Development of a dynamic micro RI imaging system for single cells

Studies on cell regulation are attracting worldwide attention in order to realize regenerative medicine. Therefore, a nuclear medicine imaging method, which can use tracers having substantially the same composition as a target biomolecule, is required. Autoradiography is a high-resolution nuclear medicine imaging method. However, this method does not have a dynamical imaging capability due to the principle on which it is based. In this research, we develop a nuclear medicine imaging system for dynamic cell observation. Specifically, in order to prevent broadening of the scintillation position because of scintillation light spreading in the scintillator, β-rays are detected by a thin scintillator plate. A scientific CMOS camera with low readout noise and high resolution was used to detect scintillation light. The scintillator plate was a CsI crystal connected to an optical fiber array. The scintillation light generated from the scintillator plate was extracted through optical fibers. The imaging lenses adopted in this research were a high-speed imaging and a conversion lens.Imaging resolution was adjusted to 6.5 × 6.5 mm ² / pixel and exposure time was 10 s. In order to evaluate the imaging performance of the proposed system, we measured samples containing a radiopharmaceutical with a prototype system. In this measurement, two different activity ¹⁸ F-solutions were used as the imaging target. They were fixed with a uniform thickness of 0.4 mm. In the imaging results, we measured different image values depending on their activities. On the other hand, in the region of no ¹⁸ F-solutions, the image value was almost constant. The output had sufficient linearity for images with activity exceeding 0.05 Bq / pixel. Imaging results showed that our system has sufficient sensitivity for imaging uptake of ¹⁸ F by single cells.