Low Cost Co Doped Scintillator for Medical CT

描述（由申请人提供）：尽管CsI：TI是广泛的医疗和工业诊断中最理想的稀释剂之一，但它从未适用于X射线计算机断层扫描（CT）。尽管CsI的其他优异性能，但它遭受持久的余辉，其衰减速度不足以提供快速的帧速率，而不会出现不可接受的先前图像的残留。我们已经发现，它是可能的抑制余辉Csl：TI多达两个数量级，如果一个合适的改性剂离子被插入到主机晶格。然而，这种抑制效应仅在短激发脉冲下最佳，而在长时间曝光（> 6s）和辐射剂量（> 6R/s）下，福尔斯急剧下降。CT扫描的特征。只有一种离子似乎在CT扫描期间实际施加的条件下保留了这种余辉抑制能力。我们打算研究这种离子对Csl闪烁性能的影响。拟议的第一阶段研究将主要集中在生长共掺杂的Csl：TI晶体与组成的变化，以确定在不牺牲Csl：TI的其他优异性能的情况下，可以获得减少余辉的最大有益效果的范围。这些晶体将在高X射线剂量率下进行长时间曝光，并在曝光之前、期间和之后评估其闪烁特性。将测量余辉和发射效率的变化，以证明我们的方法的可行性。对于第一阶段，我们将寻求在激发后2 ms将Csl：TI余辉降低到0.2%或更低的水平，最终目标是至少比其低四倍。此外，由实验结果的指导下，我们将寻求既要了解所观察到的效果负责的机制，并探讨通过一个额外的共掺杂剂的合作影响，以提高它的可能性。这项研究的成功将为CT提供Csl的上级闪烁性能，低余辉，成本远低于目前使用的闪烁器。

DESCRIPTION (provided by applicant): Although CsI:TI is one of the most desirable scintillators for a broad range of medical and industrial diagnostics, it has never been applicable to X-ray computerized tomography (CT). Despite the otherwise superb properties of CsI, it suffers from a persistent afterglow that simply does not decay fast enough to provide rapid framing rates without unacceptable carryover of the previous image. We have discovered that it is possible to suppress the afterglow of Csl:TI by as much as two orders of magnitude if a suitable modifier ion is inserted into the host lattice. The suppressive effect, however, is opti- mal for only short excitation pulses, and falls off sharply for extended exposures (> 6s) and radiation dose (>6R/s). characteristic of CT scans. Only one ion appears to retain this afterglow-suppressive capability under the conditions actually imposed during CT scans. We intend to investigate the effect of this ion on scintillation properties of Csl. The proposed Phase I research will primarily focus on growing codoped Csl:TI crystals with variations in composition to determine the range over which the maximum beneficial effects of reduced afterglow can be obtained without sacrificing the other excellent properties of the Csl:TI. These crystals will be subjected to extended exposures at high x-ray dose rates, and their scintillation properties will be evaluated before, during, and after such exposure. Changes in the afterglow and the emission efficiency will be measured to demonstrate the feasibility of our approach. For Phase I, we will seek to reduce the Csl:TI afterglow 2 ms after excitation to a level of 0.2% or lower, with an ultimate goal at least a factor of four below that. In addition, guided by the experimental results, we will seek both to understand the mechanisms responsible for the observed effect and to explore the possibility of enhancing it through the cooperative influence of an additional codopant. The success of this research will provide CT with the superior scintillation properties of Csl with low afterglow and at a cost far below scintillators now in use.