Figure 4. Chemical Shift Imaging (CSI).

(A–D) CSI of a MIA PaCa-2 (A) and an HT29 (C) xenograft obtained before and after treatment, as described in Figure 3A. Images were acquired 25 s after hyperpolarized [1-¹³C]Pyr injection. The left peak in each voxel (small square) is [1-¹³C]Lac, and the right peak is [1-¹³C]Pyr. [1-¹³C]Lac signal decreased in each 2-mm × 2-mm × 8-mm voxel in the tumor region after LDH inhibitor injection (IV, 50 mg/kg). Most of the tissue volume inside the coil is tumor (approximately 75% from analysis of the fast low-angle shot magnetic [FLASH] anatomical MRI images). False-color images of [1-¹³C]Pyr (left), [1-¹³C]Lac (middle), and the [1-¹³C]Lac/Pyr ratio (right), in before (top) and after (bottom) treatment evaluations of a MIA PaCa-2 (B) and an HT29 (D) xenograft. False-color images (B and D) are generated from the chemical shift data (A and C).

(E) The [1-¹³C]Lac/Pyr ratio calculated from these data was significantly decreased 30 min after LDH inhibitor injection in both MIA PaCa-2 (n = 4) and HT29 (n = 3) xenografts. The data are displayed as means ± SEM (**p < 0.01, t test).

(F) Representative CSIs of a MIA PaCa-2 xenograft before and 30 min after LDH inhibitor administration (left), with equivalent false-color images of [1-¹³C]pyr (middle) and [1-¹³C]lac (right). Top panels display pre-LDH inhibitor images, and bottom panels display images collected 30 min after LDH inhibitor. Data were obtained using a clinical grade imager (see Method Details).