Nakahara Tadaki, Daisaki Hiromitsu, Yamamoto Yasushi, Iimori Takashi, Miyagawa Kazuyuki, Okamoto Tomoya, Owaki Yoshiki, Yada Nobuhiro, Sawada Koichi, Tokorodani Ryotaro, Jinzaki Masahiro
Department of Radiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
Department of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1 Kamioki-machi, Maebashi, Gunma, 371-0052, Japan.
EJNMMI Res. 2017 Dec;7(1):53. doi: 10.1186/s13550-017-0300-5. Epub 2017 Jun 20.
Although quantitative analysis using standardized uptake value (SUV) becomes realistic in clinical single-photon emission computed tomography/computed tomography (SPECT/CT) imaging, reconstruction parameter settings can deliver different quantitative results among different SPECT/CT systems. This study aims to propose a use of the digital reference object (DRO), which is a National Electrical Manufacturers Association (NEMA) phantom-like object developed by the Quantitative Imaging Biomarker Alliance (QIBA) fluorodeoxyglucose-positron emission tomography technical committee, for the purpose of harmonizing SUVs in Tc-99m SPECT/CT imaging.
The NEMA body phantom with determined Tc-99m concentration was scanned with the four state-of-the-art SPECT/CT systems. SPECT data were reconstructed using different numbers of the product of subset and iteration numbers (SI) and the width of 3D Gaussian filter (3DGF). The mean (SUV), maximal (SUV), and peak (SUV) SUVs for six hot spheres (10, 13, 17, 22, 28, and 37 mm) were measured after converting SPECT count into SUV using Becquerel calibration factor. DRO smoothed by 3DGF with a FWHM of 17 mm (DRO) was generated, and the corresponding SUVs were measured. The reconstruction condition to yield the lowest root mean square error (RMSE) of SUV for all the spheres between DRO and actual phantom images was determined as the harmonized condition for each SPECT/CT scanner. Then, inter-scanner variability in all quantitative metrics was measured before (i.e., according to the manufacturers' recommendation or the policies of their own departments) and after harmonization.
RMSE was lowest in the following reconstruction conditions: SI of 100 and 3DGF of 13 mm for Brightview XCT, SI of 160 and 3DGF of 3 pixels for Discovery NM/CT, SI of 60 and 3DGF of 2 pixels for Infinia, and SI of 140 and 3DGF of 15 mm for Symbia. In pre-harmonized conditions, coefficient of variations (COVs) among the SPECT/CT systems were greater than 10% for all quantitative metrics in three of the spheres, SUV and SUV, in one of the spheres. In contrast, all metrics except SUV in the 17-mm sphere yielded less than 10% of COVs after harmonization.
Our proposed method clearly reduced inter-scanner variability in SUVs. A digital phantom developed by QIBA would be useful for harmonizing SUVs in multicenter trials using SPECT/CT.
尽管在临床单光子发射计算机断层扫描/计算机断层扫描（SPECT/CT）成像中，使用标准化摄取值（SUV）进行定量分析已成为现实，但重建参数设置在不同的SPECT/CT系统之间可能会产生不同的定量结果。本研究旨在提出使用数字参考物体（DRO），这是由定量成像生物标志物联盟（QIBA）氟脱氧葡萄糖-正电子发射断层扫描技术委员会开发的一种类似美国国家电气制造商协会（NEMA）体模的物体，目的是在Tc-99m SPECT/CT成像中使SUV标准化。
使用四台最先进的SPECT/CT系统对具有确定Tc-99m浓度的NEMA体模进行扫描。使用不同的子集与迭代次数乘积（SI）和三维高斯滤波器（3DGF）宽度重建SPECT数据。在使用贝克勒尔校准因子将SPECT计数转换为SUV后，测量六个热区（10、13、17、22、28和37毫米）的平均（SUV）、最大（SUV）和峰值（SUV）SUV。生成经半高宽为17毫米的3DGF平滑处理的DRO（DRO），并测量相应的SUV。将使DRO与实际体模图像之间所有球体的SUV均方根误差（RMSE）最低的重建条件确定为各SPECT/CT扫描仪的标准化条件。然后，在标准化之前（即根据制造商的建议或其自身部门的政策）和之后测量所有定量指标的扫描仪间变异性。
在以下重建条件下RMSE最低：Brightview XCT的SI为100且3DGF为13毫米，Discovery NM/CT的SI为160且3DGF为3像素，Infinia的SI为60且3DGF为2像素，Symbia的SI为140且3DGF为15毫米。在预标准化条件下，在三个球体中的所有定量指标中，SPECT/CT系统之间的变异系数（COV）在其中一个球体的SUV和SUV中大于10%。相比之下，标准化后，除17毫米球体中的SUV外，所有指标的COV均小于10%。
我们提出的方法明显降低了SUV的扫描仪间变异性。QIBA开发的数字体模将有助于在使用SPECT/CT的多中心试验中使SUV标准化。
