１．閉塞性頚動脈疾患の最新画像診断

Abstract

Multiple modalities for imaging of the cervical carotid artery (CA) are reviewed, and their indications for obstructive carotid diseases are discussed.Ultrasonography is a completely non-invasive modality. It is not only a primary tool for screening of the carotid artery but is capable of minute tissue characterization and flow velocity measurements, which will be discussed in detail somewhere else in this symposium.The standard method for MR angiography (MRA) for the cervical CA is contrast-enhanced MRA (CE-MRA), which employs T1shortening by intravenous gadolinium chelate injection. With use of dedicated neurovascular coil, MRA of the major cervical arteries from the aortic arch up to the skull base is obtained in 15 seconds. Although the spatial resolution is limited and there is possible signal loss from phase dispersion caused by non-laminar flow, it is a minimally invasive method for screening of the cervical arteries. Recent introduction of parallel imaging technology has added multi-phase capability to CE-MRA.CT angiography is another standard modality for carotid imaging. With advent of multi-detector CT (MDCT) scanner, it is possible to acquire isotropic three-dimensional data set of the whole range of cervical vessels in a few seconds, minimizing motion artifact from pulsation and respiration. With its capability of high spatial resolusion imaging, it will replace conventional angiography in most of the clinical settings.Plaque imaging by MRI is a novel method to evaluate carotid plaque using special high-resolution imaging technique such as black blood sequence. Its clinical goal is to identify vulnerable plaque by characterization with multi-sequence imaging. A few of the imaging features indicative of vulnerable plaque include contrast enhancement on post contrast T1-weighted images and disruption of fibrous cap on T2 * -weighted images.