New Reference Signal Injection Method for In Vivo Quantification

用于体内定量的新参考信号注入方法

• 批准号: 7658450
• 负责人: Donghoon Lee
• 金额: $ 23.4万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-15 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7658450
• 关键词: Affect; Algorithms; Amplifiers; Animals; Area; Biochemical; Biological Assay; Calibration; Cell Nucleus; Characteristics; Clinical; Coiled Bodies; Computer software; Coupled; Couples; Coupling; Data; Development; Diagnostic Procedure; Disease; Exercise; Freezing; Frequencies; Gastrocnemius Muscle; Goals; High Pressure Liquid Chromatography; Human; Image; Immune; In Vitro; Injection of therapeutic agent; Knowledge; Leg; Limb structure; Magnetic Resonance Spectroscopy; Measurement; Measures; Methods; Modification; Organ; Physiologic pulse; Physiological; Procedures; Process; Protocols documentation; Publishing; RF coil; Radiation; Rattus; Relaxation; Research; Research Personnel; Rest; Sampling; Signal Transduction; Skeletal Muscle; Surface; Techniques; Time; Tissue Harvesting; Validation; Water; Width; computerized data processing; data acquisition; design; improved; in vitro testing; in vivo; magnetic field; prototype; public health relevance; research study; tool

DESCRIPTION (provided by applicant): Magnetic resonance spectroscopy (MRS) has evolved from a strictly in vitro research tool for chemists to a powerful, non-invasive, diagnostic technique. However, the full potential of MRS-its ability to quantitatively assess metabolite content in vivo-is rarely achieved in practice. Assessment of metabolite content, commonly referred to as absolute quantification, requires accurate determination of the proportionality factor between the local magnetic field (B1m) generated by excited nuclei within the measurement volume and the integrated area of the corresponding spectral peak in the processed data. An impractical level of diligence is required to quantify or control all of the parameters that affect this proportionality factor. As a result, nearly all MRS results are presented in terms of arbitrary units or as ratios, which are difficult to interpret and of limited clinical value. We have developed a new technique, SPIRIT (Synthetic Peak Injection using a Radiation Immune Tickler coil), that could allow more practical and accurate quantification of MRS. We use a small, inductively coupled RF coil to inject an artificial signal, the pseudo-signal, in the main RF coil used to acquire the in vivo signal. The amplitude, frequency and line-width of the pseudo-signal are easily varied and are first set in proportion to a real peak corresponding to a known in vitro metabolite concentration. The same pseudo-signal is then injected during the data acquisition period of an in vivo measurement and used as a calibration factor to convert the real signals into units of metabolite concentration. The salient feature of the SPIRIT method is the use of inductive coupling to inject the pseudo-signal. Since inductive coupling is also the mechanism by which B1m couples to the main RF coil, any subsequent manipulations of the data that affect the proportionality factor- including coil loading conditions, gain of the receiver amplifiers, and data processing algorithms-have an equal effect on the real and pseudo-signals. This makes the proportionality factor immune to these data manipulations and substantially decreases the burden of the metabolite quantification process. We have built a prototype SPIRIT probe that uses a surface coil to excite and receive the in vivo signals. This simple coil was useful for demonstrating feasibility but, like all surface coils, it creates a nonuniform B1 field, which complicates the quantification process. In this project we will build two additional SPIRIT probes that create uniform B1 fields to excite and receive the metabolite signals, validate the method by comparison against biochemical assays of metabolite content in rat hind limb, and demonstrate the ability to accurately quantify changes in metabolite content in human skeletal muscle during physiological perturbations. Our project focuses on measurements in skeletal muscle but the methods could easily be transferred to other organs. Our goal is to validate a powerful new tool for noninvasive quantification of metabolite content that will allow researchers and clinicians access to the full potential of MRS. PUBLIC HEALTH RELEVANCE: We have developed a new method of converting magnetic resonance spectroscopy (MRS) data into units of metabolite concentration. We propose to validate the method in animal studies and demonstrate its value in humans. Successful completion of the project could have widespread impact on a variety of diseases by providing researchers and clinicians with a more practical noninvasive tool for measuring metabolite concentration.

描述（由申请人提供）：磁共振光谱（MRS）已从严格的化学家体外研究工具演变为强大的，无创的，诊断技术。但是，MRS-ITS在体内定量评估代谢产物含量的全部潜力 - 在实践中很少实现。通常称为绝对定量的代谢物含量的评估需要准确确定由激发核在测量量内产生的局部磁场（B1M）之间的比例因子，而所处理数据中相应光谱峰的集成面积。需要不切实际的勤奋水平来量化或控制影响该比例性因子的所有参数。结果，几乎所有MRS结果都是以任意单位或比率来呈现的，这些单位很难解释和临床价值有限。我们已经开发了一种新技术，即Spirit（使用辐射免疫滴答器线圈注射的合成峰值注射），可以更实用，准确地量化MRS。我们使用一个小的，电感耦合的RF线圈来注入人工信号，即伪信号，以用于获取体内信号的主RF线圈。伪信号的幅度，频率和线宽很容易变化，首先是与对应于已知的体外代谢物浓度相对应的实际峰成比例的。然后在体内测量的数据采集期间注入相同的伪信号，并用作将真实信号转换为代谢物浓度单位的校准因子。精神方法的显着特征是使用电感耦合注入伪信号。由于电感耦合也是B1M偶联到主RF线圈的机制，因此对影响比例因子的数据进行的任何操作 - 包括线圈加载条件，接收器放大器的增益以及数据处理算法对算法的同等影响，对真实和伪信号。这使得比例因素对这些数据操作的免疫，并大大减轻了代谢物定量过程的负担。我们已经建立了一种原型精神探测器，该探针使用表面线圈激发并接收体内信号。这个简单的线圈对于证明可行性很有用，但是像所有表面线圈一样，它会产生一个不均匀的B1场，从而使定量过程变得复杂。在这个项目中，我们将建立两个额外的精神探针，以创建统一的B1场以激发和接收代谢物信号，并通过比较该方法与大鼠Hind Limb中代谢物含量的生化测定方法进行验证，并证明能够准确量化代谢物含量变化的能力在生理扰动期间人类骨骼肌中。我们的项目着重于骨骼肌的测量值，但这些方法很容易转移到其他器官中。我们的目标是验证一种强大的新工具，用于非侵入性定量代谢物含量，这将使研究人员和临床医生能够获得MRS的全部潜力。公共卫生相关性：我们开发了一种将磁共振光谱（MRS）数据转换为代谢物浓度单位的新方法。我们建议在动物研究中验证该方法并证明其在人类中的价值。该项目的成功完成可能会对各种疾病产生广泛的影响，通过为研究人员和临床医生提供更实用的无创工具来测量代谢物浓度。