Sonographic measurement of cervical volume in nonpregnant women using the geometric formula for a cylinder versus the three-dimensional automated virtual organ computer-aided analysis (vocal).

BACKGROUND: To sonographically evaluate the volume of uterine cervix in nonpregnant women with use of the geometric formula for a cylinder and to assess agreement with the reference Virtual Organ Computer-Aided AnaLysis (VOCAL) method.
METHODS: Three-dimensional ultrasound volume datasets of the uterine cervix from 81 women were obtained prospectively within a 1-year period. Volume measurements were performed using VOCAL and the geometric formula for a cylinder. Reliability was evaluated using intraclass correlation coefficient and Bland-Altman plots were produced to examine intermethod agreement. Time needed to perform measurements was compared with Student's t test.
RESULTS: There was good agreement between VOCAL and the geometric formula for a cylinder (mean percentage difference, -0.78%; 95% limits of agreement, -17.59-16.03%). Measurements made by the formula for a cylinder were slightly greater than VOCAL by a mean (±SE) of 0.78% (±0.95%). A high degree of reliability was observed between the two methods (intraclass correlation coefficient, 0.97; 95%CI, 0.95-0.98). Cervical volume estimation with the geometric formula for a cylinder was faster to obtain.
CONCLUSIONS: This method comparison study shows that the geometric formula for a cylinder has good agreement with VOCAL and can determine the volume of the cervix in a faster way.