 2. The quality of the maps is improved while the heart phase and k-space dependent weighting prevents loss in image sharpness.

Conclusion

A fast method for T1 measurements and perfusion mapping using a retrospectively triggered reconstruction is demonstrated. The acquisition time of 3.5 min is comparable to first pass methods while all the advantages (eg. repeatability, noninvasiveness, low preparational effort) of arterial spin labeling perfusion measurements are retained.

Acknowledgements

This work was supported by grants from the Deutsche Forschungsgemeinschaft (SFB 688 B5, Z02) and the Bundesministerium für Bildung und Forschung (BMBF01 EO1004)

References

(1) Campbell-Washburn et al. Magn Reson Med. 2013 Jan;69(1):238-47. doi: 10.1002/mrm.24243. Epub 2012 Mar 12.Cardiac arterial spin labeling using segmented ECG-gated Look-Locker FAIR: variability and repeatability in preclinical studies.

(2) Vandsburger et al. Magn Reson Med. 2010 Mar;63(3):648-57. doi: 10.1002/mrm.22280.Improved arterial spin labeling after myocardial infarction in mice using cardiac and respiratory gated look-locker imaging with fuzzy C-means clustering

(3) Naresh et al., Magn Reson Med. 2015 Jul 20. doi: 10.1002/mrm.25769. Repeatability and variability of myocardial perfusion imaging techniques in mice: Comparison of arterial spin labeling and first-pass contrast-enhanced MRI.

(4) Coolen et al. Magn Reson Med. 2010 Dec;64(6):1658-63. doi: 10.1002/mrm.22588. Mouse myocardial first-pass perfusion MR imaging.

(5) Gutjahr et al., Magn Reson Med. 2014 Dec 1. doi: 10.1002/mrm.25526. Quantification of perfusion in murine myocardium: A retrospectively triggered T1-based ASL method using model-based reconstruction

Figures

Fig 1. Weighting function in dependence of the position in k-space and in the position in the cardiac cycle. Top: windowed selection, bottom: weighted selection

Fig 2. T1 maps after slice selective and global inversion recovery and the corresponding perfusion maps are shown for the windowed and weighted data selection strategy. (T1 Maps in ms, Perfusion in ml/(100 g min))



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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