Department of Radiation Oncology, Stanford University, 875 Blake Wilbur Dr., Stanford, CA 94305.
Department of Radiation Oncology, Stanford University, 875 Blake Wilbur Dr., Stanford, CA 94305; Almaden Research Center, IBM Research, San Jose, California.
Acad Radiol. 2019 Jan;26(1):38-49. doi: 10.1016/j.acra.2018.03.006. Epub 2018 Mar 29.
The objective of this study was to assess the feasibility of single-inhalation xenon-enhanced computed tomography (XeCT) to provide clinically practical, high-resolution pulmonary ventilation imaging to clinics with access to only a single-energy computed tomography scanner, and to reduce the subject's overall exposure to xenon by utilizing a higher (70%) concentration for a much shorter time than has been employed in prior studies.
We conducted an institutional review board-approved prospective feasibility study of XeCT for 15 patients undergoing thoracic radiotherapy. For XeCT, we acquired two breath-hold single-energy computed tomography images of the entire lung with a single inhalation each of 100% oxygen and a mixture of 70% xenon and 30% oxygen, respectively. A video biofeedback system for coached patient breathing was used to achieve reproducible breath holds. We assessed the technical success of XeCT acquisition and side effects. We then used deformable image registration to align the breath-hold images with each other to accurately subtract them, producing a map of lung xenon distribution. Additionally, we acquired ventilation single-photon emission computed tomography-computed tomography (V-SPECT-CT) images for 11 of the 15 patients. For a comparative analysis, we partitioned each lung into 12 sectors, calculated the xenon concentration from the Hounsfield unit enhancement in each sector, and then correlated this with the corresponding V-SPECT-CT counts.
XeCT scans were tolerated well overall, with a mild (grade 1) dizziness as the only side effect in 5 of the 15 patients. Technical failures in five patients occurred because of inaccurate breathing synchronization with xenon gas delivery, leaving seven patients analyzable for XeCT and single-photon emission computed tomography correlation. Sector-wise correlations were strong (Spearman coefficient >0.75, Pearson coefficient >0.65, P value <.002) for two patients for whom ventilation deficits were visibly pronounced in both scans. Correlations were nonsignificant for the remaining five who had more homogeneous XeCT ventilation maps, as well as strong V-SPECT-CT imaging artifacts attributable to airway deposition of the aerosolized imaging agent. Qualitatively, XeCT demonstrated higher resolution and no central airway deposition artifacts compared to V-SPECT-CT.
In this pilot study, single-breath XeCT ventilation imaging was generally feasible for patients undergoing thoracic radiotherapy, using an imaging protocol that is clinically practical and potentially widely available. In the future, the xenon delivery failures can be addressed by straightforward technical improvements to the patient biofeedback coaching system.
本研究旨在评估单次吸入氙增强计算机断层扫描（XeCT）为仅具备单能计算机断层扫描仪的临床提供实用、高分辨率肺部通气成像的可行性，并通过利用比先前研究更高（70%）的氙浓度进行更短时间的扫描，从而减少患者整体接触氙的时间。
我们对 15 名接受胸部放射治疗的患者进行了机构审查委员会批准的前瞻性 XeCT 可行性研究。对于 XeCT，我们分别进行了两次呼吸暂停单能计算机断层扫描，每次吸气均吸入 100%氧气和 70%氙气与 30%氧气的混合物，各吸入一次。使用视频生物反馈系统对患者进行呼吸训练，以实现可重复的呼吸暂停。我们评估了 XeCT 采集的技术成功率和副作用。然后，我们使用可变形图像配准将呼吸暂停图像彼此对齐，准确地对其进行减影，生成肺部氙气分布图。此外，我们还对 15 名患者中的 11 名采集了通气单光子发射计算机断层扫描-计算机断层扫描（V-SPECT-CT）图像。为了进行比较分析，我们将每个肺部分为 12 个扇区，根据每个扇区的亨氏单位增强计算氙气浓度，然后将其与相应的 V-SPECT-CT 计数相关联。
总体而言，XeCT 扫描耐受良好，15 名患者中有 5 名仅出现轻度（1 级）头晕作为副作用。由于氙气输送与呼吸同步不准确，5 名患者的技术失败，只有 7 名患者可用于 XeCT 和单光子发射计算机断层扫描相关性分析。对于两名患者，扫描中明显可见通气缺陷，其扇区相关性很强（Spearman 系数>0.75，Pearson 系数>0.65，P 值<.002）。对于其余 5 名患者，其 XeCT 通气图更均匀，且由于气道中气溶胶成像剂的沉积，V-SPECT-CT 成像出现强烈伪影，因此相关性不显著。定性而言，与 V-SPECT-CT 相比，XeCT 显示出更高的分辨率，且不存在中央气道沉积伪影。
在这项初步研究中，使用一种临床实用且可能广泛适用的成像方案，单次呼吸 XeCT 通气成像对于接受胸部放射治疗的患者通常是可行的。在未来，通过对患者生物反馈教练系统进行简单的技术改进，可以解决氙气输送失败的问题。
