Comparison of automatic versus manual procedures for the quantification of dopamine D2 receptor availability using...

I-123-IBZM-SPECT is often used to differentiate between idiopathic Parkinson's syndrome and atypical parkinsonian syndromes. The aim of this study was to compare three different procedures to quantify the receptor availability of striatal dopamine D2 receptors. (a) Manual quantification performed using individually adjusted volume of interests sets (mVoi). (b) Automatic quantification applying the commercially available Hermes BRASS software (BRASS). (c) Automatic quantification applying the open-source software IBZM Toolbox (TBX).

Using the three methods, we analyzed 100 scans. For the mVOI methods, three different investigators (two experienced, one inexperienced) carried out the analysis. We compared the different methods with each other and with the reference standard established by clinical follow-up. The diagnostic performance was assessed by calculating receiver-operating characteristic (ROC) curves.

Correlation analyses resulted in the following: mVOI versus BRASS (r=0.694) (P<0.005), mVOI versus TBX (r=0.557) (P<0.005); BRASS versus TBX (r=0.466) (P<0.005). We found a fair agreement for mVOI versus BRASS; slight agreement for mVOI versus TBX; and fair agreement for BRASS versus TBX. Moreover, we found a substantial agreement between the experienced investigators, but not with the inexperienced investigator in the case of mVOI. The ROC analysis shows the largest area under the ROC curve (Az=0.7295) for mVOI, followed by BRASS (Az=0.709) and TBX (Az=0.627).

In direct comparison, the manual quantification used by experienced observers shows the best results, although it does not differ significantly from the commercial Hermes BRASS software. Both are superior to TBX.