Four-dimensional CT analysis of vocal cords mobility for highly focused single vocal cord irradiation.
OBJECTIVE
To quantify respiratory motion of the vocal cords during normal respiration using 4D-CT. The final goal is to develop a technique for single vocal cord irradiation (SVCI) in early glottic carcinoma. Sparing the non-involved cord and surrounding structures has the potential to preserve voice quality and allow re-irradiation of recurrent and second primary tumors.


METHODS
Four-dimensional CTs of 1mm slice thickness from 10 early glottic carcinoma patients were acquired. The lateral dimensions of the air gap separating the vocal cords were measured anteriorly, at mid-level and posteriorly at each phase of the 4D-CTs. The corresponding anterior-posterior gaps were similarly measured. Cranio-caudal vocal cords movements during breathing were derived from the shifts of the arythenoids.


RESULTS
The population-averaged mean gap size+/-the corresponding standard deviation due to breathing (SD(B)) for the lateral gaps was 5.8+/-0.7mm anteriorly, 8.7+/-0.9mm at mid-level, and 11.0+/-1.3mm posteriorly. Anterior-posterior gap values were 21.7+/-0.7mm, while cranio-caudal shift SD(B) was 0.8mm.


CONCLUSIONS
Vocal cords breathing motions were found to be small relative to their separation. Hence, breathing motion does not seem to be a limiting factor for SVCI.
Department of Radiation Oncology, Erasmus MC - Daniel den Hoed Cancer Center, Rotterdam, The Netherlands. s.osman@erasmusmc.nl
Sarah O S
SO
Osman
Hans C J
HC
de Boer
Ben J M
BJ
Heijmen
Peter C
PC
Levendag
D000368:Aged; D005260:Female; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D014827:Vocal Cords / Q000000981:diagnostic imaging* / Q000473:pathology; D014833:Voice Quality