Whole Body Three Dimensional Plaque Imaging

Introduction Atherosclerosis is a systemic disease. Angiographic approaches are “luminograms” and provide no data on vascular remodeling and plaque burden which are far more important determinants of risk in vascular diseases. Assessment of overall plaque burden with current 2D MRI approaches [1-3] has important limitations. Firstly, imaging is limited to selective anatomical regions (e.g., carotid arteries [1] and/or aorta [2-3]). These regions may not reflect the involvement of other vascular territories, which may be of greater importance depending on the patient. Secondly, 2D imaging with slice gaps or thick slice are commonly used to speed up image acquisition. The partial volume effect may reduce MRI’s sensitivity in detecting subtle plaque volume changes. Thirdly, image registration with 2D images is challenging in patient follow-up. We propose here an approach for high resolution 3D plaque imaging of the whole body (from carotid to femoral arteries) that can improve the quantification of plaque burden in patients with atherosclerosis. Method Sequence: The technique is based on SPACE (a 3D turbo spin echo variant) with optimized T1 or T2 contrast [4-5]. ECG triggering and navigator gating are supported. When ECG triggering was used, acquisition was timed to systole for optimal blood suppression. The sequence was implemented on a 1.5T clinical scanner with 32 receiver channels (MAGNETOM Avanto, Siemens, Germany). Imaging protocol: Imaging was performed in 4 stations, each covering a specific section of vascular territory, using an appropriate imaging protocol based on SPACE. Station 1: carotid arteries – protocol from [6] (T2w) or [7] (T1w) was used with a 4element carotid coils (Machnet BV, Netherlands). Station 2: thoracic arteries – protocol from [8] was used with two 12-element body and spine matrix coils. The coils were positioned high up to the chin to cover the arteries coming out from the aorta to the neck. Station 3: abdominal aorta – protocol similar to [9] was used using same coils as in (2) except that they are positioned to overlap with peripheral coils to cover the iliac arteries. Station 4: femoral arteries – protocol from [10] was adapted with the 16-element peripheral matrix coils (station covered by 8 elements). Imaging: The study was approved by the institutional review board. Four healthy volunteers and two subjects with risk factors for atherosclerosis were scanned. All coils were placed on the subjects before the scan. Fig. 1 shows the workflow. For patient comfort, carotid coils were removed when station 1 was finished. No breath-holding was needed.