Acoustic Radiation Force Impulse (ARFI) elastography quantification of muscle stiffness over a course of gradual isometric contractions: a preliminary study.
OBJECTIVE
To evaluate the feasibility of quantitative analysis of muscle stiffness by Acoustic Radiation Forced Impulse (ARFI) elastography over a course of graduate isometric voluntary contractions.


METHODS
The stiffness of the bilateral biceps muscle of 13 healthy volunteers was measured in real time by ARFI elastography, while the forearm was in neutral-extended position, 90 degree self-flexed positions and 90 degree self-flexed position, with altered weights ranging from 1 to 8 kg placed on flattened palmar surfaces consecutively. The determined increases in biceps muscle stiffness were measured for both arms and correlated with the loadings weights adopted at progressive trial stages.


RESULTS
The mean shear wave velocity (SWV) values of biceps muscles in a neutral position, in 90 degree flex position and 90 degree flex position with 1 to 8 kg weights on palmar surfaces were 2.162+/-0.302 m/sec, 3.382+/-0.581 m/sec, and 3.897+/-0.585 to 5.562+/-0.587 m/sec, respectively. Significant correlations between the muscle SWV values and related palmar weights and between the SWV values of right and left sides at different trial stages were identified (r=0.951 and r=0.954, respectively). A mutual propagation path of deep regions to entire areas was described to account for the distribution of increase in stiffness with increases in palmar weights. The confidence of method regarding inter-observer difference was confirmed by the correlation analyses of the results (r=0.998).


CONCLUSIONS
ARFI elastography is a feasible imaging modality for quantifying the stiffness of isometrically voluntarily contracting muscles.
Department of Radiology, Yuzuncu Yil University, Medical Faculty, Van, Turkey. E-mail: dralpyavuz@hotmail.com.
Alpaslan
A
Yavuz
Department of Radiology, Yuzuncu Yil University, Medical Faculty, Van, Turkey.
Aydın
A
Bora
Department of Radiology, Yuzuncu Yil University, Medical Faculty, Van, Turkey.
Mehmet Deniz
MD
Bulut
Department of Radiology, Yuzuncu Yil University, Medical Faculty, Van, Turkey.
Abdussamet
A
Batur
Department of Neurology, Yuzuncu Yil University, Medical Faculty, Van, Turkey.
Aysel
A
Milanlioglu
Department of Radiology, Yuzuncu Yil University, Medical Faculty, Van, Turkey.
Cemil
C
Göya
Department of Radiology, Baskent University Medical Faculty, Adana, Turkey.
Cagatay
C
Andic
D000328:Adult; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D015588:Observer Variation; D005082:Physical Exertion / Q000502:physiology*; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical