Simultaneous Tc-99m and I-123 dual-radionuclide imaging with a solid-state detector-based brain-SPECT system and energy-based scatter correction

Wataru Takeuchi; Atsuro Suzuki; Tohru Shiga; Naoki Kubo; Yuichi Morimoto; Yuichiro Ueno; Keiji Kobashi; Kikuo Umegaki; Nagara Tamaki

doi:10.1186/s40658-016-0147-2

Simultaneous Tc-99m and I-123 dual-radionuclide imaging with a solid-state detector-based brain-SPECT system and energy-based scatter correction

EJNMMI Phys. 2016 Dec;3(1):10. doi: 10.1186/s40658-016-0147-2. Epub 2016 Jun 29.

Authors

Wataru Takeuchi¹, Atsuro Suzuki², Tohru Shiga³, Naoki Kubo⁴, Yuichi Morimoto², Yuichiro Ueno², Keiji Kobashi², Kikuo Umegaki⁵, Nagara Tamaki³

Affiliations

¹ Research and Development Group, Hitachi Ltd, 1-280, Higashi-Koigakubo, Kokubunji-shi, 185-8601, Tokyo, Japan. wataru.takeuchi.rg@hitachi.com.
² Research and Development Group, Hitachi Ltd, 1-280, Higashi-Koigakubo, Kokubunji-shi, 185-8601, Tokyo, Japan.
³ Department of Nuclear Medicine, School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
⁴ Office of Health and Safety, Hokkaido University, Sapporo, Hokkaido, Japan.
⁵ Division of Quantum Science and Engineering, Graduate School of Engineering, Hokkaido University, Sapporo, Japan.

Abstract

Background: A brain single-photon emission computed tomography (SPECT) system using cadmium telluride (CdTe) solid-state detectors was previously developed. This CdTe-SPECT system is suitable for simultaneous dual-radionuclide imaging due to its fine energy resolution (6.6 %). However, the problems of down-scatter and low-energy tail due to the spectral characteristics of a pixelated solid-state detector should be addressed. The objective of this work was to develop a system for simultaneous Tc-99m and I-123 brain studies and evaluate its accuracy.

Methods: A scatter correction method using five energy windows (FiveEWs) was developed. The windows are Tc-lower, Tc-main, shared sub-window of Tc-upper and I-lower, I-main, and I-upper. This FiveEW method uses pre-measured responses for primary gamma rays from each radionuclide to compensate for the overestimation of scatter by the triple-energy window method that is used. Two phantom experiments and a healthy volunteer experiment were conducted using the CdTe-SPECT system. A cylindrical phantom and a six-compartment phantom with five different mixtures of Tc-99m and I-123 and a cold one were scanned. The quantitative accuracy was evaluated using 18 regions of interest for each phantom. In the volunteer study, five healthy volunteers were injected with Tc-99m human serum albumin diethylene triamine pentaacetic acid (HSA-D) and scanned (single acquisition). They were then injected with I-123 N-isopropyl-4-iodoamphetamine hydrochloride (IMP) and scanned again (dual acquisition). The counts of the Tc-99m images for the single and dual acquisitions were compared.

Results: In the cylindrical phantom experiments, the percentage difference (PD) between the single and dual acquisitions was 5.7 ± 4.0 % (mean ± standard deviation). In the six-compartment phantom experiment, the PDs between measured and injected activity for Tc-99m and I-123 were 14.4 ± 11.0 and 2.3 ± 1.8 %, respectively. In the volunteer study, the PD between the single and dual acquisitions was 4.5 ± 3.4 %.

Conclusions: This CdTe-SPECT system using the FiveEW method can provide accurate simultaneous dual-radionuclide imaging. A solid-state detector SPECT system using the FiveEW method will permit quantitative simultaneous Tc-99m and I-123 study to become clinically applicable.

Keywords: CdTe; Crosstalk; Dual radionuclide; Scatter correction; Solid-state detector.