Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Department of Radiology, Akita Hospital, Chiryu, Japan.
Med Phys. 2020 Nov;47(11):5739-5748. doi: 10.1002/mp.14455. Epub 2020 Sep 22.
Astatine-211 (At-211) is a promising alpha emitter for radionuclide therapy. High-resolution in vivo imaging of At-211 in small animals is needed for the development of At-211 radiopharmaceuticals. For this purpose, we developed a low-energy x-ray camera using a thin YAlO :Ce (YAP(Ce)) plate to image the low-energy x rays (73-87 keV) from the daughter radionuclide of At-211 (Po-211).
We optically coupled a 38 × 38 × 1-mm YAP (Ce) plate to a position-sensitive photomultiplier (PSPMT) to develop an imaging detector. A pinhole or a parallel hole collimator was attached to the imaging detector, and the performance was measured for 60-keV gamma photons. With the developed x-ray camera, we carried out imaging of a mouse that had been administered At-211-NaAt.
The intrinsic spatial resolution of the YAP (Ce) x-ray camera was approximately 1.2 mm FWHM, and the energy resolution was 22% FWHM. With a 5-mm-thick parallel hole collimator, the spatial resolution was 3.8 mm FWHM with a sensitivity of 8 × 10 at 10 mm, which is a typical distance from the surface of the collimator to a subject in mouse imaging. Using a 1-mm diameter pinhole collimator, the spatial resolution was 1.8 mm FWHM with a sensitivity of 3.5 × 10 at 10 mm from the collimator. In the mouse images measured by the developed x-ray camera, we could clearly observe that the At-211 accumulated in the thyroid gland and the stomach of the mouse.
We concluded that the YAP (Ce) x-ray camera is useful for in vivo imaging of At-211.
砹-211（At-211）是一种很有前途的放射性核素治疗用α发射器。为了开发 At-211 放射性药物，需要在小动物体内对 At-211 进行高分辨率的活体成像。为此，我们使用薄的钇铝石榴石：铈（YAP（Ce））平板开发了一种低能量 X 射线相机，以对 At-211 的子放射性核素（Po-211）产生的低能量 X 射线（73-87keV）进行成像。
我们将 38×38×1mm 的 YAP（Ce）平板与位置灵敏光电倍增管（PSPMT）光学耦合，开发出一种成像探测器。在成像探测器上附加一个针孔或平行孔准直器，并对 60keV 伽马光子的性能进行测量。使用所开发的 X 射线相机对已给予 At-211-NaAt 的小鼠进行成像。
YAP（Ce）X 射线相机的固有空间分辨率约为 1.2mm FWHM，能量分辨率为 22% FWHM。使用 5mm 厚的平行孔准直器，空间分辨率为 3.8mm FWHM，灵敏度为 10mm 处的 8×10，这是小鼠成像中准直器表面到受检者的典型距离。使用 1mm 直径的针孔准直器，空间分辨率为 1.8mm FWHM，灵敏度为 3.5×10，距离准直器 10mm。在所开发的 X 射线相机测量的小鼠图像中，我们可以清楚地观察到 At-211 积聚在甲状腺和胃中。
我们得出结论，YAP（Ce）X 射线相机可用于 At-211 的体内成像。
