radiation in medical imaging

T IRI-STDelft U TU Delft IRI-ST

Inorganic Scintillators in

Medical-imaging Detectors

C.W.E. van Eijk

Amsterdam, 9 September 2002


Radiation in Medical Imaging

EnergiesX-ray imaging Mammography 25 kVp, ~18 keV

Radiography, chest 150 kVpFluoroscopy 150 kVpX-ray CT 150 kVp

Nuclear medicine Scintigraphy 80 - 140 keVSPECT 60 - 511 keVPET 511 keV

Efficiency Inorganic scintillator

Modality

emission

transmission


From: Philips Medical Systems BV300 series

Mobile C-arm system for full surgical and minimally-invasive

procedures

Interventional RadiologyFluoroscopy - Real time - Low dose

ImageIntensifier

T IRI-STDelft U TU Delft IRI-STTransjugular Intrahepatic Portosystemic Shunt (TIPS)

Interventional Radiologyminimally-invasive procedure


Flat panel detector - Amorphous silicon

also for radiography

Columnar CsI:Tl

ADCreadout

addressing

Interventional Radiology

From: Philips, Aachen

Flat X-ray Detectors for Medical Imaging

Dr. Michael Overdick

Session 5

2k x 2k40 x 40 cm2


signal depends on:– scintillator light yield– optical coupling – spectral matching– diode efficiency

400 500 600 700 8000,0

0,2

0,4

0,6

0,8

1,0

wavelength / nm

400 500 600 700 8000,0

0,2

0,4

0,6

0,8

1,0

CsI:Tla-Si:H

Photodiode


Flat panel detector - Amorphous silicon



pillar growth induced by evaporation technique– crack structure– focussing of light – >500 µm layers– high MTF

CsI:Tl




X-ray Computed Tomography

X-ray source(rotating)

+

1-D or 2-Dposition-sensitive detector(rotating)

X-ray fan beam(rotating)

+ Ceramicscintillators + photodiodes

~ 1 k x 1 mm

~ 16 x 1 mm

E. Hell et al, NIM A 454 (2000) 40-48


1974: 80 x 80 pixelsslices of 13 mm spacing

2000:1024 x 1024 pixelsspiral scanning

From: W.A. Kalender, CT, 2000, MCD Verlag



density ρZ 4 light yield dec. time afterglow wavel. max. (g/cm3) (106)

(phot./MeV) (μs) (% after (nm)

3/100 ms)

CdWO4 7.9 134 20,000 5 < 0.1/ 0.02 495

Bi4Ge3O12 (BGO) 7.1 227 9,000 0.3 480

CsI:Tl 4.5 38 66,000 8 - > 6 >2/0.3 550Gd2O2S:Pr,Ce,F 7.3 103 35,000 4 < 0.1/< 0.01 510

Gd2O2S:Pr (UFC) 7.3 103 50,000 3 0.02/0.002 510 Y1.34 Gd0.60 O3:(Eu,Pr)0.06 5.9 44 44,000 1000 4.9/< 0.01 610

(Hilight) Gd3Ga5O12:Cr,Ce

7.1

58 40,000

140 < 0.1/0.01

730 Lu2O3:Eu,Tb

9.4 211 30,000 > 1000 > 1/0.3 610


Ceramic Scintillators

T IRI-STDelft U TU Delft IRI-STFrom: W.A. Kalendber, CT, 2000, MCD Verlag

Afterglow in scintillators1 angle per < ms



Positron Emission Tomography

Detector ring (inner diam. ~ 0.8 m)

Collinearly emitted 511 keV quanta detected in coincidence

Radiopharmaceutical β+ emitter

DetectorsBGO + PMT

Bi4Ge3O1

2

T IRI-STDelft U TU Delft IRI-ST http://www.epub.org.br/cm/n01/pet/pet_hist.htm

PET systems Siemens-CTI



PET Detector Block

AB

CD

4 PMTs

BGO detector block8 x 8 columns

30 mm

of 6 x 6 x 30 mm3

Bi4Ge3O12

Efficiency


Positron Emission Tomography: 2D & 3D

Septa

Septa removed

2D 3D

T IRI-STDelft U TU Delft IRI-STFrom: G. Muehllehner et al. & SCINT 2001

Increase Random coincidences~ N2

singlesτ3D PET

Energy resolution

Time resolution


Light yieldDecay timeNon-proportionality


Bi4Ge3O12 (BGO) 7.1 11.6 / 44 9,000 300 480Lu2SiO5:Ce (LSO) 7.4 12.3 / 34 26,000 40 420Gd2SiO5:Ce (GSO) 6.7 15 / 26 8,000 60 440LuxY1-xAlO3:Ce (LuAP) 8.3 11.0 / 32 11,000 18 365Lu2Si2O7:Ce (LPS) 6.2 14.5 / 29 20,000 30 380

1/μ 511 keV light yield

(g/cm3) (mm) /PE (%) (photons/MeV) (ns) (nm)


PET Scintillators

Energy resolution poor


ΔE/E = 3.1 %

photomultiplier readoutHamamatsu R1791

LaCl3:Ce(10%)

Scintillators Energy Resolution

0 100 200 300 400 500 600 7000

200

400

600

800

1000

1200

1400

1600

1800

2000LaCl

3:Ce

coun

ts

energy [keV]

600 7000

200

400

600

800

1000

1200

1400

1600 LaCl3:Ce

coun

ts

energy [keV]

LaCl3:Ce

E (keV) E (keV)

COUN

TS

COUN

TS

E.V.D. van Loef et al Appl. Phys. Lett. 77 (2000) 1467


PET basics: Position resolutionEfficient High position resolution

parallax error orradial elongation

Off centre:

incorrect Line of Response

Remedy:Depth of Interactionmeasurement

DOI


PET: Depth of Interaction in HRRT

PMTs

LSO scintillators

Light guides

PMTs

7.5 x 2.1 x 2.1 mm3

From: D.W. Townsend, C. Morel presented at SCINT 2001K. Wienhard et al 2000 IEEE NSS/MIC CDROM 17 280

Lu2SiO5:Ce

Different decay timesin the two layers

Different pulse shape DOI


Depth of Interaction

LuAP APD array

Pulse shape discrimination

Saoudi et al IEEE Trans Nucl Sci 46(1999)462, also 479 Seidel et al IEEE Trans Nucl Sci 46(1999)485

LSO

PET: DOI CRYSTAL

CLEARCrystal Clear


From: Klaus Wienhard MPI für Neurologische Forschung, Köln

Blood flow changes under speech activation (red)Tumor (green)

Multi modality

PET + MRI



Inorganic Scintillators in Medical-imaging Detectors

Conclusion Interest in further improvement of inorganic scintillators

Fundamental research

Especially for PET also Mammography PET

Small Animal PET

Use of new light detectorsAPDsSilicon drift detectors

C.W.E. van Eijk Inorganic scintillators in medical imagingPhys.Med.Biol. 47 (2002) R85 - R106

radiation in medical imaging

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