Reproductibility of apparent diffusion coefficients measurements in diffusion-weighted MRI of the abdomen with different b values.

PURPOSE: To test the reproducibility of apparent diffusion coefficients (ADC) measurements of the normal liver, kidney and spleen parenchyma with different b values.
MATERIALS AND METHODS: Eleven healthy volunteers were imaged twice with use of the same protocol. Each DWI was performed with b-factors of 0, 100 and 500 s/mm(2). The ADCs were organized according to session (1 or 2), anatomic location and repetition (twice with two different b value per session). The ADC data were analyzed with repeated-measures analysis of variance to demonstrate the influence of anatomic location, session and different b values. The coefficient of variation was calculated for each subject, b value and anatomic location, then analyzed by using repeated-measures analysis of variance.
RESULTS: There were significant differences in mean ADCs among the three anatomic locations and with different b values (P<.05). There were no significant differences in ADCs between imaging sessions 1 or 2 for both b values (P>.05). The CV values range between 7.3% and 14.7%. There were no significant differences in CV values neither between the two b values nor for the various organ locations (P>.05).
CONCLUSION: Using the same technical parameters, patients and the same observer, CV values range between 7.3% and 14.7%. And we recommend to be careful in examination and comparison of the measured ADC values, below these limits, without knowledge technical parameters that has been used, otherwise differences that are merely because of changes in the measurement technique could be interpreted as differences because of progression of disease or therapy.