Low-contrast lesion detection enhancement using pulse compression technique

Abstract

Pulse compression methods greatly improve the quality of medical images. In comparison with standard broadband pulse techniques, these methods enhance the contrast-to-noise ratio and increase the probing depth without any perceptible loss of spatial resolution. The Golay compression technique is analyzed here in the context of ultrasonic computed tomography, first on a one-dimensional target and second, on a very low-contrast phantom probed using a half-ring array tomograph. The imaging performances were assessed based on both the point spread function properties and the image contrast-to-noise ratio. The improvement obtained in the image contrast-to-noise ratio (up to 40%) depends, however, on the number of coherently associated diffraction projections. Beyond a certain number, few advantages were observed. Advances in ultrasound computed tomography suggest that pulse compression methods should provide a useful means of optimizing the trade-off between the image quality and the probing sampling density. It could also be used to accelerate the reconstruction process during the examination of patients. The results of this study also suggest that when it is proposed to search for very low contrast lesions (such as diffuse lobar carcinomas in breast cancer), once the number of projections has been set for a given tomographic set-up, the image contrast, i.e., the probability of detection, can been enhanced by using low-power, high-energy Golay sequences