Improving postoperative MR imaging of pituitary macroadenomas: comparison of full and reduced dose of gadopentetate dimeglumine

The aim of this study was to evaluate the efficacy of contrast-medium (CM)- enhanced MR imaging of operated pituitary macroadenomas with reduced dose o f gadopentetate dimeglumine. In a prospective study 18 patients were examin ed with coronal weighted MR imaging prior to and following intravenous CM i njections. Two sets of contrast-enhanced coronal images were obtained in ea ch patient; the first set after 50 % of the recommended dose of mmol/kg bod y weight (b.w.) had been administered, and the second set immediately after additional CM had been given to make up a total dose of 0.1 mmol/kg b.w. T he images were evaluated by three neuroradiologists. The SIPAP classificati on system was used to evaluate tumour extension, whereas tumour margin cons picuity was scored using an arbitrary scale of 1-5 (1 = indistinct, 5 = wel l defined). Signal intensity measurements obtained from the most enhancing part of the adenomas demonstrated sed enhancement with increased CM dose. T umor delineation scores were significantly better on the reduced- and full- dose images than on pre-CM injection images, but, with one exception, tumou r extension was identified as the same on all imaging sequences. Postoperat ive MR imaging of large macroadenoma residues can routinely be performed wi thout intravenous CM. When CM is indicated a reduced dose of gadopentetate dimeglumine should provide sufficient diagnostic information.