Same same but different: dopamine transporter SPECT on scanners with CZT vs. NaI detectors

Felix Thiele; Franziska Schau; Julian M M Rogasch; Christoph Wetz; Stephanie Bluemel; Winfried Brenner; Holger Amthauer; Catharina Lange; Imke Schatka

doi:10.1186/s13550-023-00973-8

Same same but different: dopamine transporter SPECT on scanners with CZT vs. NaI detectors

EJNMMI Res. 2023 Mar 22;13(1):24. doi: 10.1186/s13550-023-00973-8.

Authors

Felix Thiele¹, Franziska Schau², Julian M M Rogasch^{2

3}, Christoph Wetz², Stephanie Bluemel², Winfried Brenner², Holger Amthauer², Catharina Lange², Imke Schatka²

Affiliations

¹ Department of Nuclear Medicine, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität Zu Berlin, Berlin, Germany. felix.thiele@charite.de.
² Department of Nuclear Medicine, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität Zu Berlin, Berlin, Germany.
³ Berlin Institute of Health (BIH) at Charité - Universitätsmedizin Berlin, Berlin, Germany.

Abstract

Background: The aims of this study were to establish a normal database (NDB) for semiquantification of dopamine transporter (DAT) single-photon emission computed tomography (SPECT) with [¹²³I]FP-CIT on a cadmium zinc telluride (CZT) camera, test the preexisting NaI-derived NDB for use in CZT scans, and compare the diagnostic findings in subjects imaged with a CZT scanner with either the preexisting NaI-based NDB or our newly defined CZT NDB.

Methods: The sample comprised 73 subjects with clinically uncertain parkinsonian syndrome (PS) who prospectively underwent [¹²³I]FP-CIT SPECT on a CZT camera according to standard guidelines with identical acquisition and reconstruction protocols (DaTQUANT). Two experienced readers visually assessed the images and binarized the subjects into "non-neurodegenerative PS" and "neurodegenerative PS". Twenty-five subjects from the "non-neurodegenerative PS" subgroup were randomly selected to establish a CZT NDB. The remaining 48 subjects were defined as "test group". DaTQUANT was used to determine the specific binding ratio (SBR). For the test group, SBR values were transformed to z-scores for the putamen utilizing both the CZT NDB and the manufacturer-provided NaI-based NDB (GE NDB). A predefined fixed cut-off of -2 was used for dichotomization of z-scores to classify neurodegenerative and non-neurodegenerative PS. Performance of semiquantification using the two NDB to identify subjects with neurodegenerative PS was assessed in comparison with the visual rating. Furthermore, a randomized head-to-head comparison of both detector systems was performed semiquantitatively in a subset of 32 out of all 73 subjects.

Results: Compared to the visual rating as reference, semiquantification based on the dedicated CZT NDB led to fewer discordant ratings than the GE NDB in CZT scans (3 vs. 8 out of 48 subjects). This can be attributed to the putaminal z-scores being consistently higher with the GE NDB on a CZT camera (median absolute difference of 1.68), suggesting an optimal cut-off of -0.5 for the GE NDB instead of -2.0. Average binding ratios and z-scores were significantly lower in CZT compared to NaI data.

Conclusions: Use of a dedicated, CZT-derived NDB is recommended in [¹²³I]FP-CIT SPECT with a CZT camera since it improves agreement between semiquantification and visual assessment.

Keywords: CZT; Dopamine transporter; FP-CIT; Normal database; SPECT.