Figure 2:

FLASH 2D images (476/4.9, 30° flip angle, 4 × 4 cm² FOV, 0.2 mm section thickness, 256 × 256 matrix) acquired in three orientations from the gel phantom. Column 1 images were acquired with the external pick-up loop only, separated from the gel surface by 15 mm. Column 2 images were acquired with passive coupling to the resonator but without application of pumping power. Zoomed-in views of the image regions defined by the square are shown in column 3. Column 4 shows zoomed-in views acquired with parametric amplification. Column 5 shows images acquired from a sample coil of the same dimension as the parametric resonator and having a direct connection to the MR receiver. Column 6 shows tip angle maps obtained with the double angle method (18), acquired with 60° and 120° excitations in the absence of pumping power, with repetition time of 5 seconds and echo time of 3 msec (remaining parameters same as above). One-dimensional intensity profiles in the bottom row are taken along the black dashed lines shown on the coronal sections in the third row to have the same horizontal scale. Their vertical axes are scaled to the same noise level on the images, so that their heights are a measure of MR sensitivity.