Quotient imaging with N-13 L-glutamate in osteogenic sarcoma: correlation with tumor viability

An investigation was performed to correlate the regional uptake of N-13 L-glutamate with histologic changes in tumor tissue in patients undergoing adjuvant chemotherapy for osteogenic sarcoma. A parametric image was produced by calculating the ratio of N-13 uptake in the tumor in a pixel-by-pixel fashion, using the presurgical scan as the numerator and the pretherapy scan as the denominator. The change in N-13 uptake in 2 x 2-cm regions of the tumor was compared with residual cell viability as determined by microscopic examination of multiple thin sections obtained from the surgical specimens. Regions that showed decreases in N-13 uptake of more than 30% were frequently associated with areas of highly necrotic tumor, and regions that showed increasing uptake were associated with high residual cell viability and incomplete response to chemotherapy.