Gamma | Gamma Camera에 있어 측면 선란선의 영향에 대한 평가

The Evaluation of Lateral Scatter Ray of Gamma Camera

Jae-Il Kim, Eun-Byeol Lee, Seong-Wook Cho, Kyeong-Woon Noh and Keon-Wook Kang Department of Nuclear Medicine, Seoul National University Hospital, Seoul, Korea

Purpose : Generally, a collimator that installed in front of detector set a direction of gamma ray and remove a scatter ray. By the way, a lateral or oblique scatter ray is detected into crystal through collimator. At this study, we will evaluate a mount of count and spectrums of lateral scatter ray.

Materials and Methods : We used the SKY LITE (philips, netherlands) as a gamma camera, and 99mTc, 1.11 GBq point source as a phantom. we put this point source at backside 50 ㎝ of detector. After acquiring this for 1 min, we turned a detector next 10 degrees. Likely this, we acquired images at every 10 degrees from 0° to 360°, analyzed images and spectrums. In case of patient study, we choose a 3 phase bone scan patient who had a hand disease, because scatter rays from body would detect on crystal. After acquiring blood flow and blood pool images, we analyzed images and spectrums. Additional, we put a lead gown on patient’s hand, body. And then we compared and evaluated 3 type blood pool images (non lead gown, lead gown on a hand and on body).

Results : In case of phantom study, scatter ray counts at backside (270°-90°) are same with a background count. By the way, counts of scatter ray of oblique side (0°-50°, 220°-270°) are 100-600 cps, furthermore, counts at frontside are over 4 Mcps. In case of patient study, a counts of hand blood pool scan are 1510 cps. But counts of hand with lead gown on hands and on body are each 1554 cps, 1299 cps.

Conclusion : Therefore, even though there is a collimator in front of detector, lateral scatter rays detect on crystal and affect to images and spectrums. Especially, if there is a high activity source at outside of detector when we examine low activity organs like hands or foot, we have to shield and remove the source at outside for a good image.

Key Words Gamma Camera, Scatter Ray, Collimator, Spectrum