Background:Kissing balloon technique(KBT) is essential for bifurcation treatment with either simple or complex strategies. We developed a novel method to evaluate the extent of balloon expansion during KBT and suggest how to optimize it. Method:We implanted a 3.0mm �� stent into bifurcation phantom made of plexiglass tubes(2.5mm �� side branch attached to 3.0mm �� main vessel with 30째 angle) and performed KBT using 3.0mm �� (MV) and 2.5mm �� (SB) balloons. To visualize only the MV balloon during KBT on fluoroscopy, we filled MV balloon with contrast dye and SB balloon with saline. Three different KBT methods were evaluated: simultaneous KBT, MV first KBT, SB first KBT (Figure). While inflated, two orthogonal views were taken and the images were 3D-reconstructed by means of IC3D (SIEMENS). Minimal balloon area was located at the reconstructed image and compared between each methods. KBT visualizing only SB balloon were performed in the same manner. All the above procedures were repeated three times.Result:With each methods, minimal balloon area of both MV and SB balloons were located at carina position. Minimal balloon area of MV with simultaneous, MV first, and SB first KBT were 5.80mm3, 6.39mm3, and 6.11mm3, respectively. Minimal balloon area of SB with simultaneous, MV first, and SB first KBT were 3.63mm3, 4.40mm3, and 4.62mm3, respectively. Percent expansion of MV with simultaneous, MV first, and SB first KBT were 82.08%, 90.38%, and 86.42%, respectively. Percent expansion of SB with simultaneous, MV first, and SB first KBT were 74.00%, 89.55%, and 94.03%, respectively. Total balloon area at carina level with simultaneous, MV first, and SB first KBT were 9.44mm3, 10.79mm3, and 10.73mm3, respectively. Conclusion:Compared with simultaneous KBT, MV or SB first KBT expanded both balloons more effectively, especially SB. SB ostium, where is the most common site of restenosis in vivo, was expanded most effectively with SB first KBT. Total balloon area was comparable with both MV and SB first KBT but much larger than simultaneous KBT.