Purpose: To assess the role of quantitative gallium citrate (Ga 67) single-photon emission computed tomography (SPECT) in differentiating lymphoma from benign hilar uptake, concentrations of Ga 67 in 29 sites of documented lymphoma and in 75 benign lesions were compared.
Patients and methods: One hundred seven thoracic Ga 67 SPECT studies obtained in 101 consecutive lymphoma patients were reviewed. Fifty-nine studies detected Ga 67 uptake in the hilar and or mediastinal regions. Forty-eight studies showed no such abnormality. The concentration of Ga 67 in the thoracic lesions was measured using a quantitative SPECT technique and its nature was determined by correlation with computed tomographic (CT) scans and follow-up evaluation of the sites.
Results: In 20 of 59 abnormal studies (34%), there was lymphoma in the hilar and or mediastinal regions. In the remaining 39 abnormal studies (66%), Ga 67 uptake was benign. There were 29 sites of lymphoma and 75 benign lesions. The concentration of Ga 67 in lymphoma was significantly higher than in benign hilar uptake (13.2 +/- 5.4 %ID/mL x 10(-3) v 5.6 +/- 1.5 % injected dose (ID)/mL x 10(-3); P < .001). A concentration value of 8.3 %ID/mL x 10(-3) was found to best separate lymphoma and benign uptake, with a sensitivity of 90%, a specificity of 93%, a positive predictive value of 84%, and a negative predictive value of 96%.
Conclusion: Lymphoma and benign hilar uptake differ significantly in their concentration of Ga 67. The present study shows that quantitative Ga-67 SPECT reliably differentiates lymphoma and benign uptake.