No impact of attenuation and scatter correction on the interpretation of dopamine transporter SPECT in patients with clinically uncertain parkinsonian syndrome

Abstract

Purpose: The benefit from attenuation and scatter correction (ASC) of dopamine transporter (DAT)-SPECT for the detection of nigrostriatal degeneration in clinical routine is still a matter of debate. The current study evaluated the impact of ASC on visual interpretation and semi-quantitative analysis of DAT-SPECT in a large patient sample.

Methods: One thousand seven hundred forty consecutive DAT-SPECT with ¹²³I-FP-CIT from clinical routine were included retrospectively. SPECT images were reconstructed iteratively without and with ASC. Attenuation correction was based on uniform attenuation maps, scatter correction on simulation. All SPECT images were categorized with respect to the presence versus the absence of Parkinson-typical reduction of striatal ¹²³I-FP-CIT uptake by three independent readers. Image reading was performed twice to assess intra-reader variability. The specific ¹²³I-FP-CIT binding ratio (SBR) was used for automatic categorization, separately with and without ASC.

Results: The mean proportion of cases with discrepant categorization by the same reader between the two reading sessions was practically the same without and with ASC, about 2.2%. The proportion of DAT-SPECT with discrepant categorization without versus with ASC by the same reader was 1.66% ± 0.50% (1.09-1.95%), not exceeding the benchmark of 2.2% from intra-reader variability. This also applied to automatic categorization of the DAT-SPECT images based on the putamen SBR (1.78% discrepant cases between without versus with ASC).

Conclusion: Given the large sample size, the current findings provide strong evidence against a relevant impact of ASC with uniform attenuation and simulation-based scatter correction on the clinical utility of DAT-SPECT to detect nigrostriatal degeneration in patients with clinically uncertain parkinsonian syndrome.

Keywords: 123I-FP-CIT; Attenuation correction; Dopamine transporter; Ioflupane; SPECT; Scatter correction.

Fig. 1

Standardized display used for visual interpretation of the DAT-SPECT images

Fig. 2

Histograms of the putamen SBR without ASC (left) and with ASC (right) in the sample of 1740 unselected DAT-SPECT from clinical routine. The fit by the sum of two Gaussians is indicated by a continuous line. The effect size d of the distance between the two Gaussian functions was computed according to Eq. (2)