Hyperpolarized 13C Pyruvate MRI/MRS for Characterizing Splenic Metabolism in Advanced Diffuse Large B-Cell Lymphoma: A Pilot Study.

BACKGROUND

Splenic lymphoma involvement can be difficult to assess because splenomegaly is nonspecific and focal lesions may be absent. Hyperpolarized [1-13C]pyruvate MRI/MRS may provide metabolic information beyond morphologic assessment.

PURPOSE: To assess hyperpolarized [1-13C]pyruvate MRI/MRS's feasibility for evaluating splenic metabolism in advanced-stage diffuse large B-cell lymphoma (DLBCL), and explore associations with 18F-FDG PET/CT metrics.

STUDY TYPE: Prospective pilot study.

POPULATION: 5 treatment-naïve patients (4 male, 1 female) with Lugano Stage III-IV DLBCL and splenic involvement/splenomegaly and four female reference participants from a published cervical cancer study without visually apparent splenic abnormality on imaging.

FIELD STRENGTH/SEQUENCE: 3.0 T hyperpolarized [1-13C]pyruvate MRI/MRS using a multi-echo gradient-echo spiral chemical shift imaging sequence with IDEAL-based reconstruction.

ASSESSMENT: Parameters included the apparent pyruvate-to-lactate exchange rate constant (kPL) and area-under-the-curve ratios of lactate, alanine, and bicarbonate normalized to total carbon. PET/CT metrics included splenic maximum standardized uptake value (SUVmax) and spleen-to-liver ratio (SLR).

STATISTICAL TESTS: Mann-Whitney U tests compared groups. Spearman coefficients assessed associations between hyperpolarized 13C and PET/CT metrics. p value < 0.05 indicated significance.

RESULTS

All five patients completed hyperpolarized 13C MRI/MRS acquisition without adverse events; four had dynamic datasets for kinetic analysis. Median spleen volume was 2.7-fold higher in DLBCL than in the reference cohort. Median kPL and lactate/total carbon ratio were 2.4-fold and 5.3-fold higher, respectively, but not significant (p = 0.081 and p = 0.114). Exploratory correlations were observed between kPL and each PET metric (SUVmax and SLR; ρ = 1.00; p = 0.083 for both), and between lactate/total carbon ratio and each PET metric (ρ = 0.80; p = 0.333 for both); none reached significance.

DATA

CONCLUSION

Hyperpolarized [1-13C]pyruvate MRI/MRS was completed in all five patients, with kinetic analysis feasible in four. Findings showed numerically higher splenic pyruvate-to-lactate metabolism and nonsignificant positive correlations with FDG-PET activity, warranting larger studies.

EVIDENCE LEVEL: 4.

TECHNICAL EFFICACY: Stage 1.