Functional morphology of phonation evaluated by dynamic MRI

Dynamic CT Study on the Morphology and the Motor Ability of Unilateral Vocal Fold Paralysis

OBJECTIVE

To investigate the morphological changes and motor functions of the larynx in unilateral vocal fold paralysis by using dynamic three-dimensional CT, and to explore the differences between vocal fold paralysis with different nerves involved.

METHODS

Twenty-five patients with unilateral vocal fold paralysis and 10 healthy subjects were selected as the paralytic group and the normal group, respectively. Ten dynamic sequence images of laryngeal movement from inhalation to phonation were reviewed, and the glottic morphology at the coronal position, the minimum glottic area at the horizontal position, and the overall activity of the two groups were compared. The 25 patients with unilateral vocal fold paralysis were divided into the thyroarytenoid (TA) muscle group, the TA and posterior cricoarytenoid (PCA) (TA + PCA) muscle group, and the PCA muscle group. The coronal and horizontal parameters of the three types were compared as noted above and the dynamic parameter changes were also compared between the groups.

RESULTS

The height and thickness of bilateral vocal cords, the minimum glottic area, and the whole glottic activity were different in the paralysis group and were significantly different from those of the normal group (P < 0.05). The value of the glottic gap ratio and its decrease rate in the TA + PCA group was smaller than those in the TA and PCA group, and the glottic gap ratio was the largest in the PCA group.

CONCLUSION

Dynamic CT can provide a qualitative evaluation of laryngeal morphology and quantitative evaluation of motor function in vocal fold paralysis.

LEVEL OF EVIDENCE: 4

Feasibility of vocal fold abduction and adduction assessment using cine-MRI

Objective

Determine feasibility of vocal fold (VF) abduction and adduction assessment by cine magnetic resonance imaging (cine-MRI)

Methods

Cine-MRI of the VF was performed on five healthy and nine unilateral VF paralysis (UVFP) participants using an axial gradient echo acquisition with temporal resolution of 0.7 s. VFs were continuously imaged with cine-MRI during a 10-s period of quiet respiration and phonation. Scanning was repeated twice within an individual session and then once again at a 1-week interval. Asymmetry of VF position during phonation (VF phonation asymmetry, VFPa) and respiration (VF respiration asymmetry, VFRa) was determined. Percentage reduction in total glottal area between respiration and phonation (VF abduction potential, VFAP) was derived to measure overall mobility. An un-paired t-test was used to compare differences between groups. Intra-session, inter-session and inter-reader repeatability of the quantitative metrics was evaluated using intraclass correlation coefficient (ICC).

Results

VF position asymmetry (VFPa and VFRa) was greater (p=0.012; p=0.001) and overall mobility (VFAP) was lower (p=0.008) in UVFP patients compared with healthy participants. ICC of repeatability of all metrics was good, ranged from 0.82 to 0.95 except for the inter-session VFPa (0.44).

Conclusion

Cine-MRI is feasible for assessing VF abduction and adduction. Derived quantitative metrics have good repeatability.

Key points

• Cine-MRI is used to assess vocal folds (VFs) mobility: abduction and adduction.

• New quantitative metrics are derived from VF position and abduction potential.

• Cine-MRI able to depict the difference between normal and abnormal VF mobility.

• Cine-MRI derived quantitative metrics have good repeatability.

[Functional results of treatment of early carcinoma in the glottic region of the larynx]

Early stage glottic cancer can be successfully treated with open surgery, LASER surgery or radiotherapy. During this treatment the physician obviously has to bear in mind principles of oncological radicality, but also, none the less, the preservation of all the functions of the larynx, and especially the preservation of voice quality. The aim of the study is to compare, in a specifically designed prospective study, the method of treatment with the functional results of basic characteristics of spoken voice of patients with early stage cancer of the glottis region. Then, based on the analysis of the results, to try and determine the most successful method of treatment. The first study group consisted of 72 patients operated using transoral laser microsurgery; the second study group consisted of 75 patients operated using open surgery; and the third study group consisted of 74 patients treated with radiotherapy. The voice quality is much better after laser chordectomy compared to open surgery chordectomy with reconstruction. Furthermore, the functional results of voice quality, after a laser chordectomy, are worse when compared to the group of patients treated with radiotherapy. Taking into account all objective and subjective phoniatric parameters, we determined that there is no crucial difference in the voice quality of patients operated using laser chordectomy and patients primarily treated with radiotherapy. From a functional point of view these two methods are superior to open surgery chordectomy.

Dynamic MRI of larynx and vocal fold vibrations in normal phonation

Dynamic magnetic resonance imaging (MRI) of the larynx and vocal folds during phonation was used for measuring the vertical laryngeal movements and the glottal angle of the vocal folds opening and closing in dynamic phase. The data used in this analysis were taken on 10 healthy volunteers during maximal inspiration and the prolonged phonation of the vowels [i] (as in key), [a] (as in car), [u] (as in loop), and the consonant [sh] (as in ship). The results of our MRI data have demonstrated the difference of the vocal folds movement in relation to the vowel and consonant sounds, with a large glottal opening for [sh] and a narrow opening for [i] and [u], and the difference of the laryngeal position in relation to the vowels, with [a] and [u] having a lower larynx position than [i]. Imaging the larynx's positions and the vocal folds' vibrations is possible using dynamic MRI. This technique permits measurements of laryngeal structures and glottal parameters in dynamic function with multiplanar high-resolution imaging. Analysis of laryngeal activity and vocal folds' vibration may be helpful for the evaluation of the phonation function and for the understanding of the physiology of vocal production and voice modulation.

High frequency ultrasonic characterization of human vocal fold tissue

Recently, endolaryngeal sonography at frequencies ranging from 10 to 30 MHz has been found to be useful in diagnosing diseases of the vocal folds (VFs). However, image resolution can be further improved by ultrasound at higher frequencies, necessitating the measurement of high-frequency acoustic properties of VF tissue. The ultrasonic parameters of integrated backscatter, sound velocity, and frequency-dependent attenuation coefficient were measured in both the lamina propria (LP) and vocalis muscle (VM) of human VFs using a 47 MHz high-frequency ultrasonic transducer. The integrated backscatter was -173.44+/-6.14 (mean+/-s.d.) and -195.13+/-3.58 dB in the LP and VM, respectively, the sound velocity was 1667.68+/-44.9 and 1595.07+/-39.33 ms, and the attenuation coefficient at 47 MHz was 8.28+/-1.72 and 7.17+/-1.30 dBmm. The difference between these ultrasonic parameters may be attributed to variations in the structure and fiber concentrations in VF tissue. These results could serve as a useful clinical reference for the further development of high-frequency ultrasound devices for endolarynx sonography applications.

Characteristics of Movement of the Lips, Tongue and Velum during a Bilabial Plosive

Objective: To obtain dynamic images of articulators using a magnetic resonance imaging (MRI) movie and to clarify the relationships among the articulators.

Materials and Methods: The subjects consisted of 10 volunteers. Custom-made circuitry was connected to an MRI apparatus to enable an external trigger pulse to control the timing of the scanning sequence and to provide an auditory cue for synchronization of the subject's utterance. The subject repeated a bilabial plosive, and the run was measured using a gradient echo sequence with a repetition time of 30 ms. Several variables were defined to delineate the individual movements of articulators and to determine the temporal relationships among them.

Results: It was found that (1) the change in these variables showed distinctive waveforms; (2) mean values of the standard deviations for these variables were relatively small; and (3) the movement of the velum was significantly correlated with those of the lips and the anterior part of the tongue, but not with the posterior part of the tongue.

Conclusions: These results suggest that (1) articulatory movements were clearly recorded using an MRI movie, and (2) there seems to be a central mechanism for controlling articulators, and the level of coupling may be associated with the place of articulation.