Multicenter Harmonization of ⁸⁹Zr PET/CT Performance

Abstract

This study investigated the feasibility of quantitative accuracy and harmonized image quality in 89 Zr-PET/CT multicenter studies. Methods: Five PET/CT scanners from 3 vendors were included. 89 Zr activity was measured in a central dose calibrator before delivery. Local activity assays were based on volume as well as on the local dose calibrator. Accuracy and image noise were determined from a cross calibration experiment. Image quality was assessed from recovery coefficients derived from different volume-of-interest (VOI) methods (VOI A50% , based on a 3-dimensional isocontour at 50% of the maximum voxel value with local background correction; VOI Max , based on the voxel with the highest uptake; and VOI 3Dpeak , based on a spheric VOI of 1.2-cm diameter positioned so as to maximize the enclosed average). PET images were analyzed before and after postreconstruction smoothing, applied to match image noise. Results: PET/CT accuracy and image noise ranged from 23% to 10% and from 13% to 22%, respectively. VOI 3Dpeak produced the most reproducible recovery coefficients. After calibration of the local dose calibrator to the central dose calibrator, differences between the local activity assays were within 6%. Conclusion: This study showed that quantitative accuracy and harmonized image quality can be reached in 89 Zr PET/CT multicenter studies. PET using labeled monoclonal antibodies, also known as immuno-PET, shows promise as a tool to predict the outcome of cancer treatment based on monoclonal antibodies (1). Their kinetics dictate the need for a positron label with a long half-life. An ideal radionuclide is 89 Zr (half-life, 78.41 h) because its physical half-life matches the biologic half-life of most antibodies. Additionally, it can easily and stably be coupled to monoclonal antibodies (2). To date, all 89 Zr-monoclonal antibody PET/CT studies that have been reported were performed within a single center (3-5). More recently, several multicenter studies have been initiated. Multicenter studies with 18 F-labeled tracers have shown the need for standardization of image acquisition, reconstruction, and analysis procedures, such as outlined in the European Association of Nuclear Medicine guidelines for tumor imaging (6) and implemented in the form of an accreditation (EANM Research Ltd.[EARL]). For 89 Zr, there are several additional factors that need to be considered: nonprompt emission of 909-keV g rays after each positron emission may influence cross calibration between the local dose calibrator and the PET/CT camera, and low counting rates (due to both low positron abundance and low injected activity) may potentially lead to poorer image quality. The aim of this study was therefore to investigate the feasibility of quantitative accuracy and harmonized image quality in 89 Zr-PET/CT multicenter studies. MATERIALS AND METHODS ScannersThree Gemini TF PET/CT scanners (Philips Healthcare) (7), a Biograph mCT PET/CT scanner (Siemens Medical Solutions) (8), and a Discovery-690 PET/CT scanner (GE Healthcare) (9) were us...

PET/CT-Derived Whole-Body and Bone Marrow Dosimetry of 89Zr-Cetuximab

“…The LV-based self RM dose estimate was 0.17 6 0.04 mGyÁMBq 21 (range, 0.11-0.22 mGyÁMBq 21 ). The total RM dose estimate for the plasma-and LV-based approaches was 0.48 6 0.08 mGyÁMBq 21 (range, 0.41-0.65 mGyÁMBq 21 ) and 0.51 6 0.06 mGyÁMBq 21 (range, 0.44-0.63 mGyÁMBq 21 ), respectively ( Table 3). The contribution of cumulated activity before the first and after the last scan as compared with the total RM cumulated activity was 16% 6 2% and 27% 6 4% for plasma-and LV-based methods, respectively.…”

“…The highest average absorbed dose was observed in the liver with 2.60 6 0.78 mGyÁMBq 21 , followed by the kidneys (1.04 6 0.24 mGyÁMBq 21 ), spleen (0.89 6 0.22 mGyÁMBq 21 ), lungs (0.66 6 0.17 mGyÁMBq 21 ), and RM (0.51 6 0.06 mGyÁMBq 21 ).…”

“…Rizvi et al (2) reported that, for 89 Zr-ibritumomab tiuxetan, the liver was the organ with the highest absorbed dose (1.36 6 0.58 mGyÁMBq 21 ), followed by the spleen (1.04 6 0.16 mGyÁMBq 21 ), kidneys (0.75 6 0.06 mGyÁMBq 21 ), lungs (0.63 6 0.11 mGyÁMBq 21 ), and RM (0.46 6 0.05 mGyÁMBq 21 ), whereas the effective dose was found to be 0.55 6 0.07 mSvÁMBq 21 . Borjesson et al (19) in a radiation dosimetry study of 89 Zr-cmAb U36 found the highest absorbed dose for the liver (1.30 6 0.34 mSvÁMBq 21 ), followed by the kidneys (1.00 6 0.30 mSvÁMBq 21 ), lungs (0.79 6 0.26 mSvÁMBq 21 ), and spleen (0.72 6 0.18 mSvÁMBq 21 ).…”

“…Borjesson et al (19) in a radiation dosimetry study of 89 Zr-cmAb U36 found the highest absorbed dose for the liver (1.30 6 0.34 mSvÁMBq 21 ), followed by the kidneys (1.00 6 0.30 mSvÁMBq 21 ), lungs (0.79 6 0.26 mSvÁMBq 21 ), and spleen (0.72 6 0.18 mSvÁMBq 21 ). The effective dose was estimated to be 0.60 6 0.04 mSvÁMBq 21 . However, a direct comparison of organ-absorbed dose estimates between 89 Zr-labeled cetuximab and other 89 Zrlabeled mAbs should be interpreted with care, because metabolism in the liver and specific targeting of each mAb may vary.…”

“…From a technical point of view, partial-volume effect might have resulted in underestimation of RM activity concentrations. On the basis of 89 Zr phantom studies (21), the activity concentration of a 2.5-cm sphere surrounded by a homogeneous background can be underestimated by as much as 20%. Nevertheless, the present observation of a nonconstant (increasing) BM-to-background ratio as function of time indicates that partial-volume corrections based on a fixed factor taken from phantom studies (with a sphere-to-background ratio of 10) would provide misleading results.…”