RT-4 WORLD'S FIRST HEMISPHERE-SHAPE BRAIN-DEDICATED PET FOR SMALL LESION DETECTION

Positron emission tomography (PET) is useful to detect malignant tumors by imaging glucose or amino acid metabolism. Whole-body PET with the detector arrangement in a large diameter is currently used for brain imaging, however, the detector arrangement in small diameter is better for brain imaging. Stereotactic radiosurgery (SRS) treats brain tumor with maintaining cognitive function. Therefore, it needs more dedicated PET to identify small lesions and their localization. Then, we developed the world's first brain-dedicated PET with detectors arranged in a hemisphere of 28 cm diameter, attaining 2.2 mm in spatial resolution. This development was performed with ATOX CO., LTD and the brain-dedicated PET has been commercialized as Vrain(TM). Ten normal volunteers (22 - 45 age male) underwent (18)FDG-PET using a whole-body PET (Discovery MI, GE) and the brain-PET for 10-min each, which were started 30-min and 45-min after FDG injection, respectively. A phantom with 10-22 diameter hot spheres and background (radioactivity ratio, 4:1) was also acquired by both PET systems, then estimated the radioactivity ratio in case of 2-mm diameter hot sphere. As a results, the inferior colliculus, substantia nigra, red nucleus, and brain stem raphe nucleus were identified with the brain-PET. The inferior colliculus was identified with the whole-body PET, but other nuclei were not. Based on phantom study, it was estimated that radioactivity in a 2-mm diameter sphere was measured with 1.4 - 2.9 times higher contrast than whole-body PET. The substantia nigra and the red nucleus has 5.0-6.0mm in short diameter on MRI T2WI axial image. The raphe nucleus extends laterally to 2.5mm on postmortem brain specimens. We concluded that our brain-dedicated PET can identify approximately 2.5mm diameter tumor clearly and will be particularly useful in SRS.