Advanced Treatment Endpoint Assessment in MR-guided Focused Ultrasound

摘要 热疗过程中的组织消融，如聚焦超声(FUS)，会产生组织 细胞和大分子结构的坏死和不可逆转的变化。热能的成功 治疗的定义是充分治疗所需的目标，同时避免周围环境 正常组织。这就需要能够实时、准确地确定组织活性的方法 治疗是有效、高效和安全的。可以检测到不可逆的成像方法 与长期效应相关的组织变化对终点评估和一般情况至关重要 热疗的成功和广泛采用。目前的磁共振温度成像方法 使用并不总是准确的，并且添加其他独立的组织测量 生存能力是必要的。在这一应用中，我们建议开发和测试一种新型的磁共振脉冲 序列可同时测量四个对组织损伤敏感的磁共振参数。我们的 序列将首先测量质子共振频率移动图，从哪个温度 可以计算变化和累积热剂量。同时，它测量T1- 松弛时间，这表明脂肪的温度变化和体液变化的证据 消融点，以及剪切波速度，这是组织硬度的直接衡量标准，通常 随着消融而改变。使用一种新的单翻转角方法测量T1弛豫 最近开发出来的。在MR相位图像中对PRF位移和剪切波速进行编码， 并可以使用我们开发的新方法进行分离。因为同时发生了 收购后，这些物业会自动共同登记，提供更多 关于进化中的FUS诱导的组织变化的信息比目前可用的信息更多。这个 T1标测和剪切模量值的增加将使脂肪评估成为可能 组织，在PRF方法不起作用的地方，允许在区域中进行更完整的评估 比如乳房和腹部。拟议中的项目将立即使我们目前的 在进行首例人类乳房MR引导的FUS治疗中的补充工作 支持高信噪比图像采集的新型硬件。这项工作是一项重要的 迈向我们的长期目标，即开发全面的实时测量，以 在MRgFUS期间和之后准确监测和预测组织存活。

ABSTRACT Tissue ablation during thermal therapies, such as focused ultrasound (FUS), result in tissue necrosis and irreversible changes in cell- and macromolecular-structure. The success of thermal therapies is defined in terms of adequately treating the desired target while sparing surrounding normal tissues. This demands methods for accurately determining tissue viability in real time so that treatments be efficacious, efficient and safe. Imaging methods that can detect irreversible tissue changes correlated to long-term effects are crucial for endpoint assessment and the general success and wide adoption of thermal therapies. The MR temperature imaging methods currently used are not always accurate, and the addition of other independent measurements of tissue viability are needed . In this application, we propose to develop and test a novel MRI pulse sequence to simultaneously measure four MR-derived parameters sensitive to tissue damage. Our sequence will first measure maps of the proton resonance frequency shift, from which temperature change and cumulative thermal dose can be calculated. Simultaneously, it measures the T1- relaxation time, which indicates temperature change in fat and evidence of fluid change at the point of ablation, as well as shear wave velocity, a direct measure of tissue stiffness, which often changes with ablation. T1 relaxation is measured using a novel mono flip angle approach we recently developed. The PRF shift and shear wave velocity are encoded in the MR phase images, and can be separated using novel methods we have developed. Because of the simultaneous acquisition, these properties are automatically co-registered providing substantially more information about the evolving FUS-induced tissue changes than what is currently available. The addition of T1-mapping and shear modulus measurements will enable evaluations in adipose tissues, where the PRF method does not work, allowing for more complete evaluations in areas such as the breast and abdomen. The proposed project will immediately benefit our current complementary work in performing first-in-human breast MR-guided FUS treatments with our novel hardware that enables high signal-to-noise ratio image acquisition. This work is an important step towards our long-term goal of developing comprehensive real time measurements that can accurately monitor and predict tissue viability during and following MRgFUS.