Suppression of tissue harmonics for pulse-inversion contrast imaging using time reversal

Phys Med Biol. 2008 Oct 7;53(19):5469-80. doi: 10.1088/0031-9155/53/19/013. Epub 2008 Sep 2.

Abstract

Pulse-inversion (PI) sequences are sensitive to the nonlinear echoes from microbubbles allowing an improvement in the blood-to-tissue contrast. However, at larger mechanical indices, this contrast is reduced by harmonics produced during nonlinear propagation. A method for tissue harmonics cancellation exploiting time reversal is experimentally implemented using a 128-channel 12-bit emitter receiver. The probe calibration is performed by acquiring the nonlinear echo of a wire in water. These distorted pulses are time-reversed, optimized and used for the PI imaging of a tissue phantom. Compared to normal (straight) pulses, the time-reversed distorted pulses reduced the tissue signal in PI by 11 dB. The second harmonic signals from microbubbles flowing in a wall-less vessel were unaffected by the correction. This technique can thus increase the blood-to-tissue contrast ratio while keeping the pressure and the number of pulses constant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Artifacts*
  • Calibration
  • Contrast Media*
  • Copper
  • Microbubbles
  • Phantoms, Imaging
  • Time Factors

Substances

  • Contrast Media
  • Copper