Quantitative MR parameter mapping was performed on a 3T GE MR750 scanner (GE Healthcare, Waukesha, WI). All scans for MR quantification used a 3D gradient echo sequence with ultrashort echo times (UTE) and radial readouts in order to maximize signal from the plaster (Fig. 1 ). A single-channel quadrature head coil was used to provide more uniform B1 homogeneity. T1 quantification used a variable flip angle (VFA) approach15 (link),16 (link) with flip angles of 8 and 44 degrees; the TE for these scans was 24 microseconds, with a TR of 6.4 milliseconds. T2* quantification was performed using a multi-echo sequence with 32 echo times ranging from 24 microseconds to 5 milliseconds17 (link); these scans used an 8 degree flip angle and a TR of 9.276 milliseconds. The reconstructed images were 256×256 with 108 slices and 2mm isotropic voxels.
68Ge transmission scans were acquired on a Siemens HR+ scanner. This scanner is equipped with 3 rotating 68Ge lines source (approximately 70MBq each), and 45 minutes transmission scans were performed for each arrangement of 19 containers.. These data provided direct quantitative measurement of the 511 keV photon attenuation coefficients of the different plaster formulations.
68Ge transmission scans were acquired on a Siemens HR+ scanner. This scanner is equipped with 3 rotating 68Ge lines source (approximately 70MBq each), and 45 minutes transmission scans were performed for each arrangement of 19 containers.. These data provided direct quantitative measurement of the 511 keV photon attenuation coefficients of the different plaster formulations.
