Intravascular ultrasound (IVUS) employs aminiature ultrasound probe positioned at the tip of a coronary catheter to emit ultrasound signal which is reflected from surrounding tissue and then reconstructed into a real-time tomographic gray-scale image. IVUS directly images the vessel inside, allowing measurement of plaque morphology,distribution and exact vessel composition. Recent technical developments enable processing of the backscattered ultrasound radiofrequency signal underlying the gray-scale image. Therefore, IVUS can now providemore accurate measurement of tissue properties than traditional gray-scale images by different methods of tissue characterization.Thin-cap fibroatheroma by virtual histology was a proved risk factor for future cardiac events. Clinical trials
disclosed significant improvement in patient outcome and reduced complications by IVUS-guided percutaneous coronary intervention (PCI), which can also provide more information in angiographic ambiguous lesions. 3-4 mm2 for non-left main (LM) lesion or 5.9-7.5 mm2 for LM lesion are considered the cut-off minimal lumen areas to identify significant stenosis. After stenting, in-stent minimal area ≧90% of the average reference lumen area or 100% of the lumen area of the reference segment with the lowest lumen area are IVUS-acceptable. In conclusion,
IVUS is a powerful imaging modality which can provide more information before, during and after PCI to facilitate the procedure. Therefore, it should be used more widely in order to improve clinical outcomes and quality of our interventions.