Diffusion-weighted magnetic resonance imaging of the normal endometrium: temporal and spatial variations of the apparent diffusion coefficient.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (DWI) is increasingly used in the diagnosis of endometrial disease. No complete knowledge, however, exists yet of the influence of physiology on the endometrial apparent diffusion coefficient (ADC) values on which DWI is based. PURPOSE: To establish whether the ADC values measured with DWI in the endometrium of healthy reproductive-aged women significantly vary from the early proliferative to the periovulatory phase of the menstrual cycle and between the fundus and the isthmus of the uterus. MATERIAL AND METHODS: In 17 women the endometrial ADC values measured on the fifth menstrual day, both at the fundus and at the isthmus of the uterus, were compared to the values obtained on the 14th day before the subsequent cycle. In 81 women (menstrual day: fifth through 21st) the endometrial ADC values measured at the fundus were compared to the values obtained at the isthmus of the uterus. All examinations were performed with a 1.5 T magnet (b values: 0 and 800 mm/s(2)). The results were analyzed by means of Student's t-test per paired data. RESULTS: The endometrial ADC values measured on the fifth day of the menstrual cycle were lower than those obtained in the periovulatory phase both at the fundus (mean 0.923 vs. 1.256 × 10(-3) mm(2)/s) and at the isthmus (mean 1.297 vs. 1.529 × 10(-3) mm(2)/s) of the uterus. The endometrial ADC values measured at the fundus of the uterus were lower than those obtained at the isthmus (mean 1.132 vs. 1.420 × 10(-3) mm(2)/s) through the menstrual cycle. All these differences were highly significant (P < 0.001) at statistical analysis. CONCLUSION: Physiological variations occurring in endometrial ADC values of healthy women should be considered by the radiologists when interpreting DWI examinations in patients with endometrial disease.