Development of neck filters for reducing artifact in cervical bone SPECT

In cervical bone scintillation SPECT studies using triple energy window (TEW) and ordered subject-expection maximization (OS-EM) methods, we have observed an artifact that may interfere with evaluation of the image; higher accumulation in cervical vertebra compared with in the head and thoracic vertebra. As the neck is smaller in diameter than in the thorax and head, gamma ray absorption is lower. In addition, as the distance between the neck and the detector is greater, scattered gamma rays are increased, interfering with imaging and causing artifact. To overcome these problems, we have developed special absorbers (neck filter) to make the relative absorption level of the neck comparable to that of the head and thorax and have employed these cervical filters in bone scintillation SPECT studies in combination with TEW scatter correction and OS-EM method. Our results showed that artifacts were significantly reduced and satisfactory images were obtained. (author)