Figure 3.

Magnitude spectra (A,B,D,E) and time courses (C,F) of hyperpolarized [1-¹³C]pyruvate (B,E) and [1-¹³C]lactate (A,D) acquired with narrow bandwidth (250 Hz) alternating-frequency excitation slice-selective spectroscopy in rat subcutaneous tumors at 7 T (representative results of one rat out of three measurements). Spectra were summed over 15 frames (30 s) surrounding the peaks. After [1-¹³C]lactate injection (A–C), a strong lactate signal (near 183.5 ppm) and weak [1-¹³C]pyruvate signal (near 171 ppm) are seen. The pyruvate-selective excitation has eliminated the background signal tail from the lactate peak (Figure 2C). After [1-¹³C]pyruvate injection (D–F), both pyruvate and lactate show strong signal with narrow bandwidth excitation. Small ripples in (D) correspond to [1-¹³C]alanine and [1-¹³C]pyruvate excited in the body of the rat by the lactate-targeted excitation, at shifted frequencies due to shim variations outside the tumor.