Advanced Knee ASL Imaging at 7T

摘要 骨髓灌流可以提供有关骨生理的基本知识，提高我们对 疾病病因和病理生理学，有助于区分正常和异常的骨髓， 并评估对处方疗法的反应。动脉自旋标记(ASL)磁共振成像 (MRI)作为一种无创、无对比增强的方法，非常适合于对 疾病进展和治疗反应的常规评估。但膝关节骨骺的ASL成像 骨髓是具有挑战性的，因为ASL成像是一种低信噪比的技术，并且灌注水平是 骨痂黄色骨髓明显低，主要由脂肪细胞组成，具有稀疏的网状结构 毛细血管。超强(≥7T)磁场可以特别有利于ASL成像并克服这些挑战 通过提高信噪比，延长血液和组织T1，并改善并行成像性能。然而， 目前临床批准的单次传输磁共振成像系统和相关成像方法无法 管理传输B1(B1+)场以实现所承诺的成像质量、可靠性 以及7T的稳健性，而现有的射频线圈无法为最佳ASL提供足够的B1+覆盖 成像。 我们的长远目标是开发和改进超高频成像方法，以更好地促进科学研究 和临床研究，以改善骨骼疾病的管理和患者保健。理由是 超高频成像的现有技术挑战，包括ASL，可以被克服或减轻，最终达到 实现超高频潜力，具有预期的效益和卓越的成像能力。这项建议的目的是 为新的PTX集成开发和建立优化、安全、高效的并行传输(PTX)平台 青少年剥脱性骨软骨炎(JOCD)膝关节ASL成像方法及临床意义探讨 病人。 我们将通过开发一种用于膝关节ASL成像的优化、安全和高效的PTX平台 新颖的32通道环偶极子发射和接收阵列膝线圈，使用13个人体模型建立VOP库 来自虚拟家庭(包括变形模型)，并评估高效膝盖的替代策略 ASL成像，例如分别对成人和青少年使用人群匹配的安全系数。我们会 开发和优化PTX集成的膝关节ASL成像方法，利用优化的PTX RF脉冲。我们 还将探讨7T膝关节ASL显像在JOCD中的临床潜力，以预测6和 12个月愈合状况和区分有无稳定皮损的患者并评估诊断 使用受试者工作特征(ROC)的骨髓血流量测量的预后表现 曲线分析。我们还将开发一种新的多变量Logistic回归模型，该模型具有新的诺模图 预测非手术治疗6个月、12个月后的愈合情况。

Abstract Bone marrow perfusion can provide essential knowledge about bone physiology, improve our understanding of disease etiology and pathophysiology, assist the differentiation between normal and abnormal bone marrow, and assess the response to prescribed therapies. Arterial spin labeling (ASL) magnetic resonance imaging (MRI), as a noninvasive and non-contrast-enhanced approach, is well suited for longitudinal monitoring of disease progression and routine evaluation of therapy response. But ASL imaging of knee epiphyseal bone marrow is challenging because ASL imaging is a low signal-to-noise ratio technique, and the perfusion level is significantly low in epiphyseal yellow bone marrow mainly consisting of fat cells with a sparse network of capillaries. Ultrahigh (≥7T) magnetic field can specifically benefit ASL imaging and overcome these challenges by increasing SNR, prolonging blood and tissue T1, and improving parallel imaging performance. However, the current clinically approved single-transmit MRI system and associated imaging methods are incapable of managing the transmit B1 (B1+) fields needed to realize the promised improvement in imaging quality, reliability, and robustness of 7T while existing RF coils are unable to provide adequate B1+ coverage for optimal ASL imaging. Our long-term goal is to develop and improve UHF imaging methods to better facilitate scientific research and clinical studies to improve the management of skeletal diseases and patient healthcare. The rationale is that the existing technical challenges for UHF imaging, including ASL, can be overcome or mitigated, ultimately to realize UHF potentials with promised benefits and superior imaging ability. The objective of this proposal is to develop and establish an optimized, safe, and efficient parallel transmit (pTx) platform for new pTx-integrated knee ASL imaging methods and explore their clinical potentials in juvenile osteochondritis dissecans (JOCD) patients. We will develop an optimized, safe, and efficient pTx platform for knee ASL imaging by developing a novel 32-channel loop-dipole transmit and receive array knee coil, building a VOP library using 13 human models from the Virtual Family (including morphed models) and evaluating alternative strategies for highly efficient knee ASL imaging, such as utilizing population-matched safety factors for adults and juveniles, respectively. We will develop and optimize pTx-integrated knee ASL imaging methods that will utilize optimized pTx RF pulses. We will also explore the clinical potentials of 7T knee ASL imaging in JOCD in terms of its ability in predicting 6- and 12-month healing status and differentiating patients with and without stable lesions and evaluate the diagnostic and prognostic performance of bone marrow blood flow measures using receiver operating characteristics (ROC) curve analyses. We will also develop a novel multivariate logistic regression model with a new nomogram to predict the healing status after 6, 12 months of nonoperative treatment.