CORRELATION OF RELAXOMETRY AND HISTOPATHOLOGY - THE TRANSPLANTABLE HUMAN GLIOBASTOMA SF295 GROWN IN ATHYMIC NUDE-MICE

Human gliobastomas of the brain are characterized by a wide range of p roton relaxation rates in vitro (1/T1 and 1/T2) and heterogeneous appe arance in magnetic resonance imaging. It was previously found that the ir 1/T1 values vary widely at magnetic field strengths much below imag ing fields, even at the same water content. In the present study, we m easure 1/T1 at different magnetic field strengths (NMRD profile) for a specific transplantable, human glioblastoma (SF295), grown subcutaneo usly in athymic nude mice, to search for histologic characteristics th at might correlate with the variability of 1/T1 at low fields (1/T1L). Using a field-cycling relaxometer, NMRD profiles were obtained for 32 fresh, histologically characterized, tumor specimens, 7 to 24 days po st implantation of cryopreserved SF295 fragments. Tumor volume, dry we ight, and pH of specimens were determined, the extent of hemorrhage an d necrosis rated, and specimen location within the tumor recorded. A s tatistically significant increase in the average 1/T1 was found with i ncreasing level of necrosis at 0.0024 T and below, possibly reflecting progressive protein aggregation in samples with up to 40% necrosis. T his correlation was not significant at imaging fields. Although pH was increased in central necrosis, neither pH, dry weight, sample locatio n, nor fresh hemorrhage could explain the changes in 1/T1L. The variab ility of 1/T1L among SF295 samples is much reduced compared to that of fresh surgical specimens of human glioblastomas of the brain. The het erogeneous appearance of glioblastomas in MRI may have a histologic co rrelate which reflects molecular changes involved with induction of ce ll death and necrosis. Further investigations may identify the factors responsible for affecting 1/T1L (hypoxia, radiation, chemotherapy).