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Straling en radioactiviteit in medische beeldvorming en therapie
Dr. Ir. Dennis SchaartRadiation, Radionuclides & Reactors, Technische Natuurwetenschappen
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Health• radiation and radioactivity for diagnostics
• radiation and radioactivity for therapy
• production routes for radionuclides
• radiation detection systems for imaging
Research themesResearch themes
Dennis R. Schaart, 14 oktober 2010
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radioactive
Energie + neutronen!
Kernsplijting
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Radionuclidenkaart
aantal neutronen in kern
aan
tal p
roto
nen
in
kern
n,g reactie
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Veelgebruikte Radionucliden
Molybdeen-99
Fluor-18
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• Gerichte distributie• Gerichte accumulatie• Gericht metabolisme• Gerichte clearance (klaring)
Maar dit moet dus ook inhouden:
• Gerichte productie van het radionuclide• Gerichte selectie van de chemische eigenschappen• Gerichte selectie van de stralingseigenschappen
FOCUS: Targeting (gerichtheid)
Targeting
Diseased site Free compound Targeted compound
Afwijkend weefsel
Verdeling na “ongerichte” injectie
Gerichte verdelingmet targeting
Radionuclides in Medicine
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Doelorgaan
carrier Verbinding(linker)
doelzoeker
Radionuclide
Radionuclides in Medicine
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(a)(b)
Scanning Electron Microscopy (SEM)(a) Ho-MS non-irradiated(b) Ho-MS 6 h irradiated(c) Ho-MS 10 h irradiated(d) MS 10 h irradiated.
(a)
(b)
10 m
(c)
(d)
10 m
(a) (c)
HOR 5.1012 n.cm-2s-1(Nijsen JWF et al. 2005) SEM Ho-loaded
poly (L-lactic acid) microspheres
166Ho microspheres
Radionuclide Production
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Gamma camera
Radiopharmaceutical
Multihole lead collimator crucial for image formation=> low sensitivity
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Radio-Molecular Imaging
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Two gamma cameras
Also three cameras
Radiopharmaceutical
Single Photon Emission CT
rotating
3D Imaging: SPECT
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3D Imaging: SPECT
SPECT-CT
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Cardiac SPECT
short axis vertical long axis horizontal long axis
Images courtesy of F. Verzijlbergen, St. Antonius Hospital, Nieuwegein
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The spectrum of medical imaging Jones, 1996
Structure/anatomy X-ray/CT/MRI
Physiology US, SPECT, PET, MRI/S
Metabolism PET, MRS
Drug distribution PET
Molecular pathways PET
Molecular targets PET, SPECT
Medical Imaging Modalities
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nn
np p
pp
np
n
e-
Neutron-deficient radionuclide
Detector
Detector
Positron Emission Tomography
p n + e+ + e
positron range
e+
511 keV annihilation photon
~180o
511 keV annihilation photon
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PET Scanner
Scanner: ring of gamma detectors
Collinearly emitted annihilation quanta detected in coincidence
Radiopharmaceuticalwhich binds to a specific target, such as tumour cells
Detectors:scintillator +light sensor
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Philips GEMINI PET/CT scanner with OpenView Gantry
Multimodality: PET/CT scanner
Pictures: Y. Haemisch, Philips
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Multimodality: PET + CT
Primary Pancreatic Cancer with Suspicious Chest Wall and Mediastinum Lesions
PET + CT Fused Images
PET + CT Fused Images
PET + CT Fused Images
Pictures: A.A. Lammertsma, VUmc PET Centre
PET + CT (fused images): primary pancreatic cancer with suspicious chest wall and mediastinum lesions
In principle, PET does not provide anatonical information. Hence, in cases where it is important to localize e.g. metabolic activity, PET is often combined with other imaging modalities. For example, PET/CT is regularly used in (radio-)oncology for tumor localisation and treatment planning.
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PET Image Quality used to be patient size dependent
Slim 58 kg “Normal” 89 kg Heavy 127 kg
Time-of-flight PET
From: Y. Haemisch, Philips Medical Systems
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AnnihilationAnnihilation
LORLOR
t1
t2
without TOF
with TOF
t2-t1
TOF PET: basic concept
From: Y. Haemisch, Philips Medical Systems
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x = uncertainty in position along LOR = c . t/2if, for example, t = 500 ps x = 7.5 cm
D
x
TOF reconstruction Conventionalback-
projection
TOF PET: basic concept
Accuracy of source position localization along line of response depends on timing resolution t
From: Y. Haemisch, Philips Medical Systems
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114 kg; BMI = 32.213.4 mCi; 2 hr post-inj
Colon cancer, left upper quadrant peritoneal node, PhilipsTruFlight™ scanner
TOF (~650 ps)
Non-TOF
Time-of-flight PET
From: J. Karp, University of Pennsylvania
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• Monolithic scintillation crystal
• One or more light sensor arrays (double-sided readout, DSR, shown here)
• Gamma entry position on front surface from scintillation light distribution
• Intrinsic correction for depth-of-interaction!
SiPM arrays
scintillator511 keVgammaphoton
front surface
back surface
Monolithic scintillator detectors
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Individual readout of array elements => position-sensitive light sensor
Silicon Photomultipliers
Hamamatsu
Philips Digital Photon Counting
SensL
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Density (g/cm3)
Effective Z
Atten. l. 511 keV (mm)
Decay time (ns)
# photons /MeV
Emission max. (nm)
Hygroscopic
7.13
75
10.4
300
8,500
480
no
7.4
66
11.4
35-45
26,000
420
no
NaI:Tl BGO LSO:Ce GSO:Ce LaBr3:Ce
3.67
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29.1
230
40,000
410
yes
6.7
60
14.1
30-60
8,000
440
no
5.1
47
21.3
16
70,000
380
yes
PET scintillators
Good for TOF!
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TOF setup
• SiPM signals are amplified with two
cascaded stages
• After first stage energy signals are
branched out, shaped, and fed into
peak sensing ADCs
• Timing signals are sampled at 8 GS/s
• Digitizers are triggered by coincidence
signal from two leading edge triggers
Reflective enclosure
3x3x5 mm3
LaBr3:Ce5%
or 3x3x5 mm3
LYSO:Ce
MPPC S10362-33-050c
Seifert et al, NSS-MIC 2009
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20 mm 20 mm
World-record timing resolution with LaBr3:Ce & SiPMs
100 ps FWHM=> 15 mm FWHM
Schaart et al, Phys Med Biol 2010 (in press)
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SUBLIMA Project (2010-2014)
SUB nanosecond Leverage In PET/MR ImAging
Image courtesy of Philips
Whole-body TOF-PET / MRI
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Thank You