Dynamic 2D and 3D mapping of hyperpolarized pyruvate to lactate conversion in vivo with efficient multi‐echo balanced steady‐state free precession at 3 T
Dynamic 2D and 3D mapping of hyperpolarized pyruvate to lactate conversion in vivo with efficient multi‐echo balanced steady‐state free precession at 3 T
复制标题
体内超极化丙酮酸到乳酸转化的动态 2D 和 3D 映射，具有 3 T 的高效多回波平衡稳态自由进动
作者：
Christoph A. Müller;Christian Hundshammer;Miriam Braeuer;J. Skinner;Stephan Berner;J. Leupold;Stephan Düwel;S. Nekolla;S. Månsson;A. Hansen;D. von Elverfeldt;J. Ardenkjaer;F. Schilling;M. Schwaiger;J. Hennig;J. Hövener
本研究的目的是有效地获得超极化示踪剂及其代谢产物的瞬态MRI信号，这需要专门的成像序列。在这项工作中，在临床3 T正电子发射断层扫描/MRI系统上实现了具有回声不对称迭代分解和最小二乘估计（IDEAL）重建的多回声平衡稳态自由进动（me‐bSSFP）序列，用于快速2D和3D代谢成像。进行模拟以获得用于超极化生物分子的代谢成像的信号高效序列方案。该序列在体外和体内用于探测超极化[1- 13 C]丙酮酸和[1- 13 C]乳酸的酶交换。在重建中使用最小二乘迭代化学物质分离算法实现化学位移分辨率。在体外，将me-bSSFP的代谢转化率测量值与NMR光谱和自由诱导衰变-化学位移成像（FID-CSI）进行了比较。在体内，用me-bSSFP和FID-CSI对大鼠MAT-B-III肿瘤模型成像。用me‐bSSFP获得的[1- 13 C]丙酮酸和[1- 13 C]乳酸的2D代谢物图谱显示与FID‐CSI相同的空间分布。用me-bSSFP和NMR测量的丙酮酸-乳酸转化动力学对应良好。在超极化[1- 13 C]丙酮酸盐弛豫到噪声水平以下之前，使用me-bSSFP的动态2D代谢物图谱能够采集多达420个时间帧（扫描时间：180 - 350 ms/帧）。使用me-bSSFP在8.2秒的扫描时间内进行了具有大视野（180 × 180 × 48 mm 3）和高空间分辨率（5.6 × 5.6 × 2 mm 3）的3D代谢物图谱。得出的结论是，与3 T下报告的FID-CSI或EPSI方法相比，Me-bSSFP提高了超极化[1- 13 C]丙酮酸盐和[1- 13 C]乳酸盐代谢成像的空间和时间分辨率，为临床和临床前应用提供了新的可能性。
The aim of this study was to acquire the transient MRI signal of hyperpolarized tracers and their metabolites efficiently, for which specialized imaging sequences are required. In this work, a multi‐echo balanced steady‐state free precession (me‐bSSFP) sequence with Iterative Decomposition with Echo Asymmetry and Least squares estimation (IDEAL) reconstruction was implemented on a clinical 3 T positron‐emission tomography/MRI system for fast 2D and 3D metabolic imaging. Simulations were conducted to obtain signal‐efficient sequence protocols for the metabolic imaging of hyperpolarized biomolecules. The sequence was applied in vitro and in vivo for probing the enzymatic exchange of hyperpolarized [1–13C]pyruvate and [1–13C]lactate. Chemical shift resolution was achieved using a least‐square, iterative chemical species separation algorithm in the reconstruction. In vitro, metabolic conversion rate measurements from me‐bSSFP were compared with NMR spectroscopy and free induction decay‐chemical shift imaging (FID‐CSI). In vivo, a rat MAT‐B‐III tumor model was imaged with me‐bSSFP and FID‐CSI. 2D metabolite maps of [1–13C]pyruvate and [1–13C]lactate acquired with me‐bSSFP showed the same spatial distributions as FID‐CSI. The pyruvate‐lactate conversion kinetics measured with me‐bSSFP and NMR corresponded well. Dynamic 2D metabolite mapping with me‐bSSFP enabled the acquisition of up to 420 time frames (scan time: 180‐350 ms/frame) before the hyperpolarized [1–13C]pyruvate was relaxed below noise level. 3D metabolite mapping with a large field of view (180 × 180 × 48 mm3) and high spatial resolution (5.6 × 5.6 × 2 mm3) was conducted with me‐bSSFP in a scan time of 8.2 seconds. It was concluded that Me‐bSSFP improves the spatial and temporal resolution for metabolic imaging of hyperpolarized [1–13C]pyruvate and [1–13C]lactate compared with either of the FID‐CSI or EPSI methods reported at 3 T, providing new possibilities for clinical and preclinical applications.