The Novoste Beta-Cath System is a catheter-based Intravascular Brachytherapy (IVBT) delivery device which employs an ingenious system of hydraulics to deliver the source trains to the catheter tip. The transfer device serves to transport, hold and deliver the sources during the procedure. In this study a quantitative analysis was performed to determine the magnitude of the source displacement due to inconsistency of hydraulic pressure and cardiac motion during the treatment. Cince-angiograms of the Sr-90 source trains (30 mm and 40 mm) in place were reviewed frame by frame for 75 patients. The proximal and distal source movements were measured using two gold colored radiopaque markers in reference to edge of the corresponding stent. The two frames showing the maximum source displacement were captured. After appropriate dimensional calibration, longitudinal source displacement was measured. The data were categorized for proximal vs. distal ends and for different coronary vessels (right coronary artery, left anterior descending artery and circumflex artery). The longitudinal source displacement is significant with overall mean and standard deviation of 1.3 and 0.6 mm, respectively. The observed range is from 0.0 to 4.8 mm. The data is consistent with reports using other non-centralizing device
(i.e., Ir-192 system from Cordis) and different reference points (i.e., the vessel branch). Effect of hydraulic pressure on source displacement was found insignificant among different operators, as long as there is no leaky connection in the syringe lure area.