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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

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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