Quantitative Multinuclear Musculoskeletal Imaging Group, Center for Biomedical Imaging, Department of Radiology, New York University Langone Medical Center, New York, NY, USA.
NMR Biomed. 2013 Mar;26(3):348-56. doi: 10.1002/nbm.2866. Epub 2012 Oct 13.
The rate of phosphocreatine (PCr) resynthesis after physical exercise has been extensively studied with phosphorus (³¹P)-MRS. Previous studies have used small surface coils that were limited to measuring one superficial muscle per experiment. This study focuses on the development and implementation of a spectrally selective three-dimensional turbo spin echo (3D-TSE) sequence at 3T and 7T with temporal resolution of 24 s, using two geometrically identical volume coils. We acquired imaging data of PCr recovery from four healthy volunteers and one diabetic patient, who performed plantar flexions using resistance bands. We segmented the anatomical regions of six different muscles from the lower leg, namely the gastrocnemius [lateral (GL) and medial (GM)], the tibialis [anterior (TA) and posterior (TP)], the soleus (S) and the peroneus (P) and measured the local PCr resynthesis rate constants. During the same examination, we also acquired unlocalized (³¹P-MRS data at a temporal resolution of 6 s. At 3T, the PCr resynthesis rate constants were measured at 25.4 ± 3.7 s [n = 4, mean ± standard deviation (SD)] using the MRS method and 25.6 ± 4.4 s using the MRI method. At 7T, the measured rates were 26.4 ± 3.2 s and 26.2 ± 4.7 s for MRS and MRI. Using our imaging method, we measured the local PCr resynthesis rate constants in six individual muscles of the lower leg (min/max 20.2/31.7 ). The recovery rate constants measured for the diabetic patient were 55.5 s (MRS) and 52.7 s (MRI). The successful implementation of our 3D-method suggests that imaging is possible at both fields with a relatively high spatial resolution (voxel size: 4.2 mL at 3T and 1.6 mL at 7T) using volume coils and that local PCr resynthesis rates can be obtained in a single measurement. The advantage of the imaging method is that it can highlight differences in PCr resynthesis rates between different muscles in a single measurement in order to study spatial gradients of metabolic properties of diseased states for which very little is currently known.
磷酸肌酸（PCr）在体力活动后的合成速率已通过磷（³¹P）-MRS 进行了广泛研究。先前的研究使用了小的表面线圈，这些线圈仅限于每次实验测量一个浅表肌肉。本研究侧重于在 3T 和 7T 下开发和实施具有 24 秒时间分辨率的光谱选择性三维涡轮自旋回波（3D-TSE）序列，并使用两个几何形状完全相同的容积线圈。我们从四名健康志愿者和一名糖尿病患者那里采集了 PCr 恢复的成像数据，他们使用阻力带进行了跖屈运动。我们从小腿的六个不同肌肉区域进行了分割，分别是腓肠肌[外侧（GL）和内侧（GM）]、胫骨前肌[前（TA）和后（TP）]、比目鱼肌（S）和腓骨肌（P），并测量了局部 PCr 再合成速率常数。在同一检查中，我们还以 6 秒的时间分辨率采集了非定位（³¹P-MRS 数据。在 3T 下，使用 MRS 方法测量的 PCr 再合成速率常数为 25.4 ± 3.7 s [n = 4，平均值 ± 标准偏差（SD）]，使用 MRI 方法测量的为 25.6 ± 4.4 s。在 7T 下，MRS 和 MRI 的测量值分别为 26.4 ± 3.2 s 和 26.2 ± 4.7 s。使用我们的成像方法，我们测量了小腿 6 块单独肌肉的局部 PCr 再合成速率常数（最小值/最大值 20.2/31.7）。糖尿病患者的恢复速率常数分别为 55.5 s（MRS）和 52.7 s（MRI）。我们的 3D 方法的成功实施表明，使用容积线圈可以在两个场中以相对较高的空间分辨率（3T 时的体素大小为 4.2 mL，7T 时为 1.6 mL）进行成像，并且可以在单次测量中获得局部 PCr 再合成速率。成像方法的优点在于，它可以在单次测量中突出不同肌肉之间 PCr 再合成速率的差异，以便研究目前知之甚少的疾病状态下代谢特性的空间梯度。
