Digital vs. analog PET/CT: intra-subject comparison of the SUVmax in target lesions and reference regions

Fuentes-Ocampo, Francisco; López-Mora, Diego Alfonso; Flotats, Albert; Paillahueque, Gabriela; Camacho, Valle; Duch, Joan; Fernández, A.; Domenech, Arnau; Estorch, Montserrat; Carrió, Ignasi

doi:10.1007/s00259-018-4256-0

Cited by 47 publications

(39 citation statements)

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“…The Vereos PET/CT system (Philips, Cleveland, Ohio) was recently commercialized with a digital silicon photomultiplier (SiPM), a 1:1 coupling with small lutetium-yttrium oxyorthosilicate (LYSO) crystals together with a dramatic enhancement in TOF resolution (~310 ps) comparatively with analog PET systems (> 500 ps) [8]. These properties have been shown to provide excellent image quality performance according to NEMA standards [9][10][11] while previous clinical studies have shown that digital PET improves not only image quality but also diagnostic confidence and accuracy in oncologic diseases [12][13][14][15][16][17]. However, it is not known to what extent the properties of digital PET cameras are advantageous under routine conditions favoring SNR for image reconstruction, especially with regard to analog PET cameras equipped with comparable reconstruction algorithms and similarly optimized for SNR.…”

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confidence: 99%

Head-to-head comparison between digital and analog PET of human and phantom images when optimized for maximizing the signal-to-noise ratio from small lesions

et al. 2020

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Background: Routine PET exams are increasingly performed with reduced injected activities, leading to the use of different image reconstruction parameters than the NEMA parameters, in order to prevent from any deleterious decrease in signal-tonoise ratio (SNR) and thus, in lesion detectability. This study aimed to provide a global head-to-head comparison between digital (Vereos, Philips®) and analog (Ingenuity TF, Philips®) PET cameras of the trade-off between SNR and contrast through a wide-ranging number of reconstruction iterations, and with a further reconstruction optimization based on the SNR of small lesions.Methods: Image quality parameters were compared between the two cameras on human and phantom images for a number of OSEM reconstruction iterations ranging from 1 to 10, the number of subsets being fixed at 10, and with the further identification of reconstruction parameters maximizing the SNR of spheres and adenopathies nearing 10 mm in diameter. These reconstructions were additionally obtained with and without time-of-flight (TOF) information (TOF and noTOF images, respectively) for further comparisons.Results: On both human and phantom TOF images, the compromise between SNR and contrast was consistently more advantageous for digital than analog PET, with the difference being particularly pronounced for the lowest numbers of iterations and the smallest spheres. SNR was maximized with 1 and 2 OSEM iterations for the TOF images from digital and analog PET, respectively, whereas 4 OSEM iterations were required for the corresponding noTOF images from both cameras. On the TOF images obtained with this SNR optimization, digital PET exhibited a 37% to 44% higher SNR as compared with analog PET, depending on sphere size. These relative differences were however much lower for the noTOF images optimized for SNR (− 4 to + 18%), as well as for images reconstructed according to NEMA standards (− 4 to + 12%).Conclusion: SNR may be dramatically higher for digital PET than for analog PET, especially when optimized for small lesions. This superiority is mostly attributable to enhanced TOF resolution and is significantly underestimated in NEMA-based analyses.

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Section: Introductionmentioning

confidence: 99%

Head-to-head comparison between digital and analog PET of human and phantom images when optimized for maximizing the signal-to-noise ratio from small lesions

et al. 2020

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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.

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confidence: 99%

“…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].…”

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confidence: 99%

“…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.…”

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Fuentes-Ocampo

López-Mora

Flotats

et al. 2019

Eur J Nucl Med Mol Imaging

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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.

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“…In these 22 patients, all the lesions visualized only by means of the dPET/CT were < 1 cm in size: eight were in the lungs, eight in lymph-nodes, six in the liver, four in bones, and one in seminal vesicles, in the breasts and in the skin, respectively. It is worth noting that dPET/CT changed staging in 32% of these patients (7 out of 22).In the same group of 100 oncological patients, another recent study was conducted to assess whether dPET/CT impact on the quantification of SUVmax in target lesions (the most metabolically active in each case) and in reference regions (liver and mediastinal blood pool) in comparison to aPET/CT [6]. The findings of this paper indicate that SUVmax of the target lesions and mediastinal blood pool measured by the d system were significantly higher than with those obtained by the a one, whereas liver mean SUVmax did not differ between the two devices.…”

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confidence: 99%

Digital PET/CT: a new intriguing chance for clinical nuclear medicine and personalized molecular imaging

Schillaci

Urbano

2019

Eur J Nucl Med Mol Imaging

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Clinical PET/CT is a well-known useful tool for the in vivo noninvasive quantitative imaging of physiologic and pathologic processes [1]. Actually, the key role of PET/CT in cancer staging and therapeutic responses to personalized treatments is well established; it is an essential imaging modality not only in oncology but also in neuroscience and in all the applications of molecular imaging. In recent years, there have been multiple advances in PET/CT scanners: new hardware, software, and acquisition methods to improve image quality [2]. Nevertheless, till now PET detectors have been mainly based on photomultiplier tubes (PMT), which have well-known advantages but also several limitations that affect, in particular, small lesions detection [3]. The introduction of digital detectors in PET/CT scanners may represent an important improvement in this diagnostic technology [4].In this issue of EJNMMI, Lopez-Mora et al.[5] present a step forward in this field, comparing image quality and lesion detection capability between a digital (d) and an analog (a) PET/CT system in 100 patients with oncologic diseases who were prospectively included in this study. The patients consecutively underwent a single day, dual imaging protocol (d and aPET/CT) after a i.v. injection of either FDG or fluorocholine. The first PET/CT was performed 60 min after the i.v. injection of the radiopharmaceutical, and the second imaging dataset was acquired with a mean time delay of 50 ± 14 min. In the patients referred for an initial assessment (n = 58), the dPET/CT was performed first, while in the patients who were evaluated for therapy monitoring, the aPET/CT was firstly acquired. Three nuclear medicine physicians evaluated image quality using a 4-point scale (−1, poor to 2, excellent) and detection capability by counting the number of lesions with increased uptake of the radiopharmaceutical. In 54% of patients, dPET/CT allowed a better image quality than aPET/ CT; in the remaining 46 patients, image quality did not significantly differ between both devices. Regarding lesion detection capability, dPET/CT was able to visualize lesions in three patients in whom the a system resulted negative; moreover, in 19 out of 80 cases which were positive at aPET/CT imaging, the dPET/CT detected more lesions. In these 22 patients, all the lesions visualized only by means of the dPET/CT were < 1 cm in size: eight were in the lungs, eight in lymph-nodes, six in the liver, four in bones, and one in seminal vesicles, in the breasts and in the skin, respectively. It is worth noting that dPET/CT changed staging in 32% of these patients (7 out of 22).In the same group of 100 oncological patients, another recent study was conducted to assess whether dPET/CT impact on the quantification of SUVmax in target lesions (the most metabolically active in each case) and in reference regions (liver and mediastinal blood pool) in comparison to aPET/CT [6]. The findings of this paper indicate that SUVmax of the target lesions and mediastinal blood pool measured by the d system w...

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Digital vs. analog PET/CT: intra-subject comparison of the SUVmax in target lesions and reference regions

Cited by 47 publications

References 15 publications

Head-to-head comparison between digital and analog PET of human and phantom images when optimized for maximizing the signal-to-noise ratio from small lesions

Head-to-head comparison between digital and analog PET of human and phantom images when optimized for maximizing the signal-to-noise ratio from small lesions

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Digital PET/CT: a new intriguing chance for clinical nuclear medicine and personalized molecular imaging

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