Semi-quantitative assessment of diffuse hepatic uptake seen in I-131 scans - an indicator of functioning thyroid tissue and disease burden in differentiated thyroid cancer.

HTR has good correlation with functional status of tumor cells, while it has weak correlation to therapeutic dose of I-131 administered and serum Tg. Increased HTR predicts significant disease burden in the form of distant bone and lung metastasis and may potentially be used as a second prognostic factor apart from serum Tg.