Adaptive Imaging Using the IImaS XRay Imaging System

1
Adaptive Imaging Using the I-ImaS X-Ray Imaging
System

• Dr. Matthew Noy
• High energy Physics Group
• Imperial College London
• http//www.i-imas.ucl.ac.uk/
• matthew.noy_at_imperial.ac.uk

2
Overview

• Introduction to the I-ImaS Project
• Description of the Sensor and Test System
  electronics
• Presentation of selected results
• Sensor characterisation
• Prototype System images
• Description of Final I-ImaS System
• Summary

3
Introduction

• I-ImaS (Intelligent-Imaging Sensors)
• Optimise image contrast
• Maximise image quality in areas of high
  diagnostic information content
• Ensuring correct exposure
• Minimise dose to regions of low information
  content
• Applications
• Mammography, dental, security, quality control,
  etc.
• EU funded under FP6
• 3 Year project
• Feb. 2004?Feb 2007
• 9 institutes in 5 EU countries

4
Collaboration

• M. Noy1, J. Jones1, G. Hall1, G. Iles1, J.
  Leaver1, D. Machin1, S. Greenwood, M. Khaleeq, B.
  Avset5, A. Bergamaschi4, D. Cavouras6, I.
  Evangelou7, A. Fant3, M. J. French3, P.
  Gasiorek3, H. Georgiou6, J. Griffiths2,
  R. Longo4, N. Manthos7, M. G. Metaxas2, J. M.
  Ostby5, F. Psomadellis9, G. J. Royle2, H.
  Schulerud5, R. D. Speller2, P. F. van der Stelt8,
  S. Theodoridis6, F. Triantis7, R. Turchetta3, C.
  Venanzi4
• 1High Energy Physics Group, Imperial College,
  London, UK
• 2Department of Medical Physics and Biomedical
  Engineering, University College London, London,
  UK3Rutherford Appleton Laboratory, CCLRC,
  Oxford, UK
• 4Department of Physics, University of Trieste,
  Trieste, Italy5SINTEF Information and
  Communication Technologies, Oslo, Norway
• 6Department of Informatics and Telecommunications,
  University of Athens, Athens, Greece
• 7Physics Department, University of Ioannina,
  Greece
• 8Academic Centre for Dentistry, Vrike
  Universiteit and University of Amsterdam,
  Amsterdam, the Netherlands
• 9ANCO S.A., Athens, Greece

5
The I-ImaS Principle

• Scanning step-and-shoot approach
• Single pass of a dual-line of sensors
• 1st line constant, low intensity X-Ray beam
• 2nd line Real-time adjustment of X-Ray intensity
  based on data from 1st scan line
• Adjustment uses wedge filters optimised for
  photon energy
• Data from two scans must be combined (offline)
• ? real-time feedback
• First line data feeds steering algorithm
• Implemented in programmable logic
• Customised motion control system
• translates sample ? simplifies system for
  evaluation
• moves wedge filters
• Wedge filters allow regional selection
• Separation of 2cm between scan lines
• This (patient comfort time) places a limit on
  the processing time available

6
The I-ImaS Principle
X-ray source
Real-time feedback signals control wedge filter
to regulate I-ImaS X-ray intensity
X-ray beams
Direction of scan
Wedge filter
Primary collimator
Compressed tissue
Detector collimator
Scout sensor
I-ImaS sensor
Steering algorithm
7
The I-ImaS Sensor

• 1.5D sensor, 1x16mm2
• Monolithic Active Pixel Sensor (MAPS), 3T arch.
• 0.35?m CMOS process (AMS)
• Custom designed at Rutherford Appleton Lab.
• 32x32?m2 pixel size
• 512x32 pixel active area (dummy border of 4)
• 200,000e- full well capacity, ENC 50e-
• CsI Scintillator used for photon conversion
• Camera on chip
• On-board SAR ADC array
• 14bit
• 20MHz (16 Cycles/conversion ? 1.25MS/s per ADC)
• 16 ADCs, each serves 32x32 pixel sub-array
• Sequenced externally
• FPGA controlled
• Full Frame and rolling shutter, Single and CDS
  modes.

8
The I-ImaS Sensor
9
Evaluation System Overview

• 3 boards
• Imperial DAQ (IDAQ)
• Xilinx VII Pro 2MGate FPGA
• USB2.0, 10/100 Ethernet, VME
• System ACE Bootloader
• 256MB DDR DRAM
• 272 spare I/O
• I-ImaS Sensor Test Card (ISTC)
• Xilinx Spartan-3 400kGate FPGA
• Cmd/Ctrl bus to IDAQ
• DAQ Path to IDAQ
• 12 x 10 bit digital voltage references
• Adjustable current reference
• 12 bit test DAC
• 16 bit test ADC
• 50 spare I/O
• Sensor Mount Card (SMC)
• Sensor is bonded to this
• Pitch adapter

• Evaluation of sensor performance done using this
  system
• Electrical, Optical (visible) X-Ray (Synchrotron
  (ELETTRA), Mo, W)
• Only a Single Sensor System
• Can do all evaluation work, but need a multi
  sensor array
• Final System Designed
• 2 rows of 10 sensors

10
ADC Linearity and Electronic Noise

• ADC
• Good linearity
• Shown to have no missing codes
• 14bit digitisation of 12 bit signal
• Excellent uniformity across chip
• 16 curves in this plot ?

• Noise
• Amplifier input isolated
• ADC Amp noise measured to be lt2 Counts (RMS)
  typically
• Full speed operation

11
PTC MTF

• Optical PTC at 550nm
• Measured per pixel
• Typical gain 12e-/ADU
• Typical Cpix 6.5fF
• Including parasitic

• MTF
• CsI Structured 100?m
• FOP 1mm
• 10 level 6lp/mm

12
Prototype Imaging System at UCL

• Evaluation DAQ system and motion control
  integrated
• Synchronised sample translation, triggering
  readout
• Acquisition of composite images up to 30cm in
  length
• All filter positions
• Off-line emulation of the system ? evaluation of
  steering algorithm

13
Post-Processed Example Images

• Jaw section
• edge
• front
• SMCv2 PCB

14
Multi-Sensor System

• Full System PCB
• Still used IDAQ as mother card
• 2 rows of 10 sensors
• 2cm apart
• 20 x ISTC
• V and I references
• QDR RAM
• Pedestal subtraction
• Gain correction
• Hot/dead pixel masking
• Buffering
• Large PCB
• 40cm x 35cm

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Multi-Sensor System
Digital 5V
Digital 3.3V
Digital 1.2V (A)
Analog -5V
Analog 3.3V
Analog 5V
Power Connectors
Digital 2.5V
Digital 1.8V
Digital 1.2V (B)
Power Supply Control
Power Supply
Xray Monitor
1 FE Unit
Sensor Card
Sensor Card
FE FPGA
QDR RAM
VREFs IREFs ADCs DACs
VREFs IREFs ADCs DACs
Digital 1.5V
Digital 1.2V (C)
Digital 0.75V (D)
Sensor Card
Sensor Card
Digital 0.75V (E)
Digital 0.75V (C)
Sensor Card
Sensor Card
FE FPGA
VREFs IREFs ADCs DACs
VREFs IREFs ADCs DACs
QDR RAM
Digital 0.75V (A)
Digital 0.75V (B)
Sensor Card
Sensor Card
Sensor Card
Sensor Card
FE FPGA
VREFs IREFs ADCs DACs
VREFs IREFs ADCs DACs
QDR RAM
I-ImaS Strip
Scout Strip
Sensor Card
Sensor Card
BE FPGA
IDAQ Connector
IDAQ Connector
Sensor Card
Sensor Card
VREFs IREFs ADCs DACs
QDR RAM
FE FPGA
VREFs IREFs ADCs DACs
Sensor Card
Sensor Card
Sensor Card
Sensor Card
FE FPGA
VREFs IREFs ADCs DACs
VREFs IREFs ADCs DACs
QDR RAM
IDAQ Connector
Sensor Card
Sensor Card
IDAQ Connector
Not to scale
Xray Monitor
Front End
Back End
16
SMCv2

• SMCv2
• Small SMC
• 1cm x 3cm
• Tessellates to enable stitching (offline)

17
Summary

• I-ImaS Aims
• Regionally optimise image contrast resolution
• Custom MAPS sensor designed and working
• Custom Electronics also designed and working
• Motion control system integrated to produce an
  evaluation system
• Yields evaluation data sets and nice images
• Loads of things not covered
• Software
• Firmware
• Steering algorithm implementation
• Detailed sensor characterisation results

http//www.i-imas.ucl.ac.uk/ matthew.noy_at_imperial.
ac.uk