title: Evaluation of Simultaneous Dual-radioisotope SPECT Imaging Using (18)F-fluorodeoxyglucose and (99m)Tc-tetrofosmin.
abstract: OBJECTIVE
  Use of a positron emission tomography (PET)/single-photon emission computed tomography (SPECT) system facilitates the simultaneous acquisition of images with fluorine-18 fluorodeoxyglucose ((18)F-FDG) and technetium ((99m)Tc)-tetrofosmin. However, (18)F has a short half-life, and 511 keV Compton-scattered photons are detected in the (99m)Tc energy window. Therefore, in this study, we aimed to investigate the consequences of these facts.
  
  
  METHODS
  The crosstalk correction for images in the (99m)Tc energy window involved the dual energy window (DEW) subtraction method. In phantom studies, changes in the count of uniform parts in a phantom (due to attenuation from decay), signal detectability in the hot-rod part of the phantom, and the defect contrast ratio in a cardiac phantom were examined.
  
  
  RESULTS
  For (18)F-FDG in the step-and-shoot mode, nearly a 9% difference was observed in the count of projection data between the start and end positions of acquisition in the uniform part of the phantom. Based on the findings, the detectability of 12 mm hot rods was relatively poor. In the continuous acquisition mode, the count difference was corrected, and detectability of the hot rods was improved. The crosstalk from (18)F to the (99m)Tc energy window was approximately 13%. In the cardiac phantom, the defect contrast in (99m)Tc images from simultaneous dual-radionuclide acquisition was improved by approximately 9% after DEW correction; the contrast after correction was similar to acquisition with (99m)Tc alone.
  
  
  CONCLUSIONS
  Based on the findings, the continuous mode is useful for (18)F-FDG acquisition, and DEW crosstalk correction is necessary for (99m)Tc-tetrofosmin imaging.
authors.affiliation: Department of Nuclear Medicine Technology, Gunma Prefectural College of Health Sciences, Maebashi, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Radiological Technology, Gunma Cardiovascular Center, Maebashi, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Mochiki
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, Gunma Cardiovascular Center, Maebashi, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Department of Radiological Technology, Gunma Cardiovascular Center, Maebashi, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ino
authors.affiliation: Department of Radiological Technology, National Kyushu Medical Center, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamaji
authors.affiliation: Department of Radiological Technology, Maebashi Red Cross Hospital, Maebashi, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Kawakami
keywords: 18F-FDG; 99mTc-tetrofosmin; DEW method; PET/SPECT system