This prospective study aims to determine the optimal menstrual phase and uterine location to detect the thickest junctional zone by magnetic resonance imaging (MRI). Healthy nulliparous women were subdivided according to their use of hormonal contraception. Each women was investigated three times during their menstrual cycle. Eighteen nulliparous non-users and 29 nulliparous users of hormonal contraception (mean age 26.4 and 25.8 years, respectively) underwent a pelvic MRI (1.5T) examination during the follicular, ovulatory and luteal phase. The junctional zone thickness was measured at six locations in the uterine wall. A significantly thinner junctional zone was observed at the anterior and posterior wall of the midcorpus (P = 0.01 and P = 0.004 respectively) and fundus (P = 0.009 and P = 0.023 respectively), in the contraception users compared with the non-users. No differences in junctional zone thickness were noticed between the menstrual phases and the uterine wall locations. The ratio of junctional zone versus total myometrial thickness was also different between both groups and between the assessed uterine locations. To conclude, any phase in the menstrual cycle and location within the uterine wall was validated to determine the junctional zone thickness on MRI, although the fundal location is preferred. Special thanks to Liesbeth Bruckers, Dr. Phd. of the Research Institute Center for Statistics (CENSTAT) at University Hasselt, Belgium; Ms. Marleen Kelchtermans; Mr. Pascal Hamaekers; Johan Michielsen and co-workers of Siemens Belgium, MRI applications - postprocessing; and last but not least Mrs W. Gregoor. This research was supported by the Department of Medical Imaging at Ziekenhuis OostLimburg, Genk, Belgium.
