title: Noninvasive assessment of age, gender, and exercise effects on skeletal muscle: Initial experience with T1ρ MRI of calf muscle.
abstract: To prospectively investigate age- and gender-related changes in the fast-twitch (tibialis anterior, TA) and slow-twitch (soleus, SOL) skeletal muscle of healthy rats and volunteers and to compare the exercise-related difference in health volunteers with T1ρ magnetic resonance imaging (MRI).
  
  
  
  In all, 18 rats and 70 humans were involved in this study. For the animal study, T1ρ relaxation times were measured in the TA and SOL rat muscle with a 3.0T MRI scanner and compared to histological data. For the human study, three groups (young, middle-aged, and elderly) of volunteers underwent T1ρ MRI scans (3.0T) of their calves. To further differentiate the human scans, 18 volunteers were recruited, half of them (n = 9) routinely trained with high-intensity sports, while the other half (n = 9) with no physical training. Statistical analysis was performed via paired t-test, independent-sample t-test, and analysis of variance (ANOVA). Correlations between T1ρ and age/gender/physical endurance were calculated.
  
  
  
  The average T1ρ relaxation times of the TA and SOL of female rats were higher than that of male rats (P < 0.001). The T1ρ relaxation time of TA was significantly lower compared to SOL (P < 0.001). A significant linear correlation was observed between T1ρ and the type I slow-twitch fiber proportion (%) in SOL (R2= 0.837, P < 0.001). Similarly, in human studies the average T1ρ relaxation times of TA were significantly lower than SOL for all age groups (P < 0.001). The higher T1ρ relaxation times of TA and SOL in the elderly volunteers (P < 0.001) and in the females (P < 0.05) indicated significant age- and gender-dependent differences. In high-intensity sports groups, the higher T1ρ in SOL (P < 0.01) and lower in TA (P < 0.05) were observed compared with the control group.
  
  
  
  This study demonstrated that T1ρ MRI can be used to display the differences in fast- and slow-twitch skeletal muscle as well as potentially age-, gender-, and exercise-related differences.
  
  
  
  2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:61-70.
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Xin-Gui
authors.initials: XG
authors.lastname: Peng
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Yuancheng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Shijun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Mao
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Gao-Jun
authors.initials: GJ
authors.lastname: Teng
authors.affiliation: Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, P.R. China.
authors.forename: Shenghong
authors.initials: S
authors.lastname: Ju
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D000818:Animals; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007866:Leg / Q000000981:diagnostic imaging / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D064797:Physical Conditioning, Human / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors
keywords: T1ρ; age; exercise; gender; skeletal muscle