B1 Based Localization for MRSI of Human Brain at 7T

描述（由申请人提供）：随着磁体技术的最新进展，各种研究和临床供应商都提供了孔尺寸能够容纳成人头部的双磁场磁体（7 T及更高）。增加的场强赋予增加的SNR的固有优点，并且对于光谱研究，增加的光谱分辨率和J耦合共振（例如谷氨酸和谷氨酰胺）的光谱简化。因此，在7 T下的光谱成像应该为评估这些化合物提供理想的平台。不幸的是，尽管7 T系统的存在可以追溯到20世纪90年代末，但很少有关于它们在光谱成像研究中的应用的报道。这种限制主要是由于在高场下产生足够的B1强度的固有效率低下，以及由此产生的功率沉积增加超过10倍。因此，许多传统的光谱成像序列导致长回波时间，并且当在7 T下应用时可能超过FDA组织加热指南。为了克服这些限制，我们将开发新的方法，光谱成像在7 T的联合收割机结合脉冲序列设计，B1匀场和多几何收发器阵列的发展。尽管常规使用对比增强和FLAIR成像监测恶性胶质瘤患者对放化疗的反应，但在急性和亚急性期（治疗的前60天），在没有肿瘤进展的情况下，20-40%的接受治疗的患者会出现坏死和炎症引起的假阳性（假进展）。这严重限制了早期影像学研究的解释，延迟了最佳治疗反应并缩短了生存时间。除了胆碱、乳酸盐和移动的脂质（也见于炎性细胞）增加的常见结果外，脑肿瘤似乎显示谷氨酰胺浓度升高。这与谷氨酰胺在增殖肿瘤细胞的生物合成和补肋活性中发挥的主要作用一致。因此，谷氨酰胺的短TE MRSI测量具有显著帮助肿瘤对治疗的反应的系列评价的潜力。因此，为了评估这些方法的实用性，我们将确定MRSI测量谷氨酰胺是否可以解决恶性胶质瘤患者接受放化疗治疗的假进展进展。公共卫生相关性：虽然在7 T的光谱成像应该提供一个理想的平台，如谷氨酸和谷氨酰胺的氨基酸的测量，降低传输效率，大的信号强度损失和功率沉积使用传统的方法是困难的。为了克服这些局限性，我们将开发新的方法，光谱成像在7 T，它结合了联合收割机脉冲序列设计和新的方式形成射频场空间与多元素线圈阵列，这大大减少了功率沉积和保持最佳的信号检测。我们将使用这些方法来确定谷氨酰胺的光谱成像是否可以帮助监测恶性胶质瘤对放化疗的反应。

DESCRIPTION (provided by applicant): With recent advances in magnet technology, ultrahigh field magnets (7T and higher) with bore sizes capable of accommodating the adult human head have become available from a variety of research and clinical vendors. The increased field strength confers the intrinsic advantages of increased SNR and for spectroscopic studies, increased spectral resolution and spectral simplification of J coupled resonances such as glutamate and glutamine. Thus, spectroscopic imaging at 7T should provide an ideal platform for evaluating these compounds. Unfortunately, despite the presence of 7T systems dating from late 1990s, there have been few reports of their use in spectroscopic imaging studies. This limitation is largely due to the intrinsic inefficiencies of generating sufficient B1 strength at high field and the resulting increases more than a factor of 10 in power deposition. Thus, many conventional spectroscopic imaging sequences result in long echo times and can exceed FDA guidelines for tissue heating when applied at 7T. To overcome these limitations we will develop novel methods for spectroscopic imaging at 7T which combine both pulse sequence design, B1 shimming and the development of multi-geometry transceiver arrays. Although contrast enhanced and FLAIR imaging are routinely used for monitoring the response to radiochemotherapy in patients with malignant gliomas, false positives (pseudoprogression) arising from necrosis and inflammation in the absence of tumor progression during the acute and sub-acute periods (first 60 days of treatment) occur in 20-40% of the patients being treated. This severely limits the interpretation of early imaging studies, delaying optimal therapeutic response and decreasing survival times. In addition to the common findings of increased choline, lactate and mobile lipids (which are also found in inflammatory cells), cerebral tumors appear to show elevated concentrations glutamine. This is consistent with the major role which glutamine plays in biosynthetic and anapleurotic activities in proliferating tumor cells. Thus, short TE MRSI measurements of glutamine have the potential to significantly aid the serial evaluation of tumors in response to therapy. Therefore, to evaluate the utility of the methods, we will determine if MRSI measurements of glutamine can resolve progression from pseudoprogression in patients with malignant gliomas being treated with radiochemotherapy. PUBLIC HEALTH RELEVANCE: Although spectroscopic imaging at 7T should provide an ideal platform for measurements of amino acids such as glutamate and glutamine, decreased transmission efficiency, large signal intensity losses and power deposition make use of conventional methods difficult. To overcome these limitations we will develop novel methods for spectroscopic imaging at 7T, which combine both pulse sequence design and new ways of shaping RF fields spatially with multi-element coil arrays, which dramatically decrease power deposition and maintain optimal signal detection. We will use these methods to determine if spectroscopic imaging of glutamine can aid in the monitoring the response of malignant gliomas to radiochemotherapy.