Optimization of transmission scan duration for 15O PET study with sequential dual tracer administration using N-index
Optimization of transmission scan duration for 15O PET study with sequential dual tracer administration using N-index
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DOI：
10.1007/s12149-010-0374-x
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发表时间：
2010-06-01
影响因子：
2.6
通讯作者：
Iida, Hidehiro
中科院分区：
文献类型：
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作者：
Kudomi, Nobuyuki;Watabe, Hiroshi;Iida, Hidehiro
目的 通过施用 (H2O)-O-15 和 O-15(2)，可以通过 PET 定量脑血流量 (CBF)、氧提取分数 (OEF) 和 O-2 脑代谢率 (CMRO2)。最近，通过 PET 采集和积分方法（DARG 方法）连续施用 O-15(2) 和 (H2O)-O-15 双重示踪剂，缩短了这些测量的持续时间。在 PET 扫描之前，通常需要进行透射扫描来校正光子衰减。虽然DARG方法可以将总研究时间缩短至30分钟左右，但传输扫描持续时间尚未优化，并且有可能缩短其持续时间。我们这项研究的目的是确定传输扫描的最佳持续时间。我们引入了“N-index”，它估计通过减去两个统计上独立且生理上等效的图像而获得的图像上的噪声水平。通过 N 指数研究功能图像上的噪声与传输扫描持续时间之间的关系。方法我们进行了模型研究来测试 N 指数是否反映了 PET 图像中的像素噪声。我们还通过临床患者 DARG 方法的 CBF、OEF 和 CMRO2 图像上的 N 指数估计了噪声水平，并研究了透射扫描的最佳真实计数。结果我们在体模研究中发现像素噪声和 N 指数之间存在紧密相关性。通过使用 DARG 方法研究功能图像的透射扫描持续时间和 N 指数值之间的关系，我们发现真实计数超过 40 Mcounts 的透射数据会产生具有合理定量精度和质量的 CBF、OEF 和 CMRO2 图像。 结论 本研究表明，通过缩短透射扫描可以进一步缩短 DARG 测量时间。 N 指数可用于确定检查图像质量时的最佳测量条件。
Purpose Cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of O-2 (CMRO2) can be quantified by PET with the administration of (H2O)-O-15 and O-15(2). Recently, a shortening in the duration of these measurements was achieved by the sequential administration of dual tracers of O-15(2) and (H2O)-O-15 with PET acquisition and integration method (DARG method). A transmission scan is generally required for correcting photon attenuation in advance of PET scan. Although the DARG method can shorten the total study duration to around 30 min, the transmission scan duration has not been optimized and has possibility to shorten its duration. Our aim of this study was to determine the optimal duration for the transmission scan. We introduced 'N-index', which estimates the noise level on an image obtained by subtracting two statistically independent and physiologically equivalent images. The relationship between noise on functional images and duration of the transmission scan was investigated by N-index.Methods We performed phantom studies to test whether the N-index reflects the pixel noise in a PET image. We also estimated the noise level by the N-index on CBF, OEF and CMRO2 images from DARG method in clinical patients, and investigated an optimal true count of the transmission scan.Results We found tight correlation between pixel noise and N-index in the phantom study. By investigating relationship between the transmission scan duration and N-index value for the functional images by DARG method, we revealed that the transmission data with true counts of more than 40 Mcounts results in CBF, OEF, and CMRO2 images of reasonable quantitative accuracy and quality.Conclusion The present study suggests that further shortening of DARG measurement is possible by abridging the transmission scan. The N-index could be used to determine the optimal measurement condition when examining the quality of image.