ULTRASOUND BACKSCATTER MICROSCOPE ANALYSIS OF MOUSE MELANOMA PROGRESSION

The incidence and mortality rate of cutaneous melanoma continue to inc rease throughout the world, making the study of melanoma biology an im portant area of current research. While recent breakthroughs in transg enic mouse technology have led to promising mouse skin models of melan oma, there is presently no technique available for quantitatively stud ying subsurface melanoma progression, in vivo. We demonstrate the firs t application of an imaging method called ultrasound backscatter micro scopy (UBM) for imaging early murine melanomas with spatial resolution of 30 mu m axial and 60 mu m lateral. Murine B16 F10 melanomas have b een imaged from their earliest detection, over several days, until the y are 2 to 5 mm in diameter. Melanoma dimensions measured by UBM were found to be in excellent agreement with those determined histopatholog ically on the excised tumours. The relative rms errors in UBM-determin ed melanoma height and width were found to be 8.7% and 4.2%, respectiv ely. The mean rate of increase in tumour height of early murine melano ma was found to be 0.37 +/- 0.06 mm/day. Computer-generated volumetric renderings of melanomas have been produced from three-dimensional ima ge data, allowing quantitative comparisons of tumour volumes to be mad e. Using a priori assumptions of ellipsoid tumour shape, the relative error in UBM-determined volume was shown to be less than 17%. These re sults should be of considerable interest to investigators studying mel anoma biology using mouse skin models, and have implications in the us e of high frequency ultrasound imaging for the clinical assessment of cutaneous melanoma.