Through-body TCSPC based real-time tracking to guide interventional medical procedures

对医疗设备的准确跟踪是目前需要使用电离X射线辐射和/或造影剂的关键临床要求。这些基本程序具有潜在的长期有害影响，特别是对婴儿，而且由于需要保护工作人员和等待X光设备的供应或运送，还会造成重大干扰(因此也会造成成本)。因此，开发替代跟踪方法具有重要的临床驱动力。最近，我们展示了一种突破性的方法，使用单光子成像来跟踪位于组织深处的医疗设备[1]。我们的方法利用了这样一个事实，即如果将一个点光源放置在人体内，一小部分光将以接近视线的路径从人体射出。至关重要的是，这些视线光子(光粒子)保存了有关组织内点源空间位置的精确信息，但提取这些信息并不是一件容易的事情。访问它的关键是这样一个事实，即视线光子离开人体的传输时间比更漫反射的光子更短-这一事实允许我们利用一种名为时间相关单光子计数(TCSPC)的技术来检测它们并将其与更漫反射的光子区分开来。与不记录光子到达探测器阵列上的光子到达时间的“普通”相机不同，基于TCSPC的成像依赖于使用在精确已知时间产生短脉冲光的光源，以及可以记录单个光子到达时间的单光子敏感探测器阵列。通过这种方式，TCSPC成像允许我们设计一种成像系统，该成像系统可以在漫反射光子开始出现之前选择性地检测和成像新出现的视线光子的位置，这使得我们能够定位源的精确位置。尽管我们现在已经展示了这种技术在医疗设备跟踪方面的潜力，但商业TCSPC探测器阵列的低填充因子(探测器阵列的多少是光敏的)阻碍了临床转换。这种低填充系数(~1%)实际上意味着我们损失了到达探测器阵列的99%的光，将最大帧速率限制在~0.05赫兹--太低了，无法在导管放置期间向临床医生提供足够的反馈。最近，通过STFC资助，我们证明了所谓的“光子灯笼”转变提供了一种新的、强大的途径来解决商业上可获得的SPAD阵列的低填充因数[2]。因此，该项目的总体目标将是与我们的商业合作伙伴Photon Force合作，利用这一能力，并开发一种能够以视频帧速率跟踪导管的TCSPC系统。然后，我们将与临床医生科学家合作，通过使用相关模型演示跟踪能力，将该技术转化为临床开发。该项目的结果将用于支持转化性临床研究，并与Photon Force合作开发适用于医疗市场的TCSPC跟踪系统。选择。Express 8,4077-4095(2017)[2]H.K.Chandrasekharan等人。纳特。交警。8、14080(2017年)。

The accurate tracking of medical devices is a key clinical requirement that currently requires the use of ionising X-ray radiation and / or contrast agents. These essential procedures have potential long term detrimental effects, especially on babies, and also causes significant disruption (and therefore cost) due to both the need to protect staff and waiting for the availability of, or transport to, X-ray equipment. There are therefore significant clinical drivers to develop alternative tracking methods. Very recently, we have demonstrated a ground breaking approach to tracking medical devices located deep in tissues using single photon imaging [1]. Our approach exploits the fact that if a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body with a close to line-of-sight path. Crucially, these line-of-sight photons (particles of light) hold precise information about the spatial location of the point source inside the tissue, but extracting this information is not trivial. The key to accessing it is the fact that the line-of-sight photons exit the body with a shorter transit time than the more diffuse photons - a fact that allows us to exploit a technique known as time-correlated single-photon counting (TCSPC) to detect and distinguish them from more diffuse photons. In contrast to "normal" cameras, which do not record the arrival time of the photons on the detector array, TCSPC-based imaging relies on using a source of light that produces short pulses of light at precisely known times, together with a single-photon sensitive detector array that can record the arrival times of individual photons. In this manner, TCSPC imaging allows us to design an imaging system that can selectively detect and image the location of the emerging line-of-sight photons before the diffuse photons start to emerge, and this allows us to locate the precise position of the source.Although we have now demonstrated the potential of this technique for medical device tracking, the clinical translation has been hampered by the low fill-factor (how much of the detector array is light-sensitive) of commercially available TCSPC detector arrays. This low fill-factor (~1%) effectively means that we lose 99% of the light reaching the detector array, limiting the maximum frame rate to ~0.05 Hz - too low to provide adequate feedback to the clinician during catheter placement. Recently, through STFC funding, we have demonstrated that so-called "photonic lantern" transitions provide a new and powerful route to addressing the low fill-factor of commercially available SPAD arrays [2]. The overarching goal of this project will therefore be to work with our commercial partners, Photon Force, to exploit this capability, and develop a TCSPC system capable of tracking catheters with video frame rates. We will then work with clinician scientists to translate the technology towards clinical exploitation by demonstrating the tracking capability using relevant models. The results of this project will then be used to support translational clinical studies, and to work with Photon Force to develop a TCSPC tracking system suitable for the medical market.[1] M. G. Tanner et al, Biomed. Opt. Express 8, 4077-4095 (2017)[2] H. K. Chandrasekharan et al. Nat. Commun. 8, 14080 (2017).