Department of Radiology and Biomedical Imaging, University of California, San Francisco, California.
UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, California.
Magn Reson Med. 2018 Sep;80(3):1048-1060. doi: 10.1002/mrm.27104. Epub 2018 Feb 16.
The bSSFP acquisition enables high spatiotemporal resolution for hyperpolarized C MRI at 3T, but is limited by spectral contamination from adjacent resonances. The purpose of this study was to develop a framework for in vivo dynamic high resolution imaging of hyperpolarized [1-C]pyruvate and [1-C]lactate generated in vivo at 3T by simplifying the spectrum through the use of selective suppression pulses.
Spectral suppression pulses were incorporated into the bSSFP sequence for suppression of [1-C]alanine and [1-C]pyruvate-hydrate signals, leaving only the pyruvate and lactate resonances. Subsequently, the bSSFP pulse width, time-bandwidth, and repetition time were optimized for imaging these dual resonances.
The spectral suppression reduced both the alanine and pyruvate-hydrate signals by 85.5 ± 4.9% and had no significant effect on quantitation of pyruvate to lactate conversion (liver: = 0.400, kidney: = 0.499). High resolution (2 × 2 mm and 3 × 3 mm) sub-second 2D coronal projections and 3D 2.5 mm isotropic images were obtained in rats and tumor-bearing mice with 1.8-5 s temporal resolution, allowing for calculation of lactate-to-pyruvate ratios and .
The developed framework presented here shows the capability for dynamic high resolution volumetric hyperpolarized bSSFP imaging of pyruvate-to-lactate conversion on a clinical 3T MR scanner.
bSSFP 采集在 3T 下实现了超高极化 C MRI 的高时空分辨率，但受到来自相邻共振的光谱干扰的限制。本研究的目的是开发一种框架，通过使用选择性抑制脉冲简化光谱，在 3T 下对体内产生的高极化 [1-C]丙酮酸和 [1-C]乳酸进行体内动态高分辨率成像。
将光谱抑制脉冲纳入 bSSFP 序列中，以抑制 [1-C]丙氨酸和 [1-C]丙酮酸水合信号，仅留下丙酮酸和乳酸共振。随后，优化了 bSSFP 脉冲宽度、时带宽和重复时间，以对这两个共振进行成像。
光谱抑制将丙氨酸和丙酮酸水合信号分别降低了 85.5±4.9%，对丙酮酸转化为乳酸的定量没有显著影响（肝： = 0.400，肾： = 0.499）。在大鼠和荷瘤小鼠中获得了高分辨率（2×2mm 和 3×3mm）亚秒二维冠状投影和 3D 2.5mm 各向同性图像，具有 1.8-5s 的时间分辨率，可计算乳酸与丙酮酸的比值和 。
这里提出的开发框架展示了在临床 3T MR 扫描仪上进行动态高分辨率容积极化 bSSFP 成像以检测丙酮酸向乳酸转化的能力。
