A Time-of-Flight PET scanner for dedicated breast imaging

描述(由申请人提供)：这项工作的一个长期目标是开发一种专用的乳腺PET扫描仪，可以用于准确地描述和监测早期乳腺肿瘤(I期和II期)的反应。这种扫描仪将提供非常高分辨率和灵敏度的断层重建图像，以检测、表征和监测示踪剂摄取率低的小肿瘤的反应，这在多用途临床PET扫描仪中表现不佳。它将采用部分环形扫描仪设计，以便为整个乳房(包括胸壁)和可能的腋窝成像提供灵活性，为不同的乳房大小改变探测器间隔，提供活检能力，以及与其他成像方式(如光学、乳房X光或MR)相结合的可能性。目前可用的专用乳腺PET扫描仪被迫在空间分辨率和灵敏度之间进行权衡，到目前为止，部分环形几何形状导致人们在低对比度平面图像或量化能力有限的伪断层图像之间进行选择。通过旋转探测器可以获得(改进的)高质量断层图像，但这增加了系统的复杂性，也限制了动态成像能力，而动态成像能力是测试新的无线电示踪器的关键。相比之下，我们的设计将使用飞行时间(TOF)信息，为带有固定探测器的部分环形扫描器获得高质量和定量的断层图像，同时在整个扫描器视场(FOV)中保持高空间分辨率和灵敏度。我们的目标有四个方面：(I)开发一种在使用细长晶体实现高空间分辨率和灵敏度的同时保持非常好的时间分辨率的探测器，(Ii)展示TOF信息可以在多大程度上弥补丢失的投影数据，并调查空间分辨率、灵敏度和时间分辨率以及扫描仪角度覆盖之间的权衡，以实现最佳扫描仪设计，(Iii)开发符合成像装置，以及(Iv)开发定量图像的数据校正和成像重建技术，然后描述符合装置的成像性能。这项工作将涉及探测器测量和模拟，以测试不同的晶体尺寸和表面光洁度，不同类型的光电倍增管，以及完整的探测器阵列。还将根据不同扫描仪几何形状的探测器测量结果进行全系统模拟。最后，一个最佳的探测器设计将被开发成符合探测器阵列，并将进行成像实验以证明其能力。公共卫生相关性：在临床上，对于人体成像，当前一代临床PET扫描仪的空间分辨率和灵敏度有限，导致对小型乳腺肿瘤的检测和量化减少。通过开发高分辨率和高灵敏度的专用乳房扫描仪，以及产生完整的断层图像，将有助于早期乳腺癌的检测和分期。因此，一种专用的TOF乳腺扫描仪的开发有可能对乳腺癌患者的治疗产生重大影响。

DESCRIPTION (provided by applicant): A long-term objective of this work is the development of a dedicated breast PET scanner that can be used for accurately characterizing and monitoring response of early stage breast tumors (stages I and II). This scanner will provide tomographic reconstructed images with very high resolution and sensitivity to detect, characterize, and monitor response in small tumors with low tracer uptake, something that is not performed well in the multi-purpose clinical PET scanners. It will be a partial ring scanner design in order to provide flexibility in imaging the whole breast (including chest wall) and possibly the axilla, to vary the detector separation for different breast sizes, to provide biopsy capability, as well as the potential to combine with other imaging modalities such as optical, mammography, or MR. Dedicated breast PET scanners currently available are forced to trade-off between spatial resolution and sensitivity, and until now the partial ring geometry leads one to choose between low contrast planar images or artifactual tomographic images with limited quantification capability. It is possible to achieve (improved) high quality tomographic images by rotating the detectors, but this adds complexity to the system and also restricts the dynamic imaging capabilities that are key to testing new radio-tracers. In contrast, our design will use time-of-flight (TOF) information to attain high quality and quantitative tomographic images for the partial ring scanner with stationary detectors, while maintaining high spatial resolution and sensitivity throughout the scanner field-of-view (FOV). Our aims are four fold: (i) develop a detector which maintains very good timing resolution while using small and long crystals for high spatial resolution and sensitivity, (ii) demonstrate the extent by which TOF information can compensate for the missing projection data, and investigate the trade-offs involved between spatial resolution, sensitivity, and timing resolution, as well as scanner angular coverage, to achieve an optimal scanner design, (iii) develop a coincidence imaging setup, and (iv) develop data correction and imaging reconstruction techniques for quantitative images followed by a characterization of the imaging performance of the coincidence setup. The work will involve detector measurements and simulations for testing varying crystal sizes and surface finishes, different types of photo-multiplier tubes, and full detector arrays. Full system simulations will be performed based upon detector measurement results for varying scanner geometries as well. Finally, an optimal detector design will be developed into coincident detector arrays and imaging experiments will be performed to demonstrate its capabilities. PUBLIC HEALTH RELEVANCE: Clinically for human imaging, limited spatial resolution and sensitivity of current generation of clinical PET scanners leads to reduced detection and quantification of small breast tumors. By developing a dedicated breast scanner with high resolution and sensitivity, as well as production of full tomographic images, will help in the detection and staging of early stage breast cancer. Hence, the development of a dedicated, TOF, breast scanner has the potential to significantly impact patient treatment for breast cancer.