Repeatability of SUV in Oncologic ¹⁸F-FDG PET

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to (1) describe the way test-retest studies have been used to measure SUV repeatability, (2) summarize the different methodologic approaches and complexities when analyzing SUV test-retest data, and (3) understand the implications of SUV repeatability for the quantitative assessment of tumor response to treatment.Financial Disclosure: This work was partially funded by grants from the National Institutes of Health (HHSN268201300071C and U01CA140204). The author of this article has indicated no other relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA category 1 credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, SAM, and other credit types, participants can access this activity through the SNMMI website (http://www.snmmilearningcenter.org) through April 2020.Quantitative analysis can potentially improve the accuracy and consistency of 18 F-FDG PET, particularly for the assessment of tumor response to treatment. Although not without limitations, SUV has emerged as the predominant metric for tumor quantification with 18 F-FDG PET. Growing literature suggests that the difference between SUVs measured before and after treatment can be used to predict tumor response at an early stage. SUV is, however, associated with multiple sources of variability, and to best use SUV for response assessment, an understanding of the repeatability of the technique is required. Test-retest studies involve repeated scanning of the same patient on the same scanner using the same protocol no more than a few days apart and provide basic information on the repeatability of the technique. Multiple test-retest studies have been performed to assess SUV repeatability, although a comparison of reports is complicated by the use of different methodologies and statistical metrics. This article reviews the available data, addressing issues such as different repeatability metrics, relative units, log transformation, and asymmetric limits of repeatability. When acquired with careful attention to protocol, tumor SUV has a withinsubject coefficient of variation of approximately 10%. In a response assessment setting, SUV reductions of more than 25% and increases of more than 33% are unlikely to be due to measurement variability. Broader margins may be required for sites with less rigorous protocol compliance, but in general, SUV is a highly repeatable imaging biomarker that is ideally suited to monitoring tumor response to treatment in individual patients.

Test–Retest Reproducibility of 18F-FDG PET/CT Uptake in Cancer Patients Within a Qualified and Calibrated Local Network

“…Therefore, the primary analysis emphasizes Bland-Altman limits of agreement (centered around average difference) rather than the RC (centered around zero). For testing group differences, jDj was selected as the primary endpoint to facilitate interpretation as absolute percentage difference (11). Linear mixed-effects regression models were fitted to measure associations between test-retest difference (jDj) and scanning group, patient-level, and lesion-level characteristics.…”

“…Scanner qualification (4) and standardization of patient preparation and imaging protocols (5,6) may reduce measurement error. Consistency in scanner protocol parameters such as uptake time, image reconstruction, and scanner maintenance may limit machine error to less than 10% (7-9), but inconsistent or nonoptimized protocols can add error ranging from 18% to more than 40% (7,10,11). In addition, deviations from standards are common even under the scrutiny of a test-retest study (12)(13)(14).…”

Dynamic whole-body PET imaging: principles, potentials and applications

“…In any case, the impact of such a framework on test-retest repeatability of PET measures [101] remains to be carefully assessed.…”

Kinetic analysis of HER2-binding ABY-025 Affibody molecule using dynamic PET in patients with metastatic breast cancer

“…In a pilot study, 68 Ga-ABY-025 PET uptake quantification suggested a preliminary SUV threshold of 6 for the discrimination of HER2-positive from HER2negative lesions [11,12]. SUV is a highly repeatable measurement; however, it relies heavily on the acquisition and reconstruction protocols used [13].…”