1h 13c dual tunedvolume coil

Twenty-six mg of [1-¹³-C]-pyruvic acid (Cambridge Isotopes)
containing 1.5 mM Gadoteridol (Bracco Diagnostics) and 15 mM OX063 (GE
Healthcare) were polarized using a HyperSense dissolution DNP system (Oxford
Instruments). The polarized substrate was rapidly dissolved in 4 mL of 80mM
NaOH, 50 mM NaCl, 0.1 g/L EDTA and 40 mM Trizma pH 7.6 (Sigma Aldrich) to yield
a neutral, isotonic, 37°C solution of 80mM hyperpolarized
[1-¹³C] pyruvate. Two hundred μL of the hyperpolarized
pyruvate solution was administered to the animals via a tail vein catheter.
Imaging was performed on a 7T Biospec MR system with a 1H/13C dual-tuned
volume coil (Bruker Biospin MRI) and a custom built 13C surface coil. Anatomic
imaging was performed using a fast spin-echo (FSE) sequence. Dynamic 13C data
was acquired using a previously described radial multi-band frequency encoding
sequence^{65 (link)} and a
constrained reconstruction algorithm^{66 (link)}. The constrained reconstruction results were normalized
and relative signal curves for hyperpolarized pyruvate and lactate were
generated as well as apparent relative metabolic conversion rate maps which were
co-registered with the anatomic images.

All spectroscopic measurements were carried out using a 7T Biospec small animal MR system, with BGA-12 gradients and a ¹H/¹³C dual-tuned volume coil with 72mm inner diameter (ID) (Bruker Biospin MRI). Animals were anesthetized using isoflurane and placed on an imaging sled with integrated channels for anesthesia and warm circulating water to maintain body temperature. A fast spin-echo (FSE) sequence (TR = 2500ms, TE_Eff = 16.7ms, 8 echoes) was used to visualize tumor location. Dynamic ¹³C spectroscopy was acquired using a slice-selective pulse-acquire sequence (TR = 2000ms, 10° to 15° excitation, 8mm slice thickness, 90 repetitions, spectral width = 4960 Hz, number of spectral points = 2048) with excitation through the ¹³C channel of the volume coil and signal reception using a 15mm ID surface coil placed over the tumor. The dynamic acquisition was initiated by the HyperSense system during dissolution, approximately 18s prior to injection.