Performance characteristics of a novel clustered multi-pinhole technology for simultaneous high-resolution SPECT/PET



Versatile emission computed tomography (VECTor) for small-animal imaging enables fully simultaneous SPECT/PET image acquisition based on clustered multi-pinhole collimation. The present study experimentally evaluated the detailed performance characteristics of the clustered multi-pinhole system for simultaneous 99mTc and 18F imaging from the user perspective.


Spatial resolution, sensitivity, count rate linearity were determined for the VECTor system (MILabs). Two hot-rod micro-resolution phantoms with 6 sectors were created to test the resolution of 99mTc and 18F. Sensitivity and count rate linearity were measured by scanning 99mTc and 18F point sources positioned at the center of the field of view. Furthermore, we quantified the influence of 18F on 99mTc SPECT images. The ratios of SPECT counts on the 99mTc-only and simultaneous 18F-99mTc at various time points were evaluated as a function of the 18F-to-99mTc activity concentration ratio.


The 0.5-mm hot-rods can be visually distinguished in the 99mTc image, and 0.8-mm rods for 18F remained clearly visible. The point-source sensitivity was 2800 cps/MBq for 99mTc and 2899 cps/MBq for 18F, respectively. Count rates up to 120,000 cps for one bed position were linear for the activity. Spill-over from 18F into 99mTc SPECT images was negligible when the activity concentration of the administered 18F solution exceeded that of the 99mTc solution by up to a factor of 2.


We evaluated the performance characteristics of the VECTor that lead to determination of the optimal administered doses of 99mTc and 18F tracers. We found that the VECTor achieved high resolution and high sensitivity as well as good 99mTc and 18F linearity. Simultaneous SPECT/PET imaging with 99mTc and 18F tracers, and stand-alone 99mTc and 18F imaging using clustered-pinhole collimators is feasible and practical for a wide range of research applications using small animals.

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We thank the staff of the Department of Molecular Imaging at National Institute of Radiological Sciences for assisting SPECT/PET/CT experiment. This work was supported in part by KAKENHI Grants-in-Aid for Scientific Research (B) (General) (M.I: No. 22390239, 26293282) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japanese Government, and for Challenging Exploratory Research (M.I: No. 24659140) from Japan Society for the Promotion of Science (JSPS).

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The authors declare that they have no conflict of interest.

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Correspondence to Masayuki Inubushi.

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K. Miwa and M. Inubushi contributed equally.

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Miwa, K., Inubushi, M., Takeuchi, Y. et al. Performance characteristics of a novel clustered multi-pinhole technology for simultaneous high-resolution SPECT/PET. Ann Nucl Med 29, 460–466 (2015).

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  • VECTor
  • Simultaneous imaging
  • Clustered multi-pinhole
  • Small-animal imaging