Will thallium-201 replace gallium-67 in salivary gland scintighaphy ? J Nucl Med 1996; 37:

Purpose:  We investigated and compared finding on combined99mTc pertechnetate-201Tl with those 99mTc pertechnetate-67Ga scintiscans to elucidate the advantages of 201Tl in detecting various salivary glands disorders.

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

Results and Discussion:

Sialadenitis  The criterion for diagnosis of sialadenitis was various degrees of diffuse 99mTc uptake with positive 67Ga accumulation, all but one patient with sialadenitis fulfilled this criterion.  If we consider various degrees of diffuse 99mTc uptake and early diffuse uptake without retention of 201Tl as criterion for sialadenitis, five of six patients fulfilled

 67Ga, 201Tl scan results show that both agents have similar sensitivity in detecting sialadenitis, but 201Tl has the advantages and convenience and time-efficiency  67Ga: 72 hr after injection  201Tl: 2-4 hr after injection

Benign tumor  Except for Warthin ’ s and oncocytoma, most tumors appear as cold defects on 99mTc scan.  Of the 9 benign cold lesions on 99mTc scan, 67Ga depicted five false-positive scans, whereas 201Tl demonstrated various degrees of uptake without retention on delay images for all patients except one

Malignant tumor (1)  Of the five malignant cold lesions on 99mTc scan, both 67Ga and delay 201Tl imaging had two false-negative results. 201Tl detected the tumor as well as lymph node metastasis in one patient.  In detecting malignant tumor, both 201Tl and 67Ga had similar results, but 201Tl detected cystic change in one patient.

Malignant tumor (2)  Delayed 201Tl scan and 67Ga scan are compared for all patients, the sensitivity and specificity in detecting malignancy :  201Tl : SEN=60%(3/5) SPE=73%(11/15) PPV=43%(3/7) NPV=85%(11/13)  67Ga : SEN=60%(3/5) SPE=47%(8/17) PPV=25%(3/12) NPV=80%(8/10)

Conclusion:  67Ga scan were nonspecific in differentiating benign from malignant tumor due to high uptake by inflammation  201Tl has already shown its potential to differentiate benign from malignancy and retention of 201Tl in tumor2-4 hr after injection increases the probability of malignancy.  Both 201Tl and 99mTc scan can be performed within a single day

Conclusion:  99mTc / 201Tl imaging of salivary gland disorders may be superior to 99mTc / 67Ga imaging due to sensitivity and specificity in detecting malignancy, convenience for both patients and technologists.