Infiltration Effect on SUV

Overview

A widely used semi-quantitative parameter to assess tumor status is the standardized uptake value (SUV). SUV estimation accuracy can be impacted by many variables. Today there still exists a significant amount of variability in PET/CT results in test and re-test studies. This variability can be introduced by instrumentation and subject-specific factors. Variability reduces image quality and increases the required changes in tumor quantification to reflect real tumor response or progression. PET/CT scanning process requires that the entire net injected dose of radiolabeled tracer is administered intravenously as a bolus. The quality and quantification of a PET/CT image is highly dependent on the uptake of radiolabeled tracer. Boellaard et al. have indicated infiltrations could potentially underestimate SUV measurements by as much as 50%. Infiltrations and obstructions are not uncommon. Recent studies using a novel QA/QC tool (LaraTM System) for the radiotracer injection process revealed that current means to detect infiltration do not completely identify all infiltrations/obstructions. Since infiltrations may not be visible in the standard field of view (FOV) and since the impact of a peripheral circulatory obstruction may not be visible even if an injection site is in the FOV, it is possible for reading and treating physicians to be unaware that a patient's image and quantification has been impacted. Additionally, when current means do detect an infiltration, they under-represent the severity because they are not capturing that infiltrations often resolve during the uptake period. As a result, infiltrations or obstructions may cause SUV inaccuracy and could adversely impact staging and tumor assessments. The purpose of this study will be to characterize the impact of moderate or greater infiltrations on standardized uptake values. Patients experiencing a moderate or greater infiltration on a routine clinical PET scan will be invited to return for a repeat scan with injection performed by specially trained personnel to reduce the risk of repeat infiltration. The two scans will be compared to assess for changes in tumor uptake intensity.