- Meeting abstract
- Open Access
306 Cardiac sodium imaging with phased arrays at 3 Tesla using a 3D Ultra-short TE (UTE) approach
© Robson et al; licensee BioMed Central Ltd. 2008
- Published: 22 October 2008
- Chronic Ischemic Heart Disease
- Twisted Projection
- 23Na Imaging
- Slice Selection Direction
- Shared Inductor
Sodium MR imaging has potential for assessing acute and chronic ischemic heart disease, due to increased sodium concentration after myocardial infarction. However, 23Na imaging is challenging owing to its low sensitivity. We have adopted a three-pronged approach to this problem:
1) Use a 3 T imaging system with higher SNR compared to 1.5 T
3) Implement a 3D acquisition with short TE, which is required for SNR efficiency. This needs to be compatible with non-isotropic acquisition for short-axis slicing.
Our hypothesis is that the combination of these enhancements will provide us with a more powerful scientific tool for investigation of sodium in myocardial disease. Further we anticipate that the higher SNR will allow us to further improve image quality by correcting for physiological motion.
Experiments were performed on a Siemens TIM Trio equipped with multinuclear capabilities. FID acquisitions at 1.5 T and 3 T were performed with a phantom spaced 8 cm from the anterior coil. Our standard quadrature 1.5 T surface receive coil was use for comparison with the 3 T array.
The sequence is a k-space stack of Ultra-short TE 2D acquisitions (stack of spokes). The addition of a slice phase encoding gradient after half-pulse excitation adds < 200 μs to TE. Imaging parameter were TR 20 ms 4 × 4 × 30 mm with an acquisition time of 8 min, TE ~0.5 ms is dominated by the duration of the RF pulse. No gating was performed. Reconstruction was implemented on the scanner, which performs regridding of the centric-radial data (in 2D) and then uses a conventional Fourier Transform in the slice selection direction. The accuracy of image reconstruction was confirmed at both the sodium and proton frequencies.
The Q factor of the Rx elements drops from 220 by a factor of 2.8 when loaded physiologically. The Q drop of the Tx elements is 5.5. The shared inductor method did allow decoupling of neighbouring elements resulting in a decoupling better than -20 dB. The active decoupling of the Rx elements as well as of the Tx loops is better than -20 dB.
The Q drop of the elements proves sample noise dominance and confirms that it makes sense to use array technology for improving SNR in 23Na imaging of the heart at 3 T. The 3D stack of spokes approach provides a method that offers rapid reconstruction, short TE and efficient coverage of k-space when sampling at non-isotropic spatial resolutions. It also has the benefit of being amenable to acceleration, which is challenging for the Twisted Projection method . Further developments will focus on removing blurring due to respiratory and cardiac motion.
This article is published under license to BioMed Central Ltd.