Abstract
Purpose To enable high spatial and temporal breast imaging resolution via combined use of high field MRI, array coils, and forced current excitation (FCE) multi channel transmit. Materials and Methods A unilateral 16-channel receive array insert was designed for use in a transmit volume coil optimized for quadrature operation with dual-transmit RF shimming at 7T. Signal-to-noise ratio (SNR) maps, g-factor maps, and high spatial and temporal resolution in vivo images were acquired to demonstrate the utility of the coil architecture. Results The dual-transmit FCE coil provided homogeneous excitation and the array provided an increase in average SNR of 3.3 times (max 10.8, min 1.5) compared to the volume coil in transmit/receive mode. High resolution accelerated in vivo breast imaging demonstrated the ability to achieve isotropic spatial resolution of 0.5 mm within clinically relevant 90 s scan times, as well as the ability to perform 1.0 mm isotropic resolution imaging, 7 s per dynamics, with the use of bidirectional SENSE acceleration of up to R = 9. Conclusion The FCE design of the transmit coil easily accommodates the addition of a sixteen channel array coil. The improved spatial and temporal resolution provided by the high-field array coil with FCE dual-channel transmit will ultimately be beneficial in lesion detection and characterization.
Highlights
Magnetic resonance imaging (MRI) has become a promising tool for improved diagnosis and evaluation of breast cancer, owing to its ability to provide high sensitivity and resolution [1,2,3,4]
To accurately detect and characterize breast lesions using MRI, in particular for dynamic contrast enhancement (DCE) studies [5], high temporal resolution is required in addition to high spatial resolution [6, 7]
To illustrate the gains in sensitivity achieved with the array coil, signal-to-noise ratio (SNR) maps of the homogenous phantom are shown in Fig. 4, acquired with the standalone forced current excitation (FCE) volume coil with the array removed (Fig. 4A) and with the 16-channel receive array coil (Fig. 4B)
Summary
Magnetic resonance imaging (MRI) has become a promising tool for improved diagnosis and evaluation of breast cancer, owing to its ability to provide high sensitivity and resolution [1,2,3,4]. At standard clinical fields (3T and below), the practicality of simultaneous high spatial and temporal resolution is limited by the achievable signal-to-noise ratio (SNR) [8, 9]. In order to explore the potential of recently available commercial high field scanners to address this limitation, several groups are investigating breast imaging and spectroscopy at 7T [8, 10,11,12,13,14,15,16,17]. The increase in sensitivity provided by high fields can be exploited to increase spatial and/or temporal resolution. It has been shown that further temporal acceleration can be achieved at high fields from enhanced SENSE performance due to the decrease in coil sensitivity degeneracy [18]
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