Abstract
BackgroundThe quality of phantom images was previously shown to be higher on digital (Vereos Philips®) compared to analog PET (Ingenuity Philips®) cameras. This study aimed to determine the extent to which this difference still remains significant on normal brain 18F-FDG PET images.MethodsRelative noise and contrast as well as border sharpness (a spatial resolution index) of central (striata) and peripheral (occiput) gray-matter structures were compared between 10 sets of normal brain 18F-FDG PET images recorded and reconstructed on digital and analog last-generation PET cameras, together with a subjective visual analysis of image quality provided by experienced physicians.ResultsCompared with analog PET, digital PET provided marked improvements in image quality parameters. The median relative noise was decreased (− 22%), while gray/white-matter contrast was increased (+ 27%/+ 41% for central/peripheral gray-matter structures), with these results being consistent with visual analysis. In addition, a clear enhancement in image sharpness was further documented for digital PET owing to the possible use of a 1-mm3 voxel size (+ 24%/+ 21%).ConclusionsOn normal brain 18F-FDG images and compared with a last-generation analog PET, the fully digital PET camera offers marked improvements in image noise and contrast, as well as significant potential for further enhancing spatial resolution.
Highlights
The quality of phantom images was previously shown to be higher on digital (Vereos Philips®) compared to analog PET (Ingenuity Philips®) cameras
According to the PET standards of the National Electrical Manufacturers Association (NEMA) [3], the Vereos digital PET camera exhibits certain advantages, with regard to time of flight (TOF) resolution (~ 310 ps) leading to an enhanced signal-to-noise ratio gain [2] and to an improvement in image contrast and noise level [4, 5]
The sharpness index was further enhanced for digital PET images reconstructed with the 1-mm voxel size, leading to reach a significant difference relative to the conventional images from analog PET (median increases of 24% for the striata and 21% for the occiput (p = 0.02), Fig. 3b), whereas the gray/white-matter contrast was unchanged, remaining higher than that of analog PET (median increases of 31% for the striata and 42% for the occiput (p < 0.001), Fig. 3a)
Summary
The quality of phantom images was previously shown to be higher on digital (Vereos Philips®) compared to analog PET (Ingenuity Philips®) cameras. Digital PET cameras, such as the “Vereos” (Philips®, Cleveland, Ohio), feature small digital silicon photomultipliers instead of much larger photomultiplier tubes, providing true digital photon counting with 1-to-1 crystal coupling [1] These properties are primarily likely to enhance the time-of-flight (TOF) capability and to favor signal-to-noise ratio [2]. Previous pilot clinical studies have led to consider that digital PET might improve the image quality of whole-body PET images, and diagnostic confidence and accuracy for oncologic diseases, as compared with analog PET [6,7,8] Such a significant enhancement in image quality and in diagnostic accuracy could prove helpful for various PET exams and for brain imaging where it could facilitate current dual PET/MRI analyses [9]—i.e. with a greater ability to delineate cortical gyri than with analog PET [10]. It is not known whether digital PET objectively offers a significant and quantitative gain in the quality of brain PET images
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