M4D Det Structured Scintilla Tors for Digital x Ray Imaging

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www.scint-x.com

Structured scintillators for digital X-Ray imaging

Anna Sahlholm

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Per Wiklund, CEO. M.Sc., DIHM.R&D in VLSI process and device technology. International M&S at Ericsson.

Anna Sahlholm, Process Engineer. M.Sc.

Research experience in materials chemistry.

Olof Svenonius, CTO. M.Sc.Specialist in Optronics and sensors.

Carina Näsgårde, process technicianLong experience from semiconductor process development

Jan Linnros. Professor, KTH Stockholm20 years research in solid state physics. Patent holder. Headed research activities

Advisory Board:

Professors Ulf Welander, Sture Petersson, Christer Fröjd

Scint-X Team

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8/8/2019 M4D Det Structured Scintilla Tors for Digital x Ray Imaging

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Digital vs. Analog x-ray imaging:

+No chemicals involved. Image processing. Easy distribution

+Lower dose

−But lower resolution and contrast

Scint-X solves this problem !

Scintillator technology for imaging x-ray detectors

”state of the art” scintillator  Scint-X scintillator 

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Scint-X technology

Conventional detector:

Trade-off between resolution andsensitivity

Scintillator (CsI:Tl) 

Pixellated sensor (CCD,CMOS) 

Scint-X patented solution –

Structured scintillator:

High resolution and high sensitivity

Etched channels (Si wafer) 

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66CsI(Tl  ) (n=1,79) 

SiO 2 

(n=1,46) 

X-Ray photons(~0-70 keV) 

CCD pixel 

Silicon

Scintillating waveguide

CCD pixel 

θ c =35 ° 

Light (  λ=550 nm) 

Incident X-Rays generate light at 550 nm

wavelength 55 photons/X-ray photon/keV

Critical angle 35° (NA=0,57) 

Rays at larger angles absorbed in Si

Advantages:High absorption signal +Light confinement resolution +

Challenge:Waveguide loss signal -

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Modulation Transfer Function (MTF)Ability to reproduce contrast vs. Spatial FrequencySlant edge analysis according to ISO12233- Low frequencies: coarse objects/large fluctuations- High frequencies: fine objects/pixel pitch

Characteristics

Ideal: MTF = sin(x) / x Slant edge applied at small angle

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MTF Comparison:

Characteristics

0 5 10 15 20 250

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

     M     T     F

Frequency [lp/mm]

30 µm

20 µm

40 µm

CsI needle

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Medical X-ray

Intra-oral sensorsThinner detector Improved image resolution and contrastModular scintillator – lower cost

Industrial RadiographyAXI, X-ray microscopy of materials

High resolutionModular scintillator – lower cost

Market for imaging x-ray detectors

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Process

Etched wafers

Deposition of CsI(Tl) 

Melting and filling of CsI(Tl), annealing

Polishing

Polymer spinning

Dicing

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X-Ray source:Planmeca Intra, commercial dental sourceE = 60..70 kVpt = 20..800 ms

Sensor:Hamamatsu S8981, commercial oral sensor Scintillator removed – bare FOP1000x1500 pixels, 20x20 µm

20x30 mm active area

Measurement setup

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Results - Comparison with ”state of the art” competing technology

Example: Integrated Circuit X-ray inspection

State of the art scintillator Scint-X scintillator (40 um pitch)

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Results - Comparison with ”state of the art” competing technology

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Research at KTH: publications, PhD thesis, patent

Scint-X AB founded in 2007

Four full time employees

Funding: 10 MSEK (3 MSEK venture capital)

Prototypes tested – anticipated function verified

Two ”Letter of Intent” signed (dental x-ray)

Two orders from Swedish Space Corporation (Material analysis)

Project for industrialization started 2009

Where are we now?

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Thank you!

Questions? 

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Results - Comparison with ”state of the art” competing technology

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Conversion Function (CF)Light output vs. Exposure time (dose)- X-Ray to photon conversion- Waveguide efficiency

Sample S14: 365x365 pixels

Characteristics

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VarianceVariance vs. Exposure time (dose)- Total noise: X-Ray induced & other 

Sample S14: Gain-compensatedIdeal: Variance = k x Dose

Characteristics

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Signal to Noise Ratio (SNR)Signal (CF) / Noise (√variance) vs. Exposure time (dose)

- Total noise: X-Ray induced & other 

Ideal: SNR = k x √Dose

Characteristics