European Journal of Nuclear Medicine and Molecular Imaging | 2019
Reply to the letter
Abstract
Dear Sir, We thank Koopman et al. for their comments and interest in our recent article [1, 2]. It is well known that various technical and physics issues, such as detector performance, voxel size and reconstruction parameters, influence SUV measurements [3, 4]. The aim of our study was not to evaluate the influence of such factors on SUV measurements, but to compare under true clinical conditions the values produced by a digital scanner with those produced by an analogue scanner. The patients were scanned on the same day following a single injection of radiotracer in one imaging session with a digital scanner and with an analogue scanner installed next to each other in our department. The acquisition and reconstruction parameters selected for the digital and analogue PET/CT scans were those known to produce the best image quality under clinical conditions [2] and to provide the best lesion detectability [5]. Furthermore, with the analogue scanner, the voxel size could not be modified. In coming years, digital PET/CT systems will be deployed worldwide and will coexist with traditional analogue scanners. Differences in clinical performance will guide the selection of the appropriate system for a given indication. We believe that the information derived from our study, with regard to differences in SUVs in the same patients and lesions between those produced by a digital and by an analogue system, is relevant for the selection of the appropriate scanner in patients who need to undergo follow-up studies to assess the effect of treatments over time.