This paper presents a method of extracting Pulse Transit Time (PTT) from multimodal pulsatile signals, such as Electrocardiography (ECG) and Photoplethysmograph (PPG), to facilitate research on estimating Blood Pressure based on PTT. We address the robustness issues of PTT extraction, since the pulsatile signals are subject to distortions due to sensor errors or subject movements. A cepstrum analysis method is proposed to estimate the pulse rate from each modality, and then a signal quality assessment is conducted by verifying the conformance of the pulse rate with the pulse time for a single modality as well as across multiple modalities. Erroneous peaks in the distorted pulsatile signal can be rejected by the quality screening step. Experiments were conducted using PhysioNet database MIMIC-II comprising ECG, PPG and Arterial Blood Pressure (ABP) signals, and the results demonstrated the effectiveness of the proposed method and furthermore provided insights to the MIMIC-II database.