title: Spatial resolution and image qualities of Zr-89 on Siemens Biograph TruePoint PET/CT.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 1 Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences , Seoul, Republic of Korea.
authors.forename: Young Sub
authors.initials: YS
authors.lastname: Lee
authors.forename: Jin Su
authors.initials: JS
authors.lastname: Kim
authors.forename: Jung Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Byung Il
authors.initials: BI
authors.lastname: Kim
authors.forename: Sang Moo
authors.initials: SM
authors.lastname: Lim
authors.forename: Hee-Joung
authors.initials: HJ
authors.lastname: Kim
mesh_terms: D005462:Fluorine Radioisotopes / Q000032:analysis / Q000737:chemistry; D007089:Image Enhancement; D064847:Multimodal Imaging / Q000379:methods; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D016499:Radioimmunotherapy / Q000379:methods; D011868:Radioisotopes / Q000032:analysis / Q000737:chemistry*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D015040:Zirconium / Q000032:analysis / Q000737:chemistry*
chemical_list: D005462:Fluorine Radioisotopes; D011868:Radioisotopes; D015040:Zirconium
keywords: PET; Zr-89; image quality; radioimmunotherapy (RIT); spatial resolution