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7T 下的绝热多回波 ³¹P 波谱成像(AMESING)用于测量横向弛豫时间和恢复 T₂ 值短的组织中的灵敏度。

Adiabatic multi-echo ³¹P spectroscopic imaging (AMESING) at 7 T for the measurement of transverse relaxation times and regaining of sensitivity in tissues with short T₂ values.

机构信息

Image Sciences Institute, Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.

出版信息

NMR Biomed. 2013 Oct;26(10):1299-307. doi: 10.1002/nbm.2952. Epub 2013 Apr 2.

Abstract

An adiabatic multi-echo spectroscopic imaging (AMESING) sequence, used for (31) P MRSI, with spherical k-space sampling and compensated phase-encoding gradients, was implemented on a whole-body 7-T MR system. One free induction decay (FID) and up to five symmetric echoes can be acquired with this sequence. In tissues with low T2 and high T2 , this can theoretically lead to a potential maximum signal-to-noise ratio (SNR) increase of almost a factor of three, compared with a conventional FID acquisition with Ernst-angle excitation. However, with T2 values being, in practice, ≤400 ms, a maximum enhancement of approximately two compared with low flip Ernst-angle excitation should be feasible. The multi-echo sequence enables the determination of localized T2 values, and was validated with (31) P three-dimensional MRSI on the calf muscle and breast of a healthy volunteer, and subsequently applied in a patient with breast cancer. The T2 values of phosphocreatine, phosphodiesters (PDE) and inorganic phosphate in calf muscle were 193 ± 5 ms, 375 ± 44 ms and 96 ± 10 ms, respectively, and the apparent T2 value of γ-ATP was 25 ± 6 ms. A T2 value of 136 ± 15 ms for inorganic phosphate was measured in glandular breast tissue of a healthy volunteer. The T2 values of phosphomonoesters (PME) and PDE in breast cancer tissue (ductulolobular carcinoma) ranged between 170 and 210 ms, and the PME to PDE ratios were calculated to be phosphoethanolamine/glycerophosphoethanolamine = 2.7, phosphocholine/glycerophosphocholine = 1.8 and PME/PDE = 2.3. Considering the relatively short T2 values of the metabolites in breast tissue at 7 T, the echo spacing can be short without compromising spectral resolution, whilst maximizing the sensitivity.

摘要

一种用于 (31) P MRSI 的绝热多回波波谱成像 (AMESING) 序列,在全身 7-T MR 系统上实现,具有球形 k 空间采样和补偿相位编码梯度。该序列可以采集一个自由感应衰减 (FID) 和多达五个对称回波。在 T2 低且 T2 高的组织中,与使用 Ernst 角激励的传统 FID 采集相比,这理论上可以导致潜在的信噪比 (SNR) 提高近三倍。然而,在实际情况下,T2 值≤400 ms 时,与低翻转 Ernst 角激励相比,最大增强幅度约为两倍。多回波序列可以确定局部 T2 值,并在健康志愿者的小腿肌肉和乳房的 (31) P 三维 MRSI 上进行了验证,随后在乳腺癌患者中进行了应用。小腿肌肉中磷酸肌酸、磷酸二酯 (PDE) 和无机磷的 T2 值分别为 193±5 ms、375±44 ms 和 96±10 ms,γ-ATP 的表观 T2 值为 25±6 ms。在健康志愿者的乳腺组织中,无机磷的 T2 值为 136±15 ms。乳腺癌组织 (导管小叶癌) 中磷酸单酯 (PME) 和 PDE 的 T2 值范围在 170 至 210 ms 之间,并且计算出 PME 与 PDE 的比值为磷酸乙醇胺/甘油磷酸乙醇胺=2.7、磷酸胆碱/甘油磷酸胆碱=1.8 和 PME/PDE=2.3。考虑到 7T 时乳腺组织中代谢物的 T2 值相对较短,在不影响光谱分辨率的情况下,可以缩短回波间隔,从而最大限度地提高灵敏度。

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