Inter-rater agreement was almost perfect in C-PiB PET scans. Positive or negative decision by visual interpretation was dichotomized by a cut-off value of mcSUVR = 1.5. As some cases of disagreement among raters tended to show low mcSUVR, referring to quantitative method may facilitate correct diagnosis when evaluating images of low amyloid deposition.

Standardized uptake values (SUVs) have been widely used in the diagnosis of malignant tumors and in clinical trials of tumor therapies as semiquantitative metrics of tumor 18 F-FDG uptake. However, SUVs for small lesions are liable to errors due to partialvolume effect and statistical noise. The purpose of this study was to evaluate the reproducibility and accuracy of maximum and peak SUV (SUV max and SUV peak , respectively) of small lesions in phantom experiments. Methods: We used a body phantom with 6 spheres in a quarter warm background. The PET data were acquired for 1,800 s in list-mode, from which data were extracted to generate 15 PET images for each of the 60-, 90-, 120-, 150-, and 180-s scanning times. The SUV max and SUV peak of the hot spheres in the 1,800-s scan were used as a reference (SUV ref,max and SUV ref,peak ). Coefficients of variation for both SUV max and SUV peak in hot spheres (CV max and CV peak ) were calculated to evaluate the variability of the SUVs. On the other hand, percentage differences between SUV max and SUV ref,max and between SUV peak and SUV ref,peak were calculated for evaluation of the accuracy of SUV. We additionally examined the coefficients of variation of background activity and the percentage background variability as parameters for the physical assessment of image quality. Results: Visibility of a 10-mm-diameter hot sphere was considerably different among scan frames. The CV max and CV peak increased as the sphere size became smaller and as the acquisition time became shorter. SUV max was generally overestimated as the scan time shortened and the sphere size increased. The SUV max and SUV peak of a 37-mm-diameter sphere for 60-s scans had average positive biases of 28.3% and 4.4%, compared with the reference. Conclusion: SUV max was variable and overestimated as the scan time decreased and the sphere size increased. In contrast, SUV peak was a more robust and accurate metric than SUV max . The measurements of SUV peak (or SUV peak normalized to lean body mass) in addition to SUV max are desirable for reproducible and accurate quantification in clinical situations.

Optimal image reconstruction conditions were determined for brain (18)F-FDG and amyloid PET imaging with Discovery-690 PET/CT for diagnosis and research on AD based on the JSNM phantom criteria. This supports feasibility of the phantom criteria for standardization and harmonization of brain (18)F-FDG and amyloid PET for multicenter studies.

BackgroundWhile fluorodeoxyglucose (FDG) and amyloid PET is valuable for patient management, research, and clinical trial of therapeutics on Alzheimer’s disease, the specific details of the PET scanning method including the PET camera model type influence the image quality, which may further affect the interpretation of images and quantitative capabilities. To make multicenter PET data reliable and to establish PET scanning as a universal diagnostic technique and a verified biomarker, we have proposed phantom test procedures and criteria for optimizing image quality across different PET cameras.ResultsAs the method, four physical parameters (resolution, gray-white contrast, uniformity, and image noise) were selected as essential to image quality for brain FDG and amyloid PET and were measured with a Hoffman 3D brain phantom and a uniform cylindrical phantom on a total of 12 currently used PET models. The phantom radioactivity and acquisition time were determined based on the standard scanning protocol for each PET drug (FDG, 11C-PiB, 18F-florbetapir, and 18F-flutemetamol). Reconstruction parameters were either determined based on the methods adopted in ADNI, J-ADNI, and other research and clinical trials or optimized based on measured phantom image parameters under various reconstruction conditions.As the result, phantom test criteria were proposed as follows: (i) 8 mm FWHM or better resolution and (ii) gray/white %contrast ≥55 % with the Hoffman 3D brain phantom and (iii) SD of 51 small region of interests (ROIs) ≤0.0249 (equivalent to 5 % variation) for uniformity and (iv) image noise (SD/mean) ≤15 % for a large ROI with the uniform cylindrical phantom. These criteria provided image quality conforming to those multicenter clinical studies and were also achievable with most of the PET cameras that are currently used.ConclusionsThe proposed phantom test criteria facilitate standardization and qualification of brain FDG and amyloid PET images and deserve further evaluation by future multicenter clinical studies.