Contrast enhanced high resolution MRI of cutaneous melanomas using Gd-DTPA and Gd-DTPA-polylysine: experimental results.

Abstract

An experimental model for the preclinical evaluation of contrast enhancement patterns in melanoma was developed. Melanotic and amelanotic tumor cells B16F1 and B16a implanted into murine skin were depicted with magnetic resonance imaging (MRI) at a pixel size of 78×78 urn and 1 mm slice thickness. Tumor signal intensities were evaluated in user defined ROIs (regions of interest). Signal intensity changes were determined from signal intensity-time curves. Percent enhancement, slope of the signal intensity curve and percent signal intensity increase were also determined. Percent enhancement was calculated: (SIenhanced -SIpiain )/SIplain × 100 [SI=signal intensity]. The slope of the signal intensity curve was calculated: (SImax -SIplain )/(SIplain × SImax ) × 100 (%/min). Percent signal intensity increase was calculated: (SImax -SIplai )/SIplain × 100. Following i.v. administration of Gd-DTPA and G-DTPA-polylysine, all tumors showed pronounced contrast enhancement. Contrast enhancement and the slope of signal intensity to time curves did not distinguish melanotic from amelanotic melanomas (P>0.05). The animal model presented is well suited for evaluation of contrast enhancement in melanoma by MRI. Contrast enhancement of melanoma in MRI is comparable with the enhancement seen in other tumors.