Optimization of Parameter Settings in Cine-MR Imaging for Diagnosis of Swallowing

Abstract

Videofluorography is frequently used to evaluate swallowing and is considered the "gold standard" among imaging modalities. This modality, however, has several disadvantages, including radiation exposure and limitations in the detection of soft tissues. Conversely, magnetic resonance imaging (MRI) offers excellent contrast resolution in soft tissue without radiation exposure. A major drawback of MRI in evaluating swallowing, however, is that temporal resolution is poor. The aim of this study was to investigate a new cine-MRI modality. Imaging parameters were optimized and the efficacy of this new technique is discussed. Three techniques for speeding up MRI were combined: true fast imaging with steady state precession, generalized auto-calibrating partially parallel acquisition, and key-hole imaging. The effects of the receiver coils used, receiving bandwidth, slice thickness, and flip angle on each image were determined. The optimal imaging parameters obtained comprised a reduction factor of 2, receiving bandwidth of 1,000 Hz/pixel (repetition time of 151.7 milliseconds and echo time of 1.4 milliseconds), flip angle of 50°, and slice thickness of 6 mm. Neck and spine coils were used. Under these conditions, the new cine-MR imaging technique investigated showed a temporal resolution of 0.1 sec/slice (10 frames/sec). Even with optimized parameter settings, this technique did not allow a true temporal resolution of 30 frames/sec by a large margin. Motion artifacts persisted. Further study is needed on how to speed up this technique.

A computational fluid dynamics simulation of liquid swallowing by impaired pharyngeal motion: bolus pathway and pharyngeal residue

“…Thickening agents are often used for patients with dysphagia. A high-viscosity bolus can reduce the risk of aspiration (25), but thickening agents do not necessarily improve the incidence of aspiration pneumonia (27). A review paper on the management of swallowing (18) discusses that although a chin-tucking posture improves dysphagia in patients with a reduced airway closure, a head-tilting posture improves dysphagia in patients with an oropharyngeal weakness.…”

“…Recently, there have been some reports on stereoscopic observations of swallowing. These studies used computed tomography (CT) (8,9,28), cine magnetic resonance imaging (17,25) and computational fluid dynamics (CFD) simulation (12,13,15,16,22,32). Inamoto et al (9), for example, analyzed the timing of the swallowing process, including the true vocal cord closure using CT, and concluded that the timing changes with viscosities.…”