Towards artifact-free non-invasive renal and hepatic functional MRI: development of an organ-specific navigator-based pCASL sequence with EPI acquisition

肾脏和肝脏血流灌注的细微局部变化是疾病发展的重要指标；如果量化，它们可以用来对肿瘤过程中的恶性肿瘤进行分级，并在疾病治疗期间监测器官功能。虽然肾小球滤过率被认为是评估肾功能的金标准，但它没有空间相关性，这就是为什么横断面血流灌注测量更准确和特异的原因。考虑到在严重肾功能损害和对比剂过敏的患者中使用肾毒性造影剂是不明智的，采用动脉自旋标记(ASL)技术的无创性MRI灌注测量正变得越来越重要。他们通过使用磁性标记的血液作为内源性示踪剂来提供器官灌注的定量测量。在神经成像中，伪连续性ASL(PCASL)是最近发展起来的，可以提供相对可靠的脑血流灌注评估。然而，在腹部成像环境中，运动伪影使pCASL技术的应用显著复杂化。为了解决这个问题，我们的目标是开发一种基于器官特定导航器的切片跟踪技术，使用基于回声平面成像(EPI)的序列测量肾脏和肝脏的血流灌注，以前瞻性地补偿呼吸运动伪影。这将使无伪影、自由呼吸的多层螺旋CT和非侵入性肾脏和肝脏灌注成像成为可能。该序列将为1.5Tesla MRI扫描仪(西门子Aera)开发，在志愿者中进行验证，并与标准的ASL MRI技术进行比较。后处理、数值分析和统计评估将在MatLab v9.11 R2021b、Pythonv3.10.2和R v4.1.0中执行。

Subtle local changes in renal and hepatic perfusion are important indicators of developing disease; if quantified, they can be used to grade malignancy in neoplastic processes, and to monitor organ function during disease treatment. While glomerular filtration rate is considered the gold standard of kidney function evaluation, it has no spatial correlate, which is why cross-sectional perfusion measurements are more accurate and specific. Considering that the administration of nephrotoxic contrast agent is ill-advised in patients with severe kidney function impairment and patients with allergies to contrast agents, non-invasive MRI perfusion measurements with arterial spin labelling (ASL) techniques are gaining in importance. They provide quantitative measurements of organ perfusion by using magnetically labeled blood as an endogenous tracer. In neuroimaging, pseudocontinuous ASL (pCASL) has been developed recently and shown to provide a relatively reliable assessment of cerebral perfusion. In the abdominal imaging setting, however, motion artifacts significantly complicate the application of the pCASL technique. To address this problem, we aim to develop an organ-specific navigator-based slice tracking technique using an Echo-Planar Imaging (EPI) based sequence in renal and hepatic perfusion measurements to prospectively compensate for respiratory motion artifacts. This will allow an artifact-free free-breathing multi-slice and non-invasive renal and hepatic perfusion imaging. The sequence will be developed for a 1.5 Tesla MRI scanner (Siemens Aera), validated in volunteers, and compared against standard ASL MRI techniques. Postprocessing, numerical analysis, and statistical evaluation will be performed in Matlab v9.11 R2021b, Python v3.10.2, and R v4.1.0.