31P magnetic resonance spectroscopy of animal uveal melanoma.

ABSTRACT

Scleral surface coils were used to obtain in vivo magnetic resonance spectra (MRS) of Greene melanoma implanted in the rabbit uvea. Well-localized tumor spectra (4.7 Tesla) with good signal-to-noise ratios (S/N) were obtained from the tumor with a "single-pulse" sequence in less than 1 hour. Tumor localization was confirmed with one-dimensional spectroscopic imaging studies. Serial 31P spectra were obtained during tumor growth and after both optimal and suboptimal hyperthermia. Early 31P MRS change is correlated with tumor treatment response and preceded histologic evidence of cell destruction. Twenty-four to 48 hours after successful treatment, the inorganic phosphate/nucleoside triphosphate (NTP), and phosphomonoester/NTP ratios were significantly increased from 1.2 +/- 0.1 to 1.7 +/- 0.1 and 1.3 +/- 0.1 to 1.8 +/- 0.2, respectively. In contrast, untreated or ineffectively treated tumors showed little change. Interpretation of 31P MRS data in this animal uveal melanoma model after the first week was complicated by decreased S/N, increased contamination from contiguous tissues, ingrowth of fibroblasts, macrophages, and intratumor hemorrhage.