Speaker
Description
In the field of nuclear medicine, there has been a growing demand for devices that can image gamma rays of several hundred keV. For example, radioactive gold nanoparticles have been proposed as ideal drug carriers that can be traced using their 412-keV gamma rays. However, devices offering high spatial resolution for imaging using such high-energy gamma rays have not yet been developed. Single-photon emission computed tomography (SPECT) uses an X-ray/gamma-ray imaging device equipped with a collimator that limits the arrival direction of X-rays and gamma rays. Although SPECT is widely used in clinical practice, it has two limitations. First, its typical spatial resolution is 5 mm, which is insufficient for use in animal experiments. Second, the energy of the X-rays/gamma rays that SPECT can image is below 200 keV because high-energy gamma rays tend to penetrate the collimator walls.
Therefore, we developed a novel SPECT capable of high-resolution imaging using high-energy gamma rays. To improve the spatial resolution, we used a 1-mm pitch array of Gd₃(Ga,Al)₅O₁₂(Ce) scintillators bonded with a multi-pixel photon counter array instead of a conventional photomultiplier tube. For imaging using high-energy gamma rays, we developed a novel collimator with an array of hourglass-shaped holes that were wide at the upper and bottom surfaces of the collimator and narrow in the middle. This hole shape offers thicker collimator walls while maintaining high sensitivity compared to the conventional parallel shape, enabling high-resolution imaging using high-energy gamma rays. In this study, we visualized radioactive gold in a Derenzo phantom using 412-keV gamma rays with a newly developed SPECT system. As a result, a 2-mm spatial resolution was achieved. In addition, we compare the new SPECT system with conventional SPECT and Compton cameras in the presentation.
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