Chapter 6 - Rebuilding IVUS images from raw data of the RF signal exported by IVUS equipment

Abstract

The study of composition and classification of atherosclerotic plaque has been a very active research field, both in cardiology and image processing. Intravascular ultrasound (IVUS) is an effective tool, which can insight on the cross-section of blood vessels, with sufficient accuracy to allow an accurate assessment of computed tomography slices. This enables information about blood vessel structures to be determined. During an IVUS medical examination, physicians subjectively adjust a set of parameters to improve the visualization of a region of interest and produce corresponding images in Digital Imaging and Communications format (DICOM Images), for later analysis and study. DICOM is appropriate for storage, transportation, and access, but limits subsequent changes to image parameters, such as contrast or brightness. This makes comparison across patient populations difficult and restricts image-processing operations. This article details an alternative to using DICOM, which is to rebuild IVUS images from raw radiofrequency (RF) signal data. The main advantage of this process is the independence of the acquisition parameters adjusted during the exam. This advantage makes possible the comparison between exams and can be used to monitor the evolution of cardiovascular disease. Beyond this, once the reconstructed images and the RF signal are stored, operations relating to texture and spectral analysis can be carried out and automatic classifiers employed. From a clinical point of view these reconstructed images share the same characteristics as DICOM images with an advantage that the former have a higher contrast than the latter, allowing deeper regions to be seen.