Adam L E, Watson C C
Forschungsschwerpunkt Radiologische Diagnostik und Therapie, Deutsches Krebsforschungszentrum Heidelberg, Deutschland.
Nuklearmedizin. 1999;38(2):61-5.
Using the continuous energy spectra of Compton scattered photons we measured the lower energy discriminator level of a positron emission tomograph (PET).
In PET scans, coincident photons with an energy between the lower and upper level of the energy discriminator (LLD/ULD) are acquired. Usually, the energy response of a detector is determined by measurements using various radiation sources with different energies. But this method is limited to the availability of the sources with the desired energies. The procedure described in this paper uses the energy spectrum from Compton scattered photons, providing a continuous energy spectrum for the direct measurement of the energy response of the detectors. For our measurements we used an activated Cu-64 point source (phi = 1 mm) which was positioned in an aluminium sphere (phi = 2 cm).
The measured LLD values for a whole-body PET-scanner ECAT EXACT HR+ (CTI/Siemens) were systematically lower than the nominal values (327 keV instead of 350 keV) and confirm the results of C. Watson, recently found for line sources.
This leads to an increased number of detected low energy photons (mainly scattered photons) and has to be taken into account within the scatter correction.
利用康普顿散射光子的连续能谱，我们测量了正电子发射断层扫描仪（PET）的较低能量鉴别器水平。
在PET扫描中，采集能量在能量鉴别器下限和上限（LLD/ULD）之间的符合光子。通常，探测器的能量响应通过使用具有不同能量的各种辐射源进行测量来确定。但这种方法限于有所需能量的源的可用性。本文所述程序使用来自康普顿散射光子的能谱，提供连续能谱以直接测量探测器的能量响应。为进行我们的测量，我们使用了一个活化的铜 - 64点源（直径 = 1毫米），其置于一个铝球（直径 = 2厘米）中。
对全身PET扫描仪ECAT EXACT HR +（CTI/西门子）测量的LLD值系统地低于标称值（327千电子伏特而非350千电子伏特），并证实了C. 沃森最近对线源所发现的结果。
这导致检测到的低能光子（主要是散射光子）数量增加，并且在散射校正中必须予以考虑。
