Miura S, Kanno I, Aizawa Y, Murakami M, Uemura K
Radioisotopes. 1984 May;33(5):262-8.
In positron emission computed tomographs employing circular ring arrays of detectors, the performance of the imaging device has been specified ultimately by the characteristics of the detector. The responses of NaI detector were studied when detecting positron annihilation photon (511 keV). The study was mainly by using the NaI detector used in hybrid emission computed tomography (CT) "HEADTOME" we had developed. A series of measurements were carried out positioning two detectors with 40 cm distance and scanning 22Na point source in water. Both detectors was inclined from 0 degrees through 30 degrees to change incident angle of positron annihilation toward crystal face. Energy window was set from 100 to 700 keV. The results were presented as follows: Shortening the crystal length from 7 to 5 cm made sensitivity decrease about 10% and resolution deteriorate about 1 mm (FWHM). As the results of varying the width of the crystal, 20 mm width was optimal at any incident angle. The lead septum between the detectors was the thickness of 4 mm enough to reject multiple detector interactions (crosstalk). Beam mask which was made of lead in order to improve spatial resolution and placed on crystal face worked effectively for incident angles from 0 degrees to 15 degrees but degraded uniformity of spatial resolution from 0 degrees to through 30 degrees.
在采用探测器环形阵列的正电子发射计算机断层扫描仪中，成像设备的性能最终由探测器的特性决定。研究了碘化钠（NaI）探测器在探测正电子湮灭光子（511keV）时的响应。该研究主要使用我们开发的混合发射计算机断层扫描（CT）“HEADTOME”中使用的NaI探测器。进行了一系列测量，将两个探测器相距40cm放置，并在水中扫描22Na点源。两个探测器均从0度倾斜到30度，以改变正电子湮灭朝向晶体面的入射角。能量窗设置为100至700keV。结果如下：将晶体长度从7cm缩短到5cm，灵敏度降低约10%，分辨率恶化约1mm（半高宽）。作为改变晶体宽度的结果，2 cm宽在任何入射角下都是最佳的。探测器之间的铅隔板厚度为4mm，足以抑制多个探测器相互作用（串扰）。为了提高空间分辨率而放置在晶体面上的铅制准直器对0度到15度的入射角有效，但从0度到30度会降低空间分辨率的均匀性。
