Performance characteristics of a small animal PET camera for - - PowerPoint PPT Presentation

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Performance characteristics of a small animal PET camera for - - PowerPoint PPT Presentation

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Performance characteristics of a small animal PET camera for molecular imaging Hastings DL 1 , Reader AJ 2 , Julyan PJ 1 , Zweit J 2,3 Jeavons AP 4 , Jones T 5 1 North Western Medical Physics, Christie Hospital, Manchester 2 Chemical Engineering

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SLIDE 1

Performance characteristics of a small animal PET camera for molecular imaging

1North Western Medical Physics, Christie Hospital, Manchester 2Chemical Engineering and Analytical Science, University of Manchester 3Paterson Institute for Cancer Research, Manchester 4Oxford Positron Systems, Oxfordshire 5Manchester Molecular Imaging Centre, University of Manchester.

Hastings DL1, Reader AJ2, Julyan PJ1, Zweit J2,3 Jeavons AP4, Jones T5

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SLIDE 2

HIDAC Detector Module

511 keV

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SLIDE 3

Quad HIDAC Detector

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SLIDE 4

Quad HIDAC Camera

13 million sub-millimetre detectors

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SLIDE 5

Quad HIDAC Camera

4 million sub-millimetre detectors

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SLIDE 6

Spatial Resolution

Line source glass/polyamide tube

– 50µm internal diameter – 300µm external diameter –

22Na concentration of 75 kBq/ml

Iterative reconstruction

– 0.25mm voxels – 16 iterations – 1 subset – no resolution modeling

FWHM determined according to NEMA

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SLIDE 7

Spatial Resolution

Transaxial

0.5 0.6 0.7 0.8 0.9 1 1.1

  • 100
  • 50

50 100

Distance along Axis (mm)

FWHM (mm)

Horizontal Vertical Horizontal Mean = 1.02 Vertical Mean = 1.00

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SLIDE 8

Spatial Resolution

Axial Resolution

0.5 0.6 0.7 0.8 0.9 1 1.1

  • 80
  • 40

40 80

Radial Distance from Centre (mm) FWHM (mm) Axial: Mean = 0.99mm

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SLIDE 9

Spatial Resolution

FWHM (mm) Axial Transaxial Vertical Transaxial Horizontal 0.05 0.04 0.04 Standard Deviation 0.88 0.86 0.93 Min 1.05 1.05 1.09 Max 0.99 1.00 1.02 Mean

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SLIDE 10

Sensitivity

  • Point source of 18F - 175.2 kBq
  • Electroplated 18F on tip of an Al wire
  • 5mm blu-tack ball on tip as positron annihilator
  • Iterative reconstruction

– 1mm voxels – length = 250mm; diameter = 150mm – regularization = 0 – resolution recovery = none – Iterations = 1, subsets = 32

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SLIDE 11

Sensitivity

Point Source and Profile

0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05 40 60 80 100 Position (mm) Counts

PET image

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SLIDE 12

Sensitivity

Sc = sensitivity corrected for scatter background

  • Bin data into 2D parallel projections (bin size 0.5mm)
  • Integrate over the 2D plane in the axial (z´)

– single 1D profile pi (for i=1…I bins)

% 100 × = time scan during emissions positron

  • f

Number acquired Events S

= 0.95%

0.786

1

=

∑ ∑

= ∈ I i i T i i

p p

= 0.75%

0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05 40 60 80 100 Position (mm) Counts

  • Trues are in +/- 1.5mm of peak
  • Ratio of trues to scatter-background

1 10 100 1000 10000 100000 40.0 60.0 80.0 100.0 120.0 140.0 Position (mm)

profile pi

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SLIDE 13

Count Rate Capability

  • Cylindrical phantom to simulate a mouse

– diameter 30mm, length 50mm – start activity = 74 MBq 18F

  • List mode acquisition for 21 hours

– final activity = 0.04MBq – refresh rate 120 seconds – total coincidences, singles, randoms rates recorded

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SLIDE 14

Count Rate Capability

Singles

Count Rate - Singles

200 400 600 800 1000 1200 1400 10 20 30 40 50 60 70 Activity (MBq) kcps

Detector 1 Detector 2 Detector 3 Detector 4

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SLIDE 15

Count Rate Capability Noise Equivalent Count Rate

SF = scatter fraction = 29% (Missimer 2004 * )

* Missimer et al, Phys Med Biol. 49 (2004) 2069-2081

k = proportion of the object subtended by the imaging device (?? 0.10)

( ) ( )

SF R Totals T − × − = 1

( )

R Totals SF S − × =

T S T kR T NECR + + = 2 1

T = trues rate S = scatter rate R = randoms rate

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SLIDE 16

Count Rate Capability

Coincidences

Count Rate - Coincidences

100 200 300 400 10 20 30 40 50 60 70 Activity (MBq) kcps

Total Randoms Trues Scatter (SF=29%) NEC (ko=0.10)

Trues 20% loss at 11.5 MBq

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SLIDE 17

Count Rate Capability

Count Rate - Coincidences

0.0 10.0 20.0 30.0 40.0 50.0 60.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Activity (MBq) kcps

Total Randoms Trues

Totals Trues Randoms

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SLIDE 18

Energy Dependence of Efficiency

1 2 3 4 200 400 600 800 1000 1200 1400

Energy (keV) Singles Sensitivity (% Counts/emitted gamma)

Module 1 Module 2 Module 3 Module 4

141 Tc99m 364 I131 511 F18 784 Na22 1253 Co60

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SLIDE 19

Summary of Results

Deviation = 0.0 mm Spatial Calibration 20% loss rate at 11.5MBq Count Rate Uncorrected = 0.95% Corrected = 0.75% Senstivity Transaxial horiz 1.02 (0.04) Transaxial vert 1.00 (0.04) Axial 0.99 (0.05) Spatial Resolution Measured Parameter

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SLIDE 20

Transaxial Coronal Sagittal Max Intensity Projection Mouse injected with 18-FDG Image reconstructed into 0.5mm voxels Slice thickness 0.5mm Transaxial, Coronal & Sagittal slices centred on the heart

PET Images of 18-FDG Mouse - 1

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SLIDE 21

18F-Fluoride Bone Images in Mouse

Coronal Sagittal Courtesy: Munster University Hospital

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SLIDE 22

It’s a long road ….

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SLIDE 23

It’s a long road ….