Solid-State Breast CT with X-ray Colour Imaging: A new approach to breast screening using STFC's HEXITEC imaging detector technology

平面X射线乳腺摄影术是用于检测妇女早期乳腺癌的金标准筛查方法。然而，新的数字探测器技术已经出现，以取代传统的X射线胶片暗盒，这激发了人们对使用小型专用CT扫描仪的可能性的兴趣（即计算机断层扫描，有时称为CAT扫描仪），其产生横截面切片，用于乳房成像。乳房CT的两个主要优点是：（i）避免乳房压迫，其可能是痛苦的并且导致手术拒绝;以及（ii）去除在常规乳房X线照片中总是存在的分散注意力的上/下背景杂波。该项目是利用STFC公司的HEXITEC先进的影像技术，结合X射线源技术的最新发展，开发出一种新型的乳腺CT扫描仪。该项目的目的是为了提高乳腺CT的检出率，降低目前筛查技术中存在的主要问题--癌症的误检率。该提案的想法是进行开发第一个可行的固态所需的试点工作（即无移动部件）能够进行“彩色”X射线成像的乳腺CT扫描仪-目前还没有具有这种类型的“彩色”成像能力的商业医疗扫描仪。在这方面使用“彩色”X射线成像可以被认为类似于彩色与单色（光学）摄影：单色照相机生成图像，其中每个像素具有类似于表示由照相机观看的场景的特定部分的所有光波长或颜色的“平均值”的灰色阴影（即灰度或灰度级）;然而，彩色照相机将这些波长分成分量组（通常为红色、绿色和蓝色），然后可以将这些分量组重新组合以产生彩色图像。传统的CT扫描仪也会产生灰度图像，这些图像代表扫描中使用的所有X射线波长的平均值，而HEXITEC技术将允许我们分离或分解单个X射线光子，并将其放入组成波长的组中，以产生X射线“彩色”图像。开发这种方法为生成横截面图像或乳房的虚拟切片提供了令人兴奋的新机会，这些图像将以更高的对比度显示恶性疾病，并允许更好地区分恶性和良性疾病。为了使这种方法成为现实，我们建议解决传统CT扫描过程中出现的两个主要问题：在传统的X射线CT中，X射线源和检测器阵列围绕患者（或者在这种情况下，围绕乳房）旋转需要时间。然而，使用如上所述的X射线光子计数将X射线光子脉冲分成分量波长需要比传统方法更长的扫描时间。这些瓶颈减慢了扫描过程，并且目前使其在患者吞吐量、舒适度和图像质量等临床工作中不切实际在这个新项目中，我们建议使用模拟方法来研究“无移动部件”的几何形状：HEXITEC探测器的圆环，其位于碳纳米管X射线源的圆形阵列的正下方在扫描期间，从环周围的每个源发射的短X射线爆发允许HEXITEC探测器并行工作，而不是顺序地围绕环扫描。这将大大加快扫描时间，从而解决扫描过程中的瓶颈。该项目的目的是探索下一代探测器所需的性能，以及如何充分利用这些扫描中使用的X射线剂量，使“彩色”X射线乳腺CT成为乳腺癌筛查的可行的新成像方法。

Planar X-ray mammography is the gold standard screening method used for detecting early-stage breast cancer in women. However, new digital detector technologies have emerged to replace the conventional X-ray film cassette, which has stimulated interest in the possibility of using small dedicated CT scanners (i.e. Computed Tomography, sometimes referred to as CAT scanners), which produce cross-sectional slices, for breast imaging.The two major advantages of breast CT are :(i) avoidance of breast compression, which can be painful and lead to procedure refusals; and(ii) removal of the distracting over/underlying background clutter which is always present in a conventional mammogram. This produces images that makes the detection of cancer easier for a radiologist, which can improve detection rates and reduce the probability of false cancer detection, which is also a major problem with current screening technology.This project is about using STFC's HEXITEC state-of-the-art imaging technology and combining it with new developments in X-ray source technology to develop a new type of breast CT scanner. The idea in this proposal is to undertake the pilot work needed for developing the first viable solid state (i.e no moving parts) breast CT scanner capable of 'colour ' X-ray imaging - currently there are no commercial medical scanners that have this type of 'colour' imaging capability.Using 'colour' X-ray imaging in this respect can be thought of as analogous to colour vs monochrome (optical) photography: a monochrome camera generates an image where each pixel has a shade of grey (i.e. grayscale or grey level) that is akin to an 'average' of all the optical wavelengths or colours representing a particular part of the scene viewed by the camera; however, a colour camera splits these wavelengths into component groups (usually red, green and blue) which can then be recombined to produce colour images. Conventional CT scanners also produce grayscale images that represent an average across all the X-ray wavelengths used in the scan, whereas the HEXITEC technology will allow us to separate or COUNT the individual X-ray photons and put these into groups of component wavelengths, to produce X-ray 'colour' images. Developing this approach opens up exciting new opportunities to produce cross-sectional images, or virtual slices of the breast which will show malignant disease with higher contrast, and allow better differentiation between malignant and benign conditions.To make this approach a practical reality, we propose to address two major issues that occur during a conventional CT scan: in conventional X-ray CT it takes time for the X-ray source and detector array to rotate round the patient (or in this case, the breast). However, using X-ray PHOTON COUNTING as described above, to split the X-ray photon pulse into component wavelengths, requires an even longer scanning time than the conventional approach. These bottle-necks slow up the scanning process and currently make it impractical for clinical work as patient throughput, comfort, and image quality (due to inevitable patient motion during the scan time) would be compromised.In this new project we propose to use simulation methods to investigate a 'no moving parts' geometry: a circular ring of HEXITEC detectors which sits immediately below a circular array of carbon nanotube X-ray sources During a scan, a short X-ray burst fired from each source around the ring allows the HEXITEC detectors to work in parallel rather than sequentially scanning round the ring. This will dramatically speed up the scanning time and so addresses the bottlenecks in the scanning process. The aim of this project is to explore the performance needed for the next generation of detectors and how to make best use of the X-ray dose used in these scans so as to make 'Colour' X-ray Breast CT into a viable new imaging approach for breast cancer screening.