Will thallium-201 replace gallium-67 in salivary gland scintigraphy?

We investigated and compared findings on combined 99mTc pertechnetate-201Tl with those of [99mTc]pertechnetate-67Ga scintiscans to elucidate the advantages of 201Tl in detecting various salivary glands disorders.

We studied 23 patients: 6 had sialadenitis, 12 had benign tumors and 5 had malignant tumors. All but four patients had undergone [99mTc]pertechnetate (before and after lemon stimulation), 201Tl (early and delayed) and 67Ga imaging.

Five of six sialadenitis patients showed various degrees of diffuse uptake of 99mTc. All six except one showed early uptake without retention of 201Tl on delayed imaging. The 67Ga scan showed uptake in all patients except one. Nine of 12 benign tumors showed a cold defect on 99mTc scans. Patients with Warthin's tumors and plasmacytoma showed increased 99mTc uptake at the tumor with retention. The 201Tl scan showed early uptake without retention in benign tumors except in three patients, two of whom had Warthin's tumor. Five of the benign tumors, however, were positive on 67Ga scan. None of the malignant tumors showed any uptake of 99mTc. The 201Tl scan showed uptake with tumor retention on delayed images in three patients; three other patients also had positive 67Ga scans. Overall, sensitivity and specificity of 201Tl in detecting malignant tumors were 60% and 73%, respectively, with a negative predictive value of 85%. Sensitivity and specificity for 67Ga were 60% and 47%, respectively, with a negative predictive value of 80%.

In view of sensitivity, specificity and convenience of 201Tl as well as future prospects for dual-isotope acquisition, 67Ga may be replaced by 201Tl in detecting salivary gland disorder.