A.Gektin, B.Grinyov Institute for Scintillation Materials, Kharkov, Ukraine

T IRI-STDelft U Kharkov, Ukraine ISMA

A.Gektin, B.GrinyovInstitute for Scintillation Materials, Kharkov, Ukraine

New Scintillation Materials and Engineering for Medical Imaging

Outlines:

Material vs application

Materials for different modalities

Scintillators for SPECT&PET

Last trends in detector engineering


Radiation in Medical Imaging

Energies

X-ray imaging Mammography 25 kVp, ~18 keV

Radiography, chest 150 kVp

Fluoroscopy 150 kVp

X-ray CT 150 kVp

Nuclear medicine Scintigraphy 80 - 140 keV

SPECT 60 - 511 keV

PET 511 keV

Modality

emission

transmission

Two options: Anatomic and/or Functional Image


Scintillators for Medical Imaging

Material g/

cm3

Y, ph/MeV sc, ns sc, nm 1/ sc, MHz

Gd2O2S: Pr,Ce,F 7.34 40000 2100 580 0.4

CsI(Tl) 4.51 61000 900 565 1.0

CdWO4 7.9 19700 2000 495 0.5

ZnWO4 7.87 21500 22000 480 0.05

CaWO4 6.1 6000 600 430 1.7

Bi3Ge4O12 (BGO) 7.13 8200 300 505 3.3

Lu3Al5O12:Sc 6.7 22500 610 270 1.6

LuAlO3:Ce (LuAP) 8.34 11400 17+slow 365 58

Lu2SiO5:Ce (LSO) 7.4 27000 40 420 25

Lu2Si2O7:Ce (LPS) 6.23 30000 30 380 33

LuBO3:Ce 7.4 26000 39 410 26

NaI(Tl) 3.67 40000 230 415 4.3


X — Ray screens. Digital Radiography

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

From film to digital screen

50km – spatial resolution

Amorphous silicon

Spectral MatchingColumnar CsI:Tl


density light yield dec. time afterglow wavel. max.

(g/cm3)

(phot./MeV) (μs) (% after (nm)

3/100 ms)

CdWO4

7.9 20,000 5 < 0.1/ 0.02 495

Bi4Ge3O12 (BGO) 7.1 9,000 0.3 480

CsI:Tl 4.5 66,000 8 - > 6 >2/0.3 550

Gd2O2S:Pr,Ce,F 7.3 35,000 4 < 0.1/< 0.01 510

Gd2O2S:Pr (UFC) 7.3 50,000 3 0.02/0.002 510

Y1.34 Gd0.60 O3:(Eu,Pr)0.06 5.9 44,000 1000 4.9/< 0.01 610

(Hilight) Gd3Ga5O12:Cr,Ce

7.1

40,000

140 < 0.1/0.01

730

Lu2O3:Eu,Tb

9.4 30,000 > 1000 > 1/0.3 610

X-ray Computed Tomography

Ceramic Scintillators


SPECT: current standard practice (basic!)

• dual head acquisition

• filtered back projection

• gated cardiac acquisition

• dynamic acquisition (never)

• Chang attenuation correction (sometimes)

• measured transmission (available at few sites)

• iterative reconstruction (available but underutilized)

• scatter correction (limited use)

• motion correction (available but crude!)

• resolution compensation (not usually available)

• partial volume correction (what’s this?)


NaI(Tl) gamma cameras history

www.siemens.de

Dual head camera

Single head camera

high spatial resolution

scintimamography

single head camera

circular detector

1959

whole body imaging

90th

80th

70th

cylindrical detector

curve NaI(Tl) detector

dual head detector

dual head camera

single head camera

rectangular detector

2000th

21 century

SPECT tomography

Anger invention

prototype

coincidence measurement


From conventional to dedicated and dual mode SPECT systems

Last years SPECT upgrades

“Curve Plate”technology Cylindrical detector techique

light

out

put

A – slotting

B – no slots

x

Slotted scintillator

–– quantum

Coincidence mode detector


Opportunities for developmentMulti-modality imaging as a precursor for advanced analysis


Different Designs for the Same Application

Continuouscrystal

Partly pixilatedcrystal

Matrix + light guide

Dual mode (PET/SPECT) imaging system

Anger Logics


Underlying Principle of PET. (Positron Emission Tomography)

Detector ring diameter 0.8-0.9 m

Collimated 511 keV quanta detected in coincidence


PET Detector Design


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)

Positron Emission Tomography

PET Scintillators

Energy resolution poor


New PET Developments DOI — Depth of Interaction

incorrect Line of Response

Depth of Interaction

LuAPAPD array

Pulse shape discrimination

LSO

Special resolution increase


New Scintillators. High Energy Resolution

0 100 200 300 400 500 600 7000

200

400

600

800

1000

1200

1400

1600

1800

2000

LaCl3:Ce

coun

ts

energy [keV]

600 7000

1000

1600

coun

ts

energy [keV]

LaCl3:Ce

LaCl3:Ce

LaCl3:Ce(10%)

ΔE/E = 3.1%

Energy resolution

Time resolution

Light yieldDecay timeNon-

proportionality


New Scintillation Materials and Engineering for Medical Imaging

Conclusions: Further improvement of scintillator is possible

Search and development of new scintillators are the base for imaging systems upgrade

Advance scintillation detector engineering is the option for new modality development (animal imaging, scintimammography, dedicated images)

A.Gektin, B.Grinyov Institute for Scintillation Materials, Kharkov, Ukraine

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