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Impact of acquisition time and penalizing factor in a block-sequential regularized expectation maximization reconstruction algorithm on a Si-photomultiplier-based PET-CT system for 18F-FDG

Trägårdh, Elin LU ; Minarik, David LU ; Almquist, Helén LU ; Bitzén, Ulrika LU ; Garpered, Sabine LU ; Hvittfelt, Erland; Olsson, Berit LU and Oddstig, Jenny LU (2019) In EJNMMI Research 9(1).
Abstract

Background: Block-sequential regularized expectation maximization (BSREM), commercially Q. Clear (GE Healthcare, Milwaukee, WI, USA), is a reconstruction algorithm that allows for a fully convergent iterative reconstruction leading to higher image contrast compared to conventional reconstruction algorithms, while also limiting noise. The noise penalization factor β controls the trade-off between noise level and resolution and can be adjusted by the user. The aim was to evaluate the influence of different β values for different activity time products (ATs = administered activity × acquisition time) in whole-body 18F-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT) regarding quantitative... (More)

Background: Block-sequential regularized expectation maximization (BSREM), commercially Q. Clear (GE Healthcare, Milwaukee, WI, USA), is a reconstruction algorithm that allows for a fully convergent iterative reconstruction leading to higher image contrast compared to conventional reconstruction algorithms, while also limiting noise. The noise penalization factor β controls the trade-off between noise level and resolution and can be adjusted by the user. The aim was to evaluate the influence of different β values for different activity time products (ATs = administered activity × acquisition time) in whole-body 18F-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT) regarding quantitative data, interpretation, and quality assessment of the images. Twenty-five patients with known or suspected malignancies, referred for clinical 18F-FDG PET-CT examinations acquired on a silicon photomultiplier PET-CT scanner, were included. The data were reconstructed using BSREM with β values of 100–700 and ATs of 4–16 MBq/kg × min/bed (acquisition times of 1, 1.5, 2, 3, and 4 min/bed). Noise level, lesion SUVmax, and lesion SUVpeak were calculated. Image quality and lesion detectability were assessed by four nuclear medicine physicians for acquisition times of 1.0 and 1.5 min/bed position. Results: The noise level decreased with increasing β values and ATs. Lesion SUVmax varied considerably between different β values and ATs, whereas SUVpeak was more stable. For an AT of 6 (in our case 1.5 min/bed), the best image quality was obtained with a β of 600 and the best lesion detectability with a β of 500. AT of 4 generated poor-quality images and false positive uptakes due to noise. Conclusions: For oncologic whole-body 18F-FDG examinations on a SiPM-based PET-CT, we propose using an AT of 6 (i.e., 4 MBq/kg and 1.5 min/bed) reconstructed with BSREM using a β value of 500–600 in order to ensure image quality and lesion detection rate as well as a high patient throughput. We do not recommend using AT < 6 since the risk of false positive uptakes due to noise increases.

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Contribution to journal
publication status
published
subject
keywords
Block-sequential regularized expectation maximization, FDG, Image reconstruction, PET-CT, Q. Clear
in
EJNMMI Research
volume
9
issue
1
publisher
BioMed Central
external identifiers
  • scopus:85069740078
ISSN
2191-219X
DOI
10.1186/s13550-019-0535-4
language
English
LU publication?
yes
id
6213744a-1b1e-49b7-82da-6e0438a998ac
date added to LUP
2019-08-02 08:39:44
date last changed
2019-08-28 04:57:35
@article{6213744a-1b1e-49b7-82da-6e0438a998ac,
  abstract     = {<p>Background: Block-sequential regularized expectation maximization (BSREM), commercially Q. Clear (GE Healthcare, Milwaukee, WI, USA), is a reconstruction algorithm that allows for a fully convergent iterative reconstruction leading to higher image contrast compared to conventional reconstruction algorithms, while also limiting noise. The noise penalization factor β controls the trade-off between noise level and resolution and can be adjusted by the user. The aim was to evaluate the influence of different β values for different activity time products (ATs = administered activity × acquisition time) in whole-body <sup>18</sup>F-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT) regarding quantitative data, interpretation, and quality assessment of the images. Twenty-five patients with known or suspected malignancies, referred for clinical <sup>18</sup>F-FDG PET-CT examinations acquired on a silicon photomultiplier PET-CT scanner, were included. The data were reconstructed using BSREM with β values of 100–700 and ATs of 4–16 MBq/kg × min/bed (acquisition times of 1, 1.5, 2, 3, and 4 min/bed). Noise level, lesion SUV<sub>max</sub>, and lesion SUV<sub>peak</sub> were calculated. Image quality and lesion detectability were assessed by four nuclear medicine physicians for acquisition times of 1.0 and 1.5 min/bed position. Results: The noise level decreased with increasing β values and ATs. Lesion SUV<sub>max</sub> varied considerably between different β values and ATs, whereas SUV<sub>peak</sub> was more stable. For an AT of 6 (in our case 1.5 min/bed), the best image quality was obtained with a β of 600 and the best lesion detectability with a β of 500. AT of 4 generated poor-quality images and false positive uptakes due to noise. Conclusions: For oncologic whole-body <sup>18</sup>F-FDG examinations on a SiPM-based PET-CT, we propose using an AT of 6 (i.e., 4 MBq/kg and 1.5 min/bed) reconstructed with BSREM using a β value of 500–600 in order to ensure image quality and lesion detection rate as well as a high patient throughput. We do not recommend using AT &lt; 6 since the risk of false positive uptakes due to noise increases.</p>},
  articleno    = {64},
  author       = {Trägårdh, Elin and Minarik, David and Almquist, Helén and Bitzén, Ulrika and Garpered, Sabine and Hvittfelt, Erland and Olsson, Berit and Oddstig, Jenny},
  issn         = {2191-219X},
  keyword      = {Block-sequential regularized expectation maximization,FDG,Image reconstruction,PET-CT,Q. Clear},
  language     = {eng},
  month        = {07},
  number       = {1},
  publisher    = {BioMed Central},
  series       = {EJNMMI Research},
  title        = {Impact of acquisition time and penalizing factor in a block-sequential regularized expectation maximization reconstruction algorithm on a Si-photomultiplier-based PET-CT system for <sup>18</sup>F-FDG},
  url          = {http://dx.doi.org/10.1186/s13550-019-0535-4},
  volume       = {9},
  year         = {2019},
}