van de Maat G H, de Leeuw H, Seevinck P R, van den Bosch M A A J, Nijsen J F W, Bakker C J G
Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
Magn Reson Med. 2015 Jan;73(1):273-83. doi: 10.1002/mrm.25138. Epub 2014 Mar 7.
To present a new method, S0 estimation of the free induction decay combined with a single spin echo measurement (SOFIDSE), that enables simultaneous measurements of R2*, R2, and R2' in order to quantify the local concentration of holmium microspheres (Ho-MS) for radioembolization.
SOFIDSE estimates R2* and the signal magnitude at time point 0, S0, from a multigradient echo readout of the free induction decay and subsequently estimates R2 using S0 and a single spin echo, from which R2' is deducted. The method was evaluated by comparing SOFIDSE R2 values with values obtained from shifted spin echo (SSE) measurements on a phantom setup containing Ho-MS and from dual spin echo measurements on a healthy volunteer.
On average, SOFIDSE showed a small overestimation of R2 values compared with SSE independent of the microsphere concentration. R2' values determined by subtraction of either SOFIDSE R2 or SSE R2 from R2* showed excellent agreement (correlation coefficient = 1; P = 9 · 10(-11)). The Ho-MS-induced R2' values obtained by SOFIDSE were insensitive to the R2 value of the tissue in which they resided.
SOFIDSE enables quantification of Ho-MS, in media with spatially or temporally varying R2 values, in a single acquisition.
提出一种新方法，即自由感应衰减与单次自旋回波测量相结合的S0估计法（SOFIDSE），该方法能够同时测量R2*、R2和R2'，以便对用于放射性栓塞的钬微球（Ho-MS）的局部浓度进行定量。
SOFIDSE通过对自由感应衰减的多梯度回波读出估计R2*和时间点0处的信号幅度S0，随后使用S0和单次自旋回波估计R2，并从中减去R2'。通过将SOFIDSE的R2值与在含有Ho-MS的体模设置上通过移位自旋回波（SSE）测量获得的值以及在健康志愿者上通过双自旋回波测量获得的值进行比较，对该方法进行了评估。
平均而言，与SSE相比，无论微球浓度如何，SOFIDSE对R2值的估计都略有高估。从R2*中减去SOFIDSE的R2或SSE的R2所确定的R2'值显示出极好的一致性（相关系数 = 1；P = 9·10⁻¹¹）。通过SOFIDSE获得的Ho-MS诱导的R2'值对其所在组织的R2值不敏感。
SOFIDSE能够在单次采集中对R2值在空间或时间上变化的介质中的Ho-MS进行定量。
