Fig. 3: Pulmonary [¹⁸F]FDT PET uptake into Tuberculous Lung Lesions is Reproducible within 90 min with Correlated Signal in Lesions with Higher Bacterial Loads.

A–C [¹⁸F]FDT PET/CT scan of a naïve marmoset lung (administered 1 mCi) [¹⁸F]FDT and imaged 90 min post-injection (3D volume rendering, transverse and sagittal views). D–F [¹⁸F]FDT PET/CT scan of a representative, Mtb-infected marmoset lung with lesions indicated by orange arrows (3D, transverse,and sagittal views). The target dose was 2.2 mCi/kg ( ~ 1 mCi). G, H 3D volume renderings of [¹⁸F]FDT PET uptake scans for blocked (G) and unblocked (H) uptake in the same infected marmoset. Marmosets (n = 2) were randomized as to the order of blocked scan; two days later the same animals were imaged with the treatments reversed. [¹⁸F]FDT uptake was blocked by administering excess [¹⁹F]FDT, split into two administrations 1 h and 5 min prior to radiotracer administration. I, J Reduction of [¹⁸F]FDT SUVmax and SUVmean/CMR, respectively, in marmosets administered cold [¹⁹F]FDT blocker prior to being administered [¹⁸F]FDT (1.2 mCi) compared to when administered [¹⁸F]FDT alone. In both cases the animal receiving [¹⁹F]FDT blocking dose showed significantly lower accumulation of [¹⁸F]FDT into tubercular lesions (p < 0.0001, 2-tailed paired T for both measures; n = 24 lesions [12 individual lesions measured in each of the 2 animals scanned]). Different symbols have been used, colored black or blue, with one symbol-color combination for each animal. K The [¹⁸F]FDT PET signal from Mtb-infected marmoset lungs is significantly higher than the signal from uninfected (control) marmoset lungs. The mean Standard uptake values SUV/CRM are represented as boxplots (box bounds: lower and upper quartile range) where the central bars represent the median and whiskers show all points max to minimum. At least 4 lung regions of interest (ROI) were measured from 3 infected and 2 uninfected marmosets (p < 0.0001, two-tailed unpaired, T test [n = 22 ROIs in infected lungs; n = 9 in ROIs uninfected lungs]). L [¹⁸F]FDT uptake into tubercular lesion tends to increase with higher mycobacterial loads (p = 0.0019, Pearson’s ρ = 0.63). The total SUV of each lesion ROI was compared with mycobacterial colony forming units (log CFU) measured in the 22 lesions (dots) collected from two marmosets euthanized within 24 h of FDT scan collection. The mean and 95% confidence interval lines (red) are shown on a linear regression plot. Please also see Source Data File.