[Performance of an open low-field MR unit in routine examination of knee lesions and comparison with high field systems].

The purpose of this study was to analyze the diagnostic value of a low-field open MR system in the diagnosis of knee lesions and to compare it with that of high-field MR systems. In 139 knees,arthroscopic investigations were used as the gold standard to calculate sensitivity, specificity, predictive values and accuracy of the low-field open MR system. Figures for high field systems were taken from the literature. The values for the open MR system relative to arthroscopy were as follows: sensitivity 66%,specificity 95%,positive predictive value 64%,negative predictive value 92%, and accuracy 82%. The corresponding values taken from 10 relevant publications for highfield systems were: sensitivity 81%, specificity 90%, accuracy 90%. A lower diagnostic performance has to be expected using open low field MR units for knee lesions in comparison to high field units. Sedative drugs can make it possible for claustrophobic patients to be investigated in high-field units. The use of open low-field scanners may still be indicated in very adipose patients who do not fit into closed units.