PET/CT Imaging of Tuberculosis with 68ga-Citrate

Abstract

Objective: The impact of tuberculosis (TB) on mortality and morbidity is indisputable worldwide and even more so in countries with a high prevalence of Human Immunodeficiency Virus (HIV) co-infection. The development of a non-invasive diagnostic tool that is capable of early and accurate detection, staging and follow-up evaluation of tuberculosis is crucial in minimizing its devastating effects. We evaluated PET/CT imaging with a novel tracer, 68Ga-citrate,in this setting. Methods: Thirteen patients with tuberculosis were included in this prospective pilot study and were imaged with 68Gacitrate. A diagnosis of TB was reached with bacteriological or histopathology studies (n=8) or based on a combination of clinical data, biochemistry and imaging (n=5). PET images were acquired at 60 minutes (and 120 minutes where possible) and analyzed qualitatively (relative to the liver) and semi-quantitatively (using SUVmax and change in SUVmax). PET findings were also compared to that of CT. Results: All 13 patients demonstrated abnormal tracer accumulation in the lungs or extra-pulmonary or both. 68Ga-citrate accumulated in every lung lesion noted on CT in six cases (46%). In seven cases (54%) some of the lung lesions noted on CT were not 68Ga-citrate avid, which is suggestive of non-active tuberculosis lesions. Ten patients (77%) demonstrated extrapulmonary involvement, which included various lymph node groups, skeletal lesions, pleural-, splenicand gastro-intestinal tract involvement. More extra-pulmonary lesions were detected on PET compared to CT in eight cases (80%). The results of dual-time point imaging varied significantly amongst study participants. Conclusion: Pulmonary and extra-pulmonary tuberculosis lesions demonstrate 68Ga-citrate accumulation; with more extrapulmonary lesions detected on PET compared to CT. 68Ga-citrate PET may also provide a way of distinguishing active from inactive lesions for treatment response evaluation.