Continuous Wave Electron Paramagnetic Resonance Imaging

对于用于人体生物物理剂量测定的EPR光谱强度标准，要求如下：1）固体标准品不吸湿2）应具有可在室温下测量的EPR光谱。3)频谱应与来自牙齿的辐射诱导信号不重叠。4)标准样品应易于制备和标准化。几个小组试图开发具有上述特性的EPR光谱强度标准，但没有成功。我们已经成功地制定了符合上述标准的标准。简而言之，我们通过缓慢蒸发生长抗磁性化合物4-羟基2，2，6，6四甲基哌啶的单晶。在晶体生长过程中，我们掺杂了顺磁性分子，4-羟基-2，2，6，6-四甲基哌啶-1-氧基，它与主体分子具有显著的结构相似性。我们获得的晶体使用几种浓度的掺杂剂，以达到EPR光谱的强度在牙齿中的辐射诱导的信号的范围内。

For an EPR spectral intensity standard useful for human biophysical dosimetry, the following are the requirements: 1) A solid standard which is non-hygroscopic 2) Should have an EPR spectrum which can be measured at room temperature. 3) The spectrum should be non-overlapping with the radiation-induced signals from teeth. 4) The standard sample should be easily prepared and standardized. Several groups have tried to develop such an EPR spectral intensity standard with the above mentioned properties but did not succeed. We have developed successfully a standard which complies with the criteria described above. In brief, we grew single crystals of the diamagnetic compound, 4-hydroxy 2,2,6,6 tetramethyl piperidine by slow evaporation. During crystal growth, we doped the paramagnetic molecule, 4-hydroxy 2,2,6,6 tetramethyl piperidine-1-oxyl, which has significant structural similarity with the host molecule. We obtained crystals using several concentrations of the dopant to arrive at an EPR spectrum with intensity in the range of the radiation-induced signals in the teeth.