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A 92k SPAD Time-Resolved Sensor in 0.13m CIS Technology for PET/MRI Applications International Image Sensors Workshop (IISW), 13-16 th June 2013 Richard Walker , Ahmet T. Erdogan, Robert K. Henderson The University of Edinburgh, Scotland, U.K.

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SLIDE 1

A 92k SPAD Time-Resolved Sensor in 0.13µm CIS Technology for PET/MRI Applications

International Image Sensors Workshop (IISW), 13-16th June 2013

Richard Walker, Ahmet T. Erdogan, Robert K. Henderson The University of Edinburgh, Scotland, U.K. Leo H. C. Braga, Leonardo Gasparini, Nicola Massari, Matteo Perenzoni, David Stoppa Fondazione Bruno Kessler (FBK), Trento, Italy. Lindsay A. Grant Imaging Division, STMicroelectronics, Edinburgh, UK.

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SLIDE 2

PET Imaging Background

  • MRI/CT:
  • Provide structural information
  • PET:
  • Provides functional information
  • Patient administered with

radiotracer

  • Areas of high metabolic activity

visible: applications in oncology & neurology etc.

  • Goal:
  • Enabler for multi-modal imaging

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 3

Goal: Simultaneous Combined PET+MRI

  • Several advantages over PET+CT:
  • MRI does not involve X-ray dose.
  • MRI provides improved soft tissue

contrast.

  • However, not cost effective at

present.

  • Magnetic field of MRI scanner

incompatible with current PET systems.

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 4

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International Image Sensors Workshop 13th-16th June 2013

PET Imaging Background

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Source: Ramsey Badawi, University of Washington Source: Sun

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SLIDE 5

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International Image Sensors Workshop 13th-16th June 2013

Data Extraction in a PET Module

  • Each time a Gamma photon strikes the scintillator...

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Coincidence detection Rejection of low-energy scattered gamma photons Image reconstruction

gamma photon scintillator crystal CMOS SPAD sensor

time (ns) photons time (ns) photons

pulse arrival time, τ pulse Energy, E

τ τ τ τ

pulse spatial position x-y scintillation event and visible photon burst

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SLIDE 6

Typical PET System Detectors

  • Photomultiplier tubes (PMT)
  • Classic detector of choice
  • Bulky, fragile…
  • Incompatible with magnetic fields
  • Avalanche photo-diodes (APD)
  • Analog gain – sensitive to voltage/temperature
  • Silicon-Photomultipliers (i.e. SPAD arrays):
  • Analog (aSiPM)
  • Digital (dSiPM) – emerging trend

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 7

The SPADnet Sensor Concept

The design challenge - a new sensor which:

  • Is MRI compatible
  • Is mass-manufacturable at

low cost

  • Potential to extract more

information per photon

  • Meets existing PET

system requirements

The solution:

  • Silicon based
  • Standard CMOS imaging

process

  • Leverage ability to

integrate time-stamping circuits and logic.

  • Sensitive fully-digital SPAD

array

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 8

The SPADnet Sensor Concept

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 9

Sensor Architecture

  • Two operating

modes:

  • Real time energy

histogramming

  • Pixel data readout

(spatial image data & TDC values)

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International Image Sensors Workshop 13th-16th June 2013

time counts

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SLIDE 10

Sensor Architecture

  • On-chip

discriminator:

  • Recognises valid

events

  • Controls integration

(programmable integration time)

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International Image Sensors Workshop 13th-16th June 2013

time counts

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SLIDE 11

Sensor Architecture

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 12

Sensor Architecture

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 13

Sensor Architecture

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 14

International Image Sensors Workshop 13th-16th June 2013

n+

N-well P-substrate

S T I S T I n+

Deep retrograde N-well p+

S T I

N-well P-well d ½g ½g ½g PMOS Logic P-well N-well P-well NMOS Logic NMOS Logic ½g

S T I n+

N-well ½g ½g

S T I

P Cross section PMOS Logic N-well P-well NMOS Logic

S T I

Multiplication region Guard ring

Logic per SPAD (Restricted Fill Factor)

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SLIDE 15

S T I

International Image Sensors Workshop 13th-16th June 2013

P-substrate

S T I n+

Deep retrograde N-well p+

S T I

N-well P-well d ½g ½g PMOS Logic P-well N-well P-well NMOS Logic NMOS Logic ½g

S T I n+

N-well ½g ½g

S T I

P Cross section Guard ring

n+

N-well ½g

S T I

P-well p+ d

SiPM Arrays (Fill Factor Improved)

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SLIDE 16

Implemented Device

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International Image Sensors Workshop 13th-16th June 2013

9.85mm 0.61mm 0.57mm 5.425mm

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SLIDE 17

Characterisation Overview

  • Multiple TDCs improve system timing resolution

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 18

Summary

  • 92k SPAD PET image sensor in 0.13µm CIS

technology:

  • 8×16 pixel array
  • 0.57×0.61mm pixel
  • 43% array fill factor
  • TDCs per pixel for improved timing resolution
  • 100MHz real-time energy histogram output

for event recognition

  • On-chip discriminator for improved efficiency.

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International Image Sensors Workshop 13th-16th June 2013

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SLIDE 19

Thank you for your attention

Acknowledgements:

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International Image Sensors Workshop 13th-16th June 2013

Industrial partners Sensor design

www.SPADnet.eu

This work, conceived within the SPADnet project (www.spadnet.eu), has been supported by the European Community within the Seventh Framework Programme ICT Photonics. Disclaimer: This publication reflects only the authors’

  • views. The European Community is not liable for any

use that may be made of the information contained herein.

Module assembly