Guidance
3 The procedure
3 The procedure
3.1 Optical coherence tomography (OCT) is usually performed using local anaesthesia. A guide wire and delivery sheath are introduced percutaneously into either the femoral or radial artery and passed into the target coronary artery using fluoroscopic image guidance. OCT imaging needs a blood-free field. This was first achieved by an occlusive technique, using an occlusion balloon with first-generation time-domain OCT (TD OCT), but this technique is no longer used in clinical practice. A non-occlusive technique is now used, involving continuous flushing of contrast with frequency-domain OCT (FD OCT). For non-occlusive OCT, a guide wire through which contrast can be injected is used. The imaging catheter is delivered over this wire. Injection of contrast and imaging take place concurrently.
3.2 Second-generation FD OCT devices aim to improve image quality and, more importantly, increase the speed of image acquisition by a factor of 10. FD OCT has superseded TD OCT in the UK.
3.3 The resolution of coronary OCT is reported to be 10 times higher than that of intravascular ultrasound, and has rapid 3-dimensional reconstruction capability. The aim of providing more detailed images is to improve clinical outcome.