Visibility of calcium on MR and CT: can MR show calcium that CT cannot?

PURPOSE To test the hypothesis that calcium can be visible on MR images without being visible on CT.

METHODS Five different calcium salts ranging in concentration from 0 to 0.45 g/mL were suspended in 2% agarose gel and studied using T2-weighted MR, T1-weighted MR, and CT. MR signal intensity, CT attenuation, and image noise were measured. Relative visibility was determined from these measurements.

RESULTS CT was shown to be more than 10 times as sensitive as T2-weighted MR or T1-weighted MR for the detection of calcium.

CONCLUSION MR cannot show calcium that is occult on CT.