Dynamic 31P-MRI and 31P-MRS of lower leg muscles in heart failure patients

Figures

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  Figure 1. Dynamic 31P-MRS results in healthy volunteer. (a) Shows 31P-MR spectra from a representative healthy volunteer’s calf muscle pre-exercise, post-exercise, and at end-recovery. The dashed arrows indicate the distance between Pi and PCr peaks (b) shows the kinetics of PCr signal intensity during the three phases for the healthy volunteer and (c) shows the PCr recovery time constant (k = 25.3 s for this volunteer) after fitting the phase III PCr recovery data.

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  Figure 2. Dynamic 31P-MRS results in an HF patient. 31P-MRS results in an HF patient (a) Shows 31P MR spectra from a representative HF patient’s calf muscle pre-exercise, post-exercise, and at end-recovery. The dashed arrows indicate the distance between Pi and PCr peaks (b) shows the kinetics of PCr signal intensity during the three phases for the HF patient and (c) shows the PCr recovery time constant (k = 47.1 s for this patient) after fitting the phase III PCr recovery data.

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  Figure 3. PCr imaging. Representative cross-sectional PCr image of the calf muscle from a volunteer (top) and a HF-patient (bottom), obtained from pre, after exercise and end of recovery respectively. The low SNR of HF-patient image is due to the low PCr concentration of the calf muscles compared to volunteer. The first column shows images with 10 averages to increase SNR.

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  Figure 4. Global and regional PCr recovery using PCr imaging. (a) shows an image of calf muscle for anatomical reference and the muscle ROIs drawn for soleus (SOL), gastrocnemius medial (GM) and gastrocnemius lateral (GL). Sub-figures (b) and (c) show global and regional PCr recovery time constraints assessed using 31P-MRI data from a representative HF patient and healthy volunteer by fitting phase III data to Eq. 1. The PCr recovery time constants are significantly delayed (~ 60–70 s) compared to healthy volunteers (~ 20- 25 s). The PCr recovery time in specific muscles (d) GM (e) SOL and (f) GL shows increased depletion and slower recovery in GM and GL muscle groups, suggesting glycolytic metabolism from type II fibers’.

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  Figure 5. Comparison of results between cohorts. The PCr resynthesis time constant (mean ± SD) between healthy volunteers and HF-patients of Global (31P-MRS and MRI) as well as regional (31P-MRI) in gastrocnemius medial (GM), gastrocnemius lateral (GL), and soleus muscle (SOL). Significant differences were found in all analysis between volunteers and HF-patients, while two methods globally agreed very well.

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  Figure 6. Water-fat Imaging using multi-point Dixon technique. (a) shows water-fat imaging results after processing in a healthy volunteer. The first column shows fat image, and the fat fraction in the muscle, and the second column shows the water image and corresponding water fraction. (b) shows water-fat imaging results after processing in an HF patient, with the first column showing fat image and fat fractions, while the second column shows the proton image and water fraction. HF patients show considerably increased fatty infiltration in the muscle.