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: 8449360
• 负责人: Hoby P Hetherington
• 金额: $ 6.38万
• 依托单位: YALE UNIVERSITY
• 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 2012-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8449360
• 关键词: Address; Afghanistan; Blast Cell; Blast Injuries; Brain; Brain Concussion; Brain imaging; Brain region; Choline; Clinical; Clinical Management; Clinical assessments; Cognitive; Cognitive deficits; Data Collection; Deposition; Diagnosis; Evaluation; Failure; Functional Magnetic Resonance Imaging; Functional disorder; Goals; Head; Hippocampus (Brain); Human; Image; Impairment; Injury; Iraq; Left; Link; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Malingering; Metabolic; Methods; Motivation; Neurologic; Neurologic Deficit; Output; Patient Self-Report; Performance; Phase; Physiologic pulse; Recording of previous events; Reporting; Reproducibility; Resolution; Severities; Slice; Speed; Sports; Surface; System; Testing; Time; Translating; Traumatic Brain Injury; Veterans; War; Work; disability; disability payment; experience; imaging modality; improved; rehabilitation management; transmission process

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. PUBLIC HEALTH RELEVANCE: With the recent wars in Afghanistan and Iraq, mTBI due to blast exposure has reached dramatic proportions with up to 19% of all returning veterans having a history of blast related mTBI with estimates of 20 to 50% still experiencing some form of dysfunction one year post injury. For blast related mTBI, the clinical assessment of mTBI largely relies on accuracy of self-reporting and compliance/effort during cognitive testing. Currently, performance below a threshold level on specific tests is equated to poor effort levels, which are often attributed to poor motivation or "malingering" (e.g. disability claims. A finding of poor effrt in turn raises significant concerns as to the validity of all cognitive evaluations and self- repored claims of neurologic deficits, leaving few options for objective assessment. With effort failure rates of 17 to 58% in veterans referred for TBI, methods which can objectively identify the presence of injury and anatomically link it with a specific cognitive domain can have a significant impact in prioritizing treatment and clinical management. The goal of this project is to develop advanced imaging methods which can improve the accuracy, speed and comprehensiveness of MRSI studies of the human brain to evaluate mTBI due to blast exposure. Although this project focuses on mTBI due to blast exposure, the metabolic changes seen (decreased NAA/choline ratios), are consistent with that seen in civilian mTBI and sports related concussions. Thus the findings and approaches demonstrated in blast related mTBI studies should also be applicable to the broader TBI field in general.

描述（由申请人提供）：尽管7 T系统自20世纪90年代末以来已经上市，但由于传统头部线圈（即，具有仅接收相控阵列的仅发射大体积线圈）的发射性能，7 T下的脑成像进展缓慢。在7 T下，大型单驱动发射头体积线圈的均匀性差（40-50%），效率低，SNR有限。在这些线圈内使用仅接收相控阵列显著地增强了SNR并且实现了并行接收，但是没有改善发射性能。这些限制可以通过使用收发器阵列来解决，该收发器阵列提供独立的发送和接收。使用并行传输和/或RF匀场的收发器阵列提供改进的均匀性、空间定制的激励、梯度独立的外部体积抑制和降低的SAR。到目前为止，这些收发器阵列中的线圈数量已被限制为独立发射通道的数量（通常为8个）和维持最佳SNR所需的这些线圈的小尺寸。为了解决这些局限性，我们将：i）通过开发新的脉冲序列方法（利用RF多路复用来驱动多行收发器阵列并减少功率沉积），消除多行收发器阵列对相等数量的发射和接收通道的需求; ii）通过开发多频带采集MRSI采集，提高多平面MRSI数据采集的效率并减少SAR。为了评估开发的方法，我们将研究退伍军人与爆炸暴露引起的轻度创伤性脑损伤（mTBI）。 很明显，暴露于冲击伤mTBI的退伍军人显示出延迟的神经功能缺损，通常没有明确的成像相关性。在缺乏客观确证性影像学证据的情况下，认知评估表现不佳可归因于受试者努力不足、诊断、管理、康复复杂化以及对报告残疾的有效性提出疑问。我们最近的工作已经证明，在与爆炸相关的mTBI的退伍军人中，在与努力和认知表现的评估相关的大脑皮层中观察到显著的代谢改变。使用所开发的方法提供的增强的空间覆盖范围，我们将评估以下假设：在暴露于爆炸相关mTBI的退伍军人中，认知和神经功能缺陷的存在和严重程度与功能相关脑区域的代谢异常/损伤相关。 公共卫生关系：随着最近在阿富汗和伊拉克的战争，由于爆炸暴露引起的mTBI已经达到了惊人的比例，高达19%的所有返回的退伍军人具有爆炸相关mTBI的历史，估计有20%至50%的人在受伤一年后仍然经历某种形式的功能障碍。对于与爆炸相关的mTBI，mTBI的临床评估很大程度上依赖于自我报告的准确性和认知测试期间的依从性/努力。目前，在特定测试中低于阈值水平的表现等同于努力水平差，这通常归因于动机差或“装病”（例如残疾索赔）。结果表明，疗效差反过来又引起了对所有认知评估和自我报告的神经功能缺损声明的有效性的重大关注，使得客观评估的选择很少。在因TBI转诊的退伍军人中，努力失败率为17%至58%，可以客观地识别损伤的存在并将其与特定认知领域解剖学联系起来的方法可能具有显著的临床意义。 优先治疗和临床管理的影响。该项目的目标是开发先进的成像方法，可以提高人脑MRSI研究的准确性，速度和全面性，以评估由于爆炸暴露引起的mTBI。虽然该项目的重点是由于爆炸暴露引起的mTBI，但观察到的代谢变化（NAA/胆碱比率降低）与平民mTBI和运动相关脑震荡中观察到的代谢变化一致。因此，在与冲击波相关的mTBI研究中证明的发现和方法也应该适用于更广泛的TBI领域。