Performance of a 511keV Gamma-ray Imager Using a LYSO(Ce) Crystal Array with Wave-Length Shifter
Performance of a 511keV Gamma-ray Imager Using a LYSO(Ce) Crystal Array with Wave-Length Shifter
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使用带有波长移位器的 LYSO(Ce) 晶体阵列的 511keV 伽马射线成像仪的性能
DOI：
10.1109/tns.2010.2043853
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
S. Aogaki and F. Takeutchi
中科院分区：
文献类型：
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作者：
K.Sagara;他8名;Akitaka Matumura;S. Aogaki and F. Takeutchi
正电子发射断层扫描（PET）是早期诊断癌症的强大医疗工具，但它仍然过于昂贵，无法广泛使用。这主要是由于所使用的许多晶体和光电传感器的成本。在构建PET成像器时，使用波长移位光纤（WLS）的晶体读出允许使用具有减少数量的光电倍增管的许多小晶体，从而以较低的成本保证良好的空间分辨率。然而，这种方法的主要缺点是光子收集效率低。在过去的几年里，我们的读出系统的设计改进，导致效率提高了十倍以上。结果，从检测效率的观点来看，该方法现在可以被认为适用于构造真实的装置。用2 × 16 Kuraray Y-11 WLS和Hamamatsu H6568 ModIII光电倍增管，以2 2 Na β+源，在符合测量中读出了由16 × 16 LYSO（Ce）晶体组成的垫。每个晶体的尺寸为1 mm 1 mm 20 mm，与直接读出相比，光子数的衰减约为1/47，并且这个衰减因子似乎不会因事件而异。这导致检测效率几乎等于具有相同厚度的块检测器的检测效率。晶体和插入在晶体和WLS之间的薄塑料片的折射率的匹配消除了晶体之间的串扰，这导致接近0.33mm RMS的固有分辨率的非常好的空间分辨率。检测器的定时波动使得如果在实际PET中使用一对这样的检测器，并且如果应用15 ns的时间窗，则由于符合中的定时波动而导致的事件损失将为约1.6%。用这种布置构建的具有20 cm内径的全尺寸动物PET将仅需要54个这样的光电倍增管。
Positron Emission Tomography (PET) is a powerful medical tool for the early diagnosis of cancer but it is still too expensive for widespread use. This is mainly due to the cost of the many crystals and photosensors used. In building a PET imager, crystal read-out using wavelength shifter fibers (WLS) permits the use of many small crystals with a reduced number of photomultipliers, thus promising good spatial resolution at lower cost. However, the main drawback of this method has been low efficiency of photon collection. Improvements in design of our readout system over the last several years have resulted in a factor of more than ten in efficiency. As a result, from the point of view of detection efficiency, this method can now be considered as applicable to the construction of a real device. A pad composed of 16 16 LYSO (Ce) crystals has been read out by using a 2 16 Kuraray Y-11 WLS and Hamamatsu H6568ModIII photomultipliers, in a coincidence measurement using a 22Na β+source. The size of each crystal is 1 mm 1 mm 20 mm. The attenuation of the number of photons compared with the direct readout is about 1/47, and this attenuation factor seems not to vary from event to event. This results in a detection efficiency almost equal to that of the block detector with the same thickness. The matching of the refractive indices of the crystal and of the thin plastic sheet, inserted between the crystals and WLS, removes the crosstalk between the crystals, which results in a very good spatial resolution close to the intrinsic resolution of 0.33 mm RMS. The timing fluctuation of the detector is such that if a pair of such detectors are used in an actual PET, and if a time window of 15 ns is applied, the event loss due to the fluctuation of the timing in the coincidence will be about 1.6%. A full size animal PET with 20 cm internal diameter built with this arrangement will need only 54 of such photomultipliers.