Dynamic MRI of swallowing: real-time volumetric imaging at 12 frames per second at 3 T

Objective

Dysphagia or difficulty in swallowing is a potentially hazardous clinical problem that needs regular monitoring. Real-time 2D MRI of swallowing is a promising radiation-free alternative to the current clinical standard: videofluoroscopy. However, aspiration may be missed if it occurs outside this single imaged slice. We therefore aimed to image swallowing in 3D real time at 12 frames per second (fps).

Materials and methods

At 3 T, three 3D real-time MRI acquisition approaches were compared to the 2D acquisition: an aligned stack-of-stars (SOS), and a rotated SOS with a golden-angle increment and with a tiny golden-angle increment. The optimal 3D acquisition was determined by computer simulations and phantom scans. Subsequently, five healthy volunteers were scanned and swallowing parameters were measured.

Results

Although the rotated SOS approaches resulted in better image quality in simulations, in practice, the aligned SOS performed best due to the limited number of slices. The four swallowing phases could be distinguished in 3D real-time MRI, even though the spatial blurring was stronger than in 2D. The swallowing parameters were similar between 2 and 3D.

Conclusion

At a spatial resolution of 2-by-2-by-6 mm with seven slices, swallowing can be imaged in 3D real time at a frame rate of 12 fps.

     

Prevalence study of oral white lesions with special reference to a new definition of oral leucoplakia

In this survey, the experiences with and implications of a revised definition of oral leucoplakia are described. One of the new aspects of the revised definition is the distinction between a provisional, clinical diagnosis and a definitive one for which histopathological examination is required. A prevalence study of white lesions of the oral mucosa among a selected population of 1000 consecutive patients from the Netherlands showed a prevalence of a provisional and definitive diagnosis of oral leucoplakia of 0.6 and 0.2%, respectively. For uniform reporting, a recently proposed classification and staging system has been used to stage leucoplakias with a definitive diagnosis. The use of the revised definition of oral leucoplakia, as well as the classification and staging system, seem very suitable for epidemiological studies.     

Assessment of tumour invasion into the mandible: the value of different imaging techniques

In oral carcinomas close to the mandible, tumour invasion of the mandible is important in selecting segmental or marginal resection. Imaging may play a role in assessing tumour invasion. This study compares the accuracy of panoramic X-ray, CT and MR imaging in assessing invasion of the mandible in 29 patients. At histopathology, 6 patients had mandible erosion, 12 had invasion and 11 had an intact mandible. Magnetic resonance imaging had the highest sensitivity (94%), but a low specificity (73%), with 3 of 11 intact mandibles interpreted as positive. Furthermore, MR often overestimated the extent of tumour invasion. On the other hand, CT and panoramic X-ray had a lower sensitivity (64 and 63%, respectively) and a higher specificity (89 and 90%, respectively). Computed tomography (using 5-mm sections) and panoramic X-ray had a similar accuracy, and negative findings do not exclude invasion. Magnetic resonance imaging was the most sensitive technique but had more false positives and frequently overestimated the extent of tumour invasion. Because none of the radiological techniques are accurate enough, clinical examination seems at present to remain the most important modality in deciding between segmental and marginal resection. Tumour invasion at CT or panoramic X-ray is a strong argument for a segmental resection.     

Laterality in visual speech perception.

The lateralization of visual speech perception was examined in 3 experiments. Participants were presented with a realistic computer-animated face articulating 1 of 4 consonant-vowel syllables without sound. The face appeared at 1 of 5 locations in the visual field. The participants' task was to identify each test syllable. To prevent eye movement during the presentation of the face, participants had to carry out a fixation task simultaneously with the speechreading task. In one study, an eccentricity effect was found along with a small but significant difference in favor of the right visual field (left hemisphere). The same results were found with the face articulating nonlinguistic mouth movements (e.g., kiss). These results suggest that the left-hemisphere advantage is based on the processing of dynamic visual information rather than on the extraction of linguistic significance from facial movements. (PsycINFO Database Record (c) 2011 APA, all rights reserved)