Accurate Quantification in Physiologic Phosphorus MR Spectroscopy

我们发现，在交替翻转角度下从灌流的大鼠心脏获取的数据中的变化被O-DAM校正消除。相应的模拟表明，当代谢物变化不大时，可以进行准确的饱和校正。使用典型的参数，我们发现，正如预期的那样，对于聚合酶链式反应中较小的分数变化，可以获得更大程度的准确性。减少不到12%的聚合酶链式反应，可以使聚合酶链式反应/PI测量的准确度在20%以内。对于tr=2的S，在校正比准确度保持在20%以内的情况下，PCR值可减少50%以上。对缺血-再灌注实验的模拟表明，除了浓度快速变化的时候，还可以获得很高的准确度。因此，即使在化学交换和T1变化的情况下，O-DAM程序也可以实现对代谢物浓度的准确监测。此外，由于O-DAM方法能够更准确地量化应激停止后的PCR恢复，因此可以更准确地测量代谢恢复的时间常数，这是广泛使用的线粒体合成能力的标志。 我们还在BLSA人群中进行广泛的动态31P运动研究，也从BLSA得出衰老、步行速度和其他结果指标的生物能量相关性。

We find that alternations in data acquired at alternating flip angles from the perfused rat heart are eliminated by the O-DAM correction. Corresponding simulations demonstrate that accurate saturation correction can be performed when metabolite changes are modest. Using typical parameters, we find that, as expected, greater degrees of accuracy can be achieved for smaller fractional changes in PCr. A decrease in PCr of less than 12% permits accuracy in PCr/Pi measurement to within 20%. For TR = 2 s, PCr can decrease by over 50% with accuracy of the corrected ratio remaining within 20%. Simulation of an ischemia-reperfusion experiment indicates the high degree of accuracy obtainable except at times of rapid concentration changes. Thus, the O-DAM procedure may permit accurate monitoring of metabolite concentrations even in the setting of chemical exchange and T1 changes. In addition, due to the ability to more accurately quantify PCr recovery after the cessation of stress, the O-DAM method permits a more accurate measurement of the time constant for metabolic recovery, a widely-used marker for mitochondrial synthetic capability. We are also performing extensive dynamic 31P exercise studies in the BLSA population too develop bioenergetic correlates of aging, walking speed, and other outcome measures from the BLSA.