Small animal PET as non-invasive tool for preclinical
imaging
Marta Oteo [email protected]
Biomedical Applications of Radioisotopesand Pharmacokinetic Unit
Small animal PET as non-invasive tool for preclinical
imagingPreclinical imaging- Animal models- Major challenge for small animal imaging
Available imaging modalities
Preclinical PET equipment design
Small animal PET as a tool for quick and cheaper translational research
PET tracer development
MicroPET imaging examples
Cracow PET Symposium 23/09/2014 2(C) Marta Oteo, CIEMAT, Madrid
Why do we need preclinical imaging on living animals?
Non-invasive in vivo validation of the candidate drugs and probes (observing multi-scale changes, from organ, tissue, cell, down to molecular level induced by physiological, pathological or pharmacological effects) is critical prior to perform human trials.
In vitro and ex vivo systems lack the interacting physiological factors present in vivo, facilitating investigation of systemic aspects of physiological processes and disease
What small animal models are commonly used?
Mouse is the most used, followed by rat
Mouse is the ideal model:Prolific (fast breeding cycle)Inexpensive to house Reproductive and nervous system are like those of humansSame diseases as humans99% homology with human genomeBig advances in mouse genomicsWide range of animal models of human disease
Rat is commonly used in Neuroscience (because of the bigger size of its brain)
Cracow PET Symposium 23/09/2014 3(C) Marta Oteo, CIEMAT, Madrid
Spatial resolution Sensitivity
Signal/Noise
What is the major challenge for small animal imaging?
To visualize anatomical structures and monitor physiological activitieson such a small scale
High resolution imaging modalities are required
Cracow PET Symposium 23/09/2014 4(C) Marta Oteo, CIEMAT, Madrid
Available small animal imaging modalities
Multimodality systems provide functional and anatomical information
PET/CT, PET/MR, SPECT/CT, SPECT/MR
Jürgen K.William et all (2008). Molecular imaging in drug developement. Nature Reviews
CT imaging
SPECT imaging
PET imaging
Ultrasound imaging
Magnetic resonance imaging
Optical imaging
Cracow PET Symposium 23/09/2014 5(C) Marta Oteo, CIEMAT, Madrid
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Modality Spatial resolution (mm) Clinical-to-preclinical design refinement(s)
Clinical Preclinical
MRI ~1 0.1 Higher field-strength magnets, improved gradient fields and coils
MRSI ~10 ~2 Higher field-strength magnets, improved gradient fields and coils
PET ~5 1-2 Reduced detector element size, smaller-diameter detector rings
SPECT ~10 0.5-2 Pinhole collimation (and resulting magnification)
CT 1-2 0.2 Higher X-ray flux, smaller focal spot, and higher magnification
US 1-2 0.1 Higher-f requency scan heads
Comparative spatial resolution of clinical and preclinical imaging modalities and associated design
refinements
Fabian Kiessling and Bernd J. Pichler. “Small Animal imaging” Basics and Practical Guide. ISBN: 978-3-642-12944-5
Performance parameters and logistical features of small-animal imaging modalities
Modality Time per study, min
No. of animals per study
Spatial reso-lution, mm
I ntrinsic contrast
Probe or contrast agent sensitivity
Dynamic imaging
Radiation dose, cGy
Equipment cost, $
MRI
MRSI
Up to ~60 with set-up
Up to ~10 1
0.1 ~2
High Variable
M-mM M-mM
Yes No
0 0
~ 1M
PET 5-60 1 or 2 1-2 None Sub pM Yes 10-100 600-800K
SPECT 30-90 1 0.5-2 None Sub pM No 10-100 600-800K
CT 10-15 1 0.2 High among sof t tissues/ bone; none among sof t t.
mM No 10-20 200-400K
US Up to ~60 with set-up
1 0.1 Low; high between cystic & solid structures
? Yes 0 200K
Optical: bio-luminescence
~5 Up to 5 ~10 None nM Yes 0 200-400K
Optical: fluorescence
~5 1 < 5 Variable nM No 0 100-200K
NI R: fluorescence
~10 1 < 5 None pM No 0 200-300K
Cracow PET Symposium 23/09/2014 7(C) Marta Oteo, CIEMAT, Madrid
Clinical PET equipments Preclinical PET equipments
To improve detector instrumentation and overall system design:
• novel detector geometry ( ring diameter / detector size)• new scintillators• reconstruction methods: iterative algorithms
Low positron range
Radiotracer specific activity
To spatial resolution and sensitvity:
Cracow PET Symposium 23/09/2014 8(C) Marta Oteo, CIEMAT, Madrid
Characteristics of preclinical PET Scanners
I nveon Siemens
Mosaic HP Philips
ClearPET Raytest
Argus Sedecal
Genisys4 Sofie bio sciences
NanoPet/ CT Mediso
Albira Bruker
Detector material
LSO LYSO LYSO/ LuYAP
LYSO1/
GSO2
BGO LYSO LYSO monolithic
Crystal dimension, mm
1.51x 1.51x10
2x2x10 2x2x10 1.45x1.45x71/ 82
1.8x 1.8x7 1.12x 1.12x13
40x40x10
Ring diameter, mm
161 197 135- 225
118 50+ 181 111
Axial FOV 127 119 110 48 94 94,8 40
Energy window, keV
350-625 385- 665
250- 650
560- 700
150- 650
250- 750
350- 650
Peak detection effi ciency, %
6.72 2.83 3.03 4.32 14 7.7 2
Transaxial FWHM resolution @5mm, mm
1.64 2.34 2.02 1.66 1.4 ~1.6 1.55
Cracow PET Symposium 23/09/2014 9(C) Marta Oteo, CIEMAT, Madrid
Claudia Kuntner and David Stout. Frontiers in Physics. February 2014 | Volume 2 | Article 12
Preclinical PET imaging
Clinical PET imaging
Translational research
Probes or labeled drugs evaluation and
characterization in vivo(pharmacodynamics
and pharmacokinetics)
- quicker translation to clinical practice- better scientific foundation- more rapid elimination of ineffective
compounds- reduced number of experimental
animals
Identification of the target molecule
Find a probe that binds specifcally
to the target
Radioactive labeling of the probe
In vitro tests (binding affinity, stability etc.)
In vivo experiments
Cracow PET Symposium 23/09/2014 10(C) Marta Oteo, CIEMAT, Madrid
Positron Emitter
(PET)
Half life
18F 1.83h
124I 100.3h
68Ga 1.13h
64Cu 12.7h
76Br 16.2h
86Y 14.7h
89Zr 78.4h
Labeling strategies:Direct (halogens)Indirect (metals) : using chelators
Main goal in radiotracer development
Specific probes
Peptides
mAb: Immuno-PET
- fast blood clearance- rapid tissue penetration- Low antigenicity
- high specificity - low blood clearance- high tissue penetration- immunogenic
-Diagnosis
-Treatment “THERANOSTICS”
mAb
peptide
Cracow PET Symposium 23/09/2014 11(C) Marta Oteo, CIEMAT, Madrid
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68Ga Applications
68Ge/68Ga generator GMP compliant
Eckert & Ziegler
Radioisotopes more suitable for ImmunoPET:•124I (103 h) – For Ab that do not became internalized (not residualizing)•89Zr (78,4 h) – For Ab that became internalized (residualizing)
Combines the high resolution and sensitivity of a PET camera with the unique ability of a mAbs to selectively bind specific antigens.
Application in diagnostic as well as in prognostic and therapeutic oncology
Immuno-PET
Cracow PET Symposium 23/09/2014 13(C) Marta Oteo, CIEMAT, Madrid
Melanoma overexpressing MC1R (-MSH receptor)
A CB
Cracow PET Symposium 23/09/2014 14(C) Marta Oteo, CIEMAT, Madrid
MC1R (melanocortin -1 receptor)-MSH (-melanocyte-stimulating hormone)
PET detection of pulmonary NETs overexpressing SSTR using SST analogs.
Lung Cancer transgenic mouse modelDeveloped at Molecular Oncology Unit (CIEMAT)
18F-FDG
68Ga-DOTATATE
Cracow PET Symposium 23/09/2014 15(C) Marta Oteo, CIEMAT, Madrid
Detection of NETs (Meningioma) overexpressing SSTR using SST analogs
Mouse model s.c. implanted with CH157-MN (Meningioma cell line)
Cracow PET Symposium 23/09/2014 16(C) Marta Oteo, CIEMAT, Madrid
Detection of NETs (Pheochromocytoma) overexpressing SSTR using SST analogs
Mouse model s.c. implanted with PC-12 (Pheochromocytoma rat cell line)
68Ga-DOTATATE
Cracow PET Symposium 23/09/2014 17(C) Marta Oteo, CIEMAT, Madrid
Immuno-PET
89Zr-DFO-anti-MMP14
• Nude mice• Implanted (s.c) with the glioblastoma cell line U87-MG• Two weeks later: 1-2 mg mAb/Kg (50-150 µCi) • PET performed at different times post-administration
Cracow PET Symposium 23/09/2014 18(C) Marta Oteo, CIEMAT, Madrid
Immuno-PET
Cracow PET Symposium 23/09/2014 19(C) Marta Oteo, CIEMAT, Madrid
Concluding remark
PET molecular imaging allows for the non-invasive assessment of biological and biochemical processes in living subjects, contributing to improve our understanding of disease and drug activity during preclinical and clinical drug development.
Cracow PET Symposium 23/09/2014 20(C) Marta Oteo, CIEMAT, Madrid
[email protected] PET Symposium 23/09/2014 21(C) Marta Oteo, CIEMAT, Madrid
Biomedical Applications of Radioisotopesand Pharmacokinetic Unit (CIEMAT)