Effects of injected dose, BMI and scanner type on NECR and image noise in PET imaging
Effects of injected dose, BMI and scanner type on NECR and image noise in PET imaging
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DOI：
10.1088/0031-9155/56/16/013
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发表时间：
2011-08-21
影响因子：
3.5
通讯作者：
Mawlawi, Osama R.
中科院分区：
文献类型：
--
作者：
Chang, Tingting;Chang, Guoping;Mawlawi, Osama R.
噪声等效计数率（NECR）和图像噪声是两个不同但相关的指标，分别用于预测和评估图像质量。本研究的目的是调查，使用患者研究，注射剂量（ID），体重指数（BMI）和扫描仪类型的NECR和PET成像中的图像噪声测量之间的关系。两组各90例患者分别在GE DSTE和DRX PET/CT扫描仪上成像。每组中的患者根据三个BMI（20-24.9、25-29.9、30-45 kg m（-2））和三个ID（296-444、444-555、555-740 MBq）范围被分为九个亚组，导致十名患者/亚组。所有PET数据均在3D模式下采集，并使用VuePoint HD（R）全3D OSEM算法（2次迭代，21个（DRX）或20个（DSTE）子集）进行重建。计算每例患者覆盖肝脏的床位置的NECR和图像噪声测量值。NECR是根据每位患者研究的DICOM标题中记录的真实、随机和散射事件计算的，而图像噪声则确定为每位患者肝脏中50个非相邻体素的标准差。t检验比较了具有相同BMI和ID的不同扫描仪的NECR和图像噪声。另一方面，ANOVA检验用于比较具有不同BMI但具有相同ID和扫描仪类型的患者以及具有不同ID但具有相同BMI和扫描仪类型的患者的结果。正如预期的那样，t检验显示两种扫描仪在所有BMI和ID亚组的NECR方面存在显著差异。然而，与预期相反，没有观察到图像噪声测量的结果。ANOVA结果显示，对于每个ID和扫描仪亚组，不同BMI之间的NECR和图像噪声均存在统计学显著差异。然而，对于每个BMI和扫描仪亚组，不同ID的NECR和图像噪声无统计学显著差异。尽管GE DRX PET/CT扫描仪的计数率性能优于GE DSTE PET/CT扫描仪，但在使用OSEM重建时，这种改进并不能转化为较低的图像噪声。我们的研究结果表明，BMI较大的患者始终生成较差的图像质量。剂量从>555减少到296-444 MBq对图像质量的影响最小，与所使用的扫描仪无关。ID的减少减少了患者和技术人员的暴露，并可能降低研究的总成本。
Noise equivalent count rate (NECR) and image noise are two different but related metrics that have been used to predict and assess image quality, respectively. The aim of this study is to investigate, using patient studies, the relationships between injected dose (ID), body mass index (BMI) and scanner type on NECR and image noise measurements in PET imaging. Two groups of 90 patients each were imaged on a GE DSTE and a DRX PET/CT scanner, respectively. The patients in each group were divided into nine subgroups according to three BMI (20-24.9, 25-29.9, 30-45 kg m(-2)) and three ID (296-444, 444-555, 555-740 MBq) ranges, resulting in ten patients/subgroup. All PET data were acquired in 3D mode and reconstructed using the VuePoint HD (R) fully 3D OSEM algorithm (2 iterations, 21(DRX) or 20 (DSTE) subsets). NECR and image noise measurements for bed positions covering the liver were calculated for each patient. NECR was calculated from the trues, randoms and scatter events recorded in the DICOM header of each patient study, while image noise was determined as the standard deviation of 50 non-neighboring voxels in the liver of each patient. A t-test compared the NECR and image noise for different scanners but with the same BMI and ID. An ANOVA test on the other hand was used to compare the results of patients with different BMI but the same ID and scanner type as well as different ID but the same BMI and scanner type. As expected the t-test showed a significant difference in NECR between the two scanners for all BMI and ID subgroups. However, contrary to what is expected no such findings were observed for image noise measurement. The ANOVA results showed a statistically significant difference in both NECR and image noise among the different BMI for each ID and scanner subgroup. However, there was no statistically significant difference in NECR and image noise across different ID for each BMI and scanner subgroup. Although the GE DRX PET/CT scanner has better count rate performance than the GE DSTE PET/CT scanner, this improvement does not translate to a lower image noise when using OSEM reconstruction. Our results show that patients with larger BMI consistently generate poorer image quality. Dose reduction from >555 to 296-444 MBq has minimal impact on image quality independent of the scanner used. A reduction in ID decreases patient and technologist exposure and can potentially reduce the overall cost of the study.