Sensitive ultrasonic delineation of steroid treatment in living dystrophic mice with energy-based and entropy-based radio frequency signal processing.
Duchenne muscular dystrophy is a severe wasting disease, involving replacement of necrotic muscle tissue by fibrous material and fatty infiltrates. One primary animal model of this human disease is the X chromosome-linked mdx strain of mice. The goals of the present work were to validate and quantify the capability of both energy and entropy metrics of radio-frequency ultrasonic backscatter to differentiate among normal, dystrophic, and steroid-treated skeletal muscle in the mdx model. Thirteen 12-month-old mice were blocked into three groups: 4 treated mdx-dystrophic that received daily subcutaneous steroid (prednisolone) treatment for 14 days, 4 positive-control mdx-dystrophic that received saline injections for 14 days, and 5 negative-control animals. Biceps muscle of each animal was imaged in vivo using a 40-MHz center frequency transducer in conjunction with a Vevo-660 ultrasound system. Radio-frequency data were acquired (1 GHz, 8 bits) corresponding to a sequence of transverse images, advancing the transducer from "shoulder" to "elbow" in 100-micron steps. Data were processed to generate both "integrated backscatter" (log energy), and "entropy" (information theoretic receiver, H(f)) representations. Analyses of the integrated-backscatter values delineated both treated-and untreated-mdx biceps from normal controls (p < 0.01). Complementary analyses of the entropy images differentiated the steroid-treated and positive-control mdx groups (p < 0.01). To our knowledge, this study represents the first reported use of quantitative ultrasonic characterization of skeletal muscle in mdx mice. Successful differentiation among dystrophic, steroid-treated, and normal tissues suggests the potential for local noninvasive monitoring of disease severity and therapeutic effects.
Wallace
Kirk D
KD
Washington University School of Medicine, Washington University, St. Louis, MO, USA. kirk.wallace@wustl.edu
Marsh
Jon N
JN
Baldwin
Steven L
SL
Connolly
Anne M
AM
Keeling
Richard
R
Lanza
Gregory M
GM
Wickline
Samuel A
SA
Hughes
Michael S
MS
D000465:Algorithms; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage; D004195:Disease Models, Animal; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000187:drug effects; D020388:Muscular Dystrophy, Duchenne / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D011239:Prednisolone / Q000008:administration & dosage*; D011379:Prognosis; D011846:Radio Waves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D016896:Treatment Outcome; D014463:Ultrasonography / Q000379:methods*
D000893:Anti-Inflammatory Agents; D011239:Prednisolone