Health Sci. Center, Texas Univ., San Antonio, TX.
IEEE Trans Med Imaging. 1995;14(4):681-7. doi: 10.1109/42.476109.
The purpose of this work was to determine the feasibility of using positron emitting isotopes that emit prompt gammas to acquire quantitative positron emission tomography (PET) data using standard PET instrumentation. Prompt gammas can contaminate PET data by increasing dead time, converting singles into invalid coincidences, and producing multiple coincidences which can lead to the replacement of valid coincidences by invalid coincidences. The measurements in this work were made by scanning point sources containing F-18, Na-22, and Co-60 and studying the effects of the prompt gammas on the PET data, We found that for the Na-22 point source, the annihilation photon coincidence rate was about 25 times the prompt gamma-annihilation photon coincidence rate in the entire active volume of the scanner. With scatter, the Na-22 prompt gamma-annihilation photon coincidence rate was 1.3 times higher than the F-18 scatter coincidence rate. The most significant effect of the prompt gamma was to increase dead time; the dead time correction factor for Cu-60 was 2.4 times higher than the correction factor for N-13 for the same source activity. We conclude that, in many cases, quantitative PET data can be readily obtained with isotopes that emit prompt gammas, using standard PET 2-D instrumentation. However there are some cases, such as 3-D PET, where prompt gammas could significantly contaminate the PET data.
这项工作的目的是确定使用发射瞬时伽马射线的正电子放射性同位素，利用标准的正电子发射断层扫描（PET）仪器获取定量正电子发射断层扫描（PET）数据的可行性。瞬时伽马射线可通过增加死时间、将单事件转化为无效符合事件以及产生多重符合事件来污染 PET 数据，这些多重符合事件可能会导致有效符合事件被无效符合事件所取代。本工作通过扫描含有 F-18、Na-22 和 Co-60 的点源进行测量，并研究了瞬时伽马射线对 PET 数据的影响。我们发现，对于 Na-22 点源，湮没光子符合率在整个扫描仪的有效体积内大约是瞬时伽马-湮没光子符合率的 25 倍。考虑散射后，Na-22 的瞬时伽马-湮没光子符合率比 F-18 的散射符合率高 1.3 倍。瞬时伽马射线的最显著影响是增加死时间；对于相同的源活度，Cu-60 的死时间校正因子比 N-13 的校正因子高 2.4 倍。我们的结论是，在许多情况下，使用发射瞬时伽马射线的同位素，利用标准的二维 PET 仪器，可以轻易地获取定量 PET 数据。然而，在某些情况下，如 3D-PET，瞬时伽马射线可能会严重污染 PET 数据。
