Normal reference values for I-123-Ioflupane analysis using xSPECT quantification and correlation with age

Aim: The emerging application of I-123-Ioflupane uptake quantification within basal ganglia using the latest quantitative SPECT scanners may add valuable precision in the diagnosis of neurodegenerative diseases of the nigro-striatal pathway. This study aimed to report a database of normal values of absolute and relative SUV as well as regional asymmetry and ratios in a series of normal DATscans in order to provide a basis for comparison for pathological cases. Materials and Methods:We retrospectively assessed xSPECT quantitative data in a series of 49 patients (24 M, 25 F; mean age 71 years) who underwent DATscan examination and were scored as normal on visual rating and relative metric methods. Patients were scanned (Symbia Intevo, Siemens Healthineers) and images were reconstructed using xSPECT, thus providing SUV values. SUVmax and SUVmean were extracted in a fully automated analysis using Scenium (Siemens Healthineers) for the left and right caudate nucleus, putamen and striatum, as well as for the occipital region, taken as reference region for the calculation of relative SUV (rSUV). Regional asymmetry and Putamen/Caudate ratios were also reported. SUV_max, SUV_mean and rSUV were also correlated with age using Spearman’s correlation.

Results: SUV_max and SUV_mean (g/mL) were 8.2±3.4 [95% confidence interval CI 7.6-9.9] and 3.4±1.8 [3.1-3.8] for the caudate nucleus, 9.2±3.4 [8.5-9.9] and 5.3±2.2 [4.9-5.8] for the putamen and 9.3±3.3 [8.6-9.9] and 4.4±1.9 [4-4.8] for the striatum. rSUVs were 2.2±1.0 [2-2.4] for the caudate nucleus, 3.4±1.1 [3.2-3.6] for the putamen and 2.8±1.0 [2.6-3] for the striatum. Asymmetries in the caudate nucleus, putamen and striatum were 6.7±4.9% [5.3-8.2%], 7.4±10.7% [4.3-10.5] and 5.6±6.8% [3.8-7.7] respectively. Putamen/caudate ratios were 0.89±0.09 [0.86-0.92] for the right side and 0.91± 0.17 [0.86—0.96] for the left side. We showed a negative correlation between age and SUV_max, SUV_mean and rSUV in in the caudate nucleus (ρ=-0.4, p<0.005, ρ=-0.46, p<0.005 and ρ=-0.33, p<0.005 respectively), putamen (ρ=-0.38, p<0.005, ρ=-0.43, p<0.005 and ρ=-0.25, p=0.014, respectively) and striatum (ρ=-0.38, p<0.005, ρ=-0.45, p<0.005 and ρ=-0.32, p<0.005, respectively).

Conclusions: This study reports values of I-123-Ioflupane uptake quantification of caudate nucleus, putamen and striatum regions in a series of normal DATscans including SUV_max, SUV_mean, rSUV, regional asymmetries and putamen/caudate ratios; this tool may have an important role in the diagnosis of neurodegenerative diseases of the nigro-striatal pathway due to its capacity of providing robust absolute quantification allowing to differentiate between normal and pathological cases. SUV_max, SUV_mean, rSUV of the caudate nucleus, putamen and striatum regions were negatively correlated with age.