Inter- and intra-observer reproducibility of quantitative analysis for FP-CIT SPECT in patients with DLB
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ORIGINAL ARTICLE
Inter- and intra-observer reproducibility of quantitative analysis for FP-CIT SPECT in patients with DLB Atsutaka Okizaki1 · Michihiro Nakayama1 · Kaori Nakajima1 · Takayuki Katayama2 · Takahiro Uno3 · Fumiyoshi Morikawa4 · Juichiro Naoe4 · Koji Takahashi1
Received: 8 September 2017 / Accepted: 10 September 2017 © The Japanese Society of Nuclear Medicine 2017
Abstract Background Dopamine transporter single photon emission CT (DAT-SPECT) is useful in the evaluation of dementia with Lewy bodies (DLB). The specific binding ratio (SBR) is an index to measure DAT density. However, poorly reproducible cases are occasionally experienced in clinical practice. We hypothesized that distance-weighted histogram (DWH) may be useful to improve the reproducibility of SBR. The purpose of this study was to investigate interand intra-observer reproducibility of SBR with conventional and DWH methods, and to visually evaluate the precision in reference voxel of interest (VOI) definition using these methods. Methods This study included 50 adult patients with probable DLB. They underwent brain MRI, DAT-SPECT, and cerebral blood flow SPECT with N-isopropyl-p-[123I] iodoamphetamine (I-123 IMP). SBR of the striatum was calculated using conventional and DWH method. For interobserver reproducibility validation, conventional and DWH SBR were independently evaluated by experienced nuclear medicine physicians; these measurements were repeated by the nuclear medicine physician to investigate intra-observer reproducibility.
* Atsutaka Okizaki okizaki@asahikawa‑med.ac.jp 1
Department of Radiology, Asahikawa Medical University, 2‑1‑1‑1 Midorigaoka‑higashi, Asahikawa 078‑8510, Japan
2
Division of Neurology, First Department of Internal Medicine, Asahikawa Medical University, Asahikawa, Japan
3
Division of Radiology, Asahikawa Medical University Hospital, Asahikawa, Japan
4
Asahikawa Keisenkai Hospital, Asahikawa, Japan
Results Proper reference VOI definition was achieved in 60.0% using conventional SBR and in 98.0% with DWH SBR. Both conventional and DWH SBR demonstrated good inter- and intra-observer reproducibility, however, there were statistically significant inter- and intra-observer variations with conventional SBR measurements. Average inter- and intra-observer errors of conventional SBR were 7.9 and 6.1%, respectively. Conversely, DWH SBR errors were not observed in all patients. Moreover, average inter- and intraobserver errors were significantly higher in conventional SBR with improper reference VOI definition than in that with proper reference VOI definition. Conclusions Although the reproducibility of conventional and DWH SBR was good, inter- and intra-observer bias could not be ignored in conventional SBR, particularly with improper reference VOI definition. Thus, DWH may be useful to improve inter- and intra-observer reproducibility of SBR. Keywords FP-CIT SPECT · DAT density · SBR · Histogram · DLB
Introduction Dopamine transporter single photon emission computed tomography (DAT-SPECT) is
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