Pulsed magnetization transfer contrast for MR imaging with application to breast

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Abstract
The relative populations and transverse relaxation times of the solid-like hydrogen pool (PB and T2B) and the magnetization transfer (MT) rates between the solid-like and liquid-like hydrogen pools (K) have been determined for three different agar gel concentrations (2%, 4%, and 8% by weight) as well as excised fibroglandular breast tissue specimens. PB was determined to be .003(.001), .01(.002), .02(.01), and .06(.01); T2B was determined to be 13.0(.2), 14.0(.1), 14.5(.1) and 15.2(1.3) μs; and K was determined to be 0.78(.01), 1.15(.02), 2.00(.02), and 3.55(1.5) sec−1 for the 2%, 4%, and 8% agar gels and the fibroglandular tissue, respectively. The image signal intensities of a pulsed MTC-prepared gradient-echo imaging technique are predicted using these MT parameters and are shown to agree well with experimental data obtained from a clinical MR imaging system. This technique is shown to suppress signal intensity of fibroglandular breast tissue by 40%–50% without exceeding SAR limits (≤ 8W/kg) and is helpful for visualizing lesions and silicone implants.