Sowa-Staszczak Anna, Lenda-Tracz Wioletta, Tomaszuk Monika, Głowa Bogusław, Hubalewska-Dydejczyk Alicja
Department of Endocrinology, Jagiellonian University Medical College, Krakow, Poland.
Nucl Med Rev Cent East Eur. 2013;16(1):9-16. doi: 10.5603/NMR.2013.0003.
Somatostatin receptor scintigraphy (SRS) is a useful tool in the assessment of GEP-NET (gastroenteropancreatic neuroendocrine tumor) patients. The choice of appropriate settings of image reconstruction parameters is crucial in interpretation of these images. The aim of the study was to investigate how the GEP NET lesion signal to noise ratio (TCS/TCB) depends on different reconstruction settings for Flash 3D software (Siemens).
SRS results of 76 randomly selected patients with confirmed GEP-NET were analyzed. For SPECT studies the data were acquired using standard clinical settings 3-4 h after the injection of 740 MBq 99mTc-[EDDA/HYNIC] octreotate. To obtain final images the OSEM 3D Flash reconstruction with different settings and FBP reconstruction were used. First, the TCS/TCB ratio in voxels was analyzed for different combinations of the number of subsets and the number of iterations of the OSEM 3D Flash reconstruction. Secondly, the same ratio was analyzed for different parameters of the Gaussian filter (with FWHM = 2-4 times greater from the pixel size). Also the influence of scatter correction on the TCS/TCB ratio was investigated.
With increasing number of subsets and iterations, the increase of TCS/TCB ratio was observed. With increasing settings of Gauss [FWHM coefficient] filter, the decrease of TCS/TCB ratio was reported. The use of scatter correction slightly decreases the values of this ratio.
OSEM algorithm provides a meaningfully better reconstruction of the SRS SPECT study as compared to the FBP technique. A high number of subsets improves image quality (images are smoother). Increasing number of iterations gives a better contrast and the shapes of lesions and organs are sharper. The choice of reconstruction parameters is a compromise between image qualitative appearance and its quantitative accuracy and should not be modified when comparing multiple studies of the same patient.
生长抑素受体闪烁扫描术（SRS）是评估胃肠胰神经内分泌肿瘤（GEP-NET）患者的一种有用工具。在解读这些图像时，选择合适的图像重建参数设置至关重要。本研究的目的是探讨GEP-NET病变的信噪比（TCS/TCB）如何取决于西门子Flash 3D软件的不同重建设置。
分析了76例随机选取的确诊GEP-NET患者的SRS结果。对于SPECT研究，在注射740 MBq 99mTc-[EDDA/HYNIC]奥曲肽后3 - 4小时，使用标准临床设置采集数据。为获得最终图像，采用了不同设置的OSEM 3D Flash重建和FBP重建。首先，分析了OSEM 3D Flash重建的子集数量和迭代次数的不同组合下，体素中的TCS/TCB比值。其次，分析了高斯滤波器不同参数（半高宽为像素大小的2 - 4倍）下的相同比值。还研究了散射校正对TCS/TCB比值的影响。
随着子集数量和迭代次数的增加，观察到TCS/TCB比值升高。随着高斯[半高宽系数]滤波器设置的增加，报告TCS/TCB比值降低。使用散射校正会使该比值的值略有降低。
与FBP技术相比，OSEM算法能显著更好地重建SRS SPECT研究。大量的子集可提高图像质量（图像更平滑）。迭代次数增加可提供更好的对比度且病变和器官的形状更清晰。重建参数的选择是图像定性外观与其定量准确性之间的一种权衡，在比较同一患者的多项研究时不应改变。
