Optimization of low-dose, low cost mobile 3D X-ray Imaging

数字层析合成(DT)是一种三维X射线成像模式。这种成像模式既提取了X光图像中的典型2D信息，也提取了被成像身体的深度信息。这通常是通过在设定的角度范围内改变X射线管的角度来实现的，其中在每个唯一角度创建的图像对应于被成像物体的某一层深度[1]。这些图像可以用重建算法[2]重建，从而产生一个单一的图像，在感兴趣的物体和背景之间的对比度比在2D X射线图像中看到的更强。然而，用于医疗目的的传统DT成像机需要高功率来操作，并且太大而不能携带，因此不能在床边成像中应用。由Adaptix有限公司[3]创建的便携式DT系统改变了这一点。该系统采用冷阴极平板X射线源(FPS)阵列进行设计和制作。这些阵列由25个单独的发射器组成，这些发射器按顺序发射，产生传统上由X射线管旋转产生的多个投影[4]。该设备已经成功地用于小动物和人类的骨科成像。因此，已经展示了将其放大用于胸部成像的概念验证[5]，目前正在积极研究开发这种潜在的低成本和便携式的胸部DT成像方法。这项技术在无损材料评估(NDE)和牙科领域有更多的应用。这个博士项目旨在利用蒙特卡罗模拟软件Geant4[6]来解决在这些设备的进一步开发中出现的工程和科学问题。初步的工作已经完成，以研究不同的X射线靶结构对产生的X射线谱的影响，从而对患者的剂量和输出图像的质量的影响。正在进行的工作努力通过实施现实的探测器来进一步开发这一模拟框架，以允许对从这项工作中创建的图像与从物理设备本身输出的图像进行更近距离的比较。这还应该有助于讨论这种DT方法的最佳探测器结构，并确定在这种情况下如何最好地将探测器质量参数化。未来的工作计划从这一点开始，通过应用这种基准模拟环境来研究现代X射线方法，如双能量成像，以确定如何最好地使设备适应这些新的能力。这将产生模拟数据，然后可以用设备本身进行实验验证。因此，项目说明将反映在Geant4软件内开发一个准确的模拟环境，该环境可用于解决在以比实验更省成本和更省人力的方法构建这项技术时提出的实际问题。与现有数据的比较将确保准确的基准测试，以证明模拟的可靠性，从而使其能够结合实验工作为未来的发展提供信息。参考文献[1]Shinn Huey Chou，Greg A.Kicska，Sudhakar N.Pipavath和Gautham P.Reddy。胸部数字断层合成：当前和新兴的应用。[2][2]瓦迪姆·Y·索洛维耶夫，凯特·L·伦福斯，康拉德·J·迪尔克斯，斯蒂芬·G·威尔斯。医学生物学物理学医学生物学数字断层合成的无网格重建技术。物理医学。生物，65：85010,2020年。[3]Adaptix有限公司，https://adaptix.com/.[4]Thomas Primidis。2022.1[5]Thomas G Primidis、Stephen G Wells、Vadim Y Soloviev和Carsten P Welsch。使用固定平板信号源阵列和固定探测器的3D胸部断层扫描：概念的蒙特卡罗证明。2021年

Digital Tomosynthesis (DT) is a 3D mode of X-ray imaging. This imaging mode extracts both the typical2D information you would expect from an x-ray image, as well as depth information on the body beingimaged. This is conventionally achieved by altering the angle of an x-ray tube over a set angular range,where the image created at each unique angle corresponds to a certain layer of depth of the imaged body[1]. These images can be reconstructed using reconstruction algorithms [2] to create a singular imagewith enhanced contrast between the object of interest and background than is seen in 2D x-ray images.However, conventional DT imaging machines for medical purposes require high power to be operated, andare too large to be portable and hence have no application in bedside imaging.A portable DT system created by Adaptix Ltd [3] has changed this. This system has been designed andconstructed which uses cold-cathode, flat panel x-ray source (FPS) arrays. These arrays are constructed of25 individual emitters that emit sequentially, creating the multiple projections conventionally created bythe rotation of the x-ray tube [4]. This device has been successful for small animal and human orthopaedicimaging. Hence, proof-of-concept for the scaling up of this for chest imaging purposes has been shown [5]and active research is now underway for the development of this potential low-cost and portable methodof chest DT imaging. This technology sees additional application in non-destructive material evaluation(NDE) and dentistry contexts.This PhD project aims to utilise Geant4 [6], a Monte-Carlo simulation software, to address the engineeringand science questions that arise within the further development of these devices. Initial work has beencompleted to investigate the effect of different x-ray target constructions on the x-ray spectra producedand hence the dosage to the patient and the quality of the image outputted. Ongoing work endeavours todevelop this simulation framework further by implementing a realistic detector to allow closer comparisonof the images created from this work to those outputted from the physical device itself. This shouldadditionally inform a discussion on the optimal detector construction for this DT approach and identifyhow best to parameterise detector quality in this context. Future work is planned to follow on fromthis by applying this benchmarked simulation environment to look at modern x-ray approaches, suchas dual-energy imaging, to identify how best to adapt the device for these novel capabilities. This willcreate simulation data that can then be experimentally verified with the device itself. Hence, the projectnarrative will reflect the development of an accurate simulation environment within the Geant4 softwarewhich can be used to address practical questions raised when constructing this technology in a morecost- and labour-efficient method than can be achieved experimentally. Comparison with existing datawill ensure accurate benchmarking to prove the reliability of the simulation and hence allow it to informfuture developments in combination with experimental work.References[1] Shinn Huey Chou, Greg A. Kicska, Sudhakar N. Pipavath, and Gautham P. Reddy. Digital tomosynthesisof the chest: Current and emerging applications. Radiographics, 34:359-372, 3 2014.[2] Vadim Y Soloviev, Kate L Renforth, Conrad J Dirckx, and Stephen G Wells. Physics in medicinebiology physics in medicine biology meshless reconstruction technique for digital tomosynthesis. Phys.Med. Biol, 65:85010, 2020.[3] Adaptix Ltd, https://adaptix.com/.[4] Thomas Primidis. Design and optimisation of ultra-compact, high-resolution 3d x-ray imaging systems.2022.1[5] Thomas G Primidis, Stephen G Wells, Vadim Y Soloviev, and Carsten P Welsch. 3d chest tomosynthesisusing a stationary flatpanel source array and a stationary detector: a monte carlo proof ofconcept. 2021