Tissue Doppler imaging is a routinely used diagnostic tool for assessing myocardial function in real time. The required signal processing is computationally intensive, including modified auto-correlation, scan conversion, image mapping. Parallel algorithms and implementations based on GPU platform are proposed in this paper to increase the computation efficiency. The experimental signal data is acquired from a healthy human heart. Our method achieves a frame rate of 467 fps comprising 52 scan lines, 512 samples along the axial scan line, each scan line being obtained from an ensemble size of 6. The total execution time was about 105-fold faster on GPU than on CPU.