The effect of MR contrast medium dose on pituitary gland enhancement, microlesion enhancement and pituitary gland-to-lesion contrast conspicuity.

INTRODUCTION: The purpose of this study was to compare the differences in gland enhancement, microlesion enhancement and gland-lesion contrast ratio in patient groups in which half-dose (HD), standard-dose (SD) and double-dose (DD) contrast medium was used in pituitary MR imaging.

METHODS: Pituitary gland enhancement and microlesion enhancement were measured and gland-lesion contrast ratios were calculated in 18 patients receiving HD (0.05 mmol/kg), 9 receiving SD (0.1 mmol/kg) and 13 receiving DD (0.2 mmol/kg) contrast medium. Gland enhancement and microlesion enhancement over baseline were determined employing DICOM region of interest measurements and compared after normalization to temporal lobe white matter. Contrast ratios and differences were also calculated and compared.

RESULTS: Gland enhancement and lesion enhancement were greater with larger contrast medium doses (gland: HD 50%, SD 99%, DD 132%; microlesion: HD 19%, SD 54%, DD 86%). The gland-lesion contrast ratios were similar with the three doses (25.6%), reflecting expected similar fractional contrast medium distributions in spite of different doses. The signal difference between gland and microlesion, therefore, was a fixed percentage of gland enhancement (DeltaS approximately 26%) with greater signal differences with larger contrast medium doses.

CONCLUSION: Greater gland-to-lesion signal differences with larger contrast medium doses would likely improve pituitary microlesion visualization and margin characterization aiding in microlesion detection as well as preoperative planning.