Reduced Afterglow Scintillator Films for High Speed Medical Imaging

描述（由申请人提供）：虽然现在正在开发许多异国情调的新型闪烁材料，但很少有材料在性能和多功能性上接近CsI:Tl。CsI:Tl不仅具有极好的闪烁效率，而且还可以很容易地制成用于高分辨率成像的大面积微柱状薄膜，这使其成为广泛应用的材料选择。不幸的是，CsI:Tl在其闪烁衰减中表现出强烈的余辉成分和长时间照射后的严重滞后，限制了可实现的能量分辨率和成像质量和速度。这些缺点有效地阻碍了它在放射性核素成像和医学CT等应用中的应用，在这些应用中，它的低成本可能会产生巨大的经济影响。CsI:Tl闪烁体的改进形式可以降低关键救生医疗设备的成本，如x射线CT扫描仪、透视系统和其他依赖快速数据采集的设备。在对CsI:Tl中共掺杂剂协同效应的系统研究中，我们已经确定了可以抑制其余辉多达两个数量级的添加剂，同时保持其非凡的闪烁特性。我们还发现，类似的治疗方法可以将迟滞减少十倍以上，这是几十年来研究人员未能取得的重大突破。此外，我们已经明确地确定，通过共蒸发技术，我们可以沉积这种改性材料的厚微柱状薄膜，它提供了非常高的空间分辨率，适合于诸如“纳米spect”和使用平板探测器的高速锥束CT等新的和令人兴奋的应用。由于这些特殊的性质，共掺杂CsI:Tl现在可以用于许多快速成像模式，而CsI:Tl以前被排除在外。但是，虽然我们已经在熔融生长的晶体中实现了所有这些理想的效果，但我们还没有在单一的薄膜成分中将它们结合在一起达到令人满意的水平；这是第一阶段的具体目标。在已经确定了多组分沉积工艺本身的可行性之后，我们将通过仔细和系统地改变沉积参数（如源和衬底温度、源-衬底距离以及源本身的化学组成）来实现这一目标。第一阶段将生产具有闪烁特性的材料，至少与熔融生长的单晶一样好，从而立即用于商业评估。第二阶段的目标比第一阶段要全面得多。在这里，我们将寻求在化学成分和物理形态方面优化材料。此外，在第一阶段的结果和大量新理论支持的指导下，我们将寻求理解造成观察到的效应的机制和控制沉积过程本身的动力学因素。认识到它们的最终应用，我们将生长各种尺寸的微柱状薄膜，范围从5 x 5 cm2到50 x 50 cm2，并通过评估薄膜在CBCT和SPECT操作模式下的性能来展示它们的实用性。最后，我们将通过与这项技术的潜在用户的合作项目促进商业化。公共卫生相关性：广泛使用的低成本CsI:Tl不仅具有极好的闪烁效率，而且还可以很容易地制成用于高分辨率成像的大面积微柱状薄膜，使其成为广泛应用的首选材料。不幸的是，CsI:Tl在其闪烁衰减中表现出强烈的余辉成分和长时间照射后的严重滞后，限制了可实现的能量分辨率和成像质量和速度。这些缺点有效地阻碍了它在放射性核素成像和医学CT等应用中的应用，否则它的低成本可能会产生巨大的经济影响。CsI:Tl闪烁体的一种改进形式，如这里提出的，可以降低关键救生医疗设备的成本，如x射线CT扫描仪，透视系统和其他依赖快速数据采集的设备。

DESCRIPTION (provided by applicant): While many exotic new scintillation materials are now being developed, few even come close to CsI:Tl in performance and versatility. Widely available commercially at low cost, CsI:Tl not only has superb scintillation efficiency, but also can readily be fabricated as large-area microcolumnar films for high-resolution imaging, making it the material of choice for a wide range of applications. Unfortunately, CsI:Tl exhibits both a strong afterglow component in its scintillation decay and severe hysteresis after prolonged irradiation, limiting achiev- able energy resolution and imaging quality and speed. These shortcomings effectively preclude its use in applica- tions such as radionuclide imaging and medical CT, where its low cost could otherwise have immense economic impact. An improved form of CsI:Tl scintillator can reduce the cost of critical life-saving medical equipment such as X-ray CT scanners, fluoroscopy systems and other devices that rely on rapid data acquisition. In systematic studies of the cooperative effects of codopants in CsI:Tl, we have identified additives that can suppress its afterglow by as much as two orders of magnitude while maintaining its extraordinary scintillation properties. We also find that similar treatment can diminish hysteresis by more than a factor of ten, represent- ing a major breakthrough that has eluded researchers for decades. Moreover, we have clearly established that, through a co-evaporation technique, we can deposit thick microcolumnar films of this modified material, which provide very high spatial resolution appropriate for such new and exciting applications as "nanoSPECT" and high-speed cone-beam CT using flat panel detectors. With these exceptional properties, codoped CsI:Tl is now poised for exploitation in many rapid imaging modalities from which CsI:Tl had been previously excluded. But while we have achieved all these desirable effects in melt-grown crystals, we have not yet combined them at satisfactory levels at a single film composition; this is the specific goal of Phase I. Having already established the feasibility of the multicomponent deposition process itself, we will reach this goal through careful and system- atic variation of deposition parameters such as source and substrate temperatures, source-substrate distances, and chemical make-up of the sources themselves. Phase I will produce material with scintillation properties at least as good as in melt-grown single crystals, thereby becoming immediately useful for commercial evaluation. Phase II has far more comprehensive goals than Phase I. Here we will seek to optimize the material in terms of both chemical composition and physical morphology. In addition, guided by the results of Phase I and input from substantial new theoretical support, we will seek to understand both the mechanisms responsible for the observed effects and the kinetic factors that govern the deposition process itself. Cognizant of their ultimate applications, we will grow microcolumnar films of various dimensions ranging from 5 x 5 cm2 to 50 x 50 cm2, and demonstrate their utility by evaluating film performance in CBCT and SPECT modes of operation. Finally, we will promote commercialization through cooperative programs with potential users of this technology. PUBLIC HEALTH RELEVANCE: The widely available, low cost CsI:Tl not only has superb scintillation efficiency, but also can readily be fabricated as large-area microcolumnar films for high-resolution imaging, making it the material of choice for a wide range of applications. Unfortunately, CsI:Tl exhibits both a strong afterglow component in its scintillation decay and severe hysteresis after prolonged irradiation, limiting achievable energy resolution and imaging quality and speed. These shortcomings effectively preclude its use in applications such as radionuclide imaging and medical CT, where its low cost could otherwise have immense economic impact. An improved form of CsI:Tl scintillator, such as the one proposed here, can reduce the cost of critical life-saving medical equipment such as X-ray CT scanners, fluoroscopy systems and other devices that rely on rapid data acquisition.