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J Nucl Med. 2008; 49 (Supplement 1):165P
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Novel Approaches to Molecular Imaging

Novel Approaches to Molecular Imaging Posters

Mouse brain imaging with 125I labeled compounds using a small animal SPECT/CT scanner

Hirofumi Fujii1, Izumi Umeda1, Masayuki Yamaguchi1, Kazumasa Inoue1, Toyokazu Saito1 and Yoshiki Kojima1

1 Functional Imaging, National Cancer Center, Kashiwa, Japan

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Objectives: 125I labeled compounds, which are very useful in molecular biology, are not suitable for in vivo imaging using conventional gamma cameras because of the energy of emitted gamma rays is too low; however, the current imaging devices dedicated for small animals have good potential. In this study, two kinds of 125I labeled brain imaging agents with different affinity to brain tissues were imaged by a small animal SPECT/CT scanner to investigate whether the difference of the intracerebral distribution between these two compounds could be visualized.

Methods: After the phantom study, 125I iomazenil (IMZ), which shows high affinity to benzodiazepine receptors, and 125I iodoamphetamine (IMP), which distributes according to the focal cerebral perfusion, were examined using NanoSPECT/CT (Bioscan, Washington, DC), a small animal SPECT/CT scanner. Each compound of 10MBq was injected to four ddy mice. Brain SPECT images of each mouse were obtained with the acquisition time of 30 minutes. After in vivo imaging, the autoradiograms of their excised brains were obtained, and they were compared with the SPECT images.

Results: The phantom study revealed excellent spatial resolution and high sensitivity for 125I (1.1 mm and 0.1%, respectively). Although both IMZ and IMP showed good affinity to brains of mice (IMZ: 5.1%/ID, IMP: 8.1%/ID), the intracerebral distribution of IMZ and IMP was different. IMZ was heterogeneously accumulated, predominantly in the cortical area where benzodiazepine receptors abundantly exist, whereas IMP was more homogeneously accumulated in the whole brain. Autoradiography validated this different intracerebral distribution on the SPECT images well.

Conclusions: NanoSPECT/CT would be useful to accurately visualize the biodistribution of 125I labeled compounds in mice.





This Article
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Right arrow Email this article to a friend
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Right arrow Alert me to new issues of the journal
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Right arrow Articles by Fujii, H.
Right arrow Articles by Kojima, Y.
PubMed
Right arrow Articles by Fujii, H.
Right arrow Articles by Kojima, Y.