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Volume 1 Supplement 1

Proceedings of the 3rd PSMR Conference on PET/MR and SPECT/MR

Combining MRI with PET for partial volume correction improves image-derived input functions in mice

EJNMMI Physics volume 1, Article number: A84 (2014) Cite this article

Kinetic modelling in PET requires the arterial input function (AIF), defined as the time-activity curve (TAC) in plasma. This measure is challenging to obtain in mice due to low blood volumes, resulting in a reliance on image-based methods for AIF derivation. We present a comparison of PET- and MR-based region-of-interest (ROI) analysis to obtain image-derived AIFs from the left ventricle (LV) of a mouse model. ROI-based partial volume correction (PVC) was performed to improve quantification.

MRI and dynamic PET images were obtained from a recent study investigating treatment effects in 12 mice following myocardial infarction [1], where half the mice received a new treatment and half did not. Prospectively gated MRI (4.7T Bruker BioSpec, FLASH TR/TE 400/3ms, spatial resolution 140μm in 1mm slices) were acquired prior to PET acquisition (approx. 25MBq 18F-FDG bolus, 45 minute emission listmode acquisition reconstructed with 3DRP in four cardiac frames) on a split-magnet PET camera [2]. Images were co-registered using SPMMouse [3] (see Figure 1).

Figure 1
figure 1

Mouse heart MR (left) and fused with 18F-FDG static PET (right). Arrow indicates infarcted region.

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AIF extraction AIFs were obtained by taking mean time courses from LV Lumen ROIs, shown in Figure 2. The regional geometric transfer matrix (GTM) method was applied for PVC [4], using ROIs drawn on either the co-registered MR images or directly onto the last dynamic frame PET images. ROIs covered LV lumen, myocardium, lungs/body and background. Patlak [5] analysis was performed to evaluate glucose metabolism.

Figure 2
figure 2

AIFs and TACs derived for single subject using (A) MR ROIs, (B) PET ROIs with PVC and (C) MR ROIs with PVC. Insets detail first 500s

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Uncorrected AIFs and myocardial TACs produced by manual ROI delineation displayed contamination with myocardial signal. AIFs and myocardial curves became distinguishable if GTM PVC was applied. Only MR-based PVC produced significant differences (p<0.05) in Ki values between the treated and untreated groups (see Table 1).

Table 1
Full size table

GTM-based PVC gives best results in mice when ROIs are based on MRI data, due to its high-resolution and excellent soft-tissue contrast.

References

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Authors and Affiliations

  1. Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK

    Eleanor Evans, Guido Buonincontri, Rob C Hawkes, T Adrian Carpenter & Stephen J Sawiak

  2. Athinoula A Martinos Centre, Harvard University, Cambridge, MA, USA

    David Izquierdo

  3. Department of Medicine, University of Cambridge, Cambridge, UK

    Carmen Methner & Thomas Kreig

  4. Department of Physics, University of Cambridge, Cambridge, UK

    Richard E Ansorge

  5. Behavioural and Clinical Neurosciences Institute, University of Cambridge, Cambridge, UK

    Stephen J Sawiak

Authors
  1. Eleanor Evans
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  2. Guido Buonincontri
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  3. David Izquierdo
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  4. Carmen Methner
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  5. Rob C Hawkes
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  6. Richard E Ansorge
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  7. Thomas Kreig
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  8. T Adrian Carpenter
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  9. Stephen J Sawiak
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Evans, E., Buonincontri, G., Izquierdo, D. et al. Combining MRI with PET for partial volume correction improves image-derived input functions in mice. EJNMMI Phys 1 (Suppl 1), A84 (2014). https://doi.org/10.1186/2197-7364-1-S1-A84

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  • DOI: https://doi.org/10.1186/2197-7364-1-S1-A84

Keywords

  • Arterial Input Function
  • Partial Volume Correction
  • Listmode Acquisition
  • Cardiac Frame
  • Geometric Transfer Matrix