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 × 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.