CORRELATION OF RADIOBIOLOGICAL ASSAYS OF HYPOXIC FRACTION WITH P-31 MAGNETIC-RESONANCE SPECTROSCOPY ACROSS MULTIPLE TUMOR LINES

Hypoxic fractions were measured in multiple tumor models and compared to P-31 magnetic resonance spectroscopy (MRS) parameters. Hypoxic frac tions were measured by excision assays in intramuscular and subcutaneo us RIF-1 tumors, large and small SCCVII tumors, and KHT tumors. The hy poxic fractions ranged from 3% (small SCCVII) to 21% (KHT). Measuremen ts of P-31 MRS parameters (indices of tumor metabolism) were made unde r the same conditions used in the hypoxic fraction assays. The PCr/P-i ratios in the five tumor models were strongly correlated (r(2) = 0.98 , tau = 1.00, P < 0.02) with their hypoxic fractions, and the NTP/P-i ratio was weakly correlated (r(2) = 0.67, tau = 0.60, P < 0.17) with h ypoxic fraction. Smaller values of the PCr/P-i and NTP/P-i ratios were found in the tumors with larger hypoxic fractions. These experiments indicate that P-31 MRS may provide a relative measurement of hypoxic f ractions across different tumor lines that can be applied non-invasive ly to individual tumors. (C) 1995 by Radiation Research Society