Assessment of anterior thigh muscle size and fat infiltration using single-slice CT imaging versus automated MRI analysis in adults

Ultrasound assessment of rectus femoris pennation angle and echogenicity. Their association with muscle functional measures and fat infiltration measured by CT scan

BACKGROUND & AIMS

Ultrasound can be used to measure the pennation angle between muscle fiver and the presumed axis of force generation and muscle echogenicity as an indicator of muscle fat infiltration. We aimed to assess the association of the rectus femoris pennation angle and echogenicity with muscle functional measures. Also, to assess the concordance of rectus femoris echogenicity with muscle fat infiltration as determined by CT scan.

METHODS

Rectus femoris ultrasound pennation angle and thickness were measured in 78 participants aged 69 (65,73) years (37 women). Also hand grip strength, gait speed in 4 m, the 12 min' walk and body composition by DEXA were measured. In a different group of 114 participants aged 44 (31,52) years (80 females), non-dominant rectus femoris echogenicity and thickness were measured by ultrasound and muscle fat infiltration was assessed by CT scan. Handgrip strength and quadriceps torque were also measured.

RESULTS

There was a weak correlation between the pennation angle and rectus femoris thickness in men (r = 0.31 p = 0.05) but not in women (r = 0.29 NS). Women, but not men with a low pennation angle covered a longer distance during the 12 min' walk. The concordance between the z scores of rectus femoris echogenicity and CT radiological density was 0.43 (p < 0.01) and 0.01 (NS) in men and women, respectively. Men and women with an echogenicity below the 25th percentile had a higher quadriceps torque. Men with an echogenicity 25th percentile below 25th percentile had also a higher handgrip strength.

CONCLUSIONS

Rectus femoris pennation angle had a weak or absent association with muscle performance. Rectus femoris echogenicity had a moderate overall concordance with radiological density by CT scan and was inversely associated with quadriceps torque. Therefore, echogenicity was associated with muscle strength, but pennation angle measurement did not contribute to the assessment of muscle function.

Skeletal Myosteatosis is Associated with Systemic Inflammation and a Loss of Muscle Bioenergetics in Stable COPD

Background

Common features among patients with more advanced chronic obstructive pulmonary disease (COPD) are systemic inflammation and a loss of both muscle mass and normal muscle composition. In the present study, we investigated COPD subjects to better understand how thigh muscle fat infiltration (MFI) and energy metabolism relate to each other and to clinical features of COPD with emphasis on systemic inflammation.

Methods

Thirty-two Caucasians with stable COPD were investigated using questionnaires, lung function tests, blood analysis and magnetic resonance imaging (MRI) for analysis of body- and thigh muscle composition. Bioenergetics in the resting thigh muscle, expressed as the PCr/Pi ratio, were analysed using ³¹phosphorus magnetic resonance spectroscopy (³¹P-MRS).

Results

Based on the combination of the MFI adjusted for sex (MFI_a) and the thigh fat-tissue free muscle volume, expressed as the deviation from the expected muscle volume of a matched virtual control group (FFMV_vcg), all COPD subjects displayed abnormally composed thigh muscles. Clinical features of increased COPD severity, including a decrease of blood oxygenation (r = −0.44, p < 0.05) and FEV₁/FVC ratio, reflecting airway obstruction (r = −0.53, p < 0.01) and an increase of COPD symptoms (r = 0.37, p < 0.05) and breathing frequency at rest (r = 0.41, p < 0.05), were all associated with a raise of the PCr/Pi ratio in the thigh muscle. Increased MFI_a of the thigh muscle correlated positively with markers of systemic inflammation (white blood cell count, r = 0.41, p < 0.05; fibrinogen, r = 0.44, p < 0.05), and negatively with weekly physical activity (r = −0.40, p < 0.05) and the PCr/Pi ratio in the resting thigh muscle (r = −0.41, p < 0.05).

Conclusion

The present study implies a link between systemic inflammation, excessive MFI and a loss of bioenergetics in subjects with stable COPD.