Sadato N, Yonekura Y, Magata Y, Nishizawa S, Ishizu K, Okazawa H, Tsuchida T, Tanaka F, Tamaki N, Sasayama S
Department of Nuclear Medicine, Kyoto University Faculty of Medicine, Japan.
Ann Nucl Med. 1994 Nov;8(4):239-43. doi: 10.1007/BF03165026.
In activation studies with the bolus method for O-15 water and PET, the radiotracer concentration may reach the limits of the system in terms of dead time correction and accidental coincidence. To obtain the optimal injection dose of O-15 water, we performed a normal volunteer study to evaluate the relationship between the injected dose and the radioactivity concentration in the brain and a phantom study to evaluate the performance of the PET scanner (PCT3600W) under high count rate conditions and the effect of averaging on the signal to noise ratio for the PET images. A linear relationship was noted between the injected dose (normalized for each body weight: x) and the mean radiotracer concentration in the brain measured by PET (y) (y = 2.52 + 30.1 x, n = 64, r = 0.87, p < 0.001). The percent error in the measurement of radioactivity with PET was within +/- 5% in the 100 to 2000 nCi/ml (3.7-74 KBq/ml) range. Below 100 nCi/ml (3.7 KBq/ml), the percent error increased due to the rapid increase in noise in the reconstructed images. Over 1000 nCi/ml (37 KBq/ml), on the other hand, the noise was almost unchanged. With our PET scanner, the optimal range of the radiotracer concentration in the brain is below 1000 nCi/ml (37 KBq/ml), corresponding to an injection dose of 33 mCi (1.22 GBq)/60 kg body weight. With the same total dose, the increment of number of repeated measurements for averaging provided the better signal to noise ratio. In designing a paradigm for an activation PET study, the injection dose and the number of repeated measurements for averaging should be considered.
在用团注法对O-15水进行正电子发射断层显像（PET）的激活研究中，就死时间校正和偶然符合而言，放射性示踪剂浓度可能会达到系统的极限。为了获得O-15水的最佳注射剂量，我们进行了一项正常志愿者研究，以评估注射剂量与脑内放射性浓度之间的关系，并进行了一项体模研究，以评估PET扫描仪（PCT3600W）在高计数率条件下的性能以及平均处理对PET图像信噪比的影响。观察到注射剂量（按体重归一化：x）与PET测量的脑内平均放射性示踪剂浓度（y）之间存在线性关系（y = 2.52 + 30.1x，n = 64，r = 0.87，p < 0.001）。PET测量放射性时的百分比误差在100至2000 nCi/ml（3.7 - 74 KBq/ml）范围内为±5%以内。低于100 nCi/ml（3.7 KBq/ml）时，由于重建图像中噪声的快速增加，百分比误差增大。另一方面，超过1000 nCi/ml（37 KBq/ml）时，噪声几乎不变。对于我们的PET扫描仪，脑内放射性示踪剂浓度的最佳范围低于1000 nCi/ml（37 KBq/ml），对应于60 kg体重33 mCi（1.22 GBq）的注射剂量。在总剂量相同的情况下，增加平均处理的重复测量次数可提供更好的信噪比。在设计激活PET研究的范式时，应考虑注射剂量和平均处理的重复测量次数。
