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Effect of geometrical constraints on PET performance in whole body simultaneous PET-MR

Stefaan Vandenberghe UGent, Vincent Keereman, Steven Staelens UGent, V Schulz and P Marsden (2009) IEEE Nuclear Science Symposium Conference Record. p.3808-3811
abstract
Simultaneous PET-MR scanners are being developed for whole body imaging. These systems require compact and MR compatible readout for the PET component. Another important modification is the geometry of the PET scanner which is determined by space constraints imposed by the surrounding MR scanner. The maximal radius of the PET scanner is limited and it becomes difficult to insert end shielding. The aim of this study is to determine the effect of modified geometry and reduced shielding on the PET performance with regards to spatial resolution, singles, trues, scatter and random coincidences. Materials and methods: All data were simulated using the GATE Monte Carlo simulation tool. The reference system for the simulation was a state of the art PET-CT scanner (Gemini TF scanner with LYSO crystals Philips Medical systems). This system has a diameter of 90 cm and end shields with an inner diameter of 70 cm. The energy resolution of the system is 12 % and based on this system a whole body PET scanner was designed with less modules positioned at a smaller radius. This modification enables it to fit inside a 3T MR scanner. This system was simulated without end shielding and with limited end shielding (60 cm diameter). For the three systems the trues, random and scatter were simulated to quantify the effect of the modified geometry. The object used was the 70 cm long NEMA scatter phantom containing activity in a line source at a radial distance of 4.5 cm. Results: Reducing the diameter from 90 cm to 70 cm results in an increase of the amount of trues by 28 %. The relative scatter fraction increases from 33 % to 36 % for the 70 cm diameter system without end shields. The introduction of short shields resulted in a small reduction (2 %) of scattered and random coincidence fraction. More detailed analysis about origin of the events showed that in the new design 85 % of scattered events originates from inside the FOV, while 90 % of the random coincidences is caused by outside FOV activity. Conclusions: For PET systems with good energy resolution, end shields only play a limited role in the reduction of scatter. The end shields are only blocking a limited part of the scattered outside FOV activity and are mostly effective in reducing the singles and resulting randoms from outside FOV.
Please use this url to cite or link to this publication:
author
organization
year
type
conference (proceedingsPaper)
publication status
published
subject
keyword
Monte Carlo methods, image resolution, biomedical MRI, phantoms, positron emission tomography, geometrical constraints, whole body simultaneous PET-MR, spatial resolution, magnetic resonance scanner, reduced shielding, whole body imaging, GATE Monte Carlo simulation, NEMA scatter phantom, magnetic flux density 3 T, size 70 cm
in
IEEE Nuclear Science Symposium Conference Record
editor
Bo Yu
issue title
2009 IEEE nuclear science symposium conference record, vols 1-5
pages
3808 - 3811
publisher
IEEE
place of publication
Piscataway, NJ, USA
conference name
IEEE Nuclear Science Symposium Conference 2009
conference location
Orlando, FL, USA
conference start
2009-10-25
conference end
2009-10-31
Web of Science type
Proceedings Paper
Web of Science id
000280505102094
ISSN
1082-3654
ISBN
9781424439614
DOI
10.1109/NSSMIC.2009.5401899
language
English
UGent publication?
yes
classification
P1
copyright statement
I have transferred the copyright for this publication to the publisher
id
911161
handle
http://hdl.handle.net/1854/LU-911161
date created
2010-03-23 13:52:11
date last changed
2017-01-02 09:53:12
@inproceedings{911161,
  abstract     = {Simultaneous PET-MR scanners are being developed for whole body imaging. These systems require compact and MR compatible readout for the PET component. Another important modification is the geometry of the PET scanner which is determined by space constraints imposed by the surrounding MR scanner. The maximal radius of the PET scanner is limited and it becomes difficult to insert end shielding. The aim of this study is to determine the effect of modified geometry and reduced shielding on the PET performance with regards to spatial resolution, singles, trues, scatter and random coincidences. Materials and methods: All data were simulated using the GATE Monte Carlo simulation tool. The reference system for the simulation was a state of the art PET-CT scanner (Gemini TF scanner with LYSO crystals Philips Medical systems). This system has a diameter of 90 cm and end shields with an inner diameter of 70 cm. The energy resolution of the system is 12 \% and based on this system a whole body PET scanner was designed with less modules positioned at a smaller radius. This modification enables it to fit inside a 3T MR scanner. This system was simulated without end shielding and with limited end shielding (60 cm diameter). For the three systems the trues, random and scatter were simulated to quantify the effect of the modified geometry. The object used was the 70 cm long NEMA scatter phantom containing activity in a line source at a radial distance of 4.5 cm. Results: Reducing the diameter from 90 cm to 70 cm results in an increase of the amount of trues by 28 \%. The relative scatter fraction increases from 33 \% to 36 \% for the 70 cm diameter system without end shields. The introduction of short shields resulted in a small reduction (2 \%) of scattered and random coincidence fraction. More detailed analysis about origin of the events showed that in the new design 85 \% of scattered events originates from inside the FOV, while 90 \% of the random coincidences is caused by outside FOV activity. Conclusions: For PET systems with good energy resolution, end shields only play a limited role in the reduction of scatter. The end shields are only blocking a limited part of the scattered outside FOV activity and are mostly effective in reducing the singles and resulting randoms from outside FOV.},
  author       = {Vandenberghe, Stefaan and Keereman, Vincent and Staelens, Steven and Schulz, V and Marsden, P},
  booktitle    = {IEEE Nuclear Science Symposium Conference Record},
  editor       = {Yu, Bo},
  isbn         = {9781424439614},
  issn         = {1082-3654},
  keyword      = {Monte Carlo methods,image resolution,biomedical MRI,phantoms,positron emission tomography,geometrical constraints,whole body simultaneous PET-MR,spatial resolution,magnetic resonance scanner,reduced shielding,whole body imaging,GATE Monte Carlo simulation,NEMA scatter phantom,magnetic flux density 3 T,size 70 cm},
  language     = {eng},
  location     = {Orlando, FL, USA},
  pages        = {3808--3811},
  publisher    = {IEEE},
  title        = {Effect of geometrical constraints on PET performance in whole body simultaneous PET-MR},
  url          = {http://dx.doi.org/10.1109/NSSMIC.2009.5401899},
  year         = {2009},
}

Chicago
Vandenberghe, Stefaan, Vincent Keereman, Steven Staelens, V Schulz, and P Marsden. 2009. “Effect of Geometrical Constraints on PET Performance in Whole Body Simultaneous PET-MR.” In IEEE Nuclear Science Symposium Conference Record, ed. Bo Yu, 3808–3811. Piscataway, NJ, USA: IEEE.
APA
Vandenberghe, Stefaan, Keereman, V., Staelens, S., Schulz, V., & Marsden, P. (2009). Effect of geometrical constraints on PET performance in whole body simultaneous PET-MR. In Bo Yu (Ed.), IEEE Nuclear Science Symposium Conference Record (pp. 3808–3811). Presented at the IEEE Nuclear Science Symposium Conference 2009, Piscataway, NJ, USA: IEEE.
Vancouver
1.
Vandenberghe S, Keereman V, Staelens S, Schulz V, Marsden P. Effect of geometrical constraints on PET performance in whole body simultaneous PET-MR. In: Yu B, editor. IEEE Nuclear Science Symposium Conference Record. Piscataway, NJ, USA: IEEE; 2009. p. 3808–11.
MLA
Vandenberghe, Stefaan, Vincent Keereman, Steven Staelens, et al. “Effect of Geometrical Constraints on PET Performance in Whole Body Simultaneous PET-MR.” IEEE Nuclear Science Symposium Conference Record. Ed. Bo Yu. Piscataway, NJ, USA: IEEE, 2009. 3808–3811. Print.