Abstract 15822: Phosphorus Magnetic Resonance Spectroscopy is More Precise at 7 Tesla Field Strength Than 3 Tesla in Patients With Dilated Cardiomyopathy

Abstract

Introduction: Phosphorus magnetic resonance spectroscopy ( 31 P-MRS) allows insight into cardiac energetics in vivo , but is a technique with an intrinsically low signal to noise ratio (SNR). As ultra-high magnetic field MRI scanners become more widely available this limitation will lessen, allowing detection of smaller changes in metabolite concentrations or measurement of changes in smaller patient groups, which will further the understanding of cardiac energetics. Hypothesis: We hypothesised that the 2.4x increase in SNR, predicted by theory at 7T compared to 3T, will allow more precise metabolite concentration measurements in dilated cardiomyopathy (DCM) patients. Methods: 26 idiopathic DCM patients (69% male, mean age 55±2 yr, mean LVEF 35±2%) underwent 31 P-MRS at 3T and 7T field strengths. Patients were NYHA Class I (46%), II (50%) or III (4%). Results: The mean SNR increased from 6.5 ± 0.5 to 16.2 ± 1.5 for PCr (p <0.0001, paired t-test) and from 3.4 ± 0.2 to 11.4 ± 0.8 for γATP (p <0.0001) as the field strength increased from 3T to 7T. The PCr/ATP ratio was consistent between the 2 field strengths; at 3T PCr/ATP was 1.5 ± 0.1 and at 7T 1.5 ± 0.1; there was as expected no statistically significant difference (p=0.67) (fig a). The Cramér-Rao lower bounds (CRLB) quantify the minimum precision of fitted parameters. A desirable decrease in the PCr/ATP CRLB was seen from 3T to 7T (47 ± 3% vs 25 ± 2% p<0.0001)(fig b), i.e.-metabolites are indeed quantified more precisely at 7T compared to 3T. Conclusion: This study represents the first cardiac 31 P-MRS patient data acquired at a 7T field strength. Compared to a 2.8x SNR increase from 3T to 7T previously reported in normal volunteers, we observed a 2.5x increase in this patient population. There is no significant bias at 7T as the PCr/ATP ratios are similar. In conclusion 7T 31 P-MRS is feasible in DCM patients and more accurate than at 3T, which in future should allow more accurate quantification and understanding of myocardial energetics.