Low Cost Co Doped Scintillator for Medical CT

描述(申请人提供)：尽管CSI：TI是最适合医疗和工业诊断的闪烁体之一，但它从未适用于X射线计算机断层扫描(CT)。尽管CSI在其他方面具有卓越的特性，但它存在持续的余辉，其衰减速度不够快，无法在不保留先前图像的情况下提供快速的成帧速率。我们发现，如果在主体晶格中插入合适的修饰剂离子，就有可能抑制CSL：Ti的余辉两个数量级。然而，这种抑制作用只对短的激发脉冲是最佳的，并且随着长时间的暴露(&gt；6s)和辐射剂量(&gt；6R/S)而急剧下降。CT扫描的特点。在CT扫描过程中实际施加的条件下，似乎只有一种离子保留了这种余辉抑制能力。我们打算研究该离子对CSL闪烁特性的影响。拟议的第一阶段研究将主要集中在生长成分不同的共掺杂CSL：Ti晶体，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益处的范围。这些晶体将受到高X射线剂量率的长时间曝光，并将在曝光之前、期间和之后评估它们的闪烁性能。将测量余辉和发射效率的变化，以证明我们方法的可行性。对于第一阶段，我们将寻求将激发后2毫秒的CSL：TI余辉降低到0.2%或更低的水平，最终目标至少是低于该水平的4倍。此外，在实验结果的指导下，我们将寻求了解导致观察到的效应的机制，并探索通过额外的共掺杂剂的协同影响来增强它的可能性。这项研究的成功将为CT提供CSL的优越闪烁特性，具有低余辉，并且成本远远低于目前使用的闪烁体。

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.