How much contrast is enough?. Dependence of enhancement on field strength and MR pulse sequence.

The overwhelming majority of published studies defining the clinical utility of gadolinium administration for neuroimaging have been performed at high field using conventional spin-echo imaging. Concerning the issue of field strength, several investigations have now shown that for a given dose of contrast, enhancement is less apparent at low field than at high field. Concerning the issue of pulse sequence, there is now convincing clinical and experimental evidence that all T1-weighted sequences are not equal in demonstrating contrast enhancement. Specifically, T1-weighted spoiled gradient-echo sequences do not show the same degree of visually apparent contrast enhancement compared to conventional spin-echo sequences. The use of magnetization transfer techniques which demonstrate areas of enhancement unseen on conventional pulse sequences is also addressed.