Imaging Anatomy Of The Joint Structure And Movement Of The Normal Human Larynx

Objectives:The larynx is an important organ in controling respiration, phonation, swallowing, and respiratory tract defense. In this study, multislice spiral CT (MSCT) scanning of the human larynx was run on different scan and reconstruction parameters to optimize the images The joint activities of quiet breathing, the Valsalva breathing (deep breathing, breath through closed lips), deep breathing, pronouncing the "yi" sound state in healthy volunteers were described to clarify the anatomical and functional features of the larynx.The study provides a new means for clinical evaluation of laryngeal structural and functional changes of laryngeal diseases such as laryngeal carcinoma and vocal cord paralysis before and after treatment.Methods:three health) volunteers was scanned on larynx by64-slice high-resolution multislice spiral CT was with different scan parameters. Each volunteer was told to keep in four physiological conditions during scans, quiet breathing. Valsalva breathing, deep breathing and pronouncing "yi". The scan parameters were collimator thickness0.625mm, voltage120kV. tube current of100mA,70mA,50mA, pitch1mm. reconstruction thickness of1mm, the data was transferred to the background independent workstation for reconstruction and measures. The lowest radiation dose clearly shows larvnaeal anatomic landmarks was determined by comparing different scanning parameters, display rate. and image data. The optimized low-dose scan parameters were applied on11healthy volunteers (7male.4female). images and data from laryngeal cartilage scans and three-dimensional reconstruction were collected to anatomically study laryngeal cartilage and functional joint movements.Results:1. low-dose set of tube current on70mA displayed clear images, no significant difference between images obtained from conventional dose of MSCT scan about the soft tissue, cartilage shape, size, boundaries and fine structures.2. compared to distance of the vocal processes during quiet breathing, Valsalva breathing and pronouncing "yi" showed significantly statistical difference (P<0.01). however no statistical difference for deep breathing (P>0.05). Similar results for the muscular processes measures were found. No statistical significance was found on the thyroid cartilage angle (the level of vocal cord) between male and female volunteers (P>0.05). Nevertheless, the cricothyroid space between these two groups was significantly different (P<0.01). Valsalva breathing, deep breathing and pronouncing "yi" produced no statistical difference in axial rotation angle of the right and left arvtenoid cartilage (P>0.05). Although remarkable arytenoid rotation was demonstrated during Valsalva breathing and pronouncing "yi". deep breathing hardly rotated the arvtenoids cartilase.Conclusion:1. In this study, low dose of MSCT scanning successfully described the joint structure and movement of the larynx, not only ensuring the image quality to meet the diagnostic requirements, but also reduce the X-ray radiation dose to the subjects.2. Under some physiological conditions, laryngeal cartilage movements different from traditional theories were found by MSCT. which help us further understand anatomy and physiological function of larynx.3. The study proyides a new means for clinical evaluation of laryngeal structural and functional changes of laryngeal diseases such as laryngeal carcinoma and vocal cord paralysis before and after treatment.