title: Thermoacoustic imaging of rabbit knee joints.
abstract: OBJECTIVE
  Knee joint is one of the largest and most complex joints of the body. Knee joint diseases are common, and current clinical imaging technologies such as x-ray computed tomography, magnetic resonance imaging, and ultrasound imaging have limitations in the diagnosis of knee joint diseases. Emerging imaging technologies such as diffuse optical tomography and photoacoustic imaging (PAI) have been applied to the detection of osteoarthritis (OA). However, they are limited to small joints such as the finger and difficult to be used for large joints such as the knee. Thermoacoustic imaging (TAI), also an emerging modality, provides high contrast and deep tissue penetration. Here, the authors apply TAI to the knee joint and demonstrate the potential of TAI for imaging large joints.
  
  
  METHODS
  Adult New Zealand male rabbits (average weight = 2 kg) were chosen for this study. In a TAI experiment, a rabbit was placed in a holder to keep in a genuflex position after being injected with pentobarbital through its ear margin intravenous (30 mg/kg). The holder and the rabbit were then positioned under the horn antenna of the TAI system for signal acquisition and image reconstruction. After the experiment, the imaged knee joint was dissected and photographed. Identical procedures were performed for several rabbits (n = 4). Finally, detailed comparative analyses between TAI images and anatomical pictures of the knee joint were conducted.
  
  
  RESULTS
  There were high similarities between the reconstructed TAI images and anatomical pictures of the knee joint, in terms of the shape and size of various knee joint tissues. TAI could clearly image ligament, fat pad, and other joint tissues. The differences in appearance of TAI images due to motion effect of the knee joint were also discussed.
  
  
  CONCLUSIONS
  TAI could reveal details of rabbit knee joint in high resolution. As the recovered TAI images represent the dielectric property distributions of joint tissues, TAI may offer a new tool for noninvasive detection of joint diseases such as OA.
authors.affiliation: School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China and Center for Information in Medicine, University of Electronic Science and Technology of China, Chengdu 611731, China.
authors.forename: Zihui
authors.initials: Z
authors.lastname: Chi
authors.affiliation: School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China and Center for Information in Medicine, University of Electronic Science and Technology of China, Chengdu 611731, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China and Center for Information in Medicine, University of Electronic Science and Technology of China, Chengdu 611731, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Huang
authors.affiliation: School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China and Center for Information in Medicine, University of Electronic Science and Technology of China, Chengdu 611731, China.
authors.forename: Zhu
authors.initials: Z
authors.lastname: Zheng
authors.affiliation: School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China; Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131; and Center for Information in Medicine, University of Electronic Science and Technology of China, Chengdu 611731, China.
authors.forename: Huabei
authors.initials: H
authors.lastname: Jiang
mesh_terms: D000162:Acoustics; D000818:Animals; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D011817:Rabbits; D013696:Temperature