Semiquantitative Analysis Using Standardized Uptake Value in I-FP-CIT SPECT/CT

Purpose: To evaluate potential of a semiquantitative method using standardized uptake value (SUV) in I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (I-FP-CIT) single photon emission computed tomography/computed tomography (SPECT/CT) compared with specific binding ratio (SBR).

Materials And Methods: First, we performed a phantom study to validate the accuracy of measuring SUV. 52 patients (25 male, 27 female; mean age of 75.1-year-old; 40 and 12 patients with neurodegenerative diseases with or without presynaptic dopaminergic deficits, respectively) were enrolled in a retrospective study. We measured SBR, maximum SUV, peak SUV, mean SUV, and striatum-to-background ratio of SUV (SUV) for striatum with lower I-FP-CIT uptake using commercial software. We calculated Pearson's correlation coefficient between SBR and SUV. We also calculated the sensitivity, specificity, and accuracy of each parameter for differential diagnosis.

Results: The phantom study revealed errors of <10% between theoretical and actual SUVs. Although there were significant correlations between SBR and all SUV-based parameters, SUV showed the most strong correlation with SBR (r = 0.877, p < 0.001). However, diagnostic capability of SUV (cutoff = 2.35) yielded to that of SBR (cutoff = 3.90) for diagnosing neurodegenerative diseases with presynaptic dopaminergic deficits (sensitivity of 85.0% vs 92.5%, specificity of 100% vs 91.7%, and accuracy of 88.5% vs 92.3%, respectively).

Conclusion: SBR is a promising parameter to aid differential diagnosis of neurodegenerative diseases with or without presynaptic dopaminergic deficit. Although technically acceptable, SUV may not be superior to SBR when clinically applied in I-FP-CIT SPECT/CT.