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. © 2011 Wiley Periodicals, Inc. J Clin Ultrasound, 2011