Radial cardiac real-time datasets are usually compromised by streaking artifacts. Truncated principal component analysis (PCA) has been proposed to remove streaking and improve apparent SNR of the images. However, a proper threshold for truncation of the PCA has to be selected to maintain good temporal fidelity. This work proposes a method for automatic truncation of the PCA and compares a soft against the standard hard thresholding approach. Results indicate that the proposed method in combination with soft thresholding offers reduced temporal blurring and streaking artifacts while improving apparent SNR.