Photon Factory Activity Report 2022 #40 (2023)

AR-NE7A/2022G018

High-Resolution Mouse Brain Perfusion Imaging by Multi-pinhole Based X-rayFluorescence Computed Tomography
Tsutomu ZENIYA1,*, Yuta TSUSHIMA1, Masahiro MATSUOKA2, Kazuki SATO1,Sota KUSAKARI1, Tenta SASAYA2, Naoki SUNAGUCHI3, Hidekazu KAWASHIMA4,Kazuyuki HYODO5 and Tetsuya YUASA2
1
Hirosaki University, Hirosaki 036-8561, Japan
2
Yamagata University, Yonezawa 992-8510, Japan
3
Nagoya University, Nagoya 461-8673, Japan
4
Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
5High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan
1 Introduction
We are developing an X-ray fluorescence computed
tomography (XFCT) system [1,2] for preclinical studies
as a new modality that provides biological function
images similar to positron emission tomography andsingle photon emission computed tomography (SPECT).
In this study, we constructed an ultra-high-resolution
XFCT system using a multi-pinhole collimator with 15
pinholes of 0.1-mm diameter, and attempted to image thedistribution of the non-radioactive iodine contrast agent
accumulated in the mouse brain.
2 ExperimentXFCT system was constructed at the synchrotron
radiation beamline NE7A of the High Energy Accelerator
Research Organization PF-AR as shown in Fig. 1. A
subject on a rotating stage was irradiated with highbrightness monochromatic X-rays with an energy of 33.2
keV just above K-absorption edge, which emitted a large
amount of fluorescence from iodine. Fluorescence X-rays
were detected by a two-dimensional detector placed at 90
degrees to the incident X-rays, and projected images offluorescent X-rays were obtained. The detector had pixelsof 0.172 mm × 0.172 mm arranged in 487 × 195, andthe detection area was 83.8 mm wide × 33.5 mm long.
Fluorescent X-rays passing through 15 ( 5 horizontal × 3vertical) pinholes with 0.1 mm were projected onto thedetection area without overlapping. Magnification isapproximately 1x. Projected images from 180derection/360-degree rotation were reconstructed by 3DOSEM method for multi-pinhole XFCT. To evaluate
spatial resolution, a Derenzo phantom with multiple holesof different diameters (0.35 mm to 0.7 mm) filled with 20
mg/ml iodine(I) solution was imaged for 1 minute perprojection. In addition, 127I-iofetamine (1.14 mg ofiodine) was administrated intravenously to ddY mouse(male, 25 g body weight), and the brain was removed 5
minutes postinjection. The formalin-fixed brain wasplaced in a 10-mm diameter cylindrical container filledwith water and imaged for 3 minutes per projection.
3 Results and Discussion
The reconstructed image of the Derenzo phantom
clearly depicted the smallest diameter of 0.35 mm,showing a spatial resolution better than 0.35 mm (Fig.
2(a)). In addition, in imaging of the mouse brain,
perfusion images of multiple slices were obtained, and thedistribution of iodine agent was visualized with ultra-highresolution (Fig. 2(b)). This study demonstrated thefeasibility of ultra-high-resolution functional imaging of
the mouse brain by XFCT.

Fig. 1: Ultra-high-resolution multi-pinhole XFCT system.

(a)(b)
Fig. 2: (a) The reconstructed image of Derenzo phantom.
Excellent spatial resolution of 0.35 mm or less. (b) Mousebrain perfusion multi-slice images.
Acknowledgement
This work was supported in part by JSPS KAKENHI
Grant Numbers JP22K04133, JP17H04116, JP22K19501.
References[1] T. Yuasa et al., IEEE Trans. Nucl. Sci. 44, 54 (1997).
[2] T. Sasaya et al., Sci. Rep. 7, 5742 (2017).
* zeniya@hirosaki-u.ac.jp