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201TI was used as an imaging agent in 173 malignant tumors and 76 benign lesions. The sensitivity, specificity, and accuracy were 0.64, 0.61, and 0.63, respectively. Sensitivity was good in thyroid cancer (0.91) and fair in primary lung cancer (0.70) and primary liver cancer (0.71). Compared with 67Ga, 201TI appears to have a higher sensitivity in thyroid cancer and nearly the same sensitivity in primary lung cancer. 201TI might be useful in distinguishing cold thyroid nodules and in differentiating primary liver cancer from metastases.

169-Yb-citrate was used as the tumor-scanning agent in 360 patients with malignant tumors and in 55 others with benign lesions and the results compared with 67-Ga-citrate studies in other series. In malignant tumors, the overall positive detection rate for ytterbium was 65.3%; in benign lesions, the false-positive rate was 29.1%. Good results were obtained in the extremities, head and neck, and pelvic area. Of all tumors visualized, squamous cell carcinoma was detected most effectively (77.5%). 169-Yb-citrate has a long shelf life, photon peaks of 178 and 198 kev, clears from the blood more rapidly than 67-Ga-citrate and has an extremely low soft-tissue background uptake. Its main disadvantage is its high radiation dose: 1.74 R/500 muCi whole-body and 5.77 R to the bone.