Multiplexed Multiband MR at 7T: Studies of mild Traumatic Brain Injury

7T 多重多波段 MR：轻度创伤性脑损伤的研究

• 批准号: 8656460
• 负责人: Hoby P Hetherington
• 金额: $ 42.55万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8656460
• 关键词: Multiplexed; Multiband; MR; 7T; Studies

DESCRIPTION (provided by applicant): Although 7T systems have been available since the late 1990s, progress for brain imaging at 7T has been slowed by the transmit performance of conventional head coils (i.e. a large transmit only volume coil with a receive only phased array). At 7T large single drive transmit head volume coils suffer from poor homogeneity (40-50%) and low efficiency and limited SNR. The use of receive only phased arrays within these coils significantly enhances SNR and enables parallel reception but does not improve the transmit performance. These limitations can be addressed by the use of transceiver arrays which provide both independent transmission and reception. Transceiver arrays using parallel transmission and/or RF shimming offer improved homogeneity, spatially tailored excitation, gradient independent outer volume suppression and reduced SAR. To date, the number of coils in these transceiver arrays has been limited to the number of independent transmit channels (typically 8) and the small size of these coils required to maintain optimal SNR. To address these limitations we will: i) eliminate the need for equal numbers of transmit and receive channels for the multiple row transceiver arrays by developing new pulse sequence methods which utilize RF multiplexing to drive multi-row transceiver arrays and reduce power deposition; ii) enhance the efficiency of multi-plane MRSI data collection and reduce SAR by developing multi-band acquisition MRSI acquisitions. To evaluate the methods developed we will study veterans with mild traumatic brain injury (mTBI) arising from blast exposure. It has become clear that veterans exposed to mTBI from blast injury display delayed neurological deficits, often without clear imaging correlates. In the absence of objective confirmatory imaging evidence, poor performance on cognitive evaluations can be attributed to poor subject effort, complicating diagnosis, management, rehabilitation and raising questions as to validity of the reported disability. Our recent work has demonstrated that in veterans with blast related mTBI, significant metabolic alterations are seen in the hippocampi which correlate with assessments of effort and cognitive performance. Using the enhanced spatial coverage afforded by the methods developed we will evaluate the hypothesis that in veterans exposed to blast related mTBI, the presence and severity of cognitive and neurologic deficits are correlated with metabolic abnormalities/impairments in the functionally linked brain regions.

描述(由申请人提供)：虽然7T系统自20世纪90年代末就已面世，但7T脑部成像的进展因传统磁头线圈(即具有仅接收相控阵的大容量仅传输线圈)的传输性能而变得缓慢。在7T大型单驱动器发射磁头体积线圈存在均匀性差(40%-50%)、效率低和信噪比有限的问题。在这些线圈内使用仅接收相控阵可显著提高SNR并实现并行接收，但不能改善发射性能。这些限制可以通过使用收发信机阵列来解决，收发信机阵列提供独立的发送和接收。使用并行传输和/或射频垫片的收发信机阵列提供了改进的均质性、空间定制的激励、与梯度无关的外部体积抑制和降低的SAR。到目前为止，这些收发机阵列中的线圈数量一直被限制在独立传输通道的数量(通常为8个)和维持最佳SNR所需的这些线圈的小尺寸。为了解决这些限制，我们将：i)通过开发新的脉冲序列方法来消除对多行收发信机阵列相同数量的发送和接收通道的需求，这种脉冲序列方法利用射频多路复用来驱动多行收发信机阵列并减少功率沉积；ii)通过开发多频带采集MRSI采集来提高多平面MRSI数据收集的效率并降低SAR。为了评估开发的方法，我们将研究因冲击波暴露而导致轻度创伤性脑损伤(MTBI)的退伍军人。已经很明显的是，由于冲击伤而暴露于mTBI的退伍军人表现出延迟的神经功能障碍，通常没有明确的成像相关性。在缺乏客观的验证性影像证据的情况下，认知评估的表现不佳可归因于受试者的努力不佳，使诊断、管理和康复复杂化，并对报告的残疾的有效性提出了质疑。我们最近的工作表明，在患有冲击波相关mTBI的退伍军人中，海马区可以看到显著的代谢变化，这与对努力和认知表现的评估有关。利用所开发的方法提供的增强的空间覆盖率，我们将评估这一假设，即在暴露于冲击波相关mTBI的退伍军人中，认知和神经缺陷的存在和严重程度与大脑功能相关区域的代谢异常/损害相关。