Lee Young Sub, Kim Jin Su, Kim Jung Young, Kim Byung Il, Lim Sang Moo, Kim Hee-Joung
1 Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences , Seoul, Republic of Korea.
Cancer Biother Radiopharm. 2015 Feb;30(1):27-32. doi: 10.1089/cbr.2014.1709. Epub 2014 Dec 30.
Zirconium-89 (t(1/2)=78.41 hours) is an ideal metallic radioisotope for immuno-positron emission tomography (PET), given that its physical half-life closely matches the biological half-life of monoclonal antibodies. In this study, the authors measured the spatial resolution and image quality of Zr-89 PET and compared the results against those obtained using F-18 PET, which is widely regarded as the gold standard for comparison of imaging characteristics.
The spatial resolution and image qualities of Zr-89 were measured on the Siemens Biograph Truepoint TrueV PET/CT scanner, partly according to NEMA NU2-2007 standards. For spatial resolution measurement, the Zr-89 point source was located at the center of the axial field of view (FOV) and offset 1/4 axial FOV from the center. For image quality measurements, an NEMA IEC Phantom was used. The NEMA IEC Phantom consists of six hot spheres that were filled with Zr-89 solution. Spatial resolution and image quality (%contrast, %background variability [BV], and source to background ratio [SBR]) were assessed to compare the imaging characteristics of F-18 with those of Siemens Biograph Truepoint TrueV.
The transverse and axial spatial resolutions at 1 cm were 4.5 and 4.7 mm for Zr-89, respectively. The %contrast of Zr-89 was 25.5% for the smallest 10 mm sized sphere and 89.8% for the largest 37 mm sized sphere, and for F-18, it was 32.5% for the smallest 10 mm sized sphere and 103.9% for the largest 37 mm sized sphere using the ordered subset expectation maximization (OSEM) reconstruction method. The %BV of F-18 PET was 6.4% for the smallest 10 mm sized sphere and 3.5% for the largest 37 mm sized sphere using the OSEM reconstruction. The SBR of Zr-89 was 1.8 for the smallest 10 mm sized sphere and 3.7 for the largest 37 mm sized sphere, and for F-18, it was 2.0 for the smallest 10 mm sized sphere and 4.1 for the largest 37 mm sized sphere using the OSEM reconstruction method.
This study assessed Zr-89 imaging characteristics using a Siemens Biograph Truepoint TrueV PET/CT scanner and compared the results with those obtained for F-18 PET. Although spatial resolution and image quality of Zr-89 PET were lower compared with F-18 PET, due to longer positron range and low positron branching ratio, Zr-89 is advantageous for immuno-PET due to well-matched half-life with monoclonal antibodies.
锆 - 89（t(1/2)=78.41小时）是免疫正电子发射断层扫描（PET）理想的金属放射性同位素，因为其物理半衰期与单克隆抗体的生物半衰期密切匹配。在本研究中，作者测量了Zr - 89 PET的空间分辨率和图像质量，并将结果与使用F - 18 PET获得的结果进行比较，F - 18 PET被广泛认为是成像特性比较的金标准。
部分依据NEMA NU2 - 2007标准，在西门子Biograph Truepoint TrueV PET/CT扫描仪上测量Zr - 89的空间分辨率和图像质量。对于空间分辨率测量，Zr - 89点源位于轴向视野（FOV）中心，并偏离中心1/4轴向FOV。对于图像质量测量，使用NEMA IEC体模。NEMA IEC体模由六个填充Zr - 89溶液的热球组成。评估空间分辨率和图像质量（对比度百分比、背景变异性百分比[BV]和源与背景比[SBR]）以比较F - 18与西门子Biograph Truepoint TrueV的成像特性。
Zr - 89在1 cm处的横向和轴向空间分辨率分别为4.5和4.7 mm。使用有序子集期望最大化（OSEM）重建方法时，Zr - 89对于最小的10 mm尺寸球体的对比度百分比为25.5%，对于最大的37 mm尺寸球体为89.8%；对于F - 18，最小的10 mm尺寸球体为32.5%，最大的37 mm尺寸球体为103.9%。使用OSEM重建时F - 18 PET对于最小的10 mm尺寸球体的BV百分比为6.4%，对于最大的37 mm尺寸球体为3.5%。Zr - 89对于最小的10 mm尺寸球体的SBR为1.8，对于最大的37 mm尺寸球体为3.7；对于F - 18，使用OSEM重建方法时，最小的10 mm尺寸球体为2.0，最大的37 mm尺寸球体为4.1。
本研究使用西门子Biograph Truepoint TrueV PET/CT扫描仪评估了Zr - 89的成像特性，并将结果与F - 18 PET的结果进行比较。尽管Zr - 89 PET的空间分辨率和图像质量低于F - 18 PET，但由于正电子射程较长和正电子分支比低，Zr - 89因其与单克隆抗体半衰期匹配良好而在免疫PET中具有优势。
