Validation of a resolution-independent method for the quantification of 123I-FP-CIT SPELT scans

Objective To verify the applicability of a recently described resolution-independent method for the semi-quantification of I-123-FP-CIT scans. Methods Visual interpretation,'conventional' and resolution-independent semi-quantification was performed on 60 I-123-FP-CIT scans. Using ROC analysis, the results were compared to the final clinical diagnosis after a follow-up of at least 18 months. Sensitivity and specificity values were calculated and a cut-off value of the specific binding, which differentiated between normal and abnormal scans with high sensitivity and specificity, was given. Results Application of the resolution-independent method to a new set of I-123-FP-CIT SPELT data yielded a cut-off value of the specific striatal binding of 55 ml. Corresponding values of sensitivity and specificity were 95% and 72%, respectively. Further, based on the values of the area under the ROC curve and the 95% confidence interval of different semi-quantitative methods, the resolution-independent semi-quantification agreed best with the final clinical diagnosis. Conclusion We found a similar value of the specific I-123-FP-CIT binding as the one previously described in the literature, which proved the validity of the resolution-independent method. Further, this method, among other 'conventional' semi-quantitative methods, agreed best with the final clinical diagnosis. For this reason we recommend its use to aid in the diagnostic process.