Contrast-enhanced ultrasound imaging with high CTR and improved resolution by bubble-echo based deconvolution

In microvascular perfusion imaging by contrastenhanced ultrasound (CEUS), inhibiting the strong tissue backscattering to enhance contrast-to-tissue ratio (CTR) and improving the imaging resolution to distinguish small vessels are two critical aspects. CTR has been greatly enhanced based on the strong nonlinear responses of contrast microbubbles under ultrasound insonation. However, the resolution of CEUS image is still limited by the finite bandwidth of the imaging system. In this paper, a peculiar bubble-echo based deconvolution (BED) was proposed based on a modified convolution model for CEUS to improve both CTR and resolution. A novel bubble-echo based PSF was constructed using the modified Herring equation, where bubble-echo referred to the theoretical backscattered echo from a single bubble under the insonification. Deconvolution was implemented axially using regularized inverse Wiener filtering. The efficiency of the proposed BED was verified by combining with fundamental imaging, second harmonic imaging and pulse inversion technique. Meanwhile, as comparisons, the approved cepstrum based deconvolution (CEPD) and pulse inversion bubble-wavelet imaging (PIWI) were also performed. In vivo rabbit kidney perfusion experiments were carried out to evaluate the above methods from CTR, time-intensity-curve and resolution. BED performed better than CEPD and PIWI in enhancing CTR, and had a higher resolution than PIWI. All results indicate that BED provides new CEUS methods with higher CTR and good resolution, which has important significance to microvascular perfusion evaluation in deep tissue.