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，能够容纳成人头部的孔径的超高场磁体（7T及更高）已经从各种研究和临床供应商处获得。场强的增加带来了信噪比的提高和光谱研究的内在优势，提高了谷氨酸和谷氨酰胺等J耦合共振的光谱分辨率和光谱简化。因此，7T的光谱成像应该为评价这些化合物提供一个理想的平台。不幸的是，尽管7T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使用的报道。这种限制很大程度上是由于在高场下产生足够B1强度的内在效率低下，从而导致功率沉积增加了10倍以上。因此，许多传统的光谱成像序列导致较长的回波时间，并且在7T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7T光谱成像方法，结合脉冲序列设计，B1闪烁和多几何收发器阵列的发展。虽然对比增强成像和FLAIR成像通常用于监测恶性胶质瘤患者放化疗的反应，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，由坏死和炎症引起的假阳性（假进展）发生在20-40%的接受治疗的患者中。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，减少了生存时间。除了胆碱、乳酸和流动脂质（也在炎症细胞中发现）增加的常见发现外，脑肿瘤似乎显示谷氨酰胺浓度升高。这与谷氨酰胺在肿瘤细胞增殖的生物合成和胸膜原性活动中所起的主要作用是一致的。因此，谷氨酰胺的短时间TE磁共振成像测量有可能显著地帮助肿瘤对治疗的反应的系列评估。因此，为了评估这些方法的实用性，我们将确定谷氨酰胺的MRSI测量是否可以解决接受放化疗的恶性胶质瘤患者的假进展。公共卫生相关性：尽管7T光谱成像应该为谷氨酸和谷氨酰胺等氨基酸的测量提供一个理想的平台，但传输效率降低、信号强度损失大和功率沉积使传统方法难以使用。为了克服这些限制，我们将开发7T光谱成像的新方法，将脉冲序列设计和多元素线圈阵列射频场空间塑造的新方法相结合，从而显著降低功率沉积并保持最佳信号检测。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.