title: Near-field thermoacoustic imaging with transmission line pulsers.
abstract: OBJECTIVE
  Near-field radiofrequency thermoacoustic (NRT) tomography has been recently introduced for imaging electromagnetic (EM) properties of tissues using ultrawideband, high-energy impulses, which induce thermoacoustic responses. Operation in the near-field allows for more effective energy coupling into tissue, compared to using radiating sources, which in turn enables the use of shorter excitation pulses and leads to higher image resolution. This work aimed at investigating transmission lines as a method to generate excitation pulses to improve the NRT resolution over previous implementations without compromising the energy coupled into tissue.
  
  
  METHODS
  The authors implemented a number of custom-made transmission lines to overcome the challenges of the broadband nature of the impulse excitation required in NRT. The authors further constructed phantoms and investigated the performance of the lines in regard to the pulse duration, energy coupling and the resulting resolution, and image quality achieved. Finally, the authors employed mice in order to investigate the performance of the approach in tissue imaging.
  
  
  RESULTS
  The authors found that the use of transmission lines resulted in the generation of RF impulses in the range of tens of nanoseconds and shorter. This performance resulted to resolution improvements over previous thermoacoustic imaging implementations, reaching 45 μm resolution, while retaining several tens to hundreds of milli-Joules of energy per pulse. This performance further allowed the visualization and clear differentiation of different mouse structures such as the heart, lung, or spinal cord.
  
  
  CONCLUSIONS
  The use of transmission lines significantly improved the NRT performance leading to high thermoacoustic tomography imaging quality by coupling adequate amounts of energy within short times at a relatively low cost.
authors: Institute for Biological and Medical Imaging, Technische Universität München and Helmholtz Zentrum München, Ingolstädter Landstr. 1, Neuherberg, Germany.
authors: Murad
authors: M
authors: Omar
authors: Stephan
authors: S
authors: Kellnberger
authors: George
authors: G
authors: Sergiadis
authors: Daniel
authors: D
authors: Razansky
authors: Vasilis
authors: V
authors: Ntziachristos
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D051379:Mice; D033401:Microscopy, Acoustic / Q000295:instrumentation*; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013817:Thermography / Q000295:instrumentation*