Real-time magnetic resonance imaging of normal swallowing

Real-time magnetic resonance imaging of cardiac function and flow-recent progress

Cardiac structure, function and flow are most commonly studied by ultrasound, X-ray and magnetic resonance imaging (MRI) techniques. However, cardiovascular MRI is hitherto limited to electrocardiogram (ECG)-synchronized acquisitions and therefore often results in compromised quality for patients with arrhythmias or inabilities to comply with requested protocols-especially with breath-holding. Recent advances in the development of novel real-time MRI techniques now offer dynamic imaging of the heart and major vessels with high spatial and temporal resolution, so that examinations may be performed without the need for ECG synchronization and during free breathing. This article provides an overview of technical achievements, physiological validations, preliminary patient studies and translational aspects for a future clinical scenario of cardiovascular MRI in real time.

Weight-bearing MR imaging as an option in the study of gravitational effects on the vocal tract of untrained subjects in singing phonation

Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects.

The use of high-speed, continuous, T2-weighted magnetic resonance sequences and saline for the evaluation of swallowing

OBJECTIVE

To introduce a new high-speed, continuous, T2-weighted magnetic resonance imaging (MRI) technique for the evaluation of swallowing by visualizing the flow of saline.

STUDY DESIGN

In 20 healthy participants, high-speed (10 frames per second), continuous MRI of the pharynx and larynx was performed during administration of 5 mL of saline. The extent to which fluid flow and swallowing (including flow to the esophagus or trachea) could be visualized was determined for all 20 participants.

RESULTS

Solution flow was visualized, and swallowing events, including the direction of flow to the esophagus, could be visualized with high-speed, continuous MRI for all 20 participants.

CONCLUSIONS

This initial study suggests that the visualization of saline flow using our method may facilitate functional evaluation of swallowing without side effects.

Real-time magnetic resonance imaging and electromagnetic articulography database for speech production research (TC)

USC-TIMIT is an extensive database of multimodal speech production data, developed to complement existing resources available to the speech research community and with the intention of being continuously refined and augmented. The database currently includes real-time magnetic resonance imaging data from five male and five female speakers of American English. Electromagnetic articulography data have also been presently collected from four of these speakers. The two modalities were recorded in two independent sessions while the subjects produced the same 460 sentence corpus used previously in the MOCHA-TIMIT database. In both cases the audio signal was recorded and synchronized with the articulatory data. The database and companion software are freely available to the research community.

Evaluation of swallow function after tongue cancer treatment using real-time magnetic resonance imaging: a pilot study

IMPORTANCE

Magnetic resonance imaging (MRI) has the advantage of imaging swallow function at any anatomical level without changing the position of patient, which can provide detailed information than modified barium swallow, by far the gold standard of swallow evaluation.

OBJECTIVE

To investigate the use of real-time MRI in the evaluation of swallow function of patients with tongue cancer.

DESIGN, SETTING, AND PARTICIPANTS

Real-time MRI experiments were performed on a Signa Excite HD 1.5-T scanner (GE Healthcare), with gradients capable of 40-mT/m (milli-Tesla per meter) amplitudes and 150-mT/m/ms (mT/m per millisecond) slew rates. The sequence used was spiral fast gradient echo sequence. Four men with base of tongue or oral tongue squamous cell carcinoma and 3 age-matched healthy men with normal swallowing participated in the experiment.

INTERVENTIONS

Real-time MRI of the midsagittal plane was collected during swallowing. Coronal planes between the oral tongue and base of tongue and through the middle of the larynx were collected from 1 of the patients.

MAIN OUTCOMES AND MEASURES

Oral transit time, pharyngeal transit time, submental muscle length change, and the distance change between the hyoid bone and anterior boundary of the thyroid cartilage were measured frame by frame during swallowing.

RESULTS

All the measurable oral transit and pharyngeal transit times of the patients with cancer were significantly longer than the ones of the healthy participants. The changes in submental muscle length and the distance between the hyoid bone and thyroid cartilage happened in concert for all 60 normal swallows; however, the pattern differed for each patient with cancer. To our knowledge, the coronal view of the tongue and larynx revealed information that has not been previously reported.

CONCLUSIONS AND RELEVANCE

This study has demonstrated the potential of real-time MRI to reveal critical information beyond the capacity of traditional videofluoroscopy. Further investigation is needed to fully consider the technique, procedure, and standard scope of applying MRI to evaluate swallow function of patients with cancer in research and clinic practice.

On the physiology of normal swallowing as revealed by magnetic resonance imaging in real time

The aim of this study was to assess the physiology of normal swallowing using recent advances in real-time magnetic resonance imaging (MRI). Therefore ten young healthy subjects underwent real-time MRI and flexible endoscopic evaluations of swallowing (FEES) with thickened pineapple juice as oral contrast bolus. MRI movies were recorded in sagittal, coronal, and axial orientations during successive swallows at about 25 frames per second. Intermeasurement variation was analyzed and comparisons between real-time MRI and FEES were performed. Twelve distinct swallowing events could be quantified by real-time MRI (start time, end time, and duration). These included five valve functions: oro-velar opening, velo-pharyngeal closure, glottal closure, epiglottic retroflexion, and esophageal opening; three bolus transports: oro-velar transit, pharyngeal delay, pharyngeal transit; and four additional events: laryngeal ascent, laryngeal descent, vallecular, and piriform sinus filling and pharyngeal constriction. Repetitive measurements confirmed the general reliability of the MRI method with only two significant differences for the start times of the velo-pharyngeal closure (t(8) = −2.4, P ≤ 0.046) and laryngeal ascent (t(8) = −2.6, P ≤ 0.031). The duration of the velo-pharyngeal closure was significantly longer in real-time MRI compared to FEES (t(8) = −3.3, P ≤ 0.011). Real-time MRI emerges as a simple, robust, and reliable tool for obtaining comprehensive functional and anatomical information about the swallowing process.

Dynamic real-time magnetic resonance imaging for the analysis of voice physiology

PURPOSE OF REVIEW

For a number of years, it has been possible to use dynamic real-time magnetic resonance imaging (MRI) to analyse the dynamic processes which occur in the human body. In the fields of laryngology and phoniatrics, such dynamic processes are found not only in swallowing, but also in voice and speech production. This article aims to present an overview of how the use of MRI might add to our current understanding of the dynamic processes involved in voice production.

RECENT FINDINGS

It is shown that up to now the analysis of vocal fold oscillations has been limited by MRI's relatively low sampling rate of up to 50 Hz. Nevertheless, more detailed analysis does seem possible with regard to the modulation of the power source and vocal tract.

SUMMARY

Dynamic real-time MRI offers a great opportunity for the analysis of voice production in all stages of the voice production system.

Intraoral pressure patterns during swallowing

Swallowing disturbances are common after neurological disease and oropharyngeal tumor resection. In this case the oral stage is often affected. So far the clinical evaluation of the oral phase is limited. Recently the role of pressure changes during oropharyngeal swallowing has been pointed out, but until now there are not enough data. Thereby 52 healthy adults aged between 20 and 45 years were examined using an oral shield (Silencos^®, Bredent, Senden, Germany) connected to a digital manometer (GDUSB 1000^®, Greisinger electronics, Regenstauf, Germany) able to record pressures in a range of 2,000 to −1,000 mbar at a frequency of 1 kHz. Three swallowing conditions were measured: an active bolus intake (ABI) of water, a passive bolus application of a water-bolus (PWA) and a passive application of a gel-bolus (PGA). We found negative pressures with a median value of −278.9 mbar during ABI, of −24.2 mbar during PWA and of −29.4 mbar during PGA. Significant differences in pressure amplitudes and the pressure pattern were observed depending on the kind of bolus application and its consistency. The used test presents a simple and easy to handle method to assess the oral phase of swallowing.