A long thin plastic bag (95 cm length, 15 cm width, 7 mm thick), filled with 3:1 weight/weight calcium titanate in deionized water was placed directly on top of the RF coil array below the subject’s spine. This material has a dielectric constant of ∼110 and has been shown to increase the B1 homogeneity at high-fields . A variety of imaging protocols were explored in terms of Selleck PR 171 sensitivity to motion artifacts, signal-to-noise efficiency per unit time, image contrast and SAR. The final sequence used is a multiple slice two-dimensional gradient echo sequence, acquired in the sagittal orientation (as are most clinical scans at lower field), without respiratory triggering:
TR/TE 15/2 ms (partial echo acquisition), field-of-view 450 × 240 mm, data matrix 600 × 320, in-plane resolution 0.75 × 0.75 mm, 3 mm slice thickness, 0.3 mm interslice gap, eight signal averages, seven slices, total data acquisition time ∼4 min. Eight signal averages were acquired primarily to limit motion artifacts from cardiac motion since the effective use of saturation bands causes a substantial SAR penalty. Since the coverage (left/right) through the spinal column might not be
sufficient for some applications, we have also performed imaging with 14-slices, Pexidartinib supplier total coverage 6 cm, with four signal averages and the same total data acquisition time. Data acquisition parameters were chosen to remain within the International Electrotechnical Committee
(IEC) guidelines on peak and time-averaged SAR. Due to SAR limitations, sequences that can currently be used are limited to gradient echoes. For imaging the cervical/upper thoracic spine, the top six elements of the receive array are used, and for the lower thoracic/lumbar spine the bottom four elements. Images are stitched together by simple estimation of the appropriate overlap with no further image processing. Signal-to-noise Amino acid measurements were performed on the magnitude images, by the standard procedure of dividing the mean signal intensity within a defined region-of-interest by the standard deviation of the noise. For measurements within CSF, the vertebral disk and the inter-vertebral space, five different regions of interest were taken. Five different noise regions were selected, taking care to avoid any areas in which the noise is artificially reduced (due to the Philips software) or in which motion-induced artifacts are present. A noise correlation matrix was measured as described in Roemer et al.  with a volunteer in place, and processed in MATLAB (The Mathworks, Natick, MA). For the electromagnetic simulations, the bore of the magnet is modeled as a conductive RF copper shield. Each RF coil is capacitively split to produce a resonant frequency at 298.1 MHz. As shown in Fig. 2, three different positions of the RF coil were modeled, corresponding to imaging the upper cervical, mid-thorassic, and lower lumbar spinal column.