Quantification of Prostate Cancer Metabolism Using 3D Multiecho bSSFP and Hyperpolarized [1-13 C] Pyruvate: Metabolism Differs Between Tumors of the Same Gleason Grade

BACKGROUND

Three-dimensional (3D) multiecho balanced steady-state free precession (ME-bSSFP) has previously been demonstrated in preclinical hyperpolarized (HP) 13 C-MRI in vivo experiments, and it may be suitable for clinical metabolic imaging of prostate cancer (PCa).

PURPOSE

To validate a signal simulation framework for the use of sequence parameter optimization. To demonstrate the feasibility of ME-bSSFP for HP 13 C-MRI in patients. To evaluate the metabolism in PCa measured by ME-bSSFP.

STUDY TYPE

Retrospective single-center cohort study.

PHANTOMS/POPULATION

Phantoms containing aqueous solutions of [1-13 C] lactate (2.3 M) and [13 C] urea (8 M). Eight patients (mean age 67 ± 6 years) with biopsy-confirmed Gleason 3 + 4 (n = 7) and 4 + 3 (n = 1) PCa. FIELD STRENGTH/SEQUENCES: 1 H MRI at 3 T with T2 -weighted turbo spin-echo sequence used for spatial localization and spoiled dual gradient-echo sequence used for B0 -field measurement. ME-bSSFP sequence for 13 C MR spectroscopic imaging with retrospective multipoint IDEAL metabolite separation.

ASSESSMENT

The primary endpoint was the analysis of pyruvate-to-lactate conversion in PCa and healthy prostate regions of interest (ROIs) using model-free area under the curve (AUC) ratios and a one-directional kinetic model (kP ). The secondary objectives were to investigate the correlation between simulated and experimental ME-bSSFP metabolite signals for HP 13 C-MRI parameter optimization.

STATISTICAL TESTS

Pearson correlation coefficients with 95% confidence intervals and paired t-tests. The level of statistical significance was set at P < 0.05.

RESULTS

Strong correlations between simulated and empirical ME-bSSFP signals were found (r > 0.96). Therefore, the simulation framework was used for sequence optimization. Whole prostate metabolic HP 13 C-MRI, observing the conversion of pyruvate into lactate, with a temporal resolution of 6 seconds was demonstrated using ME-bSSFP. Both assessed metrics resulted in significant differences between PCa (mean ± SD) (AUC = 0.33 ± 012, kP  = 0.038 ± 0.014) and healthy (AUC = 0.15 ± 0.10, kP  = 0.011 ± 0.007) ROIs.

DATA CONCLUSION

Metabolic HP 13 C-MRI in the prostate using ME-bSSFP allows for differentiation between aggressive PCa and healthy tissue.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Aortic valve stenosis: comparison of patients with to those without chronic congestive heart failure

Eighty-four patients with aortic valve stenosis (AS) and without other valvular or coronary artery disease were studied to investigate the pathophysiologic importance of hemodynamic and functional factors in the development of congestive heart failure (CHF). Thirty had clinical and radiographic signs of CHF. There was no significant difference between patients with and those without CHF in aortic valve index (0.26 +/- 0.09 vs 0.34 +/- 0.16 cm2/m2), mean aortic valve gradient (64 +/- 19 vs 59 +/- 25 mm Hg), left ventricular (LV) systolic pressure (201 +/- 31 vs 201 +/- 35 mm Hg), LV end-diastolic diameter (4.8 +/- 1.0 vs 4.4 +/- 0.7 cm) or posterior LV wall thickness (14.0 +/- 4.7 vs 15.0 +/- 30.0 mm). Patients with CHF had higher LV end-diastolic pressure (22 +/- 10 vs 16 +/- 7 mm Hg, p less than 0.005) and LV wall stress (370 +/- 138 vs 300 +/- 69 g/cm2, p less than 0.005) and lower cardiac index (2.0 +/- 0.5 vs 2.4 +/- 0.6 liters/min/m2, p less than 0.005) and LV ejection fraction (55 +/- 18 vs 68 +/- 13%, p less than 0.0005). An inverse linear relation (r = -0.59, p less than 0.01) was present between LV wall stress and LV ejection fraction such that as stress increased, LV ejection fraction fell. Values for both LV wall stress and LV ejection fraction overlapped considerably between the groups and, more important, only 40% of patients with CHF had a depressed LV ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)