VisR Ultrasound for Noninvasively Monitoring Renal Allograft Health

 描述(申请人提供)：肾移植是终末期肾脏疾病最理想和最具成本效益的治疗方法，但20%-30%的同种异体移植物在存活受者10年内失败，延长移植物健康是移植患者尚未满足的主要需求之一。尽管通过预防不可逆转的损害的预防性治疗延长了移植物的健康，但目前的移植监测方法并不能充分促进干预。非侵入性方法，包括连续血清肌酐水平的变化，缺乏敏感性和特异性。在缺乏可靠的非侵入性生物标志物的情况下，侵入性活组织检查仍然是评估移植健康的标准，但监督或“常规”活组织检查与发病率和费用有关，因此在病情稳定、不敏感的患者中存在争议。缺乏一种已证实的、非侵入性的同种异体移植物健康生物标志物--一种能够以足够的灵敏度和特异度识别移植物早期变性以激发适当的活检和及时干预的生物标记物--是肾移植管理中的一个重大缺口。为了填补这一空白，拟议的研究旨在展示粘弹性响应(Visr)超声，这是一种基于声辐射力(ARF)的新技术，可以无创地询问组织的粘弹性属性，用于监测同种异体肾移植的健康状况。不同的机械超声方法显示了肾脏纤维化与测量的僵硬程度之间的相关性，但这些方法受到肾脏的异质性和各向异性以及肾脏灌注和尿压的抑制。与这些方法不同的是，VisR通过只在ArF激励区域观察ArF引起的位移来估计粘弹性性质，因此扰动机械力是集中分布的，来自非均质性的剪切波扰动不会造成混淆。此外，我们的临床前数据显示，对称的ARF焦点配置消除了各向异性组织中VISR结果的角度依赖性。我们的初步数据还表明，VISR描述了纤维化和炎症，移植后一年出现的纤维化和炎症被证明预示着以后的肾功能下降和移植物衰竭。最后，我们在一项试点临床可行性研究中展示了VISR影响肾移植监测的潜力，该研究表明，与未接受活检的对照肾移植受者相比，VISR区分了肾移植患者中的肾小球疾病、中到重度血管疾病和慢性移植物肾病(CAN)，这些患者因疑似移植功能障碍而接受了临床指定的活检。我们的大量初步数据表明，VISR在改善肾移植健康的非侵入性监测方面具有很强的潜力。我们假设，体内VISR超声比肾移植受者的血肌酐浓度更早、更灵敏、更特异地显示移植肾功能障碍。为了验证这一假设，我们将追求以下具体目标：1)证明在正常、炎症和纤维化的猪肾脏中，哪些VISR结果指标独立于肾压力和组织方向；2)确定哪些VISR结果指标在临床上检测到移植肾功能障碍；以及3)比较系列VISR和血肌酐结果在检测移植肾功能障碍和检测的及时性方面的能力。我们预计，这种方法将允许项目的各个部分协同工作，而不是相互依赖。在这个项目完成后，VISR成像将准备进行后续的、更大规模的临床试验，以证实其在监测肾移植方面的有效性。

 DESCRIPTION (provided by applicant): Renal transplantation is the most desirable and cost effective treatment for end stage renal disease, but 20- 30% of allografts fail in living recipient by 10 years, and prolonging graft health is one of the major unmet needs for transplant patients. Although graft health is extended by preemptive treatments that prevent irreversi- ble damage, intervention is inadequately motivated by current transplant monitoring methods. Noninvasive methods, including changes in serial serum creatinine levels, lack sensitivity and specificity. In the absence of reliable noninvasive biomarkers, invasive biopsy remains the standard for assessing transplant health, but sur- veillance or "protocol" biopsies are associated with morbidity and cost and are therefore controversial in stable, unsensitized patients. The lack of a demonstrated, noninvasive biomarker for allograft health - one that identi- fies early graft degeneration with sufficient sensitivity and specificity to motivate appropriate biopsy and enable timely intervention - represents a major gap in renal transplant management. To fill this gap, the proposed re- search aims to demonstrate Viscoelastic Response (VisR) ultrasound, a novel acoustic radiation force (ARF)- based technology that noninvasively interrogates the viscoelastic properties of tissue, for monitoring renal allo- graft health. Alternative mechanical ultrasound approaches have shown correlation between renal fibrosis and measured stiffness, but these approaches are inhibited by the heterogeneity and anisotropy of the kidney as well as renal perfusion and urinary pressure. Unlike these methods, VisR estimates viscoelastic property by observing ARF-induced displacements in only the ARF region of excitation, so the disturbing mechanical force is focally distributed, and shear wave disturbances from heterogeneity are not confounding. Further, our pre- liminary data show that a symmetric ARF focal configuration obviates the angle dependence of VisR outcomes in anisotropic tissue. Our preliminary data also demonstrate that VisR delineates fibrosis and inflammation, the presence of which one-year post transplantation has been shown to predict later decline in kidney function and graft failure. Finally, we have demonstrated VisR's potential to impact renal transplant monitoring in a pilot clini- cal feasibility study, which illustrates that VisR distinguishes glomerular disease, moderate-to-severe vascular disease, and chronic allograft nephropathy (CAN) in renal transplant patients undergoing clinically indicated biopsy for suspected graft dysfunction versus control renal transplant recipients not undergoing biopsy. Our body of preliminary data suggests that VisR has strong potential to improve noninvasive monitoring of renal transplant health. We hypothesize that in vivo VisR ultrasound delineates renal allograft dysfunction earlier and with greater sensitivity and specificity than serum creatinine concentration in renal allograft recipients. To test this hypothesis, we will pursue the following specific aims: 1) Demonstrate which VisR outcome metrics are independent of renal pressure and tissue orientation in normal, inflamed and fibrotic pig kidneys; 2) Deter- mine which VisR outcome metrics detect renal allograft dysfunction clinically; and 3) Compare serial VisR and serum creatinine outcomes in terms of ability to detect renal allograft dysfunction and the timeliness of detec- tion. We anticipate that this approach will allow the individual parts of the project to be synergistic withut being interdependent. At the completion of this project, VisR imaging will be poised for a follow-on, larger-scale clini- cal trial to substantiate its usefulness for monitoring renal transplants.