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

描述（由申请人提供）：这项工作的长期目标是开发一种专用的乳腺PET扫描仪，可用于准确表征和监测早期乳腺肿瘤（I期和II期）的反应。该扫描仪将提供非常高分辨率和灵敏度的层析重建图像，以检测，表征和监测低示踪剂摄取的小肿瘤的反应，这在多用途临床PET扫描仪中表现不佳。这将是一个局部环形扫描仪的设计，以便为整个乳房（包括胸壁）和可能的腋窝成像提供灵活性，改变不同乳房大小的探测器分离，提供活检能力，以及与其他成像方式（如光学，乳房x线照相术或mr）结合的潜力。目前可用的专用乳房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，部分环形几何结构导致人们在低对比度平面图像或定量能力有限的人工层析图像之间进行选择。通过旋转探测器可以获得（改进的）高质量的层析成像图像，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型放射性示踪剂的关键。相比之下，我们的设计将使用飞行时间（TOF）信息为固定探测器的部分环形扫描仪获得高质量和定量的层析图像，同时在整个扫描仪视场（FOV）中保持高空间分辨率和灵敏度。我们的目标有四个：(i)开发一种探测器，在使用小而长的晶体获得高空间分辨率和灵敏度的同时保持非常好的定时分辨率；（ii）展示TOF信息可以弥补缺失投影数据的程度，并研究空间分辨率、灵敏度和定时分辨率之间的权衡，以及扫描仪的角度覆盖范围，以实现最佳的扫描仪设计；（iii）开发巧合成像设置；（iv）开发定量图像的数据校正和成像重建技术，随后对重合设置的成像性能进行表征。这项工作将包括探测器的测量和模拟，以测试不同的晶体尺寸和表面光洁度，不同类型的光倍增管和完整的探测器阵列。完整的系统模拟将执行基于探测器测量结果的不同扫描仪几何形状以及。最后，一个最佳的探测器设计将发展成同步探测器阵列，并将进行成像实验来证明其能力。公共卫生相关性：临床上用于人体成像，当前一代临床PET扫描仪有限的空间分辨率和灵敏度导致小乳腺肿瘤的检测和量化减少。通过开发具有高分辨率和灵敏度的专用乳房扫描仪，以及生产全层析成像，将有助于早期乳腺癌的检测和分期。因此，开发一种专用的TOF乳房扫描仪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.